EMERGING TECHNOLOGY: AGRICULTURAL AND ANIMAL WASTE TO ENERGY

NEW TECHNOLOGIES IN ENVIRONMENTAL MANAGEMENT

University of Maryland University College

Spring 2009 Table of Contents
1.0 Introduction
1.1 Waste to energy definition/history/uses
1.2 Agricultural / Animal waste production
1.3 Graph, chart, quantities produced in United States, etc..
2.0 Conversion of w2e
2.1 Conversion Pathways
2.1.1 Thermochemical
2.1.2 Biochemical
2.1.3 Physico-chemical
2.2 Factors affecting energy recovery
3.0 Agricultural Residue
3.1 Introduction to residue
3.2 What is it
3.3 Where is it produced
3.4 What is role in environment
3.4.1 Environmental risks
3.4.2 Health risks
3.5 Conversion of agricultural residue to energy
3.5.1 Process
3.5.2 Risks
3.5.3 Benefits
3.5.4 Future as energy source
4.0 Animal Wastes
4.1 Introduction to animal waste
4.2 What is animal waste comprised of
4.3 Where is it produced
4.4 What is its role in environment
4.4.1 Environmental risks
4.4.2 Health risks

Table of Contents (Cont’d)

4.5 Conversion of animal waste to energy
4.5.1 Process
4.5.2 Risks
4.5.3 Benefits
4.5.4 Future as Energy source
5.0 Processes/Regulations/Technology
5.1 Availability of w2e facilities, costs
5.2 Technological benefits/risks
5.2.1 Other information on technology of w2e, production, transportation, environmental implications
5.3 Regulation governing w2e
6.0 Recommendations
6.1 Policy recommendations/guidelines
6.2 Future benefits
7.0 Conclusion
7.1 Summarize w2e: Movement of agricultural residue/animal waste from waste stream to energy, reduction of environmental/health risks. Future of w2e.
8.0 Works Cited

Tables

Figures

1.0 Introduction
1.1 Waste to energy definition/history/uses With today’s unpredictable petroleum prices and Federal policies targeting a reduction in U.S dependency on oil imports and extenuating climate change, a demand for Bioenergy has been sparked. In response to this demand, production of agricultural commodities (biomass) that serve as feedstock for Bioenergy has increased. Biomass consists of all plant and plant-derived organic materials including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, animal wastes, municipal wastes, and other waste materials. It provides America an excellent prospect for using a domestic and sustainable resource for fuel, power, and chemical needs now and for the future. More appropriately, biomass energy is the solar energy stored in organic matter than man can convert to electricity or fuel. The sustainable utilization of this energy in the Bioenergy cycle imitates the Earth’s ecological cycles and reduces air, river, and ocean pollutants. Most of the carbon needed to create Bioenergy is taken from the atmosphere and then later returned to it. The nutrients required to create it are taken from the soil and then also returned to the soil. The remains from one part of the cycle form the inputs to the next step in the cycle. It is a cyclic process for continual natural and clean energy.

