of the total weight is shell which until relatively recently ... When oil wells are drilled, a liquid mud is circulated down the .... MACHINE COMPANY. P.O.BOX 5460.
Pecan Shells A Waste Disposal Problem that is Developing into a Major Economic Segment of the Pecan Industry.
Approximately 220 million pounds of pecans are produced within the United States each
year(l). Of this, over 50 per cent of the total weight is shell which
until relatively recently repre sented a costly disposal problem for the shelling segment of the pecan industry. As a conse quence, it has not been uncom
mon to find 10-15 acre fields piled
6 to 8 feet high with abandoned shells.
Until recent years, little at tempt has been made to utilize this 50 per cent of the annual crop which was discarded. While only
a portion of the total volume of shells are currently utilized, re cent advances in the utilization
of shells has presented an optimis
tic picture for the future. Shells are now beginning to be viewed as a valuable renewable resource
rather than a costly disposal problem.
The purpose of this article is to outline the major current uses of
pecan shells, a number of novel
but often economically marginal uses and a diverse array of new uses which we currently have the technical potential to develop. CURRENT Lost
Circulation
USES Material
—
When oil wells are drilled, a liquid packing
phenolic
molded
shells ^ tissue ^ extract —^ plastic
products 18
mud is circulated down the shaft to the drill bit and back out to
the surface. This drilling mud carries small particles of ground Pecan South
material generated by the action of the bit out of the hole. Circula tion from the surface to the hole and back to the surface can be
The formation of pecan LCM requires a milling operation dur ing which the packing tissue is
ton although the initial whole sale price is currently only $110120/ton.
broken when the bits drill through
25 to 30 per cent of the original
Glue Extenders. Finely ground shells which have initially been
areas of high porosity, such as a gravel bed or where there are sub
weight of the raw shells. The fin
milled similar to LCM shells are
ished product is bagged by the
used as glue extenders principal
surface failures (cracks) in the
wholesaler in 50 lb. sacks. Gen
ly in the plywood manufacturing
earth. When these areas are en
erally the price of product is
industry. The ground shells or
countered the drilling mud moves out into the surrounding strata, occasionally moving up to sev e r a l m i l e s h o r i z o n t a l l y. T h i s breaks the closed circulation pat tern of the mud, a bentonite clay, from the surface to hold and back
to surface again impairing the
drilling operation and greatly in creasing the amount of drilling mud required. Because of this, materials such as pecan, walnut, oyster shells, etc., which can be used to restore the circulation
by blocking the holes where the drilling mud is being lost are
removed. This eliminates around
marked up considerably due to transportation, handling and middle men before actually reach
ing the drilling site. Well head prices typically are around $550/
nut shell flour is added to glues
such as urea resins. The nut
shell flour physically extends the volume of the glue and helps to decrease the penetration of the
TOLEE IRRIGATION SYSTEMS, INC. ROUTE 4, BOX 73, LEESBURG, GEORGIA 31763 PHONE 912-759-6488
We offer a complete line of irrigation products, including Typo! tubing and the new E-2 emitter. We design our own systems, stand behind our work, and most importantly, we are familiar with the needs of modern pecan growers.
called "lost circulation materials"
Let us serve your irrigation needs.
or LCM's.
Contact:
Shells are added to the drilling mud and function by bridging
Thomas F. Crocker, President
together to fill the hole. For larger holes coarser materials are required. In general, the par
Distributor for:
D ,
d
912-759-6488
ticles must be at least 1/3 as large as the hole they are filling. Hence
rriga
ion Systems
IN STOCK...
for relatively tight soil forma
I M M E D I AT E D E L I V E R Y !
t i o n s fi n e r " l o s t c i r c u l a t i o n m a
T H E FA M O U S
terials" can be used. Approxi
mately 10 per cent of the oil wells require some type of "lost cir
MEYER
culation material."
