BioCycle August 2006, Vol. 47, No. 8, p. 31
A major goal of Indiana’s BioTown, USA is to convert local biomass into energy – turning corn stalks, sewage, manure and other organics into electricity and fuel through gasification and anaerobic digestion. Part I
INDIANA GOVERNOR Mitch Daniels has a bold approach to develop local renewable energy production, create a cleaner environment, find new solutions to municipal/animal waste issues, and develop new markets for Indiana products – all at the same time! BioTown, USA is quite simply the conversion of the town of Reynolds, Indiana from a reliance on fossil fuels to biomass-based fuels. With the implementation of BioTown, USA, a template will be set that simultaneously promotes energy security, rural development, profitable agriculture and a green, thriving natural resource environment.
The BioTown, USA Sourcebook on which – these two articles are based – represents the inventory of local energy use, available biomass feedstocks and emerging biomass energy conversion technologies. It was important as this project began to understand what tools were available. For the project, the Sourcebook is serving as a catalogue of available tools in our biomass energy toolbox.
BioTown, USA (aka Reynolds) is profoundly thermodynamically and technologically viable. The community used 227,710 million BTUs (MMBTU) in 2005. Not including existing bioenergy projects like the 3.2 MW generating capacity at the Liberty Landfill, White County (where Reynolds is located) annually produces over 16,881,613 MMBTU in undeveloped biomass energy resources. That is 74 times more energy than Reynolds (population 533) consumed in 2005. That is a physical assessment, not an economic assessment.
The annual liquid fuel, electricity and natural gas use of Reynolds was estimated based on 2005 energy consumption levels. Reynolds used 384,000 gallons of unleaded gasoline, 8,046,934 kilowatt-hours of residential and commercial electricity, and 147,721,090 cubic feet of residential and commercial natural gas (Table 1).
Part I of this two-part article series presents a brief overview of biomass energy and the results of an inventory of biomass feedstocks in Reynolds and the surrounding area. Part II, to appear in the September 2006 issue of BioCycle, discusses the range of biomass conversion technologies evaluated for BioTown USA, and the three systems to be developed into commercial-scale facilities.
BIOMASS ENERGY BASICS
Biomass is recently generated plant material. The time component separates biomass from the prehistoric plant-derived products like coal and crude oil. Biomass includes virgin plant products like grains, grass and wood, and processed plant material like paper, manure, and other plant-based wastes and residuals.
Biomass energy, then, is stored solar energy. One of the fundamental relationships in nature is the photosynthesis of carbon dioxide and water into carbohydrates (in this case, glucose) and oxygen through sunlight absorbed through green plants:
6CO2 + 6H2O + sunlight -> C6H12O6 + 6O2
Green plants store solar energy biochemically as sugars, starches, lipids and fibers. All the value of our food and fiber commodities (corn, beans, wheat, cotton, timber, etc.) is based on photosynthesis. Shifting the market discussion from the hidden energy value of traditional commodities to biomass products is as simple as shifting from corn, beans, manure and timber to sugars, starches, lipids and fibers.
The stored solar energy in green plants is accessible through the converse of photosynthesis, or respiration.
C6H12O6 + 6O2 -> 6CO2 + 6H2O +heat (686 Kcal / mole)
Energy is fixed in the universe. It can not be created or destroyed (First Law of Thermodynamics). Energy can only be conserved. It can not be recycled like nutrients. Solar energy strikes the planet and bounces off. This energy is captured and chemically stored in plants until it is used or lost.
There is a great deal of residual energy that passes through each farming enterprise unused. By looking at the energy balance of farming systems, the system efficiency can be increased. This can be extended beyond production systems to all food waste, trash and all organic residuals. Just like manure is “unused” corn and soybeans, all organic residuals contain stored, underutilized energy. Biomass energy technologies increase the utilization and conservation of energy by managing the unused energy in plant material.
Biomass energy systems are not composed of a single process. To conserve the stored solar energy, multiple processes are woven into a complete system. In addition to energy, biomass may be converted into other useful outputs like construction materials, compost, or industrial chemicals. For BioTown, USA, a complete integrated biomass energy system, converting carbohydrates to power, will look like Figure 1.