(Bioenergy Feedstock Information Network, 2008)
This paper focuses on two particular feedstock for Bioenergy, agriculture residue and animal waste. Agricultural residues are the non-edible remnants remaining after the harvesting of a variety of field crops. They can consist of straw, stalks, stubble, husks and cobs (Stover), wheat mids, shells, Nuts, Skins and Hulls, Switchgrass, Miscanthus, Grape, Olive and fruit Pomace and Cotton Gin. Animal waste consists of manure and litter from cow, swine, poultry, turkey, sheep, and lamb, and Dairy Washdown. The most appropriate energy conversion technologies and handling protocols for the different types of residues and waste will vary depending on their moisture content. Dry residues include the part of arable crops not intended for producing food, feed, or fiber including straw, corn Stover, and poultry litter. Wet residues/wastes are those that have high water content at collection, including animal slurry and barnyard manure. A reduction in the moisture content may be required to achieve its intended purpose in energy applications. The Biomass can be dried before and after harvesting and even harvested for reduced moisture. Biomass energy, which can be used for fuels, power, and production, is not a new concept. It was been around since people began burning wood to cook food and keep warm. Before the industrial revolution biomass fulfilled nearly all of our energy needs and until the 1860’s the U.S used biomass for nearly 91% of all energy consumption (AES, 2008). In the late 1970’s following an era of high inflation and scarce energy, Congress enacted the Public Utility Regulatory Policies Act (PURPA) in an effort to diversify and strengthen domestic energy production (CBEA, 2008). Following this development a brand new leg of the biomass industry emerged and the first small plants began producing electricity in the eighties. Tax incentives of the late 1970’s and early 1980’s also supported the production of commercial scaled digesters using livestock manure as feedstock for energy production. These new Bioenergy plants initially used combusted wood waste to generate electricity instead of non-renewable fuels like coal, petroleum and natural gas. As the facilities evolved they begin to use forest thinings, agricultural byproducts, orchard removals, and urban wood waste as feedstock for electricity. Using these feedstock, reduced the risk of wildfire in forests, avoided a lot of open burning and conserved landfill space. Before being used as feedstock, agricultural residues were traditionally disposed of by open-field burning which was very inefficient and highly polluting, especially fine particulate matter (a pollutant of significant health concern). Livestock waste, before being used as feedstock, would be left to decompose and produce large amounts of methane gas and carbon dioxide that would pollute the air and nearby water. Thankfully today, more agricultural residue and animal waste are being used to its fullest natural energy potential to create different forms of Bioenergy. These include:
• Biomass power is electricity produced from biomass fuels created from agricultural residues and gaseous fuels produced from animal wastes. Biopower technologies convert renewable biomass fuels into electricity and heat by using modern boilers, gasifiers, turbines, generators, and fuel cells (U.S Department of Energy, 2008).
• Liquid fuel (cellulosic ethanol from agricultural residues and biodiesel from animal fats) that substitutes for petroleum products such as gas and diesel. The Energy Independence and Security Act (EISA) of 2007 included provisions for a Renewable Fuel Standard (RFS) to increase the supply of alternative fuel sources by requiring fuel producers to use at least 36 billion gallons of biofuel by 2022. The RFS provisions established a level of 15 billion gallons of convenetional ethanol by 2015 and at least 21 billion gallons of cellulosic ethanol and advanced biofuels (biodiesel) by 2022 (Aillery & Malcolm, 2009)
• Anaerobic digestion (AD) is a biological process in which biodegradable organic matters (animal waste such as manure) are broken-down by bacteria into biogas consisting of methane (CH4), carbon dioxide (CO2) and other trace amounts of gases. The biogas can then be used to generate heat and electricity. The success of the AD is dependent on temperature, moisture and nutrient contents, pH, and oxygen-free.

(U.S Department of Energy, 2008)
• Bioproducts can be created by converting biomass into chemicals for making plastics and other products that would typically be made from petroleum.
1.2 Agricultural / Animal waste production The U.S Department of Energy (DOE) and the U.S Department of Agriculture (USDA) are strongly dedicated to expanding the role of biomass energy. They see the role of biomass energy as a way reduce the need for oil and gas imports; to support the growth of agriculture, forestry, and rural economies; and to foster major new domestic industries (biorefineries) that will make a variety of fuels, chemicals and other products (Oak Ridge National Laboratory, 2005). DOE and USDA has predicting a 30% replacement of the current U.S petroleum consumption with biofuels by 2030. Biomass, which has the greatest potential to provide renewable energy for America’s future, is the largest domestic source of renewable energy and currently provides over 3% of the total energy consumption in the U.S. Biomass is also the only current renewable source of liquid transportation fuel. Currently the ethanol industry, including conventional and cellulosic, saves the U.S about $2 billion a year in oil imports, benefits farm incomes by about $4.5 billion and employs about 200,000 people. Once new large-scale Bioenergy and biorefinery industries are constructed and completely resourceful these numbers will increase. Currently agricultural lands can produce nearly 1 billion dry tons of biomass annually and still continue to meet food, feed, and export demands (Oak Ridge National Laboratory, 2005). This includes 428 million dry tons of annual crop residues and 106 million dry tons of animal manures, process residues, and other miscellaneous feedstocks.
1.3 Graph, chart, quantities produced in United States, etc..
Biomass Technology Chart
Technology Conversion Process Type Major Biomass Feedstock Energy or Fuel Produced
Direct Combustion
Thermochemical Wood agricultural waste municipal solid waste residential fuel heat steam electricity
Gasification
Thermochemical wood agricultural waste municipal solid waste low or medium-Btu producer gas
Technology Conversion Process Type Major Biomass Feedstock Energy or Fuel Produced
Pyrolysis
Thermochemical wood agricultural waste municipal solid waste synthetic fuel oil (biocrude) charcoal Anaerobic Digestion
Biochemical
(anaerobic) animal manure agricultural waste landfills wastewater medium Btu gas (methane)
Ethanol Production
Biochemical
(aerobic) sugar or starch crops wood waste pulp sludge grass straw ethanol
Biodiesel Production
Chemical rapeseed soy beans waste vegetable oil animal fats biodiesel
Methanol Production
Thermochemical wood agricultural waste municipal solid waste methanol

