UK Renewable Energy Initiative
Biomass Processing & Conversion
Microbially-Based Biofuels and Bioproducts Research
Faculty from the UK College of Agriculture, in collaboration with other scientists, have been conducting basic research in the area of microbially-based biofuels and bioproducts since 1995. This research effort is based on the premise that structural plant carbohydrates (fibrous biomass) can be used as inexpensive and renewable feedstocks for biologically-mediated conversion processes. Our specific focus has been understanding and enhancing the use of thermophilic and anaerobic bacteria as bio-catalysts in the conversion of fibrous biomass to biofuels and other vendable chemicals. The major research thrusts include: biochemical and molecular characterization of sugar transport in anaerobic thermophiles, evaluation of thermophilic microbial metabolism at high pressure in supercritical solvents, development of solid-state culture techniques involving thermophilic bacteria and fibrous biomass for the production of thermo-stable enzymes, isolation of ethanol-tolerant strains and subsequent characterization of adaptation to ethanol using state-of-the-art proteomic approaches, and characterization of cellular metabolism using metabolomic approaches.
Contact: Herb Strobel (firstname.lastname@example.org), Sue Nokes, Barbara Knutson, and Bert Lynn.
Indirect Thermochemical Conversion of Biomass to Fuels and Chemicals
Like coal, biomass can be converted into fuels and chemicals indirectly by gasification to syngas followed by catalytic conversion to liquid fuels, or directly to a liquid product. Syngas can be generated from many different biomass sources or used in blends with other hydrocarbon fuels using well established gasification technology. This syngas can then be converted to liquid fuels and chemicals via the Fischer-Tropsch (FT) process. The FT process centers on the reaction of hydrogen with carbon monoxide, CO2 or mixtures of these to yield one or more types of carbon compound, e.g., hydrocarbons, alcohols, esters, acids, ketones, aldehydes, etc. The Center for Applied Energy Research operates state-of-the-art FT testing and development laboratories, including stirred reactors, a slurry bubble column reactor and several fixed bed reactors. We are exploring the use of both iron- and cobalt-based catalysts for syngas conversion to paraffin, diesel and jet fuels, as well as separation and upgrading of products.
Similarly, the Consortium for Fossil Fuel Science, a research center based at the University of Kentucky, is bringing together professors and graduate students from the engineering, chemistry, and physics departments of five universities (Kentucky, West Virginia, Pittsburgh, Auburn, and Utah) to conduct a basic research program focused on this problem. The CFFS has been investigating the conversion of coal into clean liquid transportation fuels and hydrogen for many years and has made significant breakthroughs in such areas as catalysis, co-processing of coal with waste materials, FT synthesis of transportation fuels, development of novel technology to produce hydrogen from fossil fuels, and environmental research related to coal utilization. A major part of future research will focus on the development of novel gasification and FT synthesis techniques to co-process coal and biomass into clean liquid transportation fuels that will produce less total CO2 emissions than the same fuels produced from petroleum.
Oils produced by pyrolysis are less viscous, and have higher yields at lower cost when compared to the oils produced by high-pressure liquefaction. Pyrolysis, liquefaction, and solvolysis. In this context, researchers at the Center for Applied Energy Research are investigating a novel liquefaction-extraction method for biomass conversion to crude bio-oil. In initial work, the concept of liquefaction-extraction has been demonstrated for the conversion of white oak into a valuable product suite. The proposed approach aims to utilize biomass on the farm for delayed transport to centralized bio-refineries. Given that biomass is expensive to transport, being able to pre-process and densify the biomass before transport to a centralized bio-refinery will save significant costs and potentially increase rural income.
Contact: Rodney Andrews (email@example.com), Czar Crofcheck, Kunlei Liu, Mark Crocker.
Other work in the area of biomass liquefaction is focused on an innovative biomass fast pyrolysis (BFP). BFP is the thermal decomposition of biomass in an inert atmosphere using high heating rates and short residence times. It has great potential in converting biomass into energy-dense liquids (crude bio-oil). Yields of up to 75% usable liquid products have been reported at mild operating conditions (842ºF-1022ºF, 14.7 psi). The focus of current research is to lower the viscosity and oxygen content of bio-oils, as well as improve thermal stability by developing an integrated catalytic, low-cost and highly-effective process for generating high-quality bio-oil from biomass. Our approach is to use a fast pyrolysis reactor with in-situ catalyst regeneration to promote the usable crude bio-oil production. Up to now, experiments conducted in a cold model reactor showed this novel reactor can be effectively used for catalytic BFP by supplying the unique ability to vary gas/solids residence times, while regenerating the catalyst inline. The future research will focus on the effect of novel de-oxygenation catalysts on liquid product quality and yields, as well as the in-situ catalyst regeneration capacity.
Contact: Kunlei Liu (firstname.lastname@example.org) and Mark Crocker.