INVENTORY OF AVAILABLE BIOMASS FEEDSTOCKS
Building a biomass energy system requires knowledge of the available biomass materials or feedstocks. A broad inventory was made of materials/feedstocks in Reynolds and the surrounding area for use as fuels in biomass conversion technologies. Materials that currently exist are: corn grain, corn stover, soybeans, swine manure, sewage from Reynolds and the nearby town of Monticello, White County septic tank clean-out material, brown grease, yellow grease and municipal solid waste. In addition, estimates of other biomass energy crops that could be introduced into White County were made: canola, switchgrass, miscanthus and hybrid poplar.
On the agricultural side, the Sourcebook provides data on existing and potential “fuel feedstocks” from crops:
In its National Agricultural Statistics Service (NASS), USDA reports corn production in White County, Indiana had an average five-year yield of 158.3 bushels/acre (2000 – 2004). During the same period, corn acreage averaged 131,880 acres in White County. Average total annual production was 20,874,720 bushels of shelled corn. In the 2002 Census of Agriculture, White County produced the most bushels of shelled corn in Indiana. A bright star in the bioenergy future, it has uses in ethanol and Dried Distillers Grains and Solubles (DDGS). The shelled corn functions as a natural fuel pellet for use in corn burning stoves and furnaces. The corn stover stalks also contain biomass energy and shows promise as a biomass feedstock.
For most of the last 30 years, farmers in White County have harvested nearly 130,000 acres of corn. While corn acreage has remained fairly constant, corn yields have continued to increase. Current yields are at 160 bu/acre and are forecasted to continue increasing.
Yield of 160 bu/acre across 130,000 acres produces enough corn for a 50 million-gallon per year ethanol plant (20 million bushels of corn). The Higher Heating Values (HHV) represent a reference value for energy released through combustion. The HHV of shelled corn is 8,100 BTU/lb. These HHV values serve as a starting point for comparison of biomass feedstocks. On the basis of weight, without adjusting for the energy mass balance, about one-third of a bushel of shelled corn yields 2.7 gallons of ethanol. Another third of the bushel (17-18 lbs) produces DDGS, and the final third (16-17 lbs) is carbon dioxide (CO2).
Soybean production in White County had an average 5-year bean yield of 47.0 bushels/acre. During the same five-year period, soybean acreage averaged 117,700 acres in White County. The five year average production was 5.5 million bushels of soybeans. Soybean acreage in the county has fluctuated between 100,000 and 120,000 acres for more than 10 years.
The authors of USDA/DOE’s “Billion Ton” report indicate that bean stalks can be harvested for biomass just as corn stover. The soybean stalk biomass yield is much lower than corn, but varieties are being identified that would increase crop residue significantly without lowering the bean yield. Soybeans are harvested and crushed into bean meal (80% by weight) and oil (18.5% by weight). The meal is generally 44 percent protein, has high economic value and is the protein-standard around the world. Soybean oil also has high value, such as conversion into biodiesel and glycerin (90:10 ratio). Jim Wimberly, of BioEnergy Systems LLC in Fayetteville, Arkansas estimates 7.4 million BTUs per acre for a 47 bushel/acre yield (White County five-year average), equivalent to 63 gallons of biodiesel/acre. On 117,700 acres of beans, that is 871,000 million BTUs (MMBTU) in the county.
Another oilseed crop that may have potential for energy production in White County is canola. Spring canola is harvested about the same time as wheat and has never been grown in northwest Indiana due to a lack of markets. Canola contains about 40 percent oil and 23 percent protein, which is twice the oil content of soybeans. North Dakota variety trials indicate that yields fall between 1,800 pounds and 2,400 pounds per acre.
Based on a yield of 2,100 lbs per acre, 40 percent oil, an oil bulk density of 7.6 lbs per gallon, and 90 percent process efficiency, canola could yield 99 gallons of biodiesel oil per acre (versus the estimated 63 gallons/acre of biodiesel from soybeans.
