Challenges and Opportunities for Future

Editorial The March beyond a Milestone As we visualized the issues and challenges of climate change are getting more complex and needs inter disciplinary and intra disciplinary investigations to plan for adaptations, mitigations and remediation. Climate diversity and climate change phenomena are getting noticed by financial and developmental sectors which have to plan for the challenges those sectors are going to face. The global agreements and negotiations are emerging in more realistic way to deal with the challenges and the national governance and regulations are also getting more alert. However, in many sections there is a concern that the conceptual and philosophical framework of sustainable development, which includes environmental, social and economic issues considering them interwoven, cannot be dealt by only technological considerations and Clean Development Mechanisms (CDM). We need to identify the gray area, which is lying in between the sustainable development and CDM. With completion of this issue of “Climate Change and Environmental Sustainability” (CCES), we are going to complete three years. Initial three years are considered most challenging for continuation of such projects and we must express our obligations to the authors of all six issues, reviewers and entire editorial board those made it possible to bring the issues with good contents and good presentations. We are also thankful to our production and distribution partner, Indianjournals.com New Delhi for a fruitful partnership. The Society for Science of Climate Change and Environmental Sustainability (www.ssceindia.org) is an emerging major academic organization of Indian origin to initiate and sustain debates on issues of climate change and sustainability. The entire editorial team in the leadership of Dr. D. C. Uprety has contributed significantly. The inputs and encouragements of our team leader Dr. Uprety have been very significant in bringing out all the issues in the shape we could brought. One of our Associate Editors Dr. KuldeepBauddh has put enormous inputsfor the journal and I express my special thanks to him. We hope that the society and journal will reach many milestones. Rana Pratap Singh Editor, CCES www.ranapratap.in Email: [email protected]

Climate Change and Environmental Sustainability Volume 3(2), October 2015 Contents Review Articles 1.

Applicability of Carbonic Anhydrases in Mitigating Global Warming and Development of Useful Products from CO2 Shazia Faridi and T. Satyanarayana

77-92

2.

Developments in Bioenergy and Sustainable Agriculture Sectors for Climate Change Mitigation in Indian Context: A State of Art Richa Kothari, V.V. Pathak, A.K. Chopra, Shamshad Ahmad, Tanu Allen and B.C. Yadav

93-103

3.

A Review on Methods to Estimate CH4 and N2O Fluxes in Terrestrial Ecosystem Ajeet Kumar Singh and S. Jayakumar

104-113

4.

Effects of Changing Urban Environment of Madurai - Challenges and Opportunities for Future Environmental Sustainability Subhashini, S., Thirumaran, K. and Madhumathi, A.

114-124

Research Articles 5.

Impact of Salinity on above Ground Biomass and Stored Carbon in a Common Mangrove Excoecaria agallocha of Indian Sundarbans Kakoli Banerjee and Abhijit Mitra

125-130

6.

Variability in Phenology, Physiology and Yield Response of Different Maturity Duration Pigeon Pea Genotypes at Elevated CO2 M. Vanaja, M. Maheswari, P. Sathish, P. Vagheera, N. Jyothi Lakshmi, G. Vijay Kumar, K. Salini, N. Sridhar, Jainender and S.K. Yadav

131-136

7.

Phytodiversity and Seasonal Variations in the Soil Characteristics of Shrublands of Dachigam National Park, Jammu and Kashmir, India Arif Yaqoob, Mohammad Yunus, G.A. Bhat and D.P. Singh

137-143

8.

Productivity Enhancement among Cereal Crops by Mitigating Climate Change Effect through Deployment of Climate Resilient Varieties in India: Evidence from the Field R.P. Singh

144-156

Short Communication 9.

Enhanced Dose of Azotobacter chroococcum and Bacillussubtilis, Co-immobilised in Vermicompost Based Organic Granules, Increase Biomass Yield and Harvest Index of Wheat (Triticumaestivum L) Rose P. Minj and Rana Pratap Singh

157-162

Opinion 10. Microbes Play Major Roles in the Ecosystem Services Jay Shankar Singh

163-167

Technical Report 11. Technological Input Required for Certain Climate Change Studies S.B. Pal

168-171

Printed and Published by: DIVA Enterprises Pvt. Ltd. on behalf of The Society for Science of Climate Change and Sustainable Environment (SSCE), New Delhi Printed at: Process and Spot, C-112/3, Naraina Industrial Area, Phase-1, New Delhi-110028, Published at: DIVA Enterprises Pvt. Ltd., B-9, A-Block, LSC, Naraina Vihar, New Delhi-110028, Editor-in-Chief: Dr. D.C. Uprety, Editor: Prof. Rana Pratap Singh

Climate Change and Environmental Sustainability An official publication of “The Society for Science of Climate Change and Sustainable Environment” (Registered under the Societies Act-XXI of 1860) The society was founded in 2009 to inculcate the multidisciplinary expertise among professionals to address the emerging environmental concerns. The recent realization of the adverse effects of climate change, energy depletion, water crisis, loss of biodiversity and pollution of water, air and soil ecosystems has created a deep concern in people of all walk of life to the environmental issues. The membership of the society is open to researchers, teachers, professionals and anyone else who share its goal and are willing to contribute for the cause. Both annual and life memberships are available subject to a formal approval by the society. The application forms and more details about the foundation are available online at www.ssceindia.org. The executive committee of the society at present is as follows: President

Vice Presidents

Dr. D.C. Uprety (New Delhi)

Professor A.K. Bhatnagar (New Delhi)

Dr. A. Arunachalam (New Delhi)

Secretary

Treasurer

Professor Rana Pratap Singh (Uttar Pradesh) Email: [email protected]

Shri Ashok Datta (New Delhi)

Prof. P.W. Ramteke (Uttar Pradesh)

Joint Secretaries

Prof. Kusum Arunanchalam (Uttarakhand)

Dr. Kuldeep Bauddh (Jharkhand)

Mr. Sanjeev Kumar (Uttar Pradesh)

Members

Prof. K.K. Baruh (Assam)

Prof. M.L. Khan (Madhya Pradesh)

Prof. Uma Melkania (Pant Nagar, Uttarakhand)

Prof. P.S. Khilare (New Delhi)

Climate Change and Environmental Sustainability (October 2015) 3(2): 77-92 DOI: 10.5958/2320-642X.2015.00009.5

REVIEW ARTICLE

Applicability of Carbonic Anhydrases in Mitigating Global Warming and Development of Useful Products from CO2 Shazia Faridi1 • T. Satyanarayana2*

Abstract Carbonic anhydrase is a biocatalyst which is universally present in all prokaryotic as well as eukaryotic cells that catalyses the reversible conversion of CO2 to bicarbonate with a turnover rate (kcat) ranging between 104 and 10 6 s -1 . Because of the extremely efficient CO 2 conversion catalysed by CAs, their use is gaining considerable attention for applications wherever conversion of CO2 or use of bicarbonate is involved. Since CAs are ubiquitous, extensive efforts are being made to survey CAs from various sources including microorganisms. This review focuses on various classes of CAs, their occurrence and possible uses in various environmental applications, in particular sequestration of CO2 from industrial emissions for mitigating global warming. Mineralization of CO2 is one field where the captured CO2 is utilised to generate stable mineral carbonates. Bicarbonates produced after hydration of CO2 can be utilised further in the production of biofuels and other value added products. CAs can also be used in the development of biosensors and in various medical applications such as in artificial lungs and in blood substitutes. Keywords Carbonic anhydrase, CO 2 sequestration, Mineralisation of CO2, Artificial lungs, Biosensors 1. Introduction Carbonic anhydrase (CA) [EC 4.2.1.1] is an incredibly important enzyme for all living forms. Anhydrase refers to an enzyme that catalyses the removal of a water molecule from a compound; thus, carbonic anhydrase derives its name from the reverse reaction catalysed by it (removal of water molecule from carbonic acid; forward reaction being the conversion of CO2 and H2O to bicarbonate and proton). The enzyme, therefore, interconverts CO2 and H2O to bicarbonate and proton as shown in the reaction below: CO2 (aq) + H2O → HCO3- +H+ (1)

CA accelerates reaction (1) dramatically provided the pH is above the pKa of CO2/HCO3- equilibrium. CA is one of the highly efficient and fast metalloenzymes with a prodigious turnover rate (kcat) ranging from 104 to 106 s-1; the reaction rate being controlled by the physical process of diffusion and proton transfer from the active site. Recently CA from a thermophilic bacterium Sulfurihydrogenibium azorense (SazCA) has been reported as the fastest CA followed by Human isozyme HCAII (Luca et al., 2013). Most CAs contain Zn in their active site with one Zn atom per subunit. 2. Classes of Carbonic Anhydrases Five different evolutionarily unrelated classes of CAs have been identified (α, β, γ, δ and ζ). Each class has a different structure, molecular weight, oligomeric forms and they even differ in their catalytic efficiencies. Functions of various classes of CAs are summarised in Table 1. CAs do not share any significant primary amino acid sequence similarity between them, and thus, are considered as an excellent example of convergent evolution. The catalytic domains of all human CAs have highly conserved sequence and three-dimensional structures. α-CAs) 2.1 α-Carbonic Anhydrases (α All mammals have been shown to possess α-CAs only. Sixteen different isozymes have been reported for human CA which belongs to α-class. In addition, α-CAs are also present in prokaryotes and viruses, but none is found in archaea. Apart from catalysing the physiological reaction of hydration of CO2, α-CAs show a strong esterase activity and also catalyse a variety of less studied reactions as well, such as hydration of cyanate to carbamic acid, hydration of cyanamide to urea, the aldehyde hydration to gem-diols, and the hydrolysis of carboxylic or sulfonic acids (Kanth et al., 2012). Among the prokaryotes, α-CA (28 kDa) from

Scholar, 2Professor, Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi 110021, India *Corresponding author Email Id: [email protected]

1

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Climate Change and Environmental Sustainability (October 2015) 3(2): 77-92

Neisseria sicca was the first to be purified (Adler et al., 1972). The recombinant form of N. gonorrhoeae α-CA was also produced by cloning and expression in Escherichia coli (Chirica et al., 1997). α-CAs are generally monomeric having a molecular mass ranging from 29 to 35 kDa. Crystal structures of human CAs have been solved and all of them are composed of a tertiary fold with a 10-stranded beta-sheet at the central position (Figure 1A). Zn(II), is situated at the bottom of a 15 Å deep active site cleft, being coordinated by three histidine residues (His94, His96 and His119) and a water molecule/hydroxide ion. The zinc(II) is present in a coneshaped 15 Å deep active site cleft and is coordinated by histidine residues (His94, His96 and His119) and a water molecule. The zinc bound H2O molecule is hydrogen bonded to Thr199, which in turn is connected to the Glu 106 through carboxylate group. These interactions increase the nucleophilicity of the zinc-bound water molecule and helps in orienting CO 2 in an appropriate location for the nucleophilic attack. Substrate binding pocket is composed of Val121, Val143 and Leu198 in hCAII (Briganti et al., 1997). β -CAs) 2.2 β-Carbonic Anhydrases (β β-CA class is widespread in plant kingdom particularly in their chloroplasts encompassing both monocot and dicot

plants as well as in algae, archaea and bacteria. First β-CA was isolated from Methanobacterium thermoautotrophicum (Smith and Ferry, 1999). Other well known β-CAs are from are PPCA from Porphyridium purpureum, PSCA from Pisum sativum, ECCA from E. coli. β-CAs generally are oligomeric (exists in dimeric, tetrameric and octameric forms) with a molecular mass ranging between ~45 and 200 kDa. The basic subunit is a dimer. All β-CAs are composed of a unique α/β fold which is not present in any other proteins (Figure 1B). Crystal structure of β-CA from P. purpureum CA (PPCA) has been determined which is a pseudo-tetramer comprising two pseudo-dimers (Mitsuhashi et al., 2000). Its monomeric unit consists of two internally repeating structures, which are folded as a pair of equivalent motifs of an α/β domain with three projecting α-helices. Although it is homodimeric in nature, it looks like a tetramer. As two homologous repeats are present in PPCA, the two active site Zn(II) ions are coordinated by the four amino acids (Cys149/Cys403, His205/His459, Cys208/Cys462, and Asp151/Asp405) (Smith and Ferry, 1999). The active site of β-CAs varies in organisation and ligation state of zinc ion. Based on this, βCAs are further categorised into two structural classes, type I and type II (Rowlett, 2010). The active site zinc in the prokaryotic β-CAs is coordinated to four amino acids two cysteines, a histidine residue and an aspartate residue. In plants, the Zn2+ is coordinated to 2 cysteines, a histidine and a H2O molecule (Kimber and Pai, 2000; Mitsuhashi et al., 2000). In the vicinity of each Zn(II) ions a water molecule is present connected by a hydrogen bond with oxygen of Asp151/Asp405. Asp151/Asp405 is involved in the proton transfer event. Still another CA that belongs to the carboxysomal shell of a chemolithotrophic bacterium Halothiobacillus neapolitanus has been put in β-CA subclass. It was purified and sequenced and has a theoretical molecular mass of 57.3 kDa. Based on the crystal structure, its tertiary structure is composed of two domains as present in the basic subunit of all β-CAs as a result of gene duplication, out of which only one has the functional Zn2+ binding site. The same enzyme can also be found in the shells of marine cyanobacteria Prochlorococcus and Synechococcus (Heinhorst et al., 2006). 2.3 γ-Carbonic Anhydrases (γγ-CAs)

Figure 1 Ribbon diagrams of different classes of CAs: (A) α-CA (HCAII) showing the active site zinc in the centre, (B) β-CA, (C) γCA, and (D) δ-CA

γ-Class CAs have been reported till now only in archaea domain (Alber and Ferry, 1994), isolated and characterised from a methanogenic archaeon Methanosarcina thermophila (Zimmerman et al., 2010). γ-class CA is characterised by a typical homotrimeric structure with a monomeric subunit mass of 20 kDa. γ-CA, like alpha CAs, also shows esterase activity, although it is significantly weak. Crystal structure analysis of γ-class CA is characterised by a typical homotrimeric structure (Figure 1C). Each


monomeric subunit is composed of a left-handed β-helix motif that is characterised by the presence of tandemlyrepeated ‘hexapeptide repeat’, [LIV]-[GAED]- X-X[STAV]-X. The β-helix motif is intervened by three protruding loops and contains α helices, which are present at the C-terminus, antiparallel to the β-helix. As in α-CAs, active site is occupied by Zn(II) ion which is coordinated to a water molecule and three histidine residues (His-81 and His-122 from one monomer, while the third His-117 residue is from the adjacent monomer). Therefore, each of the three active sites is located at the interface between adjacent monomer pairs (Iverson et al., 2000). Asp59, Glu62, Glu84 and Asn-202 present near the active site are other catalytically important residues with Glu84 working as a proton shuttle. 2.4 δ-Carbonic Anhydrases δ-class CA has been reported by Robert et al. (1997) from Thalassiosira weissflogii having a molecular mass of 27 kDa (Lane and Morel, 2000). As in alpha and gamma CAs, the active site Zn2+ is bonded to three histidine residues. Crystal structure revealed a completely new fold that is not present in other CAs made of seven α-helices, three 310helices, and nine β-strands organised in three β-sheets (Figure 1D). The active site is situated in a funnel-shaped cavity on the protein surface and the active site metal ion is placed at its bottom where it is coordinated in a highly distorted tetrahedral geometry by two cysteine and one histidine residues, and a water molecule (Xu et al., 2008). ζ-CA) Carbonic Anhydrases 2.5 Zeta-class (ζ Zeta-class CA (ζ-CA) is also found in the marine diatiom Thalassiosira weissflogii. This class is particularly interesting as it is produced when T. weissflogii is grown in the presence of Cd2+ or at low CO2 pressure and under low concentration of Zn(II) ions (as in the sea water) (Roberts et al., 1997; Lane and Morel 2000 and Lane et al., 2000). ζ-CA is found specifically in bacteria, particularly in chemolithotrophs, marine cyanobacteria containing cso-carboxysomes (So et al., 2004) and diatoms. Instead of Zinc, ζ-CA naturally uses Cd(II) in its active site (Tripp et al., 2001; Lane et al., 2000). Its expression is controlled by the presence of cadmium and CO2 in seawater. It also differs in the primary amino acid sequence and has a molecular weight of 69 kDa. Cd present in the active site is bound to thiolates in a roughly tetrahedral geometry. CA from T. weissflogii is composed of three tandem CA repeats (R1-R3), (R1-R3) sharing 85% identity in their primary sequences (Lane et al., 2000). 3D structure analysis revealed that CA from T. weissflogii shares some structural resemblance to β-CA, in particular near the metal ion site. This CA has also the ability to exchange Cd(II) with Zn(II)

