Volume 1, Issue 1, July, 2012 Energy and Environmental Engineering Journal
Synthesis and Characterization of Biodiesel from Industrial Starch Production Byproduct Solomon Giwaa,*, Abayomi Layenia and Clement Ogunbonab a
Department of Agricultural and Mechanical Engineering, College of Engineering and Environmental Studies, Olabisi Onabanjo University, Ibogun Campus, Ifo, Ogun State, Nigeria. b Chemical Sciences, College of Natural Sciences, Bells University of Technology, Ota, Ogun State, Nigeria. * Corresponding Author E-mail:
[email protected] Tel: +2348091757240 Abstract This present study focuses on the use of oil-based industrial starch byproduct called corn germ as biodiesel feedstock. Corn germ oil (CGO) was extracted using n-hexane and the fatty acid profile of the oil analyzed using gas chromatography. The synthesis of CGO to biodiesel was conducted via two-stage method (esterification, followed by transesterification) due to the oil having a relatively high acid value of 3.05 mg KOH/g. The physical and chemical properties of the oil, and fuel properties of corn germ oil methyl esters (CGOME) were measured in accordance with standard test methods. Specific gravity, kinematic viscosity, cloud and pour points of blends (B2, B5, B10, B15 and B20) of CGOME in petrodiesel were also determined. A moderately high yield (85.5 ± 0.7 wt.%) of CGOME was obtained under classic reaction conditions. The fuel properties of CGOME measured were found to fulfill both ASTM D6751 and EN 14214 biodiesel standards except oxidative stability and iodine value. In addition, the results for kinematic viscosity, specific gravity, cloud and pour points of CGOME-petrodiesel blends satisfied both ASTM D975 and ASTM D7467 and were in agreement with previous studies. Conclusively, the properties of CGOME, both neat and blended with petrodiesel, were analogous to other usually encountered biodiesel fuels, such as soybean, sunflower, canola, and palm oil methyl esters. Keywords: biodiesel; fuel properties; corn germ oil; petrodiesel; transesterification
1 Introduction Recently, biodiesel is gaining more attention as substitute for fossil-diesel due to the decline in known oil reserve, instability in supply and cost, and environmental effect of the gases emitted into the atmosphere by fossilderived fuels. The most important of these is the environmental concern which has led to global warming resulting in flooding, change in world climatic condition amongst others. However, biodiesel is environmentally friendly and carbon neutral, contributing far less to environmental degradation compared to fossil fuels. Biodiesel is a renewable fuel and consisted of monoalkyl esters of medium and long chain fatty acids (FAs) derived from lipids. It is seemingly becoming a surety fuel for energy independence and energy security of nations against fossil-derived diesel. Biodiesel is a region-dependent fuel because its raw material varies according to geography, climate and economics and can be produced from most prevalent raw material. Thus, rapeseed oil is mainly used in Europe, palm oil predominates in tropical countries (Malaysian and Thailand), and soybean oil and animal fats are principally used in the US [1]. Oils for biodiesel production has be sourced from vegetable oil (VOs), animal fats, waste cooking oil, algae, and grease [2,3], and even insects
[4,5]. Of all these oils, VOs are mostly utilized for biodiesel production. Traditional VOs used for this purpose are; soybean oil, sunflower, safflower, palm oil and rapeseed oil. However, due to high cost and competition in the use of VOs for fuel and food biodiesel, cheaper sources of feedstock for biodiesel production have been researched. This has led to the use of waste cooking oils [2] and other oil-based wastes [3,6]. Coming from the background that the cost of raw material (VO) accounts for 70-95% of the total cost of production of biodiesel [7], the need for less expensive feedstocks become apparent. Feather meal, a waste product of the poultry industry [3], crude fish oil from discarded fish products [2], leather industry fleshing wastes [6], dairy waste scum [8] and pork wastes [9] have been investigated as low-cost feedstocks for biodiesel production. The key reaction parameters affecting transesterification are molar ratio of oil to alcohol, catalyst type and amount, reaction time and temperature, and the amounts of free fatty acids (FFAs) and water present in the oil [10]. However, the oil to be used in alkali-catalyzed transesterification must contain reasonably low content of FFAs and the alcohol must be