DEDICATED (CELLULOSIC) ENERGY CROPS
The Department of Energy and others have invested significant resources in determining the biomass fuel capacity for the U.S. studies based on projections more than historical yield data. Few fiber crops are grown for energy production and little data is collected on crops that are grown. The biomass energy studies are interesting from an academic perspective, because they allow a glimpse of what a biorenewable economy will look like.
The USDA/DOE “Billion Ton” report did a comprehensive analysis of “if” and “how much” U.S. biomass could replace our transportation fuels. The report found that 1.3 billion dry tons of biomass could be produced: one billion from agricultural lands and 0.37 billion dry tons from forest lands. The 1.3 billion dry tons of biomass would be sufficient to replace one-third of U.S. demand for transportation fuels by the year 2030.
We produce a great deal more biomass than we know. In White County, Indiana, the 130,000 acres of corn already produces 500,000 tons of corn stover that is not harvested for energy production. A goal of biomass energy advocates is to replace some grain and soybean crop acreage with energy crops. It is not an unrealistic objective, but farmers will want to make as great a return, or more, from their dedicated energy crops as they are making now from the traditional grain and soybean crops.
The 2005 Indiana Renewable Energy Resources Study reports that by planting all agricultural land to switchgrass, 90 million tons of biomass could be produced each year. That is 180 times more than the current volume of White County corn stover. They convert this to an energy value of 1.54 quadrillion BTU/year (a billion MMBTUs). But to succeed at growing only energy crops, the sale of the new energy crops would have to exceed the 2004 value of crop sales in Indiana of $3.7 billion (USDA-NASS). It may happen at some point, but this will take time.
The simple reason folks get so excited about the production of dedicated energy crops on prime farmland is that on a dry ton basis it is possible to more than double the yield of biomass produced by corn (shelled corn plus stover). As energy prices climb, the energy market will continue to drive crop planting decisions. A lot has to happen before energy crops become profitable. One challenge is that the processing/conversion technologies must improve.
Dedicated energy crops can be converted into alcohols like ethanol. The cellulose and hemicellulose components of plant fiber are more complicated versions of the five and six carbon sugars (pentose and glucose) currently used to make alcohols like ethanol. They are bound together by another carbon compound – lignin. Lignin is a complex carbon compound that does not break into smaller carbohydrates as easily as cellulose and hemicellulose.
The three most significant dedicated energy crops are switchgrass, miscanthus and hybrid poplars.
Much of the existing work on dedicated energy crops has been done with switchgrass – a perennial crop that utilizes C4 photosynthesis pathways (like corn). C4 plants utilize solar radiation up to 40 percent more efficiently than C3 plants (like soybeans). Switchgrass has a deep-rooting rhyzominous structure that has great environmental benefits. Since switchgrass is a perennial crop, there are no annual planting or field tillage operations to manage. However, harvesting energy crops can be a challenge. Energy crops use either large round or square baling technologies, or they are harvested by silage choppers and wagons. Since the energy grasses are harvested at the end of the growing season, they are tall and woody, which adds more difficulty than harvesting green forages.
New research at the University of Illinois with elephant grass (miscanthus x giganteus, a sterile hybrid), shows excellent promise as a future biomass energy crop. It grows 10-13 feet tall and yields between 10-13 tons/acre. The fact that this plant is a sterile hybrid causes some interesting challenges. First it can only be planted by using a piece of rhizome (root) from an existing plant. There are a multitude of challenges remaining to commercialize production of miscanthus (seedstock production, distribution, harvesting technology, processing technology: combustion, gasification, or hydrolysis to alcohol). Even so, efforts are underway to develop sufficient root stock to supply commercial production a few years out.
Hybrid poplars are likely not high on the list of profitable biomass feedstocks for BioTown and White County, Indiana, but they deserve mention. Like switchgrass, hybrid poplars are recognized for their environmental benefits. Hybrid poplars are a softwood tree that is commercially under production by the pulpwood industry. It is a renewable source of pulpwood and is an excellent source of biomass energy. Hybrid poplars can produce as much as 10 tons per acre of biomass annually. Once a cellulosic energy infrastructure develops for planting, harvesting and processing fiber for energy, hybrid poplars may have appeal for the BioTown area.