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without losing the catalytic efficiency, while other classes of CAs are severely inhibited by the Cd(II) ions (Xu et al., 2008). The function of CA in prokaryotes is not well studied and needs further research to unravel and understand their functions. 3. Mechanism of Action of CA Although diverse in their primary structure, all CAs catalyse the same basic mechanism which occurs in two steps via a ping pong mechanism as shown below: CO2+ ZnOH- → Zn-HCO3- → ZnH2O + HCO3- (2) ZnH2O + B → ZnOH- + BH+ (3) Zn2+ present in the active site of the enzyme has a central role in catalysis. Zn2+ brings the two reactants Zn bound H2O and CO2 bound in the hydrophobic substrate binding pocket of the enzyme in close proximity. This leads to attraction of oxygen by the positive charge on the Zn2+, which in turn brings down the pKa of water molecule from 15.7 to 7.0 and facilitates the removal of proton, leaving a strongly nucleophilic hydroxide ion bound to zinc (Berg et al., 2007). The hydroxide ion now attacks CO2 forming H2CO3. Steps involved in catalysis by CA: E-ZnH2O → E-ZnOH- + H+ (A) E-ZnOH- + CO2 (aq) → E-ZnHCO3- (B) E-ZnHCO3- + H2O → E-ZnH2O + HCO3 (C) HCO3- bound to zinc is then released from the active site leaving H2O molecule bound to Zn, displaced from the zinc by a water molecule. At the end of the reaction, the active site of the enzyme is regenerated by a proton transfer reaction between the zinc-bound water and external environment or buffers assisted by the PSR (proton shuttle residue). The regeneration of the active site (intramolecular proton transfer reaction) is the rate limiting step. Among all the human CA isozymes, this proton transfer is assisted by the His 64 residue present at the entrance of the active site along with a cluster of histidine residues which extend from the border of the active site to the surface ensuring a very efficient proton transfer event. Since the catalytically active residues in both α- and βCAs are different, it is reasonable to expect some changes in the mechanistic details and energetics of the reaction catalysed by β-CAs. In the type I class, the zinc ion is indirectly coordinated to a H2O molecule via Asp ligand of zinc. Proton transfer may initiate from this H2O molecule to the carboxylate moiety of the aspartate residue leading to generation of a OH- ion. The OH- ion thus formed may coordinate to the Zn2+ generating strong zinc bound OH- ion. After the formation of bicarbonate, the Asp residue that was originally bonded to zinc is now believed to form a hydrogen bond with the zinc bound bicarbonate. Finally the bicarbonate ion along with a proton is released into the

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Table 1 Different classes of CAs and their functions α-CAs

In mammals, α-CA is involved in various physiological processes that involves transport of CO2 and HCO3- such as in respiration, in maintaining pH and CO2 homeostasis, supply of bicarbonates for various biosynthetic reactions (e.g. gluconeogenesis, lipogenesis, and ureagenesis), in bone resorption, calcification, tumorigenicity, etc. It also has a role to play in various pathological reactions.

Tashian (1989), Henry (1996), Smith and Ferry (2000)

In prokaryotes, such as in the Helicobacter pylori, colonising in the human stomach, CA maintains both periplasmic and cytoplasmic pH to near neutral and also periplasmic α-CA helps in maintaining the urease activity and urea flux through pH gated urea channel, thereby helping in the pathogenesis.

Bury-Moné et al. (2008)

The halotolerant alga Dunaliella salina possesses two forms of CA, one of which is engaged in supply of carbon dioxide for photosynthesis. The other one is proposed to be involved in imparting halotolerance to it.

Bageshwar et al. (2004)

In plants β-CAs are an essential component of CCM (carbon concentrating mechanism) and functions to transport inorganic carbon into the chloroplasts by rapidly converting the dissolved CO2 into HCO3- as it passes from the chloroplast envelope into the stroma and maintains the supply of CO2 and concentrate it in the vicinity of rubisco.

Reed and Graham (1981), Badger and Price (1994)

In prokaryotes, β-CAs are involved in cyanate degradation as in the case of E. coli (Cyn T), in CO2 fixation in case of cyanobacteria..

Sung and Fuchs (1988), Kozliac et al. (1994), Bedu and Joset (1991), Bedu et al. (1992)

β-CA from Methanobacterium thermoauto-trophicum has been implicated a role in methanogenesis by facilitating the acquisition and retention of CO2 by converting it to membrane impermeable HCO3-. M. thermoautotrophicum reduces methane by reducing CO2 to methane using H2 and synthesises all cell carbon using CO2. Furthermore, CA is also involved in the supply of CO2 or bicarbonate for various biosynthetic reactions.

Smith and Ferry, (1999)

In various pathogenic prokaryotes, they are involved in the survival of pathogen inside the host.

Valdivia and Falkow (1997)

γ-CA

γ-CA present in M. thermophila is involved in acetate metabolism. It functions in decreasing the concentration of CO2 produced in acetate metabolism by converting it to HCO3" outside the cell. In presence of high concentrations of acetate, M. thermophila is to use acetate to produce methane from reduced methyl group and CO2 from the oxidised carbonyl group. CO2 formed is removed by γ-CA to drive forward the reaction of acetate to methane.

Iverson et al., 2000 Alber and Ferry, 1994

ζ-CA

ζ-CA plays a crucial role in anthropogenic CO2 sequestration by the marine diatom. As this CA can utilise cadmium as a nutrient from the sea water, though cadmium is biologically toxic, this may have given ζ-CA containing diatoms competitive advantage which may be a clue to their extraordinary success.

Amata et al. (2011)

β-CAs

solution. The free Asp now re-coordinates with the zinc ion and the accompanying H2O molecule again forms a hydrogen bond with it regenerating the active site. 4. Applications of Carbonic Anhydrase Carbonic anhydrase can be employed in various environmental and clinical applications as discussed briefly below: 4.1 Application of CA in Mitigating Green House Effect The increasing levels of CO2 in the environment are compelling us to look for ways to safely capture and store

CO2 that is being released into the atmosphere, mainly from fossil fuel-based power plants. The process has been termed as CCS (carbon capture and sequestration). The term CCS has been expanded to CCUS, i.e. carbon capture, utilization and storage (CCUS) to make the entire process of carbon sequestration economical. Among the three components of CCUS, capturing of CO2 from the flue gas, its concentration and transportation to the storage site are energy and cost intensive processes. CO2 content of flue gas varies from 10% to 20% and its separation from other contents of flue gas requires very expensive and harsh chemical processes besides elevated


temperature (Benson and Surles, 2006). Capturing of CO2 is done basically by three widely used methods, postcombustion, pre-combustion, and oxyfuel combustion. All these are highly energy intensive and costly CO2 scrubbing techniques. An alternative approach would be to convert CO2 specifically from the flue gas into bicarbonates as shown in the reactions below and bicarbonate may further be utilised for various applications. The uncatalysed conversion of CO2 to bicarbonate is, however, a very slow reaction (0.037 s”1) (Dodds et al., 1956; Boron, 2010). (1) CO2 (g) → CO2 (aq) CO2 (aq) +OH →H2CO3 (2) H2CO3 → HCO3- + H+ (3) An alternative greener and economical approach to CO2 capture from flue gas is by using the enzyme carbonic anhydrase which can specifically aid in capturing CO2 from the flue gas and converting it into bicarbonate. Nature holds the key to accelerate the formation of bicarbonate, and hence, by being endowed with CO2 a highly efficient enzyme, the carbonic anhydrase. As discussed above, CA catalyses the extremely rapid interconversion of CO2 and H2O to HCO- and H+; thus speeding up the otherwise slow formation of bicarbonate. Capturing CO2 employing CA is a viable, fast and greener method, which can be developed to sequester CO2 from anthropogenic sources. In

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addition to providing an on-site way for sequestering CO2 from industrial emission such as flue gas, this can directly be used for CO 2 capture without prior capturing and transportation of CO2 that makes the entire process cost effective. It has been showed by Goff and Rochelle (2004) that using CA-based CO2 capture is economical as compared to other non-biological capture methods such as an amine solution. Thus the use of CA in capturing CO2 makes the large scale CCS commercially attractive. In this direction, research is underway in designing CAbased bioreactors to sequester CO 2 from flue gas. For example, the CO2 Solution Company has proposed large scale CA-based reactor for capturing CO2 from coal-ûred power plant, oil sands, and other CO2 intensive industries (www.co 2solutions.com/en/the-process). The technical design involves a bioreactor containing CA immobilised onto a solid matrix. At the bottom of the reactor, there is an entry point for the flue gas. Water is sprinkled with a pump from the top of the bioreactor to maintain aqueous condition. As the flue gas bubbles up through the reactor it gets dissolved into the water. The dissolved CO2 now gets converted into bicarbonate ions by the action of immobilised CA (Figure 2). Several changes in the designs of such basic bioreactors have been made since then to increase the efficiency of

Figure 2 Schematic representation of CO2 sequestration process using CA and development of useful products (Faridi and Satyanarayana, 2015)

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carbon capture by CA. Bhattacharya et al. (2003) have shown the possibility of increasing the rate of CO2 dissolution from flue gas using a water sprayer and immobilising CA by covalently grafting it on silica coated porous steel. They have concluded that the best CO2 capture is possible when there is a horizontal inflow and outflow of the CO2 carrying gas (at 60°C) and water is continuously sprayed from the top of the reactor. Several other parameters are also being made to optimise the parameters for efficient capturing of CO2 in a bioreactor. A bioreactor has also been designed by NASA (National Aeronautics and Space Administration) for capturing CO2 directly from the ambient atmosphere of confined inhabited cabins which have CO2 concentration of 0.1% or less. They employed thin aqueous films carrying dissolved CA (Ge et al., 2002; Cowan et al., 2003) in a reactor. CA selectively allowed CO2 to diffuse through the membrane in a ratio of 1400 to 1 by comparison with N2 and 866 to 1 by comparison with O2. 4.2 Screening for CAs for Efficient CO2 Capture As a matter of fact the use of CA for CO2 sequestration is limited to some extent due to harsh operating conditions of the bioreactor. Apart from CO2, flue gas is composed of other gases and many impurities such as sulphur and nitrogen oxides, organic amines, metal ions and others which may exert an inhibitory effect on CA and rendering it inactive. Also flue gas is very hot with temperature ranging from 50 to over 125°C. Such high temperature can denature the enzyme. Furthermore, for efficient CO2 sequestration, alkaline condition needs to be maintained and not all CA can function well in alkaline condition. There is, therefore, a need to search for CAs that are alkalistable, thermostable and that maintain high catalytic activity even in presence of other impurities present in flue gas. Research is underway to screen and characterise robust CAs having the desirable properties for use in CO 2 sequestration. And the best organisms to search for these are microbes as they are known to thrive at elevated temperatures and pH; thus, may contain CAs with desirable properties. CA from Bacillus subtilis was characterised by Ramanan et al. (2009) and is found to be stable over the pH range of 7.0–11.0 with optimum activity at pH 8.3. The effect of various inhibitors and metal ions particularly those present in flue gases were also checked on the activity B. subtilis CA and it was found that Pb2+ and Hg2+ inhibited the activity of CA, and metal ions such as Co2+, Cu2+ and Fe3+ stimulated enzyme activity. SO42-, the main component of flue gas, is generally known to inhibit CA, surprisingly was found to activate CA (Ramanan et al., 2009). Sharma and Bhattacharya (2010) characterised and compared CAs isolated and purified from Pseudomonas fragi

(PCA), Micrococcus luteus 2 (MTCA), and Micrococcus lylae (MLCA). Among them, CA from P. fragi displayed the highest specific activity next to BCA. CA from M. luteus 2 was found to be highly stable in a temperature range of 35–45°C followed by CAs from P. fragi, M. lylae, and BCA. The effect of other metal ions and anions on the activity of these CAs was checked and it was found that Cd2+, Zn2+, Co2+ and Fe2+ stimulated CA activity and PCA and MLCA were able to retain 80% and 90% activity, respectively, in the presence of 100 mM sulphate ion and 50 mM nitrate ion. A γ-class CA has been purified and characterised from Methanosarcina thermophila (CAM) which is optimally active at 55°C, and has a kcat value of 105 s”1 with a T1/2 of 15 min at 70°C (Alber and Ferry, 1994). A comparatively more thermostable CA belonging to β-class has been studied from Methanobacterium (CAB) which has a lower kcat value than that of CAB (104 s”1) with a T1/2 of 15 min at 85°C and gets inactivated at 90°C (Smith and Ferry, 1999). A γ-class CA from Pyrococcus horikoshii has become a centre of attraction (Jeyakanthan et al., 2008) as this strain shows optimum growth at 98°C but the CA has not been fully characterised (Ferry, 2010). A thermostable α-class CA from Bacillus clausii has been studied by Borchert and Saunders (2010), which has been reported to be more thermostable than CAM showing 17 % residual activity after 15 min at 80°C at pH 8.0. Also, 0.6 g/L of this CA is capable of sequestering >99% of CO2 from a 15 % CO2 gas stream as compared to only 33% removal in the control (Borchert and Saunders, 2010). They have also studied another highly stable CA from the thermophilic organism Caminibacterium ediatlanticus DSM 16658 which has a T1/2 of 109°C at pH 9.0 and has a residual activity of 40% after 15 min at 100°C. As compared to the control, this CA also shows increased CO2 sequestration with 1.0 M sodium bicarbonate at pH 9.0. Recently, a β-class CA from the cyanobacterium Coleofasciculus chthonoplaste has been characterised. It has a kcat of 2.4×105 s-1 and a kcat/Km of 6.3×107 M-1 s-1. The effect of various inorganic anions and small molecules on the activity has also been studied. This CA is not affected by perchlorate and tetrafluoroborate while selenate and selenocyanide were found to be weak inhibitors with KIs of 29.9–48.61 mM. Various other halides, pseudohalides, carbonate, bicarbonate, trithiocarbonate and heavy metal ions inhibited the activity of this enzyme at submillimolar– millimolar range with KIs ranging from 0.15 to 0.90 mM (Vullo et al., 2014). The extraction and purification of enzymes from wild type microbes is a costly issue. Cloning of the genes encoding the particular enzymes and their over expression provides a cost-effective way of producing a protein in large quantity. CAs can be successfully cloned and over expressed as a


fusion protein in E. coli easing their purification. CAencoding genes (can, cynT, caiE, pay and yrdA) from E. coli have been cloned and their expression profiles have been studied in response to different growth conditions (Merlin et al., 2003). Premkumar et al. (2003) cloned plasma membrane associated α-type carbonic anhydrase (Dca) from the extremely salt-tolerant, unicellular, green alga Dunaliella salina and showed to be active over broad salinity of 0–4 M NaCl. Kaur et al. (2010) cloned and overexpressed a putative γ-CA encoding gene from Azospirillum brasilense in E. coli. This CA has been shown to be induced in the presence of high CO2 in the stationary phase. This CA is co-transcribed with the N-acetyl-γ-glutamate-phosphate reductase suggesting a possible link between arginine metabolism and an unknown CO2 dependent metabolic route that utilises the CA. An α-type CA of Neisseria gonorrhoeae was cloned and overexpressed in E. coli. The recombinant CA, in pure as well as in crude form, exhibits a comparable CO2 hydration activity to commercial BCA, and further, considerably enhances the formation of CaCO3 (Kim et al., 2012). A thermostable CA from Myceliophthora thermophila has been patented by Carbozyme Company. It can work at temperature as high as 85°C. While Kanth et al. (2012) cloned, expressed and characterised a codon optimised αtype CA from Dunaliella sp. (Dsp-aCAopt). Its mineralisation potential was studied in terms of CO 2 sequestration in calcite form and concluded that Dsp-aCAopt is an efficient enzyme which can sequester CO2 to the calcite form yielding 8.9 mg of calcite per 100 µg (172 U/mg enzyme) in the presence of 10 mM of Ca2+. Another α CA (SspCA) was cloned and expressed in E. coli by Capasso et al. (2012) (SspCA) from a thermostable bacterium Sulfurihydrogenibium yellowstonense YO3AOP1 which thrives in hot springs at temperatures up to 110°C. The recombinant CA remains stable at 70°C for several hours. The effects of oxides of nitrogen and sulphur (typically contained in flue gas) were studied on SspCA by Luca et al. (2012), and the inhibition constants were in the range of 0.58–0.86 mM for the anions NO2", NO3" and SO42". The high temperature stability exhibited by SspCA (about 53 days at 40°C and about 8 days at 70°C) makes this CA suitable for industrial use. 4.3 Immobilisation of CA for Use in Carbon Capture Immobilisation of enzymes on suitable matrices is an efficient way to stabilise them for increasing their reusability, operational stability and to limit exposure to denaturing conditions. Immobilisation of CA also enables the bioreactors to operate continuously without losing the enzyme. Therefore various techniques for immobilization of CA are being investigated for efficient CO2 capture under relevant process conditions. Different sodium alginate and chitosan-based

