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Journal of Scientific & Industrial Research
Vol. 64, November 2005, pp. 854-857
Biodiesel: Current perspectives and future
M A Hanna1, Loren Isom1 and John Campbell2
1
University of Nebraska, Industrial Agricultural Products Center, 209 LW Chase Hall, Lincoln, NE 68583-0730
2
Ag Processing Inc. (AGP), 12700 West Dodge Road, Omaha, NE 68154, USA
Biodiesel, a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fat (or
mixtures thereof), is produced by transesterification with glycerol being produced as a co-product. Worldwide, 1 billion ton
of diesel fuel are consumed annually. The total feedstocks available for biodiesel production are 115 million tons. This
represents less than 12% of diesel fuel use. The opportunities for the future for biodiesel include improvements in the
conversion technology, which appears promising, and expanding the amount of available feedstock through various plans to
increase oil yields or oilseed production.
Keywords: Animal fat, Biodiesel, Transesterification, Vegetable oil
IPC Code: C11C 3/04
Introduction Conversion Technologies
Biodiesel1 comprises mono-alkyl esters of long Transesterification (alcoholysis), most widely
chain fatty acids derived from vegetable oils or accepted and almost exclusively used technology for
animal fat (or mixtures thereof). When biodiesel is the conversion of natural fats and oils to biodiesel, is
blended with diesel, the designation indicates the the reaction of a fat or oil with an alcohol to form
percentage of it in the blend, e.g, B2 [2% biodiesel, esters and glycerol. Fat or oil will depend on what is
98% diesel (v/v)] and B100 (pure biodiesel). available in the region of the biodiesel production
Worldwide, the feedstocks for biodiesel production in facility, their respective prices and the flexibility of
greatest supply are soybean oil, palm oil and rapeseed processing facility to handle multiple feedstocks.
oil (Fig. 1). When alternative fuels are considered, Alcohol is methanol because it is low cost, easily
their energy contents and conversion efficiencies are recyclable and toxic. Because the reaction is
of particular interest, even though petroleum based reversible3, excess alcohol is used to shift the
fuels require more energy to produce than what they equilibrium to the products side. Typical mole ratios
contain. Biodiesel has tremendous potential in this of alcohol to triglycerides range from 5.25:1 to 6.1:1.
respect. A life cycle analysis2 concluded that biodiesel A catalyst is usually used to improve the rate of
yields 3.2 units of fuel product energy for every unit reaction and yield. The amount (0.1-0.5 % v/v) and
of fossil fuel used to produce it; other projections go type (base vs acid) of catalyst used depends on the
as high as 3.6. quality [free fatty acid (FFA) and moisture] of
If biodiesel is to be accepted as a fuel for diesel triglycerides.
(compression ignition) engines, it will have to be
produced and handled in such a way so that the
variations in it’s properties and performance
characteristics will be less than or equal to what the
consumer is used to with (petroleum based) diesel
fuel. A single, widely accepted, standard for biodiesel
is not available. Instead, the standard ASTM D6751-
02 was developed for the USA. and CEN 14214 for
the European Union (EU).
______________
*Author for correspondence
E-mail: mhanna1@unl.edu; lisom@unl.edu;
jcampbell@agp.com Fig. 1Worldwide feedstocks for biodiesel production
HANNA et al: BIODIESEL: CURRENT PERSPECTIVES AND FUTURE 855
Even though conversion efficiencies are good with Reducing the combustion temperature5 can reduce
conventional transesterification and feedstock costs the increased NOx emissions resulting from biodiesel
represent 65 to 75 percent of the cost of producing fuel or biodiesel fuel blends. Vaporized injection,
biodiesel, there are significant research interests in rather than spray injection, better distributes the fuel
improving the process and thereby the economics of and avoids hotter areas during combustion that
biodiesel production. These interests include the contribute to NOx generation. Controlling the timing
development and evaluation of heterogeneous catalyst of engine using injection sensors that determine the
systems, the use of ethanol, in situ transesterification, concentration of biodiesel in the fuel and adjusting the
reducing NOx emissions, and adding value to the timing accordingly can reduce the combustion
coproducts (oilseed meals/presscakes and glycerol). temperature. Exhaust gas recirculation, which also
Additionally, efforts in the area of standardization of results in a lower combustion temperature; and NOx
biodiesel will enhance its marketability. traps similar to catalytic converters that store NOx
Heterogeneous catalyst systems have major and which are regenerated by injecting more fuel in
advantages over the homogeneous catalysts currently the cylinder or upstream from the trap to convert NOx
used in biodiesel production. The use of to CO2 and unreactive nitrogen. Exhaust after
heterogeneous catalysts will eliminate the need for a treatment combined with engine management controls
water wash to remove excess catalyst. This will appears to provide the best NOx reduction at this
reduce both the capital cost of a plant and the time.