Manure has become an underutilized resource. Traditionally, manure has been land applied, but as livestock farms have become larger and more specialized, there has been a tendency to focus on the livestock operation and less on the crop nutrient opportunities. The economic reality is that as livestock farms have become larger and more specialized, there are even more opportunities to utilize a consistent, continuous supply of manure into multiple treatment/processing technologies like biomass energy and composting.
A significant source of farm revenue in White County is from hogs. The 2002 Census of Agriculture reports that 313,131 hogs were sold on 95 farms in White County. Ninety-seven percent of the White County hogs (303,089 head) were produced on 50 large hog farms. Average farm sales from these larger farms were about 6,000 hogs per year. That means locating large quantities of fairly consistent manure supplies will be manageable. For biomass energy, the manure can be utilized as a liquid feedstock (such as a methane digester). Liquid manure can also be converted to a dry biomass feedstock by drying or separating the solids. The dry biomass conversion technologies include combustion, gasification and pyrolysis.
One of the challenges of using White County hog manure to power BioTown is that White County is a large place and most of these hogs are more than a few miles from Reynolds. Another challenge is that large hog farms use lots of energy. Most on-farm, manure-derived energy projects provide just a little more electricity than the farm requires. This is a desirable accomplishment, but the large hog population in White County will not automatically provide a complete power solution for BioTown.
There is one large beef feeding operation on the north edge of Reynolds. The beef manure is dry and is composted with bedding. The low moisture content of the manure and the added organics from the bedding open up opportunities for utilizing dry biomass energy conversion technologies. This facility also operates a hog facility. The close proximity to Reynolds may open other opportunities to combine the dry, bedded, composted beef manure with other liquid or dry biomass feedstocks from Reynolds.
MUNICIPAL SEWAGE/BIOSOLIDS, SEPTAGE, BROWN GREASE
Municipal sewage, if it is primarily residential, is largely organic in nature. The direct association of sewage to human digestive systems makes pathogens and waste carbohydrates that feed the pathogens, the primary concerns of municipal sewage treatment. Generally, cost-effective sewage treatment occurs by aeration of the waste, which burns off the carbon (reducing the risk of pollution potential).
Most sewage treatment technologies involve carbon reduction and chemical sterilization. Biomass energy technologies utilize the carbon and generally remove human pathogens at the same time. An added challenge with using municipal sewage as a biomass feedstock is that these materials are heavily regulated. Even so, like the other organic feedstocks, municipal sewage can be a viable biomass energy feedstock. In the Reynolds/BioTown area, the human sewage waste/feedstocks that are in significant quantities are Reynolds sewage, Monticello sewage, White County septage (cleanout from septic systems), and restaurant brown grease.
The Reynolds municipal sewage treatment plant has a design capacity of 800 people with a design flow of 100 gallons per capita per day (80,000 gallons/day). The treatment facilities are designed on an influent Biological Oxygen Demand (BOD) of 0.17 lbs/capita/day and total suspended solids (TSS) of 0.20 pounds/capita/day.
The Monticello Sewage Treatment Plant has inquired if the sewage in Monticello could be considered a BioTown feedstock. If the proper system could be designed, the additional BOD and TSS from Monticello could be a biomass energy windfall for Reynolds. Monticello has a daily flow of 750,000 to 800,000 gallons of raw sewage per day.
Godlove Enterprises, Inc. has been contacted about the rural septic tank cleanout material as a biomass feedstock in BioTown, USA. Because this septic tank material has similar characteristics as municipal sewage, it can add to the available biomass feedstocks if an appropriate conversion technology is identified. Godlove Enterprises, Inc. also cleans out restaurant brown grease traps. Annually, about 1.3 million gallons of septage and brown grease are cleaned out. Roughly 70 percent is septage (910,000 gallons) and 30 percent (390,000 gallons) is brown restaurant grease.
USED VEGETABLE OIL AND NUMBER 2 YELLOW GREASE
Although quality and variability issues are real challenges, used vegetable oil and animal fat hold potential for the conversion to biodiesel fuels. While the challenges are real, the quantities and prices paid for the used oil are near zero, relative to virgin vegetable oil. There is a different economic dynamic with used oil.