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materials were checked for entrapment of whole cells of Bacillus pumilus (extracellular CA producer) by Prabhu et al. (2009). Immobilised cells showed enhanced CA activity as compared to the free cells. Immobilisation of purified CAs from different bacterial species (Pseudomonas fragi, Micrococcus lylae, Micrococcus luteus and Bacillus pumilus) was also attempted on chitosan and alginate beads and it was shown that immobilised CAs exhibit improved storage stability with a retention of 50% of its initial activity after 30 days (Sharma and Bhattacharya 2010). Using the same immobilisation system, Wanjari et al. (2011) reported an increase in the precipitation of CaCO3 compared to the free enzyme. Prabhu et al. (2011) immobilised CA on chitosan activated alumina–carbon composite beads and studied its kinetic constants. Yadav et al. (2010) silylated chitosan beads have been used to immobilise CA, which showed increased storage stability over the free enzyme with a residual activity of 50% up for 30 days. The best CO2 sequestration capacity and improved stability was achieved with CA immobilised on core-shell CA-chitosan nanoparticles (SEN-CA), obtained by covering the surface with CA by applying a thin layer of chitosan (Yadav et al., 2011). The use of ordered mesoporous aluminosilicate has also been attempted for CA immobilisation. The immobilised CA exhibited Km, Vmax, and kcat values of 0.158 mM, 2.307 µmole min-1 mL”1and 1.9 s-1, respectively (Wanjari et al., 2012). Vinoba et al. (2012) studied immobilisation of BCA by using octa (aminophenyl)silsesquioxane-functionalised Fe3O4/SiO2 nanoparticles and reported a 26-fold improvement in activity compared to free enzyme. Furthermore, the immobilised enzyme could be used over 30 cycles with the retention of 82% activity after 30 days. A very efficient immobilisation of CA has been reported by Park et al. (2012) using CA from Rhodobacter sphaeroides. The CA has been cross linked to electrospun polystyrene/poly(styrene-co-maleic anhydride) nanoûbers (CLEA) and the immobilised CA showed more than 94.7% residual activity over 60 days of storage at 4°C and retained more than 45% activity after 60 cycles. In order to minimise leaching of immobilised CA, Bhattacharya et al. (2003) studied immobilisation of CA on γ-amino-propyltriethoxysilane coated iron particles by grafting via DCC (dicarbocarbodiimide) bonds or dicarboxy bonds or by copolymerization of CA with gluteraldehyde in methacrylic acid polymer beads. These methods (particularly the DCC and dicarboxy coupling) proved to be proficient in minimising leaching with 98% activity retention. CA immobilisation has also been attempted on CLEAs (crosslinked enzyme aggregates) by using purified CAs from Micrococcus lylae and M. luteus. Immobilisation on CLEAs resulted in enhanced temperature stability that is up to 67.5 and 74°C for M. lylae and M. luteus CAs, respectively, with

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the operational stability (T1/2) of 7.7 and 12.0 h, respectively at 55°C (Bhattacharya et al., 2013). Recently Migliardini et al. (2013) have attempted the use of polyurethane foam as an immobilisation support for studying the CO2 capture potential of recombinant SspCA. The immobilised CA showed improved stability with retention of catalytic activity. Moreover, the immobilised CA efficiently sequestered CO2 when used in a bioreactor, supplied with CO2 closely mimicking conditions that exist in power plant emissions. The same recombinant enzyme SspCA, has also been characterised and immobilised by silanisation of a siliceous support (Sipernat ® ) with subsequent activation with glutaraldehyde. The Sipernat immobilised CA also emerged as a potential biocatalyst for CO2 capture based on regenerative absorption into alkaline solutions (Russoa et al., 2013). Sharma et al. (2011) also studied the mineralisation potential of immobilised CA and reported greater than 2fold improvement in CaCO3 precipitation over a period of 5 min with purified CA from Pseudomonas fragi immobilised on chitosan. A significant enhancement in precipitation rates were also achieved with CA from Bacillus pumilus adsorbed on chitosan beads (Wanjari et al., 2011). 4.4 CA-based Sequestration of CO 2 Into Mineral Carbonates One major area of CCUS is mineralisation-based sequestration of CO2. Mineralisation of CO2 has long been known to occur in nature and is responsible for large amount of limestone present on the Earth. The process utilises atmospheric CO2 and naturally occurring mineral rocks such as wollastonite (CaSiO3), serpentine (Mg3Si2O5(OH)4), and olivine (Mg2SiO4). These mineral rocks are weathered slowly by the action of wind and rain releasing free mineral ions which react with CO 2 and water forming silica and carbonates (Santos et al., 2007; Huijgen et al., 2007). The reactions involved in the process are depicted below (Farrell, 2011): HCO3–+ OH– → CO32– +H2O (4) CO32– +Ca2+ → CaCO3↓ (calcite) CO32– +Mg2+ → MgCO3↓ (magnesite) CO32– +Ca2+ +Mg2+ → CaMg(CO3)2↓ (dolomite) 2+ 2– CO3 +Fe → FeCO3↓ (siderite) The pH is an important factor which controls the outcome of the carbonation reaction. High pH favours the formation of HCO 3– (bicarbonate) and CO3– leading to precipitation of mineral carbonate. Therefore, pH needs to be buffered in alkaline range for continuous precipitation of mineral carbonate with increasing CO2. Direct capture and mineralisation of CO2 is a potential technology and has attracted attention as it offers several advantages over other sequestration methods; such as it provides a leak proof

method for CO2 sequestration, which has been proved as an environmentally benign and effective method by researchers worldwide (Seifritz 1990; Favre et al., 2009; Mirjafari et al., 2007; Ramanan et al., 2009). Raw material needed for mineralisation of CO2 is plentiful. Huge amounts of suitable and easily accessible mineral silicates are present which can be used to sequester all anthropogenic CO2 emissions. Mineral carbonates containing the sequestered CO2 can not only be permanently stored in silicate mines but also used to produce several industrially important and useful byproducts such as chemicals, cements and construction materials, white pigment in paints, cement component, a therapeutic source in antacids and calcium supplements, and tableting excipient as well as remediation of waste feed stocks (Ciullo, 1996). While calcium carbonate can be used in construction either as a building material (cement) or limestone aggregate for building roads or as the starting material for the preparation of builder’s lime by burning in a kiln and also in the purification of iron in a blast furnace, and in oil industry where it is added to drilling fluids as a formation-bridging and filter cake-sealing agent. Furthermore, it is possible to optimise the mineralisation process parameters to specifically produce high purity valuable metals, silica and carbonate mineral powders (www.cacaca.co.uk). The pure form of carbonates is quite valuable for applications such as white pigments or fillers for instance in paper making where they are required in large quantities. Similarly high purity silica powders of desirable particle size are worth thousands of pounds per tonne and have application in the electronics, glass, construction and plastics industries. The feasibility of the process has been studied at pilot scale level also (Reddy et al., 2010). Although mineral carbonation is a safe and potential method for a CO 2 sequestration method; it suffers a drawback in being an extremely slow process under ambient temperature and pressure. The formation of HCO3" is the rate limiting step and makes the entire mineralisation process, extremely slow (Dreybodt et al., 1997) and limits its use as a CO 2 sequestration method. This limitation is overcome by the use of CAs as discussed above. CaCO3 present in the shells of a variety of marine organism such as snails and eggs, exoskeleton in invertebrates, bivalves, silicates in algae and diatoms is formed via CA-based mineralisation of CO2 (Miyamoto et al., 1996). Apart from this a large number of microbial strains (various cyanobacteria, eukaryotic microalgae, Bacillus, Pseudomonas, Vibrio and sulphate reducing bacteria) capable of carrying out CA-based calcification of CO2 have also been reported (Ercole et al., 2007; Barabesi et al., 2007; Pomar and Hallock ., 2008). A proof of concept has been provided by Liu et al. (2005) for CA-based mineralisation of CO2. They used a


contactor which is composed of a column within which CA is immobilised in chitosan–alginate beads and a liquid mixer. CO2 dissolved in deionised water was pumped into the column where it gets converted to bicarbonate by the action on CA. The effluent from the column was made to enter another chamber where it mixes with an aqueous solution containing metal ions. This aqueous solution has the composition similar to the water streams produced by oil/ gas wells. The level of CaCO3 formed was monitored by varying the concentration of CO2 that was being pumped into the column. They have shown that the rate of carbonate precipitation increases when the enzyme activity is constantly maintained in the presence of a buffer. In addition to CaCO3, CA-based CO2 mineralisation can also be used to produce glycerol carbonate which has several potential uses. It can be used as a substitute for ethylene and polypropylene carbonate. Also it can be utilised in the synthesis polycarbonates and polyurethanes in their polymeric form which are commonly used as plastics for food and beverage containers, as flexible hosing and foam insulation (Nguyen and Demirel, 2011). 4.5 CA-based Sequestration of CO2 Into Other Valuable Products Bicarbonate formed after the sequestration of CO2 from flue gas can also be utilised to produce other value added chemicals such as 3-phosphoglycerate. An innovative unit for simultaneous capture and conversion of CO2 into 3phosphoglycerate has been proposed by Bhattacharya et al. (2004). The capturing unit is composed of a spray fixed bed absorber with CA immobilised on porous particles and is included in a series of reactors. The reactor series is composed of multi-enzyme catalytic steps and solar panels for ATP production as claimed in an associated patent (Bhattacharya, 2001). HCO3" formed after CA-based CO2 conversion can also be used to produce methanol when combined with a mixture of formate dehydrogenase, aldehyde dehydrogenase and alcohol dehydrogenase (Amao and Watanabe, 2009). Furthermore, HCO3- produced after CO2 capture can also be used to generate biofuel by serving as a carbon source for the cultivation of microalgae. The algal biomass thus generated can be used not only to produce biofuel but also for various other byproducts such as pharmaceuticals, food supplements and fertilizers. Different strains of microalgae can be made to produce a particular type of lipids or hydrocarbons by simply playing with the nutrient supply (Gonzalez-Fernandez and Ballesteros, 2012). In addition to capturing CO2 from industrial point sources, CA can also be used to directly sequester CO2 from air as shown by Walenta et al. (2011). They have successfully employed CA in cement compositions and used this for the

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production of civil engineering materials which can capture CO2 from air and can sequester it in the form of solid carbonates within the porous coatings of building walls. Mahinpey et al. (2011) studied the application of CA catalysed mineralisation for sequestration of CO2 in saline formations. He proposed the use of CA in minimising the risk of leakage of CO2 from the injection wellbore. A sufficient volume of CA solution can be pumped at the end of CO2 injection period through the injection wellbore. When the CO2 would come in contact with the enzyme solution, solid particles would precipitate speeding up pore occlusion resulting in reduced permeability of porous media near the wellbore. After CA-based CO2 capture and subsequent conversion to HCO3-, CO2 in the pure form can be produced back from by utilising the reverse reaction of CA or by the addition of acid. Pure CO2 is a valuable chemical and can be further used as a substrate to synthesise myriads of value added chemicals and fuels. There are three major pathways for CO2 utilisation: conversion of CO2 into fuels, utilisation of CO2 as a feedstock for synthesis of value added chemicals and direct use of CO2 as a solvent or as a working fluid. Some of the conversion routes of CO2 into chemical feed stocks and various other intermediates are shown in Figure 3. Production of methanol and formic acid from CO2 has been widely targeted. These are formed by hydrogenation of CO2 using wide range of catalysts. For the synthesis of methanol three equivalents of hydrogen per molecule of CO2 are required, out of which two are incorporated into the product while the third is consumed in the production of water. Formic acid is another valuable product, as it can store hydrogen in a more manageable liquid form and requires only a single equivalent of hydrogen for the synthesis and also no by-product is formed, therefore, is highly efficient (Styring et al., 2011). 5. Carbonic Anhydrase as a Probe for the Detection of Dissolved CO2 Dissolved CO2 detection methods, that are in use today, are not very sensitive. CA can be used in the development of electrochemical biosensors which are more reliable and the detection is easier. Cammaroto et al. (1998) attempted to immobilise CA behind the hydrophobic membrane of CO2 potentiometric electrode. The biologically modified membrane showed significantly increased response. Furthermore, when CA was used in amperometric biosensor in combination with p-benzoquinone (PBQ) as a redox mediator, a 10-fold faster response was obtained compared to the control. The performance parameters of the amperometric biosensor employing CA were also optimised for the amount of mediator and enzyme, applied potential and temperature. They have also shown that these biosensors