operating cost. It also is perceived that FFAs present Adding value to the coproducts of biodiesel
in feedstocks, particularly in yellow and brown production, or at least maintaining their current
greases, could be converted concurrently to alcohol values, will enhance the economic viability of
esters rather than being separated out and used for biodiesel. The oilseed meals/press cakes are used
some other, lower value purpose. Yet another predominately as animal feeds. Their values as feeds
potential advantage is that a higher quality glycerol or feed supplements are functions of their protein
may be obtained. content and quality, and the need for additional
Because ethanol is produced in large quantities processing to inactivate or remove anti-growth factors
from readily renewable resources and because it is such as trypsin inhibitors and glucosinolates.
more environment-friendly than methanol, there is Opportunities for adding value to the meals include
interest in using it in biodiesel production. From a industrial uses for the proteins, such as adhesives, and
reaction standpoint, ethanol will work fine albeit the the extraction of higher value materials, such as
reaction may be slower. The primary problem arises policosanols. Glycerol, a coproduct of biodiesel
in the recycling of the excess alcohol. Around twice production, may be used to produce 1,4 propanediol, a
as much anhydrous alcohol is used in the process as commodity chemical and a precursor for many
what is required stoichiometrically. The reclaimed products.
ethanol will not be anhydrous with simple distillation A universally accepted standard for biodiesel, and
as with methanol and there will be the issue of adherence to the standard, by all producers will
breaking the azeotrope before it can be reused. enhance the acceptability of biodiesel and its blends,
both by the blenders and the consumers. The primary
In situ transesterification4, a method that utilizes difference in the current USA and EU standards is the
the original agricultural feedstock as the source of way stability and iodine number are handled (ASTM
triglycerides for direct transesterification, eliminate D6751-02 and CEN 14214). This difference is
the hexane extraction process and works with traceable to soybean oil being the oil of preference in
virtually any lipid bearing material. In this process, the USA as opposed to rapeseed oil in the EU.
soybeans are dehulled, cracked, rolled into flakes,
dried to remove moisture and incubated in a solution Biodiesel Production and Use
of methanol and sodium hydroxide to yield fatty acid Global Scenario
methyl esters (95-100 %). Similar research has been The 1.0 billion ton of diesel fuel used annually
conducted with other feedstocks including distillers worldwide or even the 188 million tons used annually
dried grains with solubles from ethanol production in the USA6 dwarfs the current and future production
and meat and bone meal from animal slaughter and capabilities of the vegetable oil and animal fat
rendering. industry. Hence, petroleum based hydrocarbons will
856 J SCI IND RES VOL 64 NOVEMBER 2005
continue to be the workhorse for diesel engines. which is less than 0.6 percent of the diesel fuel used
Biodiesel use has the greatest penetration in the EU7 in the USA.
with an estimated 1.9 million tons having been used In the USA, both vegetable oils and animal fats are
in 2004. The use of biodiesel in the USA1 pales in imported and exported. If biodiesel demand exceeds
comparison, with an estimated 86 thousand ton used the estimated demand benchmark of 450 to 900
in 2003 and 120 thousand tons used in 2004. thousand tons, domestic to foreign fat and oil spreads
Production capacity is expanding rapidly in the USA, would widen and exports would decrease, imports
with an estimated plant capacity of 770 thousand tons would increase or both. Some USA based
and considering current and planned facilities, econometrics were used to predict price impacts from
production capacity could exceed 1.5 million tons by a demand shock. Assuming petroleum diesel fuel
20078. Vegetable oil feedstocks, worldwide, are stays at historically high prices of around $0.32 US/l
estimated to be 100 million tons9. Currently, rapeseed (rack untaxed) and that soybean oil is $0.51 US/kg,
oil is the feedstock of choice for biodiesel production approx 300 thousand tons of soybean oil demand
in the EU, soybean oil is the feedstock of choice in would raise the price of soybean oil $0.07 US/kg and
the USA, and the use of palm oil for biodiesel 680 thousand tons would raise it $0.14 US/kg. This
production is growing in Asia. A total for animal fats, would cause B2 blends to move from a slight discount
worldwide, is estimated at 15 million tons10. The to diesel to a premium between 300 and 680 thousand
vegetable oil feedstocks, if converted to biodiesel by tons of use. As a result, at current diesel fuel prices,
transesterification, and assuming roughly a volume biodiesel can only pull about 300 thousand tons from
per volume conversion rate, would supplant only domestic soybean oil supplies before B2 blends move
10 percent of diesel used in the world. Using the total to a premium over diesel. After that, either B2 must
animal fats, and assuming same conversion efficiency be sold at a premium or trade flows will be impacted
as for vegetable oils, equivalent biodiesel production to keep feedstock prices in check11.