A simple query was done of restaurants by town and distance from Reynolds. The restaurant inventory showed there are 55 restaurants within 10 miles of Reynolds, 70 restaurants within 15 miles, 110 restaurants within 20 miles, and 354 restaurants within 25 miles. It appears that the BioTown area may support a pilot-scale used food-grade oil to biodiesel project, but may need to expand beyond the immediate BioTown area to site a commercial-scale plant.
MUNICIPAL SOLID WASTE
EPA reports that nationally, per capita MSW generation is 4.3 pounds of trash per day. EPA also reports that for 2003, 65 percent of U.S. Municipal Solid Waste (MSW) by weight, was composed of paper (35.2%), yard trimmings (12.1%), food scraps (11.7%) and wood (5.8%).
STATS Indiana reports a 2004 population of White County at 24,846 people. Assuming Indiana per capita waste generation is close to the national average, White County would generate 19,500 tons of MSW per year. Based on the estimated organic composition of this MSW, 65 percent (of 19,500 tons) is 12,700 tons of biomass that is going into a landfill.
The Indiana Department of Environmental Management (IDEM) reports, in 2004, the Liberty Landfill in White County took in a total of 583,735 tons of MSW and non-MSW. Of that total, only 22,388 tons – less than 4 percent – were from White County. This is an excellent example of net gains from importing biomass feedstocks.
One final point, in 2005, Liberty Landfill began generating electricity from its methane gas. They have installed four, 800-kilowatt generators – producing enough electricity to power 2,600 homes.
Some biomass energy advocates argue that landfill gas is not the best use of biomass energy resources. This argument is based on the sheer volume of underutilized biomass going into a landfill. Using the EPA breakdown of organic, biomass materials going into a landfill (65 percent), 355,678 tons of the MSW entering the Liberty Landfill are biomass feedstocks. Using the value of 4,830 BTU/lb, 356,000 tons of landfilled-biomass materials contain 3.4 million MMBTUs. That is a lot of underutilized fuel. However, a new separation and energy production process would not be simple and would require significant changes in the current collection system.
IMPORTS AND EXPORTS OF BIOMASS FEEDSTOCKS
As mentioned above, biomass feedstocks move into and leave the BioTown area and White County. The Liberty Landfill imports 96 percent of its waste material from outside White County. This is a benefit from the standpoint that the landfill is producing enough electricity to power 3.2 megawatts of generating capacity. A local farm, Transfarm Inc., is listed with IDEM as a permitted Indiana composting facility. They import clean biomass fiber to make their compost a high quality product.
Biomass feedstock materials are also exported out of White County. Permitted land application of septic tank cleanout material is the conventional practice for disposal of this material. When land application is not possible (ground is frozen or wet), Godlove Enterprises, Inc. must export the septic tank cleanout material from White County to the next closest permitted receiving facility in Elkhart, Indiana.
There are benefits to importing and keeping White County surplus biomass feedstocks in the BioTown area and converting them to local, green power.
SUMMARY OF AVAILABLE FEEDSTOCKS
Table 2 provides a summary of the raw energy value of individual feedstocks. Based on the current, undeveloped White County biomass production, 16,881,613 MMBTUs are available for conversion into energy. The energy values for soybeans and canola only consider the oil and do not include the valuable protein and fiber of those crops. The swine manure energy is also based on estimates of potential methane gas created. There are other ways to create energy from feces, but they are not presented in this broad overview. All other values in Table 1 represent the Higher Heating Value (HHV) of the raw feedstock.
This local inventory of available biomass feedstocks is a giant leap forward from the conventional pathways and management of organic waste materials. As BioTown projects are implemented, even better data can be collected about available feedstocks, including the development of new energy crops and materials. The realization of BioTown, USA will lead the way for improved, more robust data collection of biomass feedstocks.
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.
August 20, 2006 | General
Biotown, USA Creates Power From Waste Resources
BioCycle August 2006, Vol. 47, No. 8, p. 31