Bioenergy Research and Development at the University of Arkansas
Charles West1, Michael Popp2, D. Julie Carrier3, Ed Clausen4, Andrew Proctor5, Robert Bacon1
Departments of 1Crop, Soil and Environmental Sciences, 2Agricultural Economics and
Agribusiness, 3Biological and Agricultural Engineering, 4Ralph Martin Dept. of Chemical
Engineering, and 5Food Science.
Introduction
The University of Arkansas is the primary Land Grant institution in Arkansas, and as
such is taking the lead in cultivating the state’s biofuel production and refining capabilities. The
UA Division of Agriculture and the College of Engineering, through their research and education
missions, are devoting efforts ranging from field production of biofeedstocks to refining valueadded byproducts to innovative conversion technologies for biofuels. This report summarizes
the current strengths and planned thrusts of the University to help launch Arkansas into a major
role in bioenergy production. Some paragraphs refer to specific research projects, followed by
names and email addresses of corresponding researchers.
Geography and Industry
Arkansas comprises 7 million acres of cultivated annual cropland, 6 million acres of
perennial grassland, and 18 million acres of forests. As in other southeastern states, agriculture
and forestry are very large, high-value industries in Arkansas. The state’s generally abundant
rainfall and conducive soils allow relatively low-cost production of plant biomass. Arkansas lies
along major river barge and truck routes and possesses extensive agricultural and forestry
infrastructure, thus positioning this state to flexibly adapt to alterative crop production and
biorefining. Much feedstock material already exists in the form of oilseed crops (e.g. soybean),
which can immediately enter the biodiesel manufacturing stream. Furthermore, crop (e.g. rice
hulls) and wood product residues (e.g. sawdust and shavings) are already used in combustion to
power the rice, paper, and wood processing industries.
Abundant, potentially useful feedstocks exist as unharvested forest residue, cereal straw,
hay, and animal manures. Several lignocellulosic energy crops are adapted to Arkansas, such as
switchgrass and short-rotation tree crops; however, little is known of their site adaptations, yield
potentials, and economics of production. Information is also lacking on the long-term effects of
off-land removal of crop and forest residues on soil quality, water quality and quantity, and
wildlife habitat. Because of such diverse geography, no single alternative energy crop or
production system will emerge in Arkansas, but rather several approaches will allow for the most
efficient use of spatially and seasonally available renewable energy resources. Consistent with
the ideals of national energy independence, rural economic development, and environmental
quality improvement, the University of Arkansas emphasizes long term sustainability in its
approach to bioenergy development.
Feedstock Potentials
Annual crops. Ethanol production from corn grain does not have favorable economic
potential as a biofuel in Arkansas because of low acreage and high energy inputs in the form of
nitrogen fertilizer and irrigation. The biodiesel industry, however, is growing rapidly, with
several existing or planned refineries in the eastern Mississippi Delta area to handle the oilseed
crops, mainly soybean, and possibilities with cottonseed and rice bran. Soybean is Arkansas'
largest grain crop, but insufficient crushing facilities currently limits availability of oil feedstock.
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Also, high yields cannot be attained without irrigation on most soils. Canola is a crop with
excellent potential because, as a winter annual, it can fit into rotations with summer crops, thus
enhancing annual per-acre energy yield. Its oil concentration is twice that of soybean ($40% vs.
20%), and needs no irrigation. Sunflower has potential as a low-water requiring summer crop,
and therefore will be evaluated for oil yield, net energy ratio, adaptability, and economic
potential. Sweet sorghum has potential as a water-frugal annual crop, and will be investigated
for fermentable sugar and cellulose yields and ability to take up excess soil phosphorus in
manure-treated fields. [Contacts: Robert Bacon, rbacon@uark.edu; Michael Popp,
mpopp@uark.edu]
Lignocellulosic feedstocks. Switchgrass has been touted in many states as a desirable
perennial herbaceous feedstock crop because of its adaptation across widely different soil types
and low requirements for fertilizer, pesticide, and water inputs. It is native to Arkansas, and field
trials have shown typical annual biomass dry matter yields of 6-7 tons/acre with no irrigation and
receiving only 50-60 lbs/acre of nitrogen. Its net energy ratio for ethanol production exceeds 3.3,
compared with 1.2-1.4 for corn. Costs of fermentation to ethanol need to decline substantially
before a refining industry develops; however, switchgrass shows high potential as a future
feedstock. Drawbacks to adoption would include 1) low flexibility in land use since it is a slowestablishing, long-lived perennial, 2) moderate difficulty in establishment, and 3) substantial
transportation costs for shipping a low-density material to refineries. In Arkansas, switchgrass
has excellent potential as an alternative crop on the intensively cropped soils of the lowland
Mississippi Delta region to restore soil organic matter, structure, and permeability. It also
provides an alternative grass in the upland areas of northern and western Arkansas now typified
by hay and pasture grasses.
Research is planned to evaluate the yield potential of improved switchgrass varieties
across Arkansas environments, fine-tune weed control tactics, and improve the success of no-till
establishment in existing grasslands. The ALMANAC model (Kiniry et al. 2005. Biomass and
Bioenergy 29:419-425) will be used to develop yield prediction capabilities based on soil
characteristics, fertilizer input, and weather variables. Switchgrass will also be evaluated as a
dual purpose biomass crop and riparian buffer strip for intercepting sediment and nutrients in
runoff from manure-amended fields. Hybrid miscanthus, widely used in Europe as a biomass
crop, will also be evaluated for yield potential. [Contact Chuck West, cwest@uark.edu]
Forest products. Research is underway at the University of Arkansas-Monticello, School
of Forestry, on the economics and logistics of gathering and transporting residue from pine
plantations harvested for lumber and pulp. While biomass yields are large, bulkiness and
distance from processing facilities currently limit the economic viability of forest residue
utilization. Innovative packaging techniques show potential for lowering costs. Research is
planned on testing the biomass yield, effects on soil nutrient cycling, wildlife populations, and
economics of dedicated woody energy crops such as hybrid poplar, sycamore, cottonwood, and
willow in southeast Arkansas. [Contact Matthew Pelkki, pelkki@uamont.edu]
Animal byproducts. A very large poultry industry produces fat as a byproduct from meat
processing, which is a potential feedstock for biodiesel. Poultry and swine manures offer
potential as sources of dry combustible material or liquid substrate for methane production. As
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with all low-value, bulky materials, transportation cost of the manures is a limiting factor to
exploitation of these potential feedstocks.