A U T O M AT I C P E C A N CRACKER
HIGH SPEED CRACKING
There are as one would expect
• A U TO M AT I C
a reasonably large number of
• POLISHED NUT POCKETS
LCM available in addition to pecan shells (2, 8, 9, 10). Walnut shells
HIGH RECOVERY OF PERFECT MEATS • ONE CRACKER DOES IT ALL
have an advantage in that they are thicker and can be made into a somewhat coarser LCM. Pecan
shells have a relatively high level of availability and low unit price ($10/ton for raw shells). Numer
ous other products, natural and synthetic and formulations, are available each generally having
certain advantages and disad
PRESSURE
SUSPENDED CRACKING
Write for Bulletin 914
MEYER M A C H I N E C O M PA N Y P. O . B O X 5 4 6 0 . S A N A N T O N I O . T E X A S 7 6 2 0 1
512/736-1811 D E S I G N E R S A N D M A N U FA C T U R E R S O F CONVEYING AND PROCESSING EQUIPMENT
Wrile lor Bullelm 927 lor Inlormtllon
vantages. March 1979
19
glue into the wood by moving into
LIMITED AND NOVEL USES
impeding excessive penetration. While some of the commercially
A wide range of other uses of pecan shells have been suggested,
the pore structure of the wood
available glue extenders do have
tried, and in some instances,
a chemical effect on the bonding
used on a limited scale. These
process in addition to the physi cal effect, a chemical effect has not been substantiated for pecan
1. Mulches for home gardeners.
s h e l l fl o u r .
The construction plywood in
dustry is estimated to currently use up to 150 million pounds of filler material each year. The major glue extenders are a lignocellulosic by-product of corn cobs (the ground waste from corn cobs after the chemical furfural
has been extracted), wheat flour and others. Nut shell flours made
principally from pecan and wal nut shells are used to a much
lesser extent. The wheat flour in
dustry has in the past been a
include:
2. Burning the shells as fueldone to a limited extent by some of the northerft shellers during t h e w i n t e r.
3. Used in the manufacture of charcoal.
4. A substitute for snow on
beginner ski slopes. 5. An abrasive for cleaning jet
engines (walnut shells, however, are superior for this due to their shape and strength charac teristics).
6. As a roughage for cattle. 7. Used in the leather tanning
given the present economic sit uation. NEW
USES
Relatively recent advance ments in the application of exist ing technology have opened enormous opportunities in the utilization of pecan shells\ A chemical, phenol, which forms the basic building block for many
plastics and other synthetic poly mers can be extracted easily, in
expensively and in substantial volume from pecan shells. Be cause of this, it is now possible to manufacture a diverse array of
plastics and plastic products from phenols extracted from pecan shells. Cast, molded and extruded
bakelite plastics, laminated ma terials, particle or composition boards, thermal insulation ma
terials, etc. can be produced. One does not have to look far to
see a multitude of plastic prod ucts we use daily. The extraction and/or produc
tion of chemic£ils from wood prod ucts is not a new phenomenon.
♦ •—^ #
#
In the 1800's considerable interest and research was directed toward
this end. However, a relatively
complete shift from wood to fossil fuels (oil, coal and natural gas) was made during the 1900's for the production of a wide variety of chemicals used in the produc
tion of synthetic polymers. Fossil fuels are not, however, renewable resources and the beginning of the end of an era of extremely
glue extenders _ intermediate y lost circulation material
shells packing ^ phenolic y bakelite tissue
extract plastic i n d u s t r y. major buyer of pecan shell flour which was used as an additive to 8 . M a n u f a c t u r e o f fi r e p l a c e " d e n a t u r e " w h e a t fl o u r s d e s t i n e d logs. for the glue industry so that it 9. As a substitute for pine bark
would no longer be classed as a food product. Pecan shell flour currently wholesales for $110120/ton FOB at the mill.
Anticipated future trends in the glue extender industry will probably involve a greatly ex panded use of tree barks as fillers. 2 0
as a media in the container nurs
ery plant industry. 10. Manufacture of molded furniture.
While several of these possi bilities are currently or theoreti
cally economically viable, others are at best marginal to unrealistic
inexpensive energy and chemicals was signalled by the new price structure on petroleum imposed by the Arabic petroleum cartel. During this brief period, 1972 to 1975, the price of phenols in
creased from 8 cents per pound to 27 to 33 cents per pound (5). As it turns out, our world supply of
petroleum has been substantially depleted even before the plastics industry has entered its major growth phase.(3). It is, as a conse quence, essential that new sources of chemicals for the plas tics industry be developed and exploited.