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Figure 3 Some chemical transformations of CO2 (Styring et al., 2011)

are only very mildly affected by environmental factors such as temperature and thus could be especially suited for field applications. They have also shown that the use of stable CA such as that from the algae Dunaliella salina instead of commercially available CA, could make the production of CA-based biosensors cost effective. 5.1 Carbonic Anhydrase-Based Biosensing of Metal Ions The affinity of CA for metal ions can be exploited to develop fluorescence-based biosensors for detecting free metal ions in solutions. The concentrations of Zn2+ Cu2+, Co2+, Cd2+, and Ni2+ have been determined down to picomolar range (Fierke and Thompson, 2001; Thompson and Jones, 1993; Mey et al., 2011). The concentration can be determined by changes in the fluorescence emission (Thompson et al., 2000) and excitation wavelength ratios (Thompson et al., 2002a, 2002b). The idea for flourometric determination of zinc ions in solution using CA has emerged from the work of Chen and Kernohan (1967). They found that when aryl sulphonamide and DNSA (dansylamide) bind to CA, the

fluorescence is enhanced significantly and blue-shifted. Later Thompson and Jones (1993) showed that DNSA binds very weakly to apo-CA, and therefore, at any time point the fraction of CA bound to DNSA is the measurement of the fraction of zinc-bound CA, which in turn is determined by the free zinc concentration. Therefore the free zinc concentration can be determined by the ratio of emissions from free and bound dansylamide. To further optimise CAbased fluorescence biosensors for precise quantitation, the metal ion binding has been transduced using wavelength ratiometric indicators as well as lifetime (Thompson and Patchan, 1995) and polarization or anisotropy (Elbaum et al., 1996; Thompson et al., 2000). The optimal interaction between the active site zinc ligands and the bound zinc determines the metal affinity. Metal affinity of HCAII can be altered by changes in the metal ligands and their numbers. Using site directed mutagenesis, metal affinity of HCAII can be enhanced or decreased. The affinity can be decreased by at least 105 fold by substituting one of the histidine side chains with alanine


and the affinity can be increased up to 100-fold by introduction of a fourth ligand into the metal coordination sphere by replacement of T199 with Glu, Asp or Cys (Kiefer et al., 1993; Ippolito et al., 1995). Also, altering the hydrophobic residues (Phe-93, Phe-95 and Trp-97) beneath the binding site of zinc decreases the metal affinity up to 100 fold (Hunt et al., 1997, 1999). Thus these CAII variants provide an array of proteins which vary in their metal affinity ranging from subpicomolar to micromolar; thus, can be used to measure a broad range of zinc concentrations. CA-based sensors can also be developed to detect copper ions as Cu2+ affinity of HCAII is 10 fold higher than zinc (Finney and O’Halloran , 2003). CA-based Cu2+ sensing relies on binding of copper to the His3 metal and quenching the fluorescence of a fluorophore, such as Oregon Green which is attached through covalent binding to a unique Cys residue near the metal site, such as L198C (Thompson et al., 2006). Cu2+ binding to fluorophore-labelled HCAII results in a simultaneous decrease in fluorescence intensity and lifetime which can be measured and used to determine free Cu2+ concentration when compared to a standard curve (Thompson et al., 1995, 1996). CA-based Cu2+ biosensor has actually been applied to obtain real-time measurement of free Cu2+ at picomolar concentrations in seawater (Zeng et al., 2003) and the CAbase Zn2+ biosensor has been applied for measurement of free Zn2+ at picomolar levels in cultured cells (Bozym et al., 2004). CA-based bio-sensing of free metal ions represent a viable approach to determine readily exchangeable Zn2+ concentrations in a wide variety of cells and sub cellular organelles and also in tissues. The HCAII-based zinc biosensors have been used in the measurement of trace amounts of zinc in sea and waste waters. 5.2 Carbonic Anhydrase-Based Bioassay Development of diagnostic tools to detect toxic chemicals present in the environment is gaining much attention. In recent years, the quest for efficient and effective monitoring of environmental pollution has led to the development of bio-based detection tools. They are based on the measurement of cellular and sub-cellular responses to chemical contaminants (referred to as biomarkers) in living organisms. They can provide valuable information about bioavailability of pollutants, their toxic effect for biota, and also enable screening of large numbers of samples, thereby decreasing the detection time and the associated cost. One such bio-based detection system employs the enzyme carbonic anhydrase. CA has been revealed to show sensitivity to many chemical pollutants, heavy metals and xenobiotics in a dose dependent response and a decline in activity of CA by pollutants could put the survival of the organisms at risk. In addition, the ubiquitous nature of this enzyme makes it a

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versatile new biomarker which can successfully be employed in the investigation of pollutant effects in different trophic levels and in different environments. CA-based bioassay for environmental pollution detection system covers evaluation of pollutant-induced stress at the biochemical-cellular level in an easy, sensitive, and inexpensive way in addition to applicability both in the laboratory and field. In an attempt to develop a novel CA-based in vitro biomarker assay (Lionetto et al., 2006), commercially available HCAII from bovine erythrocytes was used. It was shown to be significantly inhibited by major classes of environmental chemical pollutants such as heavy metals (Cd, Cu and Hg), organochlorate compound arochlor and by the carbamate pesticides (carbaryl) in a dose-dependent manner. In addition the synergistic effects that a mixture of heavy metals at low concentration can exert on biological systems could also be revealed. However, further research is called for characterising the responses of CA to pollutant exposure in living organisms and implementing the potential of this enzyme in environmental monitoring and assessment. 6. CA as a Component of an Antidote Delivery System Carbonic anhydrases also have application in treating analgesic overdoses. Already available medicines, like opioids, have very strong analgesic effects but their overdoses can lead to respiratory hypoventilation, leading to increased CO 2 and decreased O2 levels in the body, eventually leading to an acidosis-induced death. When CA is employed in CO2-responsive cationic hydrogels in antidote delivery, the harmful effect of analgesic overdose (Satav et al., 2010) can be treated. The antidote delivery system is composed of cationic hydrogel-based on DMAEMA (N,Ndimethylaminoethyl methacrylate) polymers modified to have a pKa ~7.5, and functions to monitor blood pH. When CA is employed as a CO2 sensor in this feedback-regulated antidote delivery system, it responds to high CO2 level or decreases in pH and enhances the efficiency of these antidote-delivery systems with CO2, bicarbonate or pH changes acting as signalling molecules (Satav et al., 2010). Other hydrogels which can undergo a transition from gel to sol upon exposure to CO2 have also been designed with a switchable co-block polymer (Han et al., 2012). Thus CA can be used for delivery of drugs if triggered by specific stimuli particularly if it involves sensing of CO2, bicarbonate or pH changes. 7. Use of CA in Artificial Blood Another use of CA is in blood substitutes. In trauma and major surgeries, a continuous supply of blood is needed. As natural blood is often in inadequate supply, there has been advancement in the use of artificial blood substitutes. They offer several advantages over transfused whole blood

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such as they can be sterilised, stored for long periods and contain no blood antigens. These blood substitutes consist primarily of 4–5 cross-linked stroma-free haemoglobin molecules (Gould et al., 2002). But these substitutes do not adequately remove CO2 which leads to increased in CO2 levels in the body causing acidosis, and will end up in coma and death, if left untreated (Sly et al., 1995). To overcome this, enzymes like catalase, superoxide dismutase and CA are being incorporated as in PolySFHb substitute (PolySFHb-SOD-CAT-CA) (Bian et al., 2012). 8. Use of CA in Artificial Lungs Respiratory failures including both acute and acute-onchronic types have become considerable health problems. There is thus a rise in number of patients requiring a lung transplant. But the lung donors as expected are too few. Therefore, to treat such respiratory problems, MVs (mechanical ventilators) are frequently employed to provide breathing support. However, the use of MVs often create problems in patients being treated with them, as they involve input from patients’ own lungs also. Very often MVs may further damage the lungs by causing over pressurising the lung tissue (barotraumas) or may cause over distending of lung tissue (volutrauma) causing lung injury and an exacerbation of lung dysfunction (Ricard et al., 2003; Meade et al., 1997; Weinacker and Vaszar , 2001; Rouby et al., 2004) leading to increased mortalility and morbidity. The use of AL (artificial lungs) is, therefore, replacing mechanical ventilators for the treatment of respiratory failure as AL assists respiration without the involvement of natural lungs. An AL is a prosthetic device that serves to provide oxygen to and remove carbon dioxide from blood. Artificial lungs assist respiration without input from patients own lungs. Artificial lungs can be generally classified into extracorporeal, paracorporeal, intravascular, or intrathoracic. Currently ALs are composed of bundles of polymeric HFMs (hollow fiber membranes) as the interface between blood and gas pathways. HFMs are small size polymeric tubes with microporous walls. The pore size is typically less than 0.1 mm and porosity can vary about 30–50%. For artificial lungs, HFMs prepared from hydrophobic polymers (such as polypropylene) are used so that the pores of the membrane wall remain filled with gas and respiratory gases can readily diffuse across it and also hydrophobic nature of the polymers prevents intrusion of blood plasma into the fiber pores under normal conditions. But there are a few significant challenges that are to be dealt with before ALs can be successfully employed to replace ventilators. For instance, AL must maintain appropriate blood pressure, should be able to sustain the gas exchange needs of a standard functioning lung, minimise injury to blood cells and minimise clotting and immune response.

The main problem associated with the use of ALs is the inadequate transfer of CO 2 per square inch across the polymetric HFM which is based on passive diffusion. Oxygen diffuses into the blood following its concentration gradient across the fiber wall, while CO2 escapes from the blood down its concentration gradient and enters into the sweep gas flowing through the fibers which is ultimately removed when the sweep gas exits the device. One approach to effectively increase the transfer rate of CO2 could be by immobilising the enzyme carbonic anhydrase onto the HFM. In a study, CA dissolved in phosphate buffer is applied to the surface of the HFM which is pre-activated with cyanogen bromide within acetonitrile (Kimmel et al., 2013). CA forms covalent bond with the surface of activated HFM. The CA immobilised HFM showed a 75% enhancement in CO2 transfer rate as compared to the untreated HFM. Considering the stability issues, a promising source of stable CA would be from prokaryotes. Since CAs are ubiquitous in nature and prokaryotes are found in extremes of environmental conditions, a highly stable and active CA could be recovered from a bacterial source. 9. Other Applications of CA Enzymes which can hydrolyse bulky benzoate ester have several potential medical and industrial applications. The commonly used lipases lack good activity with benzoate ester substrates such as paranitrophenyl benzoate. The active site of CA can be modified to catalyse hydration of such esters. In a study by Host and Jonsson (2008) human carbonic anhydrase II (HCAII), active site was engineered and a variant was developed that can catalyse the hydrolysis of pNPBenzo (para-nitrophenyl benzoate) with almost the same efficiency as some naturally occurring esterases. The engineered HCAII variant also displayed highest paranitrophenyl acetate hydrolysis efficiency reported till date. Using biocatalysis for catalysing non-natural reactions is an emerging trend. Some enzymes have even been commercialised for catalysing such reactions. Pyruvate decarboxylase is one such an enzyme which catalyses acyloin condensation of benzaldehyde and acetaldehyde forming an enantiopure hydroxyketone for ephedrine synthesis (Rosche et al., 2002). A newer addition in such biocatalysts is carbonic anhydrase which upon substitution with manganese in the active site is endowed with the ability to work as a peroxidase. Although haeme-based naturally occurring peroxidases are already there which catalayse oxidations with hydrogen peroxide, they suffer from disadvantages such as rapid inactivation, show moderate to low enantioselectivity and form aldehyde byproducts (up to 50%) and the high enzyme cost limits its application. Okrasa and Kazlauskas (2006) substituted the active site Zn atom of CA with manganese that yields CA(Mn) which shows peroxidase


activity in a bicarbonate dependent mechanism. This enantioselectivity shown by CA(Mn) is similar to that for naturally existing haeme-based peroxidases, with an added advantage of avoiding the generation of byproduct aldehyde. 10. Conclusions Carbonic anhydrases are among the fastest known enzymes present in almost all living organisms, which catalyse the hydration of CO2 forming bicarbonate and protons. The utility of CAs in various industrial applications has now been well documented particularly in mineralisation-based sequestration of CO2. Immobilised CA can provide a cost effective and greener way to sequester CO2 from the industrial flue gas that enables reuse of the enzyme, besides improving the operational stability of CA. Bicarbonates thus produced in the reaction can be utilised to generate value added products such as calcium and magnesium carbonates, glycerol carbonates, 3phosphoglycerate and can be utilised in producing biodiesel via cultivation of algae. The applications of CAs are further extended to other environmental applications such as in metal biosensing. CAs are also attracting considerable attention in many clinical applications, blood substitutes and artificial lungs. With the renewed efforts in the direction of finding novel CAs, specific CAs with desirable characteristics to suit specific applications are expected to be available in the nearest future. Acknowledgements We wish to thank University of Delhi for awarding NonNET fellowship to SF while writing this review. References Adler L, Brundell J, Falkbring S, and Nyman PO (1972). Carbonic anhydrase from Neisseria sicca, strain 6021. I. Bacterial growth and purification of the enzyme. Biochim. Biophys. Acta, 284: 298–310. Alber BE and Ferry JG (1994). Carbonic anhydrase from the archaeon Methanosarcina thermophila. Proc. Nat. Acad. Sci. USA, 91: 6909–6913. Amao Y and Watanabe T (2009). Photochemical and enzymatic methanol synthesis from HCO3" by dehydrogenases using watersoluble zinc porphyrin in aqueous media. Appl. Catal. B, 86: 109–113. Badger MR. and Price GD (1994). The role of car-bonic anhydrase in photosynthesis. Ann. Rev. Plant Physiol. Plant Mol. Biol., 45: 369–392. Bageshwar UK, Premkumar L and Zamir A (2004). Natural protein engineering: a uniquely salt-tolerant , but not halophilic , a-type carbonic anhydrase from algae proliferating in low- to hypersaline environments. Protein Eng. Des. Sel., 17: 191–200. Barabesi C, Galizzi A, Mastromei G, Rossi M, Tamburini E and Perito B (2007). Bacillus subtilis gene cluster involved in calcium carbonate biomineralization. J. Bacteriol., 189: 228–235. Bedu S, Laurent B and Joset F (1992). Membranous and soluble carbonic anhydrase activity in a cyanobacterium. In: Murata N,

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REVIEW ARTICLE

Developments in Bioenergy and Sustainable Agriculture Sectors for Climate Change Mitigation in Indian Context: A State of Art Richa Kothari1*

•

V.V. Pathak2 • A.K. Chopra3 • Shamshad Ahmad4 • Tanu Allen5

Abstract This review article provides the state of art for Indian energy scenario in areas of climate change in respect of various types of biomass available (forest, agricultural and aquatic). Present biomass conversion technologies for commercial and research and development sector with accurate methodologies are also studied. Based on the findings of the available literature, development policies for bioenergy sector incorporation with climate change mitigation and sustainable agriculture provide an induced impact on the environmental sector. The need for proper management among end users of government policies in India through a sustainable framework is highlighted by the authors of this review article. Keywords Climate change, Biomass, Bioenergy, Sustainable, Government policies 1. Introduction 1.1 Energy Scenario and Climate Change Indian energy sector is seriously affected by increasing living standard, economy, rapid industrialisation and population growth. Although the country is recognised as big economy in the world, there is a vast inequality of power distribution among different section of society. At present the total installed capacity for electricity generation in India has led from 45,755 MW to 266,644 MW, with a CAGR (compound annual growth rate) of 7.84% (Energy Statistics Report, 2014). Thermal power plants have registered highest rate of annual growth (14.71%) in installed capacity followed by hydro power (1.28%) (Energy Statistics Report, 2014). Hence due to high rate of annual growth in installed capacity,

•

B.C. Yadav6

thermal power plants was accounted for an overwhelming 67.16% of the total installed capacity in the country, with an installed capacity of 1,79,072 MW, at the end of March 2013. To meet the petroleum demand, India depends on import of the oil, as an increase of 7.61% in import of crude oil has been recorded during 2012–2013 (Energy Statistics Report, 2014). Although more than 70% of oil demand is met by import, India has developed adequate processing capacity over the years to produce different petroleum products so as to become a net exporter of petroleum products. The consumption of energy resource in India is mainly influenced by power sector, transportation and industrial sector. Electricity generation plays the biggest consumer in coal consumption (444.29 Mt) followed by steel and washery industry (15.88 Mt), cement industry (13.55 Mt) and paper industry (2.13 Mt) during the year 2012–2013 (Qaisar and Ahmad, 2014). High speed diesel accounts for 39.55% consumption in total petroleum product followed by refinery (10.49%), petrol (9.0%), LPG (8.92%) and naptha (7.05%). A lions’ share of oil is consumed (83%) by miscellaneous sector followed by transportation (7%) and industrial sector (6%) (Energy Statistics Report, 2014). Industrial sector accounted for the largest consumption of electricity (44.87%), followed by domestic (21.79%), agriculture (17.95%) and commercial sectors (8.33%) (Energy Statistics Report, 2014) in the year 2012–2013. Per capita energy consumption and energy intensity during the last year (2012– 13) have changed and increased by 8.76% (Figures 1 and 2); while the CAGR was found to increase by 8.56% (Energy Statistics Report, 2014). The impact of energy consumption in all sectors can be easily predicted by change in energy intensity which is found to increase from 0.1374 kwh in

