Technologies are described to facilitate the conversion from fossil fuels to biomass-based power — including anaerobic digestion, fermentation and distillation, gasification, biodiesel conversion and hybrid systems. Part II.
BioCycle September 2006, Vol. 47, No. 9, p. 62
As discussed in Part I in last month’s BioCycle, there is at least 74 times more raw energy in locally available biomass in the Reynolds, Indiana area than the town uses each year. The state’s governor, Mitch Daniels, decided to use Reynolds as an example of how a community could convert from a reliance on fossil fuels to biomass-based power. While feedstocks are highly variable and outputs can change, the key to economic success is to manage the biomass energy products and coproducts through the appropriate mix of conversion technologies. The BioTown, USA Sourcebook, on which thesetwo articles are based, explains thermal and biological biomass conversion technologies featuring anaerobic digestion, fermentation and distillation, gasification, pyrolysis, chemical conversion of biodiesel, and finally hybrid systems (see sidebar).
Because solid biomass feedstocks are less dense than coal, they require a greater volume to achieve the same level of power; thus transportation costs and storage requirements are greater for biomass fuels. The Coaltec Energy USA gasifier required to power a 1.5 MW generator, for example, requires two tons of biomass per hour, while the larger Alliant Energy 726 MW Chariton Valley power plant, now preparing to cofire with switchgrass, has cofired at rates as high as 16.8 tons per hour.
The fluid nature of liquid biomass feedstocks can be utilized in conveyance, but when these materials must be hauled more than a mile or two, the liquid becomes freight. Most liquid feedstocks need to have a biomass conversion facility near the site where material is produced.
Part II of this article summarizes the various biomass-to-energy technologies reviewed in the Sourcebook. As part of the review, technologies and systems were analyzed for current stages of development and/or commercialization. Table 1 indicates the business stage of development (pilot- or commercial-scale) for the technologies discussed. It should be noted that in the six months since the Sourcebook was released, there already have been numerous announcements about new ethanol and biodiesel plants. While the bioenergy industry is moving at a rapid pace, the fundamental processes and technologies involved in conversion of biomass to bioenergy remains the same.
Burning organic material in the presence of oxygen, combustion technologies include wood stoves, fireplaces and industrial burners.
Small-scale furnaces (heat) – Demand for residential corn-burning stoves and furnaces is much higher than the supply. Stoves and furnaces cost between $2,800 and $3,200; sales of corn stoves have doubled every year for the last five years with 30,000 wood stoves purchased in 2005.
Dennis Buffington, an agricultural engineer at Pennsylvania State University, maintains a website with very useful information regarding burning shelled corn in furnaces and stoves (http://energy.cas. psu.edu/burncorn/shellcorn.html). At $1.85/bushel, one ton of corn ($66) is about the same price as one ton of coal. However, on a BTU energy basis, it takes 1.7 tons of corn to replace one ton of hard coal. Corn burns much cleaner and produces less ash/cinders than burning firewood or coal.
Most corn stoves and furnaces also burn pelleted fuels. Warming Trends, Inc. lists eight pellet manufacturers, the foundation material used in the pellets, and the heating value range in BTUs for each brand of pellet (http://www.warmingtrendsstoves.com/fuel.html). Price of pellets, as posted on their site, ranges from $109/ton to $160/ton.
Large-scale biomass power plant (heat & electricity) – Two recent commercial power plants that are either under construction or consideration are a 55 MW Fibrominn power plant and a 20 MW Rahr Malting power plant. Both are located in Minnesota.
When construction is finished on the 55 MW Fibrominn Benson, Minnesota power plant, it will be powered by 700,000 tons/year of turkey litter. This technology has been commercialized in Great Britain by Fibrowatt, the parent company of Fibrominn. Fibrowatt currently operates four poultry manure-powered plants with a combined generating capacity of 99 MW. When completed, the Fibrominn plant will be the largest plant in operation using the Fibrowatt technologies.
Minnesota has a large turkey industry and lots of turkey litter (manure plus bedding) to manage. The litter will be delivered to the Fibrominn plant in tightly covered trucks and unloaded in negative pressure buildings to prevent the escape of odors. The furnace will operate at over 1500ºF, heating water in a boiler to produce steam. The steam drives a turbine and generator to produce electricity. Fibrowatt in the United Kingdom has converted more than three million tons of poultry litter to electricity.