The demand for phenol and re lated compounds is great. In 1974, over 18 million tons of syn thetic polymers were produced; of these, 6.6 million tons were Pecan South
derived from phenols(5). An esti mated 7,500,000 pounds of these
phenols couls be readily ex tracted from pecan shells. The value of this raw product at cur rent prices for phenols is between
2 and 2.5 million dollars per year. The phenolic portion of the pecan shell is found principally (approximately 95 per cent) in the packing tissue, which incidentedly is removed as a waste product in the milling operation for lost circulation materials and
glue extenders. In effect, we are
dealing with a waste product of a waste product. Approximately 30 per cent by weight of the shell of for example Stuart pecans
ever indirectly it may be. Per
production-processing-marketing
haps the most pronounced im
R E F E R E N C E S
mediate effect will be in the shell
utilization portion of the pecan industry since exclusive licensing of the patent rights for the ex traction of phenolics and their
1. Anon. 1978. Pecan Marketing: Can we get it together? Pecan South
production into plastics(7) will
T. K . P e r k i n s . 1 9 7 0 . U . S . P a t e n t
5:260.
2. Cleary, J. M., L. R. Kern and
give the licensee a virtually in
3:396.902.
age in the competition for raw
from wood, p. 71-76 in Proc. 8th
3. Deanin, R. D. 1975. Plastics
surmountable economic advant
Cellulose Conf., 1. Wood Chemicals—
product or shells.
A Future Challenge; Applied Poly mer Symp. No. 28, John Wiley and Sons, N. Y. 377 pp.
The future for the utilization
of pecan shells is extremely bright. If current petroleum prices continue to increase, the
4. Goldstein, I. S. 1975. Perspec
tives on production of phenols and
*
is packing tissue of which 25 per
cent by weight is extractable phenolics. This varies somewhat between varieties, however, as *
does the precise amount of phe nolics in the non-packing tissue part of the shell.
Removal of the phenolic ma terial from pecan shells is both vastly cheaper and easier than the production of phenols from other wood products. For ex ample, if one started with wood pulp, the removal of lignin is re quired followed by a relatively expensive hydrogenation or hydrogenolysis process (4,6). This,
i
t
-2.
JLft11
... 0
1
. ■ ■ .
0
00 0
o'o 0
0
'
0
•
0
0^
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c-'ftr 9
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'9
in addition necessitates rather
elaborate facilities requiring a
substantial capital outlay. Final costs are estimated at 15 cents or
more per pound of phenol pro duced from wood pulp. Phenols from pecan shells, on the other
production of a diverse array of other chemicals (e.g. benzene,
hand, can be obtained for only a fraction of the cost (estimated at
nol, etc.) and products from the
1 cent per pound) with little modi fication of the existing equipment in a shell milling operation. In
short, phenols can be produced from pecan shells cheaper than
they can be produced from vir tually any other source, including petroleum! It
is
doubtful
if
these
new
changes in the use of pecan shells will have an immediate or sub stantial
effect
on
the
current
price of pecans at the farm. The shell will still be of minor value
in comparison to the kernel. En hancing the value of any segment of the pecan industry cannot
help but benefit everyone how22
furfural, ethanol, acetone, metha actual shell material will become
economically feasible. The devel opment of this potential will act as a hedge against the unexpected loss of one of our current majoruses of shells.
pecan shells has increased mar-
ke^y in the past few years to the point where this valuable re resource
Conf., 1. Wood Chemicals—A Future
Challenge; Applied Polymer Symp. No. 28, John Wiley and Sons, N. Y. 377 pp.
5. Goldstein, I. S. 1975. Potential for converting wood into plastics. Science 189 (4206):847-852. 6. Goldstein, I. S. 1976. Chemicals and Plastics from Wood. Northern
In conclusion, it is evident that the utilization potential for
newable
phenolic acids from lignin and bark, p. 259-268 in Proc. 8th Cellulose
has
lost
its
status as a "waste product." We are on the verge of the develop ment of a diverse new segment of the pecan industry which will d i r e c t l y o r i n d i r e c t l y b e n e fi t
everyone throughout the entire
Logger and Timber Processor 24 (10)16-17.
7. Kays. S. J. and G. V. OdeU. 1978. U.S. Patent 4,098,765. 8. Lummus, J. L. and B. V. Ran dall. 1968. U.S. Patent 3,375,888. 9. McDermott. J. 1973. Drilling Mud and Fluid Additives. Noyes Data Corp., Park Ridge, N.J. 305 pp.
10. Rogers, W. F. 1963. Composi tion and Properties of Oil Well Drill ing Fluids. Gulf Pub. Co., Houston, 818 pp. Pecan South