Giwa et al./Energy and Environmental Engineering Journal, 2012 1(1); 45-51 anhydrous. Otherwise, soap formation occurs and affects the yield of ester produced. Mostly, methanol is the choice alcohol for biodiesel production because it is cheap and brings about a high level of yield [10]. Thus, it is important to characterize the oil and the practicability to convert the oil into biodiesel. Corn, also referred to as maize (Zea mays L.), is one of the most important cereal crops that is a commercial source of vegetable oil. About 600 million tons of maize is produced annually worldwide [11]. It is produced in different parts of the continent under diverse climatic and ecological conditions. The United States is by far the largest corn producer in the world followed by Mainland China (Table 1). Table 1 Top Corn Producing Countries in the World (FAO, 2008) S/N Countries Corn Production (ha)
(Mt)
1
United States of America
20261250
307142010
2
China
6959063
166032097
3
Argentina
2042438
22016926
4
Brazil
1925338
58933347
5
India
1442042
19730000
6
Mexico
1292539
24320100
7
Indonesia
1286208
16323922
8
South Africa
1004019
12700000
9
France
908509
15818500
10
Nigeria
688353
7525000
Corn grown in the United States contains about 65% starch and 3-4% oil [12]. Since maize is cheaper than other cereals such as rice and wheat, it is more affordable to the vast majority of the population, and therefore occupies a prominent position in the agricultural development agenda of several countries in Africa and the world at large [13]. A large fraction of the maize crop is used as livestock feed. However, in many developing countries, corn is used only for human consumption. Maize is also used for numerous industrial products, in distillation and fermentation industries, and for the production of starch, corn syrup and fuel. Unlike most edible plant oils that are obtained directly from oil-rich seeds by either pressing or solvent extraction, corn seeds (kernels) have low levels of oil (4%), and commercial corn oil is obtained from pressing or extracting the isolated corn germ (embryo), which is an oil-rich portion of the kernel. The corn germ contains 85% of the oil and 80% of the minerals present in the whole grain [12]. Most commercial corn oil is obtained from corn germ that is one of the three common coproduct of the wet milling industry developed to extract pure corn starch [14] and accounts for a relatively small portion of the economic value of the whole plant. Mass production of bioethanol from corn as alternative fuel may have been the reason why very few
literatures are found on biodiesel synthesized from corn. Additionally, little or no work has been carried out on the production of biodiesel from corn germ (a byproduct of the wet milling process in starch production). The forementioned has necessitated this present study, which investigates the extraction, synthesis and characterisation of biodiesel from corn germ. Besides, the change in density, kinematic viscosity, pour and cloud points of corn germ oil biodiesel when blended in various proportions with diesel fuel was examined.
2 Materials and methods 2.1 Materials The corn germ (Fig. 1) - industrial starch byproduct was collected dry from the store of Tempo starch and glucose Limited, Adigbe, Abeokuta, Ogun State, Nigeria in a fresh condition. In order to reduce the particle size for effective oil extraction, a Moulinex A320 R grinder was used.
2.2 Reagents The reagents methanol 99.5% (Fischer Scientific), sulphuric acid 95-98% (Aldrich), sodium hydroxide powder 97% (Aldrich), hexane >95% (Merck), hydrochloric acid 37% (Aldrich), heptane 99.5% (Fluka), methyl heptadecanoate 99.7% (Fluka) and triacetin 99% (ALFA AESAR) were purchased from Belward Scientific (Nig.) Ltd. (Ikeja, Lagos, Nigeria). All the chemicals were of analytical reagent grade.
Figure 1 Milled corn germ
2.3 Extraction Corn germs (1000 g) were ground and charged into the soxhlet apparatus. The extraction was carried out using n-hexane in the soxhlet apparatus for 8 h. The solvent was removed via a rotary vacuum distillation at 40-50 ºC. The residue (oil) was filtered through steel micromesh, weighed and stored at 20 ºC until it was analyzed. The weight of the corn germ oil (CGO) extracted from 40 g of the seed powder was determined to calculate the total lipid content according to AOAC official method 963.15. The result was expressed as the lipid percentage in the dry corn germ powder. Water content of the CGO is an important parameter and should be kept below 0.06% w/w for better conversion of oil to 46
Giwa et al./Energy and Environmental Engineering Journal, 2012 1(1); 45-51 esters. Hence, the raw oil was kept in an oven at 110 ºC for 2 h to make it considerably anhydrous prior to transesterification reaction. After this, the oil was stored in cool dry and safe place wrapped with aluminium foil until usage.
2.4 Physical and chemical properties of the oil The physical and chemical properties were conducted in accordance with standard test methods described in the AOAC (1998) [15]. The properties are: density, kinematic viscosity, iodine value, saponification value, acid value, and peroxide values. These were conducted in triplicate and the average values reported.
2.5 Esterification procedure The FFA of CGO (6.10%) is higher than the value (