Rahr Malting, a malting plant located in Shakopee, Minnesota, conducted a feasibility study of generating heat and electricity from biomass (primarily switchgrass) in 2001. Total cost of the project was estimated at $32 million and included technologies for direct combustion and gasification. By producing switchgrass in Minnesota on marginal land, the project estimated 3,000 to 5,000 acres of land could be located within 50 miles of the plant. The study used target prices for switchgrass delivered at $30/ton and $40/ton to determine economic feasibility. Air emissions reported in the Rahr Malting feasibility study indicated the biomass fuels were superior on SO2, NOX and CO2.
Cogeneration Power Plants – The Department of Energy (DOE), the Tennessee Valley Authority (TVA), the Electric Power Research Institute (EPRI) and the electric utility industry have been looking at burning biomass with coal since 2000. Cofiring biomass with coal requires special coal handling procedures. Northern Indiana Public Service Company (NIPSCO) has had two of the nine power plants involved in these cofiring tests, burning between five to 10 percent biomass. DOE cogeneration priorities were shifted to gasification in 2003. The research has shown that there is a slight decrease in efficiency by cofiring with biomass, but there are significant reductions in nitrogen oxides (NOX), sulfur dioxide (SO2), and carbon dioxide emissions (CO2). Similar air emission reductions were found in the Rahr Malting feasibility study above.
The 725 MW Alliant Energy Chariton Valley power plant has been running tests examining the feasibility of cofiring switchgrass with coal since 2000. Much of its work has been focused on developing an efficient system to move 1,000 pound, square bales of switchgrass from many different fields into the power plant burner. A system has been developed to off-load semitrucks very rapidly. The handling system also debales the twine, shreds and grinds the switchgrass and meters it into the burner. The company also has been running emissions tests and monitoring slag buildup of the burner.
Gasification is the liberation of volatile, gaseous compounds at high temperatures with the controlled restriction of oxygen. This creates a flammable producer gas ready to combust. One of the challenges with a gasifier is that this producer gas does not substitute directly for natural gas. In addition, the composition of the gas varies with the feedstock entering the gasifier.
Gasifiers produce three products: heat, producer gas and ash. To operate as an efficient system, beneficial uses need to be developed for all three products. Many processes require heat or drying. If the heat cannot be used directly by the gasifier operators, there may be opportunities to market it to a nearby school or industry. The ash contains phosphorus and may be developed into a soil amendment or plant fertilizer.
Producer gas contains many valuable organic compounds that can be used to produce power directly, or can be used to develop further refined fuels and products. It is important to understand that to fully utilize the gasifier producer gas for any kind of power generation, additional equipment is necessary.
Benefits and Liabilities of Gasification – The U.S. DOE rates gasifiers as very good at converting the lignin (25 to 30 percent of the biomass) into useful products (www.eere.energy.gov/biomass/
large_scale_gasification.html). Lignin has an energy value, but it is often difficult to separate from simple sugars for efficient recovery. Gasification converts most biomass feedstocks into a clean producer/synthesis gas.
Another significant benefit is the low air emissions relative to coal. Data emissions presented on the Rahr Malting plant in Minnesota showed significant reductions over coal and diesel fuel. In addition, research conducted in Texas found that gasifying small amounts of beef feedlot manure (seven to 15 percent) with coal reduced the nitrous oxide emissions levels with potential to reduce energy costs of delivering less coal to the power plant. Other benefits of gasifiers are: Reduction of waste volume by over 90 percent, reducing it down to ash content; Gasifiers generally have few moving parts; and Gasifiers design and construction is best based on the characteristic of the specific biomass fuel to be used.
The University of Minnesota just recently purchased gasifiers to be installed at its Morris, UMN Experiment Station. The university will be feeding corn stover, corn earlage, wheat straw, soybean residue, native grasses and hybrid poplar. In addition, it plans to develop best management practices and templates for pricing structures and contracts and environmental permitting. Operation of the gasifiers will provide power to the University of Minnesota Morris facilities and allow research in biomass collection and storage.
The DOE report also lists the technical barriers for gasification:
Feedstock processing and handling: Processing and handling of all biomass feedstocks can be a challenge. Various gasifiers feed some kinds of biomass materials in more easily than others, so switching feedstocks also may have limitations.
Producer/syngas cleanup and conditioning: The gaseous compounds leaving the gasifier do not meet standards for other more conventional fuels, like natural gas, and must be further treated or cleaned up to meet those standards. Cleanup and conditioning are required to remove tar, particulates, alkali, ammonia, chlorine, and sulfur.