Assistant Professor, 4Research Scholar, Bioenergy and Wastewater Treatment Laboratory, Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh, India 2 Research Scholar, DST-Centre for Policy Research, Babasaheb Bhimrao Ambedkar University, Lucknow, India 3 Professor, Gurukula Kangri Vishwavidyalya, Haridwar, Uttarakhand, India 5 Assistant Professor, Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India 6 Associate Professor, Department of Applied Physics, Babasaheb Bhimrao Ambedkar University, Lucknow, Uttar Pradesh, India *Corresponding author Email Id: [email protected] 1

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Figure 1 Consumption of energy from conventional sources

Figure 2 Percentage share of various conventional energy sources in total energy consumption

2005–2006 to 0.1518 kWh in 2012–2013 (Energy Statistics Report, 2014). It is clear from the Indian energy scenario that coal still plays major role to meet the energy demand. India is one of the biggest consumers of petroleum that causes huge emission of green house gases (GHG). According to the IEA (International Energy Agency), India would be among the top three emitters by year 2030 (currently it ranks sixth) (IEA, 2007). Therefore, India is on priority target to reduce carbon emission. The report of Intergovernmental Panel on Climate Change also stated that, climate change will severely affect India’s agriculture and natural resources such as rapid melting of Himalayan glacier would cause water shortage for 500 million people (Jayakarana, 2011). Indian government has realised the importance of lowering GHG emissions as a part of international effort to mitigate the

climate change. India has set its voluntary targets to reduce the carbon emissions by 20– 25% by 2025 compared to the level of 2005. Renewable energy can play major role in accomplishment of these goals and in decarbonising of Indian economy. Although, India has a large abundance of solar wind and hydro power, it has also more potential for bioenergy production due to abundance of forest and an agricultural residue; hence, India needs integration of bioenergy sector with agricultural practices for establishment of sustainable development. Indian Government has decided various regulatory framework and developmental strategies for promotion of bioenergy and sustainable agriculture. This paper is an effort to review the biomass potential in integration with agriculture for power generation and climate change mitigation with keeping a focus on governmental policies in Indian scenario.

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Figure 3 Different sources of biomass

1.2 Potential of Biomass to Meet the Energy Demand Biomass is a combined term that consists of all materials of biogenic in origin. Fuelwood was the pioneer biomass used for energy generation till the industrial revolution. In 2013 biomass accounted for about 10% of total global energy supply which was equivalent to 56.6 EJ (Renewables, 2014). A major portion of the biomass-based heat and power generation involve traditional biomass (60%) such as fuelwood, animal dung and crop residues; while the remaining is used for modern bioenergy options (organic waste, purpose-grown energy crops, algae, etc.). Biomass energy has been used by Indian rural households since long time and still it has dominated over the commercial energy in India due to its low cost and wide availability. Various forms of biomass are used as a primary cooking fuel such as approximately 62.5% rural household used biomass in form of firewood, 12.3% rural household used crop residue while 10.9% used dung as a cooking fuel. In urban areas more than 3% people used crop residues for cooking purposes while 20% people use firewood as cooking fuel (India census, 2011); and Gauri et al., 2013). Figure 3 describes the various types of biomass sources presently available with potential to reduce the energy demand in Indian prospects. According to the origin, two categories are defined in literature for biomass i.e. plant derived and animal derived biomasses. The present article mainly focuses on the potential of plant derived biomass resources only because it has an area that directly matches with agricultural based power generation and climate change mitigation practices. Major states of India contribute to biomass-based power generation capacity which mainly includes agro-biomass and

woody biomass that provides an important view to overcome the energy crisis at national level. Table 1 shows the aggregate biomass generation in India while biomass based power generation in various states is given Table 2, which indicates the potential of biomass for power generation. 1.3 Potential of Forest Biomass The potential of surplus biomass in India is about 63– 310 Mt annually (Ramachandran et al., 2007). Energy potential of annual biomass ranges from 930 to 4650 PJ. According to Energy Statistics Report, 2013, the total energy consumption from all conventional sources during 2011– 2012 was about 47,265 PJ; thus plantation biomass had a Table 1 Aggregate biomass generation in India (Varshney et al., 2010) Source of biomass

Estimate of the quantity generated (Mt)

Agriculture/ agro-industrial, excluding sugarcane derived materials

439.43

Sugarcane-based materials including tops and trash

84.01

Roadside growths

10.74

Forest residues

157.18

Growths on wastelands

27.12

Agro forestry waste

9.06

Dung live stock Poultry droppings Total

267.76 4.86 1000.17

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Table 2 Biomass-based power generation capacity of major states of India State

Surplus agro biomass (Mt/yr)

Power generation potential of agro biomass (MWe)

Surplus woody biomass (Mt/yr)

*Power Total capacity generation of installed capacity from project by woody biomass MNRE (MWe) (MW)

Tariff fixed by commissions (Rs/kWh)

Andhra Pradesh

7.1

830

28.3

3956.9

363.25

@ Rs. 4.28/kWh (BM), @ 3.48/kWh (cogen)

Bihar

5.7

655

3.6

504.3

9.50

@ Rs. 4.17/kWh (BM), @ 4.46 /kWh (cogen)

Gujrat

7.4

916

13.5

1884.2

0.50

@Rs. 3.93/unit (BM)

Karnataka

6.9

859

8.6

1204.7

365.18

@ Rs. 3.66/kWh (BM), @ 4.14 /kWh (cogen)

Maharashtra

13.1

1711

27.8

3886.4

403.00


Punjab

18.3

2092

0.1

10.6

73.30

@ Rs. 5.05 /kWh (BM), @ 4.57/kWh (cogen)

Tamil Nadu

13.7

1186

8.8

1237.0

488.20


Uttar Pradesh

26.5

3169

4.8

670.4

592.50

@ Rs. 4.38/kWh with 4 paisa escalated per year

Chhattisgarh

1.3

150

0.6

87.0

231.9

@Rs.3.93/unit

Haryana

7.5

884

1.6

225.7

35.80

@ Rs 4.0/kWh (BM), @ 3.74/kWh (cogen)

Madhya Pradesh

8.4

1,059

41.3

5789.8

1.00

@ Rs.3.33–5.14 per unit paise for 20 yr

West Bengal

4.7

563

2.3

316.5

16.00

@ Rs. 4.36/unit fixed for 10 yearsbiomass

Uttaranchal

0.8

95

5.2

14.65

10.0

@ Rs. 3.06/unit and @ 3.12/ unit (cogen)

Source: Official website of Ministry of New and Renewable Energy.

power to supply about 9% of projected total energy consumption during 2011–2012. In 2011 the growing stock of the country was about 6047.15 million cubic metre and average growing stock in the recorded forest area per hectare was about 59.79 cubic metre. In 2005, growing stock under tree cover was 1616 million cubic metre and for forest cover was 4602 million cubic metre (FSI, 2005, 2008). The proportion of growing stock for tree cover as compared to that for forest cover is 35.12% and 34.14% in 2005 and 2003, respectively (FSI, 2005, 2008). As per the CSO (Central Statistics Office), fuel wood contributes highest i.e. 85% of the total reported output from the forests (Madguni and Singh, 2013). In the southern transition zone of India, about 127,769 hectare of wasteland are available for energy plantation. The extent of wastelands in hilly and coastal zones, is about 237,371 hectare and 880,189 hectare, respectively (Ramachandra et al., 2007).This can be utilised to raise energy plantation comprising of Acacaia auriculiformis,

Casuarina and Eucalyptus species. Assuming an average biomass productivity of 5 t/ha/year, the total amount of exploitable biomass available from these plantations would be 440,0945 t annually (Ramachandra et al., 2007). Chauhan and Silori (2004) explored the biomass potential of Uttarakhand state under four Taluks (Rishikesh, Purola, Almora and Champawat). According to them forest biomass is a major source for biomass consumption (62%) and huge amount of surplus biomass is available for power generation (Ramachandra et al., 2007). 1.4 Potential of Agricultural Residues India is the nation with dominant agricultural sector that can provide strength in bioenergy production. Agriculture sector contributes 17% to Indian GDP with 60% land under agricultural cultivation (Hilodhari et al., 2014). Various agricultural products are harvested in India with different climatic conditions among which India holds first rank in jute production and second rank in rice wheat, sugarcane,


cotton and ground nut. Approximately 686 Mt of crop residue is produced annually by 26 crops (Hilodhari et al., 2014). The estimated crop residue in India is about 84–141 Mt/yr where cereals and fibre crops contribute 58% and 23%, respectively. The remaining 19% is contributed by sugarcane, pulses, oilseeds and other crops (Hilodhari et al., 2014). Uttar Pradesh ranks first in total surplus crop residue followed by Maharashtra, Madhya Pradesh, Andhra Pradesh, Karnataka, Odisha and Punjab, accounting for almost 60% of the total national generation of biomass. The net surplus biomass (left after conventional use) is highest in Punjab followed by Uttar Pradesh, Maharashtra, Madhya Pradesh, Haryana, etc. (Hilodhari et al., 2014). The crop wise residue potential is estimated by MNRE (Ministry of New and Renewable Energy sources) and it was reported that among various crops, cereals produces about 352 Mt residue followed by fibres (66 Mt), oilseed (29 Mt), pulses (13 Mt) and sugarcane (12 Mt). Among various cereals crop, rice crop alone contribute around 34% of crop residue. Wheat crop contributes about 22% of crop residue; whereas fiber crops contribute 13% of residues generated from all crops. 1.5 Potential of Aquatic Biomass Various aquatic biomasses are available for bioenergy production such as water hyacinth, chest nut, seaweeds, microalgae, etc. Water hyacinth has already been reported for biogas production; for instance, in lakes of Bhopal water hyacinth continues to present daunting environmental and economic problems, which is a potential source for bioenergy production. Similarly, Powai Lake in Mumbai is severely affected by water hyacinth which reduces water quality of that area (Salaskar et al., 2008). Water hyacinth can be harvested from the lake and used for biogas production. Water hyacinth as a feedstock for biogas is used by Sudhakar et al. (2013) and according to their findings a yield of 0.326 L/day of biogas was obtained from slurry of water hyacinth and cow dung. Among various aquatic biomass, microalgae is one of the most promising sources of renewable biomass and now days it is gaining significance for biodiesel production. In a broader sense, alga is the sustainable feedstock for bioenergy production as it plays major role in carbon sequestration with high oil productivity. Potential for algal biofuels production was well explained by Sudhakar et al. (2012). According to them most of the potential can be found in southern India with a considerable amount of 80,000 L/ha/ yr. The maximum productivity can be expected from the Rajasthan and the lowest productivity in parts of northeastern states due to difference in received solar radiation. However, their assumption has suggested an average productivity of 80 g/m2/day. Marine algae are reported for high oil content and distributed in large costal area in India. Biodiversity of

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marine algae along the east and west coast region of India was studied by various authors (Srinivasan, 1946; James, 2004; Venkataraman, 2005). Rath and Adikary (2005) reported various marine algal strains for high oil productivity. 1.6 Biomass Feedstock Conversion Technologies Biomass resources can be converted to energy product by various processes depending on the type of biomass and desired product. Combustion: Direct Combustion of Biomass for Heat and Power This technology can be applied to biomass with water content up to maximum 60%. Besides carbon, hydrogen and oxygen other undesired substance are formed since they cause pollution and deposit particulate matters and ash (Tasneem et al., 2012). Native wood is the most favourable biomass feedstock for combustion due to its low content of nitrogen and ash as compared to herbaceous biomass such as straw, miscanthus, switch grass, etc. The urban waste wood and demolition wood are also used for combustion but in a very limited extent because of contamination (Krook et al., 2003). Wood is the most prominent source of biomass feedstock for energy generation and contributes 56% of total biomass energy (Sinha et al., 1994). There are serious concerns with combustion of biomass feedstock for energy generation such as high emissions of NOX and particulates (Nussbaumer, 2003). On the basis of the mode of application (manual, pellet, automatic and co-firing) a number of designs are available for combustion for biomass feedstock (wood stove, log wood boilers, pellet stove and boilers, under stoker furnace, moving grate furnace, stationary fluidised bed, etc). The main aim of using combustion furnace is to reduce the emission, increase combustion and reduce particulate deposition. Complete combustion mainly depends on the temperature, time and turbulence (Rahmanain et al, 2014). Mixing of combustible gases and air act as a limiting factor in the combustion process which demands for high temperature (80 °C) and a resident time of 0.5 s (Williams et al., 2012). Good quality of mixing can be achieved by fixed bed combustion, fluidized-bed combustion and twostage combustion; however for further improvement computational fluid dynamics is used to calculate the flow distribution in furnace. Different technologies are available to reduce the pollution during combustion of biomass feedstock as depicted in Table 3. Gasification: Biomass to Producer Gas Gasification of biomass feedstock is useful for various energy devices for example, gas obtained from biomass gasification can be burned directly for heating and cooking purposes, converted into electricity through conversion

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Table 3 Technology available for efficient biomass combustion Targeted pollutants

Cause of generation

Technology

Unburnt fraction

Limited mixing of combustible gases and air

•

Fixed bed combustion

•

Fluidised bed combustion

•

Two stage combustion

•

CFD (computational fluid dynamics)

Thermal NOX and prompt NOX are formed from

•

Staged combustion process.

nitrogen in the air at high temperatures with

•

SNCC (selective non-catalytic combustion)

presence of hydrocarbon

•

SCC (selective catalytic combustion)

NOx emission

Particulate emission

Particles from wood combustion mainly formed due

•

Understoker furnace

to nucleation, coagulation and condensation

•

Fluidised bed combustion

device and can be used for production of high quality fuels such as hydrogen or methanol (Gasification involves partial combustion of biomass under controlled air supply (Dhingra and Arora, 2011) leading to the generation of producer gas constituting of combustible gases H2 (20%,), CO (20%), CH4 (1–2% and rest are inert gases). In India a number of institutions are working in research and development of biomass gasification technologies such as the IISc (Indian Institute of Science); TERI (The Energy and Resources Institute); SEES (School of Environment and Energy Studies); Devi Ahilya University, Indore; SPRERI (Sardar Patel Renewable Energy Research Institute), Gujarat and SSS-NIRE (Sardar Swarn Singh National Institute of Renewable Energy), Punjab. TERI has developed a biomass gasifier system ideally suited to provide remote and rural electrification at an affordable cost. The produced gas is burnt in an efficient producer engine having good field performance and reliability. Under the VESP (village energy security program) of MNRE (Ministry of new and Renewable Energy), four systems are installed in the states of Chhattisgarh, Orissa and Rajasthan. India is now creating the success stories of efficient gasification system to produce electricity. Jamera, a village in Korba District in Chhattisgarh has annual surplus woody biomass of 3567.46 t enough to keep a biomass gasifier of 10 kWe. Inhabitants of that village avail the benefits of biomass based lighting with two light bulb of 40 W for about 4 h (610 PM) on daily basis (Awasthi and Deepika, 2013). In another case in Karnataka two villages (Hosahalli and Hanumanthe Nagara) were provided with gasifier of 20 kW capacity by IIsc Banglore (Buragohain et al., 2010). The supply of woody biomass is managed through social forestry. Besides this technological success current technical research, development and demonstration efforts to advance the biomass gasification are focused in three general areas: progress in scale-up; exploration of new and advance applications; and improvement of operational reliability. Various types of gasifiers such as Downdraft, Updraft and Crossdraft are available for gasification of

biomass feedstock (Kuo et al., 2014). Their relative advantages and disadvantages are discussed in Table 4. Anaerobic Digestion: Biomass to Methane This is a commercial accepted technology globally used for recycling and treatment of wastewater and wet organic waste. Fermentation is the key process which converts organic materials in to biogas (approximately 60% CH4 and 40% CO 2) and comparable to landfill gas. Anaerobic digestion includes various steps such as hydrolysis, acetogenesis, and methanogensis. The hydrolysis step involves an extra cellular process in which hydrolytic and acidogenic bacteria excrete enzyme to catalyse hydrolysis of complex organic materials into smaller units. These hydrolysed substrates are utilised by acidogenic bacteria (Krishania et al., 2012). The products of these steps such as acetate, hydrogen and carbon dioxide are directly used by Methanogenic bacteria, while other more products such as alcohol and volatile fatty acids are further oxidised by acetogenic bacteria in syntrophic with the methanogens (Sotirios, et al., 2010). Biogas plants were installed at a large scale (1.76 million) in India since 1993 and used for cooking, lighting and running engines for water irrigation, moreover about 15 lakh of rural families are availing the benefits of this renewable energy (Sharma et al., 2002). The popular biogas plant designs in India include, floating drum type and fixed dome type biogas plant. Other designs are plug flow reactor, CSTR (Continuous Stir Tank Reactor), and UASB (Upflow anaerobic sludge blanket) are less developed. Biomass to Liquid Biofuel Rapid industrialisation and energy crisis have enhanced the consumption of fossil fuel with an alarming rate. Fossil fuel burning contributes into emission of GHG emission and causes atmospheric pollution. Therefore renewable fuel such as biodiesel has been developed as alternative to fossil fuel.