Biofuels Upgrading and Bio-oil Stabilization
The crude bio-oils afforded by thermochemical conversion processes such as pyrolysis are chemically complex and are typified by a high oxygen content. The oxygenated compounds present in raw bio-oils impart a number of unwanted characteristics such as thermal instability (reflected in increasing viscosity upon storage), corrosivity and low heating value. This instability is associated with the presence of reactive chemical species, notably aldehydes, ketones, carboxylic acids and guaiacol-type molecules. Upon prolonged storage, condensation reactions involving these functional groups result in the formation of heavier compounds. The quality of bio-oils can be improved by the partial or total elimination of the oxygenated functionalities present. In this context, we are studying new approaches for catalyst-assisted stabilization of crude biomass-derived pyrolysis oils, for the ultimate production of fuels and high value chemicals. This work is performed in collaboration with the UK Department of Biosystems and Agricultural Engineering.
Contact: Czar Crofcheck (email@example.com) or Mark Crocker.
The production of biodiesel from vegetable oil represents another means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance. Commercially, biodiesel is produced from vegetable oils, including rapeseed, sunflower and soybean oil, as well as from animal fats. These oils and fats are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are converted to the respective alkyl esters (with glycerin as a co-product) by base-catalyzed transesterification with short chain alcohols. Commercially homogeneous base catalysts are used, such as NaOH. However, solid base catalysts are attractive on the basis that their use should (i) result in a reduction in the amount of soaps and salts that need to be removed (thereby improving the quality of the glycerol co-product), and (ii) enable biodiesel production to be more readily performed as a continuous process. We are therefore studying the use of a variety solid base catalysts for this purpose, such as layered double hydroxides.
Contact: Mark Crocker (firstname.lastname@example.org) or Czar Crofcheck.
Other work in the area of biodiesel production is focused on utilization of glycerin byproducts in plant heat and power operations. Novel burner designs are being developed to allow direct utilization of glycerin for the production of heat and electricity on site in more efficient manner than is currently available.
Contact: Rodney Andrews (email@example.com) or Kunlei Lui.
Producer Gas from Biomass Gasification
An area of biomass utilization we would like to explore is the use of producer gas derived from biomass gasification as supplemental fuel for landfill gas-fired power generation sets. Along with this, there is a great deal of interest from the electric power industry in the use of producer gas for use in coal-fired power plants for reburn fuel to reduce NOx emissions.
Contact: Kunlei Liu (firstname.lastname@example.org) or Jim Neathery.
Production of Biomass Briquettes as an Alternative Fuel Source
The numerous industrial and process heat boilers found at pulp mills, food plants, and other industrial sites are relatively small, often less than 25 MW units, which are essentially unregulated. The substitution of CO2-neutral biomass represents an attractive approach to decreasing the release of air pollutants such as SOx, NOx, and mercury, as well as reducing fossil energy consumption in this often overlooked, but significant industrial sector. One promising approach is to substitute a briquetted fuel manufactured from the agricultural or wood waste that is generated at or near the industrial site where the fuel is to be used, thereby significantly reducing prohibitive transportation costs. In addition to being sustainable and cleaner burning, such a briquetted biofuel can be more economically stored, conveyed, and processed in existing equipment. Further, the development of low-cost, briquetting binders from agricultural-processing residues would create a market for these low-value byproducts while decreasing the energy required for the briquetting process. The overall goal of the project is to produce a premium, durable briquetted biomass fuel from agricultural and wood wastes that is an attractive alternative energy source for coal-fired boilers. Specific objectives include: investigate corn stover, fescue, wheat straw, switch grass, and wood waste as a briquetted-fuel source; assess the performance of inexpensive binders available from farms and agricultural-processing facilities (e.g., poultry litter, gum residue from soybean oil extraction, and distillers grain from ethanol production), and estimate the economics and net energy balance for briquetted biomass fuels.
Contact: Mike Montross (email@example.com), Darrell Taulbee, Scott Shearer or Rodney Andrews.
Production of a Premium Fuel from Timber and Coal Wastes
The University of Kentucky has been continuously active in binder and briquetting research for the past decade. The primary goal of this effort is the development of technologies that can economically move biomass residues and fine waste coal from the areas where it is available in abundance, to the utility site, where it can be used to generate power. Kentucky is the largest producer of timber products east of the Mississippi. We also discard about 3 million tons of fine coal each year and have in excess of 500 million tons of additional waste coal stored in impoundments and waste piles around the state, often in close proximity to the major sources of timber production. However, utilization of these significant resources is hindered by problems associated with storage, handling, and processing as well as capital expenditures required to utilize these non-conventional fuels. One promising approach for addressing the marketing issues posed by fine coal and biomass is to co-briquette these materials to produce a high-quality fuel that can be transported as dense, free-flowing solids, and then stored, crushed, and conveyed in existing equipment at the utility site. In a prior study, waste coal was cleaned, combined with waste sawdust, and co-briquetted to produce a premium quality, high Btu fuel. An economic analysis indicated that fine coal/sawdust briquettes can be produced for less ~$17/ton which compares favorably to a comparable-quality steam coal used to generate electricity of ~$45-$50/ton. Work in this area is ongoing with a continued emphasis on development of cost effective binders and an expanded focus on co-briquetting coal with agricultural residues.
Contact: Rick Honaker (firstname.lastname@example.org) and Darrell Taulbee.