Gas storage: The gas produced by gasifiers can not be stored. It must go directly into the next process.
System integration: It is important to integrate all feedstocks and products with existing enterprises and operation. Anything less than full utilization will not be efficient.
Material design: There are often issues in dealing with abrasive ash and the containment vessel. This includes development of sensors and analytical instruments necessary to optimize systems.
Fast Pyrolysis Bio-Oils
In the process of combustion, pyrolysis occurs after the moisture has been driven from the biomass fuel. It occurs at lower temperatures than gasification (400° to 600°C or 750° to 1,100° F). Volatile carbon-based materials are turned into a gaseous state and liberated from the remaining char. Once the gaseous organic materials leave the reaction chamber, they are condensed into a liquid, pyrolytic bio-oil.
When the feedstock is dried to less than 10 percent moisture, there can be 60 percent pyrolytic bio-oil, with about 20 percent becoming a biogas and 20 percent resulting in char. Assuming a conversion of 60 percent of the biomass feedstock to liquid by weight, pyrolytic bio-oil will yield about 133 U.S. gallons/ton. Fast pyrolysis is an energy intensive process, but recycled combustible gases can supply about 75 percent of the required energy.
The fast pyrolysis technology is in the initial stages of commercialization. A fairly current summary of North American commercial-scale fast pyrolysis plants is provided in a report from the Wisconsin BioRefining Development Initiative (http://www.wisbiorefine.org/proc/fastpyro.pdf). It notes the following:
In 2003, Ensyn announced construction of a CN$9 million biorefinery in Renfrew, Ontario. This facility would employ 16 people and process 60 tons/day of dry feedstock. Between 1989 and 2003, the Ensyn Company had six plants operating which were reported to produce five million gallons of bio-oil per year. The Dynomotive Corporation has recently reached the commercialization stage. Finally, the Biomass Technology Group (BTG) BV is involved in the engineering of a 50 ton/day fast pyrolysis plant that would use clean wood residues as a feedstock.
Benefits and Liabilities – The benefits of fast pyrolysis bio-oil are similar to gasification. Fast pyrolysis is unique from the perspective that it can be condensed at the feedstock production site and then transported more cost-effectively to another central facility for further processing. Bio-oil is appealing because it produces a liquid fuel. There are significant environmental benefits regarding air emissions and waste reduction.
The liabilities are related to the fledgling level of commercialization that this technology faces. The bio-oil is similar to heating oil, but differs in character depending on the biomass feedstock used. Like the gasification producer gas, fast pyrolysis bio-oil is not directly usable in many applications. It can be cleaned and used in conventional liquid fuels. Because there are only a handful of commercial fast pyrolysis plants, there is less confidence and understanding of the technology and economic commitments necessary to operate a fast pyrolysis plant.
Anaerobic digestion is the cultivation of methagenic bacteria in the absence of oxygen. The efficiency of conversion of manure to methane gas depends on many factors like quality of manure entering the digesters, intensity of digester management (retention time of manure in digester, temperature of the digester and whether it is continuously loaded or not), and also the species of livestock. As the management intensity of the conversion efficiency is increased, the possibility of the digester system being upset also increases.
While digesters can be complex, there is some stability in the buffering nature of the digester’s biological ecosystem. Natural buffers will compensate for small fluctuations in the chemical nature of the liquid material within the digester.
Anaerobic Digestion Process –
Anaerobic digesters are similar to the rumen (digestive system) of cows. When a cow eats plant material, it gets broken down into smaller molecular units (sugars, starches and fibers) by physical, biological and chemical processes. In a digester, the same thing happens. Here the manure that enters the digester contains partially digested plant parts. Acid forming bacteria feed on these carbohydrates and produce volatile organic acids. These acids are what the methane-forming bacteria eat. As these methagenic bacteria respire, they release methane. While this is described here as a linear process, in a conventional digester all these steps are happening at the same time.
Operating temperature – The descriptive temperature ranges with which digesters operate are: psychrophilic (less than 68°F), mesophilic (95° to 105°F) and thermophilic (125° to 135°F). The psychrophilic digesters are not heated. Mesophilic digesters are heated to about 100°F. The thermophilic digesters are heated even more. They are the most efficient, but also the most sensitive to shocks within the digester system. Anaerobic lagoons (outside earthen containers) are also digesters. The operating temperatures of these earthen, anaerobic lagoons fluctuate with the season. They will warm up in the summer, and during the winter methane production is reduced.