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Table 4 Relative advantages and disadvantages of various gasifiers Sr. no.

Gassifire type

Advantages

Disadvantages

References

1.

Updraft

• • •

Small pressure drop. Good thermal efficiency. Little tendency towards slag formation

• Higher sensitivity to tar and moisture content of fuel • It takes long time for start up of IC engine • Lower reaction capability and heavy gas load

Sarvankumar et al. (2007)

2.

Downdraft

• • •

Flexible adaptation of gas production to load Low sensitivity to charcoal Low dust and tar content of fuel

• Tall design • Less suitable for small particle size fuel • The gasifier has lower overall efficiency

Clarke (1981) and Reed et al. (1999)

• • •

Low height design Rapid response time to load Gas production is flexible

• High opportunity for slag formation • High pressure drop

Srivastav (2013)

3.

Crossdraft

Table 5 Different types of liquid biofuels and their applications Type of biofuels

Production process

Applications

References

Bioethanol

Hydrolysis and fermentation

Used as biofuel E5 (5% ethanol and 95% petrol) or as biofuel E85 (85% ethanol and 15% petrol)

Savaliya et al. (2013)

Biodiesel

Cold pressing/extraction and transesterification

PME (pure vegetable oils), RME (rapeseed methyl esters) and FAME (fatty acid methyl esters) are produced from vegetable oil, animal oil or recycled fats and oils

Escobar et al. (2009)

Biomethanol

Synthesis from syngas

Used as a biofuel

Larson (2008)

ETBE (bioethyltertio-butyl-ether)

Chemical synthesis

Used as a petrol additive (47%) to increase the octane rating and to reduce knocking

Kumar and Sharma (2011)

MTBE (biomethyl- Produced from biomethanol tertio-butyl-ether)

It is used for the same purposes as BioETBE and added to petrol (36%)


BtL

Liquid fractions produced from biomass

Used as biofuels or fuel ingredients

Larson (2008)

PVO (Pure vegetable oils)

Cold pressing/extraction

Used as biofuel if compatible with the engine involved


Biodiesel has various technical advantages over the fossil fuel such as less toxic emissions, biodegradability, low sulphur content, etc. According to Stamenkovi´c and veljkovi (2012), it is essential to convert biomass into liquid fuel, which can reduce our dependency from import of petroleum and diesel fuel. Biofuels are solid, liquid and gaseous fuels obtained from biomass from various conversion routes. On the basis of feedstock source and technological process of conversion biofuel can be categorised into first, second and third generation biofuel. According to literature, classifications for liquid biofuels are shown in Table 5. In India traditional biomass such as molasses, sugarcane, corn, etc. are used for ethanol production, but have social and economical barriers. Apart from conventional feedstock lignocellulose feedstock which is present in abundance on

the earth has potential for ethanol production (Kim et al., 2002). This biomass including forest residues such as wood; agricultural residues such as sugarcane, bagasse, corn cob, corn stover, wheat and rice straw; and energy crops such as switch grass are the most potential feed stocks for fuel ethanol (Daroch et al., 2013). Biodiesel can be produced widely through the transesterification process in which fatty acid of long chain of hydrocarbon of plant biomass is converted in methyl esters. The process may be catalytic or non-catalytic such as supercritical processes and co-solvent systems process (Iqbal and Theegala, 2013). Role of Biomass Energy in Climate Change Mitigation India is the world’s third largest energy consumer with 5% global carbon dioxide emission. The cause of major concern is increasing GHG emissions with continuously

100


growing population and economic activities. In order to follow the global 2°C pathway India has set some voluntary target to reduce adequate GHG emissions. Renewable energy can play significant role in accomplishment of the reduction targets if used in a sustainable manner. Because renewable energy sources depend on climate, global climate change will affect base of renewable energy resources but the impacts are uncertain due to precise nature and magnitude of events (Wilbanks, 2008). Whereas, impact on biomass production will be greatly influenced by climate change, i.e. soil condition, precipitation, etc. Although India has huge potential for solar, wind and hydro powers but the major hurdle is its installation cost (Khare et al., 2013). In this way biomass energy can play a major role because it is cost effective and carbon neutral source. Application of biomass for energy and industry reduces significant amount of hydrocarbon without addition of carbon dioxide into the atmosphere; hence it makes a positive contribution in mitigation of climate change issue. Developing as well as developed countries, both are increasing the use of biomass energy that can reduce the carbon dioxide emission which is projected to grow by 9.8 million by 2020 (CampbellLandrum and Corralan, 2007). In rural households, incomplete combustion of biomass fuel causes about 500,000 deaths of women and children (below 5 year) (Murray and Lopez, 1996). The products of incomplete combustion in densely located households are a major source of outdoor pollution and significantly contribute in GHG emissions. Traditionally, burning of biomass fuel produces more GHG emissions in compare to kerosene or LPG. Modern usage of biomass for energy production has more potential for reduction in GHG emission in comparison to its conventional application. Biogas has lowest global warming capacity emitted by stove per meal than LPG and kerosene. The potential of biomass energy in reduction of GHG was efficiently studied by Anandrajha and Gambhir (2014). Their study was to find out the role of renewable biomass to meet India’s possible 2050 climate change mitigation targets using a multi-region global energy system model called TIAM-UCL. The model observed a low carbon scenario with carbon capture and storage based on biomass based power generation, which makes the electricity sector carbon-neutral by 2040 and carbon-negative by 2050. Hence, bioenergy options can contribute to a more secure energy supply, although specific challenges for the integration must be considered. Similarly, reduced GHG emissions also provide other environmental benefits. Most of the bioenergy systems are currently in use including liquid biofuels, which are resulting in higher GHG mitigation. According to literature, the sustainability of biomass energy options particular in terms of lifecycle, GHG emissions, are influenced by land and biomass resources management.

Strategic Developments for Bioenergy and Sustainable Agriculture Government of India has taken various policy frameworks to promote the bioenergy across the country. Bioenergy is based on biomass feedstock and its quality with high productivity. Integration of sustainable agriculture with bioenergy promotion policy would be the best practice to achieve sustainability. The following sections provide a policies overview in context of bioenergy and sustainable agriculture. Developmental Policies for Promotion of Bioenergy Bioenergy policies and programme were initiated in 1970 to strengthen the energy security especially in villages. The main concern of the policy was to improve the traditional use of biomass, supply of biomass (social forestry and wasteland development), technological improvements (introduction of biomass based technologies) and collaboration with institutions, agencies, stakeholders for programme implementation and formulation (TERI, 2010a). Promotion of bioenergy programme got momentum from mid of 1990 and till date various programmes on bioenergy have been launched by MNRE with respect to the modern use of biomass. India on the strategic path of renewable energy has achieved an installed capacity of 101.61 GW of energy from RE sources. The share of biomass-based power in total RE based energy is about 1118 MW by the end of the tenth plan (2007) (MNRE, GOI). Government of India has targeted to increase the installed grid connected renewable energy capacity of over 74 GW by the end of 13th plan (year 2022). Biomass-based energy generation is anticipated to increase up to 7500 MW by the end of year 2022 (MNRE, GOI). In order to promote the biomass power among rural as well as industrial sector capital subsidies or interest subsidies are provided under the scheme of central financial assistance (Ramachandran et al., 2007). Ministry of New and Renewable Energy has initiated biomass combustion and cogeneration program for optimum use of biomass resource for power generation. About 16,000 MW of power of grid quality has been estimated by MNRE. The technology involves biomass gasifier for combustion of biomass. The programme involved various demonstration projects for 100% producer engine coupled with gasifier for off grid and grid power operation. Biogas-based grid power was also promoted by the ministry to meet the small scale power distribution. Animal, agricultural, kitchen, forestry and industrial waste can be utilised for biogas production. In this context the central finance assistance of rupees 30,000–40,000 per kW is provided (depending upon the capacity of the power projects) by the ministry. Improve cook stove programme was another programme to provide efficient combustion and replacement of traditional cook


101

Figure 4 Analytical framework for sustainable agriculture

stove from improved cook stove. Around 35.2 million improve cook stoves were disseminated in the year of 2003. In December 2009 this programme was re-launched with the name of National Biomass Cook stove Initiative. This initiative involved various pilot scale demonstration projects, biomass processing models (Ravindranath and Balachandra, 2009). Development of biofuel was promoted through national biofuel’s policy and biodiesel mission. One of the main approaches of these missions were to use wasteland, marginal land and degraded land for Jatropha cultivation and to achieve blending target of 20% with diesel and petrol by 2017; however various obstacles are there in this way such as socioeconomic and technological issues (TERI, 2010b). Developmental Policies for Sustainable Agriculture Agricultural sustainability is essential to increase the crop productivity as well as to ensure the less environmental impact. The analytical framework of sustainable agriculture is shown in Figure 4 which is adopted from Barnett et al. (1995). The growth of agricultural productivity that was increased during 1970s and 1980s declined in 1990s (Singh and Pal, 2010). This reduction in agricultural productivity is a serious issue that not only affects livelihood and food security but also environmental conditions. The major challenge in India is to maintain balance between environmental safety and higher crop productivity (Kumar and Mittal, 2006). It includes conservation of the resources which determine the agricultural productivity for example, land, water and air. Various environmental impacts are associated with agricultural practices among which land

degradation is the major issue. By the early 1980s about 53% of geographical area of India had been considered degraded according to the Ministry of Agriculture. Water logging in crop field affected 6% of crop fields and about 3% of crop field was affected by acid and alkali soils. Recently (2010), ICAR (Indian Council of Agricultural Research) has reported that out of total geographical area of 328.73 million hectare, about 120.40 million hectare (37%) is affected by various kinds of land degradation including water and wind erosion (94.87million hectare), water logging (0.91 million hectare), soil alkalinity/sodicity (3.71 million hectare), soil acidity (17.93 million hectare), soil salinity (2.73 million hectare) and mining and industrial waste (0.26 million hectare) (Department of Agriculture, GOI). Water availability for irrigation is still a challenge among Indian farmers. Irrigation accounted for 83% of total water use in the country during 1990s. India is having the largest irrigated land area in the world; the coverage of irrigation is only about 40% of the gross cropped area as of today. This is due to bad practice of irrigation in which water consumption is high with less water uptake by plant such as flood method (Narayanamoorthy, 2006). Water use efficiency under these method estimations is only about 35–40% because of huge conveyance and distribution losses (Rosegrant, 1997; INCID, 1994, 1998). In brief, sustainable development of agriculture would require government support to millions of farmers with a focus on optimum resource utilisation and adaptations under climate change risk. To achieve the goal of sustainable development, Natural Resource Management division of Ministry of Agriculture

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has implemented region specific soil and water conservation programme. This division has also responsibility to formulate the strategies, policies and programmes to address the issues of sustainable agriculture in context of risk associated with climate change and adaptations to combat the adverse impact of climate change. Scientific database of soil and land use for better planning of watershed based interventions, recharging of ground water by reducing runoff, sustaining irrigation potential and improving water enhancing capacity of reservoir across the country (Department of Agriculture, GOI). Conclusions India has huge potential for power capacity addition through its biomass sources. The mapping of surplus biomass in different states of India has already showed its abundance across the country (Singh, 2015). Traditional use of these biomass sources is playing a significant role to meet the energy demand in rural sector. The main challenge with biomass resources is its application as a modern biomass energy application. Hence, proper governance of land use, zoning and choices of biomass production systems are playing considerations for policy makers of agricultural, climate change and bioenergy sectors (Edenhofer et al., 2011). Policies available to avail the benefits from bioenergy options, overall improvements of agricultural management and the contribution to climate change mitigation are realised by government and various polices are launched in this regard. Here this study focuses on accounting of the government policies for bioenergy sector in integration with climate change mitigation and sustainable agriculture. There is a need to increase the awareness among the end users regarding bioenergy, climate change mitigation and agriculture related government policies. References Anandarajah G and Gambhir A (2014). India’s CO2 emission pathways to 2050: what role can renewables play? Appl. Energy, 131: 79– 86. Awasthi M and Deepika KR (2013). Energy through agricultural residues in rural India: potential, status and problems. Int. J. Energy Technol. Adv. Eng., 3:160–166. Barnett V, Payner R and Steiner R (1995). Agricultural Sustainability: Economic, Environmntal and Statistical Considerations, Jhon Willey and Sons, UK pp. 266. Buragohain B, Mahanta P and Moholkar VS (2010). Biomass gasification for decentralized power generation: The Indian perspective. Renew. Sustain. Energy Rev., 14: 73–92. Campbell-Landrum D and Corralan C (2007). Climate change and developing countries cities: implications for environmental health and equity. J. Urban Health, 84: 109–117. Chauhan S and Silori C (2004). Assesment of Biomass Availability For Power Generation In Selected Talukas of Uttaranchal State. ENVIS Bulletin: Himalayan Ecology. 12(2): 27-34. Clarke SJ (1981). Thermal biomass gasification. Agric. Eng., 62:14– 15.