would amount to an additional 1.5 percent of the
diesel use in the world. Future Prospects
Future raw material availability for biodiesel
USA Scene production, worldwide, is significant. Additional
Soybean oil carryover in the USA has been sources include expanded oilseed production, higher
between 450 to 900 thousand tons, of which only 225 oil content varieties, and substitution of higher oil
to 450 thousand tons (< 0.3% of total diesel fuel use content crops. In the USA, it is estimated that roughly
in the USA) can be diverted to biodiesel industry. expanding oilseed production by releasing productive
Other edible oils (corn, cotton, sunflower), which land currently in government set aside programs 4
account for around 1.6 million tons of total million ha and switching from lower value small
consumption, are typically higher priced than soy and export grains, 8 million ha could produce additional
unlikely to be used for biodiesel purposes. However, vegetable oil feedstocks of 2.1 million and 4.2 million
450 thousand tons of soybean oil represents 5 percent tons. If the average oil yield from soybeans would
of total domestic soybean oil use and most of the improve to 20 percent versus the current 18 percent,
current carryover stocks. Animal fats and waste which has been proven with several improved
greases are consumed for use in soap, food, feed, varieties, an additional 800 thousand tons of vegetable
industrial and export markets. The historic price oil would be available, or if future improvements
discount between these feedstocks and soybean oil could increase oil yields to an average of 22 percent
has varied from 25-75 percent. In 2003, the total US oil, 1.60 million tons would be available. If oil
tallow and grease production was 3.9 million tons. At demand outpaces protein demand, soybean production
the right price and assuming no technical barriers, a could be replaced with higher yielding oil crops such
significant portion of these feedstocks, say 450 as sunflower and canola, which produce approx
thousand tons, could be bid away from their current 100 l/ha more oil than soybeans. Assuming soybean
uses. It is expected that animal fats would be the production at 29 million ha12 and a 20 percent
feedstock of choice as long as it is priced below soy conversion to higher yielding oil crops an additional
and biodiesel demand rises. In summary, the total 2.6 million tons would be available. Overall,
available feedstocks in the USA that can be readily conversion of all existing and potential feedstocks in
converted to biodiesel are 450 to 900 thousand tons, the USA will not generate more than 12 percent of the
HANNA et al: BIODIESEL: CURRENT PERSPECTIVES AND FUTURE 857
diesel demand. Therefore, biodiesel will be consumed Conversion technologies will continue to improve and
primarily in niche markets: 20% biodiesel blends for will allow biodiesel production to remain competitive
emission benefits and 5% or less blends as a fuel as government incentives are phased out.
additive for lubricity benefits in ultra low sulfur diesel
fuel11.
References
1 National Biodiesel Board, 2005, http://www.nbb.org.
Conclusions 2 Sheehan J, Camobreco V, Duffield J, Graboski M &
The opportunities for expanded biodiesel Shapouri H, An overview of biodiesel and petroleum diesel
life cycles, NREL/YP-580-24772, 1998, NREL, Golden, CO.
production are bright considering the high demand for 3 Ma F, & Hanna M A, Biodiesel production: A review, Biores
petroleum products in both industrialized and Technol, 70 (1999) 1-15.
developing regions of the world. As a result, the 4 Kotrba R, The in situ method, Biodiesel Mag, June 2005.
increased awareness of the negative environmental 5 Kotrba R, Knocking out NOx, Biodiesel Mag, June 2005.
factors associated with petroleum fuels and a desire to 6 USEIA, World Apparent Consumption of Refined Petroleum
Products-2001, International Energy Annual 2002 (United
move to renewable fuels, biodiesel production is States Energy Information Administration, Washinton)
growing significantly. However, it represents only a http://www.eia.doe.gov/pub/international/iea2002/table35.
small fraction of the current diesel fuel demands. xls.
Even as biodiesel production and available feedstocks 7 European Biodiesel Board, 2005, http://www.ebb-eu.org.
8 Bocovsky D & Worgetter M, Report on the National
expand, that growth will be challenged to keep pace Biodiesel Conference and Expo 2005,
with the growing demand for renewable or diesel fuel. http://www.bioenergy.org.nz/documents/National%20Biodies
Biodiesel feedstock availability, the price, and the el%20Conference.pdf .
resulting by-products, combined with government 9 Oilseeds: World Markets and Trade, United States
incentives based on economic or environmental Department of Agriculture–Foreign Agricultural Service,
Circular Series FOP5-05, May 2005.
issues, ultimately will determine the competitiveness 10 Rossell B, Oils and Fats Vol 2: Animal Carcass Fats,
of biodiesel as a direct substitute for petroleum diesel. Leatherhead Food International, 2001,
It is anticipated that biodiesel will drive the industrial http://www.leatherheadfood.com/lfi/pdf/animalcar.pdf
applications for vegetable oils and animal fats but will Campbell J, Nat Biodiesel Board Annu Meet,
http://www.soygold.com/news/NBB Speech.pdf.
not displace food applications which will continue to 11 World Agricultural Production, United States Department of
lead vegetable oil price for most desirable oils, while Agriculture–Foreign Agricultural Service, Circular Series
lower grade oils will become industrial feedstock. WAP 05-05, May 2005.
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