Digester structure – The least management-intensive digester is an anaerobic lagoon. These digesters were very popular in the 1980s and 1990s because they did not require much maintenance. Innovations in lagoon technology have added liners in the bottoms and covers on the top to collect the methane. These covers are relatively inexpensive, but the yield of methane gas is also the lowest for covered earthen lagoons.
There are in-ground concrete digesters and above-ground tank digesters. Plug-flow digesters have a new batch of manure added as an equivalent volume of liquid is pushed out of the digester at the other end. Mixed digesters are agitated. Theoretically, thermophilic mixed digesters keep all the bacteria growing and digesting most efficiently. Costs increase as digesters operate at higher temperatures and get mixed. The yield of methane gas also increases with management intensity.
Manure quality – The criteria used for loading an anaerobic digester is volatile solids. These are the organic portion of the total solids. Two factors weaken the concentration of volatile solids in manure. The first factor is the addition of water. A certain amount of water is necessary to get the appropriate loading rate (manure digesters are designed for liquid manure). If too much water is added, the concentration of volatile solids will be less than optimal.
The second factor that weakens the concentration of volatile solids is time. The longer the duration of time between when feces are produced until they are utilized, the more degraded the volatile solids will be. So if manure sits in a pit for four to five months before it is utilized, some of the methane-producing potential will be lost. To get the most energy out of manure it must be utilized when it is produced.
Manure By-products – Just as important as producing methane, or electricity from methane, is utilizing all the things that go along with using the carbon and hydrogen from the methane. The effluent coming out of a digester has fiber in it. Some of the energy is still in it, and the nitrogen and phosphorus in the manure are in a more available form than they are in fresh manure.
Benefits and Liabilities – Anaerobic digesters have many benefits. These include: Heat and electricity production; Fly and odor control; Weed seed and pathogen reduction; Enhanced manure nutrient availability; Sanitary bedding for dairy cattle; and Carbon-credit revenue.
The list of anaerobic digester liabilities is equally as exciting. First, they haven’t always worked. The digester vendors listed in the Sourcebook (see vendor sidebar) are using technologies with track records of success. The hard reality is that in the last 20 years, a lot of digesters that have been built are no longer running, but we know more about digester performance now. Second, revenue from the sale of methane-generated electricity may not provide economic security since it is difficult to obtain a good price for electricity generated on the farm. There are often also interconnection costs. Sometimes the cost of being connected to the grid costs as much as the revenue from electricity sales. New policies are being developed, and things are changing, slowly. Third, the methane gas generated from a manure-digester can not be stored. It has to be used as it is produced or flared off into the atmosphere. Finally, it is less costly and more efficient to build a digester that is designed from the ground up as an integrated component of the livestock operation and buildings. It is difficult to just “try it out” for a while. Once you make the commitment to build and operate a digester, it is a long term decision.
The conversion of corn into ethanol by fermentation is one of the bright stars of the biomass renewable fuels industry. There are nearly 100 existing ethanol plants currently listed on the Renewable Fuels Association (RFA) website (http://www.ethanolrfa.org/industry/locations) with expansion or new construction planned at 40 more facilities. Ethanol prices continue to remain high. Liquid fuel prices are high and the demand for renewable fuel oxygenates (MTBE replacement) will keep ethanol prices high. Ethanol fermentation/distillation from corn is a proven and profitable technology.
Currently, Indiana has only one operating ethanol plant — a 102 million gallons/year plant located in South Bend. Other ethanol plants (and their annual operating capacities) that have begun construction or announced plans to build are: The Central Indiana Ethanol, LLC, in Marion – 40 million gal/yr; ASAlliances Biofuels, LLC, in Linden – 100 million gallons gal/yr; Iroquois Bio-Energy Company, LLC, in Rensselaer – 40 million gal/yr; The Andersons Inc., in Clymers – 100 million gal/yr; Maize AgriProducts Inc. in Fowler – 50 million gal/yr; and Rush Renewable Energy in Rushville – 60 million gal/yr. When these proposed projects come on-line, they will provide an additional 390 million gallons of Indiana ethanol annually.