Daroch M, Geng S and Wang G (2013). Recent advances in liquid biofuel production from algal feedstocks. Appl. Energy, 102: 1371–1381. Department of Agriculture. Online: www.agricoop.nic.in Dhingra S and Arora A (2011). Energy transitions related to biomass gasification and its applications in for rural households and enterprises innovation and sustainability transition. International Conference on Innovation and Sustainability Transitions in Asia, University of Malaya, Kuala Lumpur, Malaysia. Edenhofer OR, Pichs-Madruga Y, Sokona K, Seyboth D, Arvizu T, Bruckner J, Christensen JM, Devernay A, Faaij M, Fischedick B, Goldstein G, Hansen J, Huckerby A, Jäger-Waldau S, Kadner D, Kammen V, Krey A, Kumar A, Lewis O, Lucon P, Matschoss L, Maurice C, Mitchell W, Moomaw J, Moreira A, Nadai LJ, Nilsson J, Nyboer A, Rahman J, Sathaye J, Sawin R, Schaeffer T, Schei S, Schlömer R, Sims A, Verbruggen C, Von Stechow K, Urama R, Wiser F, Yamba T and Zwickel (2011). Summary for Policy Makers. In: IPCC special report on renewable energy sources and climate change mitigation, eds. Edenhofer O, PichsMadruga R, Sokona Y, Seyboth K, Matschoss P, Kadner S, Zwickel T, Eickemeier P, Hansen G, Schlömer S, Stechow CV. Cambridge University Press, Cambridge: United Kingdom and New York, USA. Energy Statistics (2013). Ministry of Statistics and Program Implementation. Central Statistics Office, Government of India. 21th Issue. Energy Statistics (2014). Ministry of Statistics and Program Implementation. Central Statistics Office, Government of India. 21st Issue. Escobar JC, Lora ES, Venturini OJ, Yanez EE, Castillo EF and Almazan O (2009). Biofuels: environment, technology and food security. Renew. Sustain. Energy Rev, 13: 1275–1287. Gauri P Minde, Sandip S Magdum and Kalyanraman V, (2013). Biogas as a sustainable alternative for current energy need of Indian. J. Sustain. Energy Environ., 4:121–132. Hiloidhari M, Das D, Baruha DC (2014). Bioenergy potential from crop residue biomass in India. Renew. Sustainable Energy Rev. 32, 504-512. Indian National Committee on Irrigation and Drainage (INCID) (1994). Drip irrigation in India, Indian National Committee on Irrigation and Drainage, New Delhi. Indian National Committee on Irrigation and Drainage (INCID) (1998). Sprinkler irrigation in India, Indian National Committee on Irrigation and Drainage, New Delhi. International Energy Agency (IEA) (2007). World energy outlook: China and India Insights. International Energy Agency: Paris, France. Iqbal J and Theegala C (2013). Microwave assisted lipid extraction from microalgae using biodiesel as co-solvent. Algal Res, 2: 34– 42. James JE, Kumar RAS and Raj ADS (2004). Marine algal flora from some localities of southeast coast of Tamil Nadu. Seaweed Res. Util., 26: 3–39. Jayakarna Sevarani (2011). Carbon sequenstration – The future key to meet the climate change. Online: www.ssrn.com/ abstract=1950726. Khare V, Nema S and Baredar P (2013). Status of solar-wind renewable energy in India. Renew. Sustain. Energy Rev., 27:1–10. Kim KH, Tucker MP and NguyenQA (2002). Effects of pressing lignocellulosic biomass on sugar yield in two stage dilute acid hydrolysis process. Biotechnol. Prog., 18: 489-494. Krook J, Martensson A and Eklund M (2003). Metal contamination in recovered waste wood as energy source in Sweden. Resour. Conserv. Recycl., 41:1–14.

Climate Change and Environmental Sustainability (October 2015) 3(2): 93-103 Kumar A and Sharma S (2011). Potential non edible oil resources as biodiesel feedstock: an Indian Perspective. Renew. Sustain. Energy Rev., 15: 1791–1800. Kumar P and Mittal S (2006). Agricultural productivity trends in India: sustainability issues. Agric. Econ. Res. Rev., 19: 71–88. Kuo PC, Wu W and Chen WH (2014). Gasification performances of raw and torrefied biomass in a downdraft fixed bed gasifier using thermodynamic analysis. Fuel, 117: 1231–1241. Larson ED (2008). Biofuel production technologies: status, prospects and implications for trade and development. Report no. UNCTAD/DITC/TED/2007/10. United Nations Conference on Trade and Development, New York, Geneva. Madguni O and Singh DN (2013). Potential of forest biomass for energy conversion Appl. Nat. Soc. Sci. (IJRANSS), 1(1): 53–58 Murray C and Lopez A (1996). Global Burden of Disease. World Health Organization, World Bank, and Harvard School of Public Health. Cambridge, MA, Harvard University Press. Narayanamoorthy A (2006). Potential for drip and sprinkler irrigation in India. Draft, IWMI-CPWF Project on Strategic Analyses of India’s National River-Linking Project, Ministry of New and Renewable Energy. Online: www.mnre.gov.in International Water Management Institute, Colombo, Sri Lanka. Nussbaumer T (2003). Combustion and co-combustion of biomass: Fundamentals, technologies, and primary measures for emission reduction. Energy Fuels, 17: 1510–1521. Qaisar SH and Ahmad MA (2014). Production, consumption and future challenge of coal in India, Int. J. Curr. Eng. Technol., 4(5):3437– 3440. Rahmanain B, Safaei MR, Kazi SN, Ahmadi G, Oztop HF, Vafai K (2014). Investigation of pollutant reduction by simulation of turbulent non premixed pulverized coal combustion. Appl. Therm. Eng., 73:1222–1235. Ramachandra TV (2007). Geospatial mapping of bioenergy potential in Karnataka, India. J. Energy Environ., 6:28–44. Ramachandran A, Jayakumar S, Haroon RM, Bhaskaran A and Arockiasamy DI (2007). Carbon sequestration: estimation of carbon stock in natural forests using geospatial technology in the Eastern Ghats of Tamil Nadu, India. Curr. Sci., 92 (3): 323– 331. Rath J and Adhikar SP (2005). Distribution of marine macro algae at different salinity gradients in Chilika Lake India. Indian J. Mar. Sci., 34(2): 237–241. Ravindranath NH and Balachandra P (2009). Sustainable bioenergy for India: technical, economic and policy analysis. Energy, 34:1003–1013. Reed TB, Walt R, Ellis S, Das A and Deutche S (1999). Superficial velocity – the key to downdraft gasification. Proceedings of the 4th Biomass Conference of the Americas. Oakland, CA, USA. Renewables (2014). Global status report REN 21, Renewable Energy Policy Framework for 21st century. Rosegrant MW (1997). Water resources in the twenty-first century: challenges and implications for action, food and agriculture, and the environment discussion paper 20. International Food Policy Research Institute: Washington, D.C., USA. Salaskar PB, Yeragi SG and Gordon R (2008). Environmental states of Powai Lake, Mumbai (India). Proceedings of Taal: the 12th World Lake Conference, pp 1650–1654. Sarvankumar A, Haridasan TM, Reed TB and Bai RK (2007). Experimental investigation on long stick wood gasification in a bottom lit updraft fixed bed gasifier. Fuel Process Technol., 88:617–622.

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Savaliya ML, Dhorajiya BD and Dholakiya BZ (2013). Recent advancement in production of liquid biofuel from renewable resource: A review. Res Chem Intermed, DOI 10.1007/s11164013-1231-z. Sharma DP, Chandramohan PS, Nair C and Balsubramaniam (2002). Demand for commercial energy in the state of Kerala, India: an economic analysis with medium range projection. Energy Policy, 30:781–792. Singh A and Pal S (2010). The shifting patterns of agricultural production and productivity worldwide. The Midwest Agribusiness Trade Research and Information Center: Iowa State University, Ames, IA, USA. Singh J (2015). Overview of electric power potential of surplus agricultural biomass from economic, social and environmental perspective – a case study of Punjab. Renew. Sustain. Energy Rev., 42: 286–297. Singh NB, Kumar A and Rai S (2014). Potential Production of bioenergy from biomass in an Indian perspective. Renew. Sustain. Energy Rev., 39: 65–78. Sinha CS, Venkata RP and Joshi V (1994). Rural energy planning in India – designing effective intervention strategies. Energy Policy, 22: 403–414. Sotirios K, Boukis I, Kontopoulos G (2010). Development of an investment decision tool for biogas production from agricultural waste. Renew. Sustain. Energy Rev., 14:1273–1282. Srinivasan KS (1946). Ecology and seasonal succession of the marine algae Mahabalipuram (Seven pagodas) Near Madras. In Indian Botanical Society, ed. Sahni B. pp. 267–278, M.O.P. Iyengar Com. Srivastav T (2013). Renewable energy (gasification). Adv. Electron. Electr. Eng., 3:1243–1250. Sudhakar K, Ananthakrishnan R and Goyal A (2013). Biogas production from a mixture water hyancith, chest nut and cow dung. IJSETR, 2:35–37. Sudhakar K, Rajesh M, and Premlatha M (2012). A mathematical model to assess the potential of algal biofuels in India. Energy Source A: Recover. Util. Environ. Eff., 34: 1114–1120. Tasneem A, Tarseef SM and Abbasi SA (2012). Anaerobic Digestion for global warming control and energy generation – An overview. Renew. Sustain. Energy Rev., 16: 3228–3242. TERI (2010a) Biomass energy in India. Proceedings of International ESPA Workshop on Biomass Energy. International Institute for Environment and Development (IIED): Parliament House Hotel, Edinburgh. TERI, New Delhi, India. TERI (2010b). Bioenergy for rural development and poverty alleviation New Delhi. The Energy and Resources Institute. [Project Report No. 2008DG10]. Varshney R, Bhagoria JL and Mehta CR (2010). Small scale biomass gasification technology in India: an overview. J. Eng. Sci. Manag. Educ., 3:33–40. Venkataraman K (2005). Coastal and marine biodiversity of India. Indian J. Mar. Sci. 34: 57–75. Wilbanks TJ, Bhatt V, Bilello DE, Bull SR, Ekmann J, Horak WC, Huang YJ, Levine MD, Sale MJ, Schmalzer DK and Scott MJ (2008). Effects of climate change on energy production and use in the United States, Washington, DC: US climate change science program. Synthesis and Assessment Product 4.5. Williams A, Jones JM, Ma L and Pourkashnain M (2012). Pollutant from the combustion of solid biomass fuel. Progress Energy Combust. Sci. 38:113–137.


REVIEW ARTICLE

A Review on Methods to Estimate CH4 and N2O Fluxes in Terrestrial Ecosystem Ajeet Kumar Singh1 • S. Jayakumar2*

Abstract It has been found in the last 3–4 decades that different ecosystems in the tropical regions contributed maximum trace gases (CH 4 and N 2 O) to atmosphere. Terrestrial ecosystems in tropics, sub-tropics and in temperate regions are the well-known sources and sinks of important GHGs (green house gases). Nowadays, developing countries of Asia Pacific regions are contributing a maximum amount of these trace gases at the global scale. Anthropogenic activities and changing environmental conditions alter the dynamics of different ecosystems that stimulate GHGs emission in the last few years. A higher concentration of CO2 and temperature in soil enhance microbial activity. The techniques for sampling, estimation and future prediction of fluxes of these trace gases from different types of ecosystem are still undergoing changes with the advancement in knowledge of microbiology, geology and technology. This review discusses GHG, mainly methane (CH4) and nitrous oxide (N2O) emission estimated from different ecosystems, advancement in estimation technology and the key controlling factors for their emission around the world. Keywords Terrestrial ecosystem, Methane and Nitrous oxide, Modeling, Remote sensing 1. Introduction Methane (CH4) and nitrous oxide (N2O) are the most important greenhouse gases, which contribute significantly in global warming. In the last few decades, a dramatic increase of these gases in the atmosphere from different terrestrial ecosystems has been observed. CH4 and N2O are the gases, with radiative forcing of 25 and 298 times more than carbon dioxide, respectively, at a 100-year time horizon (Dijkstra et al., 2012). CH 4 is the second important greenhouse gas after CO2, which accounts for 18% of total radiative forcing (IPCC, 2007; Akumu et al., 2010).

Terrestrial ecosystems, including both uplands and lowlands, either natural including peat lands, bogs/fens, coastal wetlands and mangroves or the managed one like small ponds, lakes, tanks, paddy fields, STPs (sewage-treatment plants), etc. are important sources of methane and nitrous oxide, as these are produced through various biological processes (Dijkstra et al., 2012). Several studies have indicated significant spatial and temporal variations in fluxes of CH4 (Bhuller et al., 2013; Bridgham et al., 2013; Ly et al., 2013; Hou et al., 2012; Wang et al., 2012; Carter et al., 2011; Couwenberg et al., 2011; Danevcic et al., 2010; Koelbener et al., 2010; Long et al., 2010; Dinsmore et al., 2009; Datta et al., 2009) and N2O (Aboobakar et al., 2013; Audet et al., 2013; Chang et al., 2013; Ly et al., 2013; Machacova et al., 2013; Liu et al., 2012; Page et al., 2011; Liu et al., 2011; Ahn et al., 2010; Galbelly et al., 2010; Lohila et al., 2010; Matthews et al., 2010; Huang et al., 2013) from different ecosystems. The fluxes of these gases are controlled by different physical, chemical and biological phenomena. In addition, their fluxes are also influenced by the methods and techniques, which have been used to estimate. In most of the studies, a close chamber method has been frequently used. But this method might have influenced the fluxes inside due to variation in the temperature. For this paper, a large number of research articles on the production of CH4 and N2O, and transport to atmosphere from different ecosystems are reviewed, to discuss the key controlling factors for their estimation. It mainly focuses to identify and summarise the recent progress in technology that refines global and regional estimates of these gases. 1.1 Global Estimates of GHG Emission Previous global level GHG flux studies pointed out that tropical regions (about 60%) and northern terrestrial ecosystems (about 34%) contributed the maximum, while the temperate ecosystems had minimum contribution of

Research Scholar, 2Associate Professor, Environmental Informatics and Spatial Modeling Lab (EISML), Department of Ecology and Environmental Sciences, School of Life Sciences, Pondicherry University, Puducherry 605014, India *Corresponding author Email Id: [email protected]

1

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about 5% (Barlett et al., 1993). This might be the reason that maximum areas of this region are naturally occupied by forested and non-forested bogs. It is reported that areas between 50° and 70° N in Alaska, Canada and USSR occupy bogs and fens, while the area between 10° N and 20° S are swamps and flood plains in Amazon, southeast Asia and Africa. These areas are globally important terrestrial carbon pools, and play crucial role in soil-atmosphere carbon balance. At present, these carbon stocks have been degraded rapidly and carbon gases are released into the atmosphere, that lead to significant alteration in the atmosphere carbon balance (Page et al., 2011). These areas are the natural sources of some of the trace gases like methane and nitrous oxide in atmosphere. In addition there are other important and major sources of these gases like agriculture, industries, power plants, transport and waste management systems that have maximum contribution at global scale. The total GHG emission from terrestrial ecosystem around the globe ranges from 11931.495 to 18100 Tg CO2 equivalent/year (UNFCC report, 2005, 2012). According to UNFCC report (2005), the maximum emission of GHGs was reported from Asian Pacific continent (7614.071 Tg CO2 equivalent/year) which is followed by Latin America and Caribbean (2986.460 Tg CO2 equivalent/year), Africa (1201.794 Tg CO2 equivalent/ year) and others (129.170 Tg CO2 equivalent/year). In Asia Pacific region, there are so many small island nations, which constitute large coastal areas. This continent also contains significant portions of natural tropical and sub-tropical rainforests. The tropical and sub-tropical rainforests sequester ultimately a large amount of CO2 to soil and sediments and provide a good quality and quantity of Csubstrate for soil microorganisms. Most of the countries in this sub-continent are highly populated, and their population growth is more with respect to other continents of the world that also have an important role in GHG emissions from different sectors. Most of the historical GHG emissions were contributed by developed countries of Europe and America. However, it has been projected on the basis of different studies that the southeast Asian countries will contribute maximum GHG in coming decades at a global scale. In the Latin America and the Caribbean region, Brazil, Mexico and Argentina are the highest emitter of GHGs. In this region, changes in land use pattern cause highest contribution of GHG emission than in rest of the world. At regional/local level, emission of these trace gases (CH4 and N2O) are highly variable (Table 1), as their production and transport are influenced by all biotic and abiotic factors. 2. Processes and Controlling Factors The emission of CH4 and N2O from terrestrial systems into atmosphere is dependent on their production, oxidation

and transport mechanisms. Methane is produced when organic matters undergo anaerobic decomposition deep inside the surface. After production, it is released into the atmosphere through three possible pathways: first, through diffusion of dissolved methane; second, transport through vascular plants and third, by ebullition. In the process of diffusion, concentration gradient of dissolved methane is the driving factor. Vegetation mediated transport is mainly through roots of existing vegetation, while ebullition is the process of formation and release of bubbles in saturated to unsaturated soil pore space. Nitrous oxide is produced by microbes in soils and sediments through the process of nitrification and denitrification and transported directly to atmosphere. Biogenic production of these gases depends on biological (microbial processes, enzyme activity, and substrate availability), physico-chemical (pH, salinity, redox potential and soil texture) and environmental (hydrology, topography and meteorology) phenomenon. 2.1 Microbial Processes It is well known that CH4 and N2O are produced in the soil and sediments of different ecosystems, through several pathways, by the activity of microorganisms. CH4 is usually produced at significant depth under anaerobic situation through two most accepted pathways called: acetoclastic methanogenesis and hydrogenotrophic methanogenesis (Eqs. (1) and (2)) (Thauer, 1977). CH3COO-+ H+ CO2+4 H2