Economics. Inasmuch as the dawn of the bioenergy paradigm stimulates optimism in a
newly vibrant agricultural economy, many economic questions arise, not least of which concern
the effects of diverting agricultural products from feed and food to energy use. Grain markets
are already reacting to rising ethanol demand by the increase in grain prices, which raises the
cost of producing items from tortillas in Mexico to milk in Vermont. The success of Arkansas in
developing a viable bioenergy industry depends on the ability to sustainably maximize returns to
land, labor and capital in a climate of increasing costs of fuel, fertilizer, pesticides and irrigation.
Research is underway on determining costs of producing energy units from switchgrass, oilseed
crops, crop residues, and the system impact of new crop rotations that favor biofeedstock
production. For example, the breakeven price for switchgrass production in Arkansas over a 12year stand life and stored at the field's edge in large round bales is predicted to be $24.66 per dry
ton. Long stand life and high biomass yield are critical to lowering costs of production. Round
baling and direct-chopping biomass into modules are being compared for cost efficiency for
harvest, storage and transport. The latter is more labor demanding in the field, but has lower
transportation and processing costs for the refinery. High-density packaging, low moisture
content, and short transport distance are key to lowering biorefinery breakeven costs. [Contact
Michael Popp, mpopp@uark.edu]
Value-Added Byproducts
Extraction of high value chemicals. The economics of converting cellulosic biomass to
energy might be significantly enhanced if high value co-products are extracted from the biomass
prior to energy production. Research in this area at the University of Arkansas has concentrated
on extracting nutraceuticals from cellulosic biomass including the extraction of hyperoside,
quercitrin and saponins from mimosa (Albizia julibrissin); silymarins from milk thistle (Silybum
marianum); and robinin from kudzu (Pueraria lobata). Organic solvents and subcritical water
have been used as extraction solvents. Many of the phytochemicals extracted from these plants
have been shown to inhibit the oxidation of low density lipoprotein, which is an important step in
the development of atherosclerosis in humans. At the University of Arkansas we are extracting
these phytochemicals with a subcritical water extraction process. By extracting with subcritical
water, this opens the possibility of coupling the phytochemical extraction step directly to that of
feedstock pretreatment.[Contact Julie Carrier, carrier@uark.edu; Ed Clausen, eclause@uark.edu]
Rice hulls. Research has been conducted on the use of rice hull amorphous silica residue
and carbon after combustion for energy production to produce sodium silicate solution and
activated carbon. This has now been brought to commercial production, and we are assisting
industry in optimizing product quality. The University of Arkansas has produced rice hull silica
based products such as silica gel, silicates and xerogels from amorphous rice hull silica, and we
are looking to further develop new innovative products from rice hull ash. [Contact Andrew
Proctor, aproctor@uark.edu]
Conversion Technologies
Subcritical water as a biomass pretreatment step. Feedstocks that are contemplated for
cellulosic ethanol production include woody and herbaceous energy crops, agricultural and
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forestry residues, and municipal solid wastes. No matter which feedstock is utilized, sugars must
first be released from the biomass in order to proceed to ethanol production. This sugar release
step rests on the design of pretreatment operations that are effectively coupled to enzymatic
hydrolysis. Pretreatment of the biomass is imperative to maximize the activity of cellulose,
hemicellulose and lignin hydrolyzing enzymes. Using corn stover, Wyman et al. (2005,
Bioresource Technology 96:2026-2032) determined that each of seven pretreatment technologies
had a specific sugar release pattern. Mosier et al. (2006, Bioresource Technology 96:1986-1993)
was successful in obtaining the release of hemicellulose with subcritical water (190°C for 15 min
using 16% corn stover residue slurry). Therefore, the use of subcritical water can be
contemplated as an effective way to pretreat the biomass before enzymatic hydrolysis. In
addition, the use of a subcritical water pretreatment can be easily coupled to that of a subcritical
water phytochemical extraction step. At the University of Arkansas, we are interested in
understanding the effect of subcritical water pretreatment and its contribution to facilitating the
activity of cellulose, hemicellulose and lignin hydrolyzing enzyme activity. [Contact Danielle
Julie Carrier, carrier@uark.edu; Ed Clausen, eclause@uark.edu]
Hydrogen production from biomass by gasification/fermentation. Biomass may be
converted to synthesis gas (a mixture of carbon monoxide, hydrogen and carbon dioxide) by
thermal gasification using air, oxygen or steam as the gasifying medium. The hydrogen content
of the synthesis gas may be increased by fermentation using the water gas shift reaction:
CO + H2O → H2 + CO2
Bacillus smithii is a non-photosynthetic bacterium which carries out the water gas shift
fermentation at 50°C. Continuous bioreactor studies are being carried out at the University of
Arkansas aimed at developing the best companion fermentation system for producing hydrogen
by gasification/fermentation. [Contact Danielle Julie Carrier, carrier@uark.edu; Ed Clausen,
eclause@uark.edu]
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