Ethanol Fermentation Process (Corn) – The ethanol industry has successfully commercialized the dry-mill process of converting a bushel of corn into ethanol (2.5 to 2.6 gallons/bu.), dried distillers grains and solubles (17 lbs DDGS/bu.) and carbon dioxide (16 lbs. CO2/bu.). The dry-mill is more specialized than the other commercial ethanol process, the wet-mill. The wet-mill process produces other valuable co-products, such as high fructose corn syrup and gluten, but is also far more costly to build. Another emerging ethanol process is dry fractionation. Experimentally, this process increases the value of nonstarch components before fermentation and greatly reduces the quantity of distiller’s grains after fermentation. Current construction of commercial ethanol facilities are primarily dry-mill plants. Therefore, the discussion here is limited to the dry-mill process.
Between the current and planned Indiana ethanol plants, they will have committed to using 197 million bushels of corn. These seven plants will produce 492 million gallons of ethanol, 1.6 million tons of DDGS, and nearly 1.5 million tons of CO2.
DDGS have value as a feed ingredient, but require marketing and management to keep the high volume of DDGS from becoming a liability to the ethanol facility. DDGS have a high protein content (25 to 29 percent) and can be fed to livestock in small quantities. Feeding DDGS increases the excretion of nutrients in beef, dairy and swine. Feeding DDGS in swine rations above 20 percent of ration, can create softening of pork.
Ethanol Fermentation Process (Cellulose/Fiber) – This technology is not at the commercial-scale at this tie. Iogen, a Canadian-based company, announced in January 2006 that it is working with Royal Dutch Shell to build the first industrial-scale cellulosic ethanol plant in Germany. Others continue to encourage the construction of a commercial-scale plant in the U.S. The process for making ethanol from celluosic fibers is similar to the process of making ethanol from corn. The difference is a pretreatment process that reduces the fibers to sugars.
Converting BioTown Corn and Fiber to Ethanol – The benefits include: Dry-mill ethanol conversion is a proven and profitable technology investment with nearly 100 plants operating or under construction; Advances to the dry-mill ethanol conversion process continue to improve energy efficiency and co-product value; Demand for ethanol continues to increase more rapidly than the supply due to an increased demand for MTBE oxygenate replacements and increasing pressures on oil supplies (wars and hurricanes); and White County, Indiana produces enough corn (20 million bushels) to support a 50 million gallon per year ethanol plant.
The liabilities include the following:
Energy intensive – As conventional energy prices rise, the cost of producing ethanol also increases. This will be reduced as ethanol power shifts to biomass energy sources.
Creating DDGS markets – Transportation and demand for DDGS must be managed. A 50 million gallon/year ethanol plant produces 162,000 tons of DDGS/year. It can not completely replace corn in feed rations and increases nutrient excretion rates in manure.
Economic limits of corn supplies – In 2004, Indiana harvested 929 million bushels of corn. Upon completion, the seven Indiana plants listed above will account for 21 percent of 2004 Indiana corn production. Three of the “planned” plants are in counties that adjoin White County, where Reynolds is located.
The National Biodiesel Board (NBB) estimates there is currently the capacity for producing 354 million gallons/year in the U.S. Thirty-five companies have announced plans to build biodiesel plants in the next 18 months. That will increase U.S. capacity by 278 million gallons of biodiesel fuel. The NBB points out that capacity is not the same as actual annual production. Biodiesel plants will operate at full capacity only when the demand for biodiesel is high enough.
The Biodiesel Process – The conversion (transesterification) of vegetable oil to biodiesel is not a complicated process. It is a relatively simple chemical reaction that results in nearly a complete conversion of vegetable oil to biodiesel fuel. About 10 percent of the material leaving the process is glycerin. Glycerin has market value but like the DDGS of ethanol, the quantities produced through the biodiesel conversion process are large enough to create marketing challenges.
Virgin Vegetable Oil as a Feedstock – Commercial biodiesel plants begin with vegetable oil as a feedstock, not soybeans. This is different from the conversion of corn to ethanol, where corn is delivered to the ethanol plant. Soybeans contain about 18.5 percent oil which is separated from the high-valued protein soybean meal. A 60 pound bushel of beans yields about 11 pounds of oil and 48 pounds of meal.
To separate the oil from the meal, beans are crushed/extruded at a soybean crushing plant. This is not a challenge, but it is another step in the delivery and conversion of soybeans to biodiesel fuel.
As described in Part I, the 117,700 acres of White County soybeans, producing 63 gallons/acre of biodiesel fuel, would generate 7.4 million gallons of biodiesel fuel. This would also generate 6.3 million pounds of glycerin.