CH4+CO2 CH4 + 2 H2O

(1) (2)

Different groups of bacteria involved in CH4 production are called methanogens, and the pathway followed is intrinsically depending on their metabolic features. The metabolic feature includes diverse species of methanogenic bacteria that has capacity to couple hydrogen oxidation with the reduction of carbon dioxide. Acetoclastic methanogenesis pathway is more dominant in nutrient enriched ecosystems compared to oliogotrophic systems. Methanogenesis is controlled by the availability of substrates and terminal electron acceptors such as Fe3+, NO3-, Mn4+, SO42- in anaerobic conditions. All these electron acceptors compete for H2 and inavailability of Fe3+, acetate in soil is converted to CO2 rather than CH4. Production of N2O in these ecosystems is explained by both chemical and biochemical pathways, including nitrification (Eq. (3)) (Poth and Focht 1985) and denitrification (Eq. (4)) (Firestone 1989). In the process of nitrification, N2O is produced as a byproduct of nitrifying bacterial respiration under aerobic condition. In this process, its emission is controlled by activity and expression of three enzymes named as ammonia mono-oxigenase (Amo),

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Table 1 CH4 and N2O emission in different ecosystems Methane and nitrous oxide emission at regional/local scale reported from various countries Study site

Country/ region

N2O emission (mg/m2/year)

CH4 emission (g/m2/year)

References

Riparian wetland

Denmark

–

0.2 - 0.38

Audet et al. (2013)

Riparian wetland

Denmark

250–500

–

Audet et al. (2014)

Riparian alder forest

Estonia

40–70

–

Soosaar et al. (2011)

Riparian forest

USA

290

–

Kim et al. (2009)

Tropical rain forest

Australia

96

–

Luo et al. (2013)

Lgume paster land

Australia

35±3

–

Galbelly et al. (2010)

Temperate forest

Germany

67

–

Luo et al. (2013)

Steppe

Mongolia

22

–

Luo et al. (2013)

Wetland and paddy fields

South/SE Asia

>300

10–30

Tian et al. (2014)

1.5–15.6

Paddy fields

USA

25.8–107.7

Managed rice field

China

4–170

Pittelkow et al. (2013) Chen et al. (1997)

Permanent inundated marsh

China

0.07–0.17

32.41–46.39

Seasonal inundated marsh

China

“0.24

2.57–6.15

Song et al. (2009) Song et al. (2009)

Shrub swamp

China

0.17–0.39

0.11–0.31

Song et al. (2009)

Croplands

South/SE Asia

286

–

Yan et al. (2003)

Drained peat land

Europe

20% in 2015 in rice and in wheat it has been ~20% during 2014– 2015 and 2015–2016. Keywords Abiotic stresses, Climate resilient varieties, Varietal replacement rate (VRR), Seed replacement rate (SRR), Productivity increase and variability in yield 1. Introduction Cereals are the major and the cheapest source of energy as compared to other food items and are vital for food and nutritional security. An extremely important key input resulted into increased productivity is the genetic improvement of crop plants. Overall, it is estimated that at least half of the yield increases attained in wheat and rice between the 1960s and 1990s was due to the utilisation of genetically improved varieties. Continuous improvement of crop varieties has supported the steady increase in crop yields over the past several decades (Evenson and Gollin, 2003; Miller et al., 2010). Wheat experienced the greatest boost during the Green Revolution, largely due to the success and spread of high-yielding variety (HYVs) seeds and due to GR technologies India achieved second rank in wheat, rice and third in total cereals production globally. The productivity has remarkably increased since 1950–1951 to


2010–2011 by 4.5 times in wheat and maize, 4 times in pearl millet, 3.4 times in rice and 2.7 times in sorghum. In India, in spite of having ranking globally in the production in a number of crops, the productivity levels are even below than the world averages among cereal crops (MOA, 2012). In India, yield of coarse grains is about 1433 kg/ha (less than half) as compared to world average yield of 3512 kg/ha. In India, coarse cereals are grown over an area of 27.67 million ha (22% of total food grains), with a production of 39.95 million tonnes during 2007–2008 to 2011–2012 and contributed about 17% to national food basket (Directorate of Millets Development, 2014). Moreover, India ranks 54th in wheat, 57th in rice productivity and 81st in maize at global level (Dastagiri et al., 2013). India has the first rank in the world in terms of total irrigated areas but average crop yields of around 2.3 t/ha are very low and thus have serious concern. The existing productivity of arid (0.2 t/ha), semi-arid (0.6 t/ ha) and sub-humid (1.0 t/ha) is 5, 3 and 3 times less of their potential productivities of 1.0, 1.9 and 3.0 t/ha, respectively (Planning Commission, 2011). Despite the success of green revolution, India still houses one-fourth of the world’s hungry and poor and 40% of the world’s malnourished children and women (NAAS, 2009). The country faces major challenges to increase its food production to the tune of 300 mt by 2020 in order to feed its ever growing population which is likely to reach 1.30 billion by the year 2020 (Kumar and Gautam, 2014). The effect of climate change reflected through increase in the frequencies of extreme events (droughts, flood, etc.), change in the precipitation regime, increase the average temperature, climate change is also a reality now, which hinders crop production (ICRISAT, 2010). Since 1950–1951 to 2012–2013, there have been instances in food grain production (24), rice (20), wheat (16), coarse cereals (28), maize (19), sorghum/Jowar (31) and in pearl millet/Bajra (33) instances in which total production in India failed to exceed the production level from the previous years and virtually it was lower than the previous year. Coinciding with rising temperatures, a large part of India is prone to extreme precipitation events causing torrential rains and flash floods. This phenomenon has become increasingly common in eastern and central India over the past several decades (NAAS, 2013b).The rainfed crop yield is expected to increase to 1.6 t/ha in 2015, 1.8 t/ha in 2030 and 2.0 t/ha in 2050. The irrigated cereal yields are projected to increase from 3.5 to 4.6 t/ha during the same period (Venkateswarlu and Prasad, 2012). The cultivable land has reduced by 3 million ha within 3 decades (average 1 Mha per decade) (MOA, 2013a). Water is the most critical agricultural input in India, as 55% of the total cultivated areas do not have irrigation facilities (Kumar and Gautam, 2014). Nevertheless, in the backdrop of diminishing natural resources in terms of land and water, and declining factor productivity, to increase

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the food grain production in a sustainable manner without degradation of natural resources further is a herculean task. Being a tropical country, India is more challenged with impacts of looming climate change (Chahal et al., 2008). Historical data analysis has also indicated that the low intensity rainfall events have decreased while the medium and high intensify rainfall events have increased over the hundred years (Singh, 2012). The semi arid regions of the country had maximum probability of prevalence of droughts of varying magnitudes (20–30%), leading to sharp decline in water tables and crop failures (Lal, 2003; Fand et al., 2012). Overcoming abiotic stresses in crops through crop breeding has proven to be an effective means of increasing food production (Evenson and Gollin, 2003), and arguably mitigating climate change effects (Burney et al., 2010; Vermeulen et al., 2012). New varieties are needed with higher level of yield and stability to replace the older ones since the development of new varieties is a continuous programme of almost all coordinated crop improvement programme in India since genetic improvement is a highly cost effective intervention (Yadavendra et al., 2005). The key to ensuring long-run food security lies in targeting cereals productivity to increase significantly faster than the growth in population (Ramasamy, 2013). The challenge of food grain production is generation of sufficient number of new varieties of field crops with threshold potential in changing climate scenario (Brahmanand et al., 2013). In the present paper, the impact of new varieties of cereal crops in terms of productivity enhancement has been analyzed and the results are reported. 2. Materials and Methods Due to the implementation of various measures, schemes, missions and plans National Food Security Mission (NFSM), Rashtriya Krishi Vikas Yojna (RKVY), Bringing Green Revolution in Eastern India (BGERI), National Seed Policy – 2002 and National Seed Plan – 2005 among others, the major emphasis has been placed to increase varietal and seed replacement rates (VRR and SRR) of cereal crops. Also various abiotic stress tolerant varieties need to be inducted into seed chain. Under NFSM schemes the emphasis is placed to provide subsidies on the seed of varieties which have been released recently (less than 10 years old) in order to make seed available to the farmers. The present study is an analytical one in which attempts have been made to analyze the impact of these schemes through the increase in productivity of cereals (rice and wheat) and coarse cereals (maize, pearl millet and sorghum) among states in which these crops are being grown during period I (2001–2002 to 2006–2007) and period II (2007–2008 to 2012–2013) by deployment of new/improved climate resilient varieties among these crops. The yield difference between the two periods were tested statistically as significant/non-significant by applying paired t-test. Also, the correlation between yield

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and variability in yield, the association between yield and irrigation percentage, and the association between variability in yield and irrigation percentage were also worked out in order to quantify the resiliency of the new climate resilient varieties. 3. Result 3.1 State Wise Trend in Yield and Variability in Yield from 2001–2002 to 2012–2013 in Cereal Crops State wise yield, variability in yield, actual yield gain/ loss including in terms of percentage yield gain/loss and irrigated area under rice and wheat from year 2001–2002 to

2012–2013 are given in Table 1. Also the significant mean yield gain/loss during 2007–2008 to 2012–2013 (period II) over mean yield during 2001–2002 to 2006–2007 (period I) tested by applying paired t-test is quantified to see the impact of increased varietal and seed replacement rates (VRR and SRR) including the deployment of climate resilient varieties (varietal replacement rate). At all India level, the irrigated area under rice crop is only 58.6%, while in states like Haryana, Punjab, AP and TN the irrigated area is >90%. In UP and Karnataka the coverage of irrigated area in rice 75– 80% and in Gujarat, Bihar and WB, the irrigated area under rice is 50–60% while in Chhattisgarh, Orissa, Jharkhand, Maharashtra and MP, the irrigated area under the crop is

Table 1 State wise yield and yield variability in cereal crops from 2001–2002 to 2012–2013 Sr.

State

no.

2001–2002 to 2006–2007 Av. yield

CV1

2007–2008 to 2012–2013 Av. yield

(kg/ha)

(kg/ha)

(6 years)

(6 years)

M1

M2

CV2

Actual mean

Percent yield

Test of

Irrigated area (%)

yield gain/

gain/loss

mean

loss (kg/ha)

M2 vs. M1

difference

M2-M1

(M1 vs. M2)

Rice 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Haryana Punjab Andhra Pradesh Tamil Nadu Uttar Pradesh Karnataka Gujarat Bihar West Bengal Chhattisgarh Orissa Jharkhand Maharashtra Madhya Pradesh Assam All India

Wheat 1 Haryana 2 Punjab 3 Uttar Pradesh 4 Rajasthan 5 Gujarat 6 West Bengal 7 Bihar 8 Madhya Pradesh 9 Uttaranchal 10 Maharashtra 11 Himachal Pradesh AIl India

2893 3736 2936 2756 1969 2629 1709 1293 2526 1224 1394 1462 1618 855 1464 2019

7.78 4.86 6.01 16.58 8.1 24.45 17.83 22.79 1.91 22.37 22.28 24.43 15.15 19.16 4.87 7.11

3032 3935 3160 2970 2209 2636 1958 1578 2627 1459 1628 1900 1741 1071 1751 2261

8.27 3.05 3.69 8.94 7.32 5.81 8.43 36.20 3.54 17.87 9.53 15.17 11.64 20.75 12.05 5.68

139 199 224 214 240 7 249 285 101 235 234 438 123 216 287 242

4.8 5.3 7.6 7.8 12.2 0.3 14.6 22.0 4.0 19.2 16.8 30.0 7.6 25.3 19.6 12.0

1.103 1.737 2.139 0.862 2.224 0.033 2.827* 1.224 3.667* 1.834 1.941 2.431 1.143 1.815 2.612* 4.256**

99.8 99.6 97.1 93.2 80.4 77.0 61.5 55.6 48.2 33.6 33.2 32.0 26.1 20.4 4.9 58.0

4012 4258 2666 2775 2460 2202 1812 1677 1893 1319 1616 2669

3.60 3.17 4.13 1.60 10.80 3.96 9.90 8.42 8.17 6.22 16.00 2.52

4477 4574 3001 3053 2875 2696 2127 1950 2202 1594 1421 2966

7.11 4.45 4.61 5.93 10.11 4.93 7.86 16.65 7.17 6.66 18.23 4.78

465 316 335 278 415 494 315 273 309 275 -195 297

11.6 7.4 12.6 10.0 16.9 22.4 17.4 16.3 16.3 20.8 -12.1 11.1

2.736* 2.903* 3.585* 3.211* 4.295** 7.352*** 3.469* 2.474 3.456* 5.361** 1.811 3.986*

99.4 98.8 98.1 98.1 98.0 95.9 93.2 87.1 85.8 73.9 20.6 92.1


just 20–33%. Fifteen states jointly cover >95% of area under rice and their contribution to the national bowl is of similar magnitude.With respect to yield variability it decreased in most of the states (TN, Karnataka, Gujarat, Chhattisgarh, Orissa, Jharkhand and Maharashtra) while the variability in yield was increased only in Bihar during two periods. In rice in all major states the yield gains have been seen in all states which ranged from as low as 7 kg/ha (0.3%) in Karnataka to as high as 438 kg/ha (30%) in Jharkhand. However, the significant yield gains between two periods 2007–2008 to 2012–2013 over 2001–2002 to 2006–2007 (M2 over M1) found only in Gujarat (249 kg/ha), West Bengal (101 kg/ha) and Assam (287 kg/ha) at 97% area and their joint contribution in production was to the time of >98% in 2012– 2013. For wheat, the irrigated area varies from 20.6% in Himachal Pradesh 70–90% in Madhya Pradesh, Maharashtra and Uttarakhand while >90% in West Bengal, Bihar, Gujarat, Uttar Pradesh, Punjab and Haryana. In Himachal Pradesh the mean yield of wheat was reduced by 195 kg/ha (12.1%) from 1616 kg/ha during period I (2001–2002 to 2006–2007) to 1421 kg/ha during period II (2007–2008 to 2012–2013) for other major wheat growing states the yield increased from as low as 273 kg/ha (16.3%) in Madhya Pradesh to as high as 4.94 kg/ha (22.41%) in West Bengal during period II. Overall at all India level the mean yield of nearly 3 quintal/ ha was seen during period II which is significant at