The greatest advantage of using virgin vegetable oil in the biodiesel conversion process is cost associated with feedstock variability. Because the oil quality of fresh vegetable oil is relatively consistent, biodiesel plants can move large quantities of consistent oil through large facilities. The more specialized a facility is, the lower the costs of the processing operation. The trade-off is that the fresh vegetable oil has many other uses and is more costly.
Used Vegetable Oil and Animal Fat as Feedstocks – Virgin vegetable oil is not the only source of biodiesel feedstocks. Used vegetable oils, animal fats, Number 2 yellow grease and brown grease from restaurant grease traps, can all be converted into biodiesel fuel. These used materials are extremely variable and may not make the near-100 percent conversion to biodiesel fuel like that of fresh vegetable oil. The economic trade-off with used oil and fat is that it is considered waste material and suppliers (used-oil generators) pay to have it collected.
Increasing energy prices and the added benefit of recycling a waste product are driving the commercialization of used oil feedstocks in the production of biodiesel fuels. One of the leaders in establishing a business model and developing a used oil technology is Piedmont Biofuels of Pittsfield, North Carolina. They are a multiservice cooperative that offers both biodiesel fuel from used oils, as well as education and training opportunities in setting up a facility. Piedmont Biofuels has been composting the glycerin.
White County and the BioTown, USA area have a significant supply of used oil, fat and grease. Within a 25-mile radius of Reynolds, there are 354 reported restaurants, most of which generate used vegetable oil. Steve Godlove reports about 390,000 gallons of brown grease were cleaned out from restaurant grease traps in 2005 in the White County area. Furthermore, Purdue University has pioneered the use of modified soybean oil for use in heating oil. Heating oil standards are not as stringent as the motor vehicle fuel standards and may be an excellent market for the used oil materials.
Benefits and Liabilities – Benefits to convert vegetable oils and animal fats are: Conversion of oil and fat to biodiesel is a proven and profitable technology investment with nearly 50 plants operating and another 35 under construction; Biodiesel conversion is relatively simple and very compatible with conventional diesel fuel; As diesel fuel price increases, the economics of bioconversion of biodiesel fuel also improve; Engines burning biodiesel emit no sulfur dioxide, and less carbon monoxide, hydrocarbons and particulates. Biodiesel also adds lubricity; and Recycling used vegetable oil and animal fat, especially brown grease from restaurants, reduces environmental pressures from disposal of organic wastes.
Liabilities are: Because vegetable oil is very valuable already, converting millions of gallons into biodiesel fuel will raise the price of vegetable oil for all uses; Marketing or disposal of the co-product glycerin is not automatic, but markets exist if the glycerin is managed well; and Burning biodiesel in engines has been reported to increase the nitrogen oxide levels slightly.
Selection Of Technologies
The only conclusion that could be made from the Sourcebook is that BioTown, USA is profoundly thermodynamically and technologically viable. Reynolds, Indiana used 227,710 million BTUs (MMBTU) in 2005. Without including existing bioenergy projects like the 3.2 MW generating capacity at the Liberty Landfill, White County annually produces over 16,881,613 MMBTU in undeveloped biomass energy resources. That is 74 times more energy than Reynolds consumed in 2005.
This comprehensive review of available materials and technologies served as the foundation for selecting the biomass energy technologies to be used in generating electricity — Phase II of the BioTown, USA Project. A “suite” of three technologies was identified to produce a targeted generation capacity of 2.4 MW of electricity — gasifier, fast-pyrolysis and anaerobic digester. The three technologies allow the use of both solid and liquid biomass feedstocks, converting them into volatile gas, liquid and solid fuels for further processing.
The gasifier is targeted to power a turbine producing roughly two-thirds of the electricity, while the anaerobic digester will be used to generate the remaining third in an internal combustion generator set. The fast-pyrolysis technology is included primarily for the production of liquid fuels (bio-oil). In addition, all three technologies operate at three distinctly different temperature regimes. The BioTown, USA Power Plant will be able to leverage the surplus heat generated in one technology to fuel the other conversion technologies and run dryers.
Mark Jenner of Biomass Rules (www.markjenner.com) in Greenville, Illinois is author of The BioTown, USA Sourcebook and is working with the Indiana State Department of Agriculture and Reynolds, Indiana on development of the biomass energy infrastructure for BioTown, USA.