2.0 Conversion of Waste to Energy
2.1 Conversion Pathways
There are three main pathways for conversion of organic waste material to energy – thermochemical, biochemical and physicochemical. These various process transfer wastes into useable fuels, reducing environmental impacts of wastes, and the burden waste puts on landfills and other waste management systems. Although source reduction is an important method of limiting waste production, the following process transform waste into useable products, or eliminate the need for further disposal. Thermochemical, biochemical, and physiochemical processes provide fuels, electricity and products from solid waste, ultimately aiding in the management of solid waste and providing alternatives to landfill methods.
2.1.1 Thermochemical
Although combustion of waste has been used for many years as a way of reducing waste volume and neutralizing many of the potentially harmful elements within it. Combustion can only be used to create an energy source when heat recovery is included. Heat recovered from the combustion process can then be used to either power turbines for electricity generation or to provide direct heating. Thermochemical conversion is characterized by higher temperatures and conversion rates and includes combustion pryolosis, and gasificiation. Both pryolosis and gasification are alternatives to incineration and transform waste into gas and fuels for future energy use.
Combustion – Combustion is a process that reduces wastes volume through simultaneous mass and heat transport. During this process, waste is treated at extremely high temperatures. The composition of the waste determines the nature of its emissions; however, burning waste at extremely high temperatures destroys chemical compounds and disease-causing bacteria (U.S. EPA, 2008 Wastes). Systems can convert water into steam for fuel to generate electricity. Refuse derived fuel (RDF), recovers recyclables then continues incineration. About ten percent of the total ash formed in the combustion process is used for beneficial use such as daily cover in landfills and road construction (U.S. EPA, 2008 Wastes).
Pyrolysis– Pyrolysis is a form of incineration that chemically decomposes organic materials by heat in the absence of oxygen. Materials are transformed into gases, small amounts of liquid as well as carbon and ash. Pyrolysis has many benefits including: reduction of material weight and volume, reduction of bad odors, and increased handling capability.
Gasificiation – In gasification, materials (such as coal, petroleum, biofuel or biomass) are converted into carbon monoxide and hydrogen to produce fuel. The gasification can turn low value feedstocks into high valued products such as fertilizers, liquid fuels, or hydrogen (Gasification Technologies Council, 2008). There are many benefits to gasification. First, gasification produces lower quantities of criteria air pollutants than other thermochemical processes. Gasification also reduces the impact of waste disposal, ultimately generating products from otherwise disposed wastes. Similarly, gasification results in non-hazardous products and lower water usage. Modifications in design of gasification facilities can recycle water and capture carbon dioxide as well (Gasification Technologies Council, 2008).
2.1.2 Biochemical
The bio-chemical conversion processes, which include anaerobic digestion and fermentation, are preferred for wastes having high percentage of organic biodegradable matter and high moisture content.
Anaerobic - Anaerobic digestion is optimal for the treatment of wet, organic waste. The process is conducted without oxygen and results in a fuel gas called biogas containing mostly methane and carbon dioxide. The produced biogas can be used for engines, gas turbines, boilers, and in the manufacturing of chemicals biogas can be used for engines, gas turbines, fuel cells, boilers, industrial heaters, other processes, and the manufacturing of chemicals (Williams, Jenkins, & Nguyen, 2003).
Fermentation - Although similar to anaerobic digestion in that oxygen is absence in the process, fermentation produces different produces. Fermentation transfers organic constituents to ethanol through biochemical reactions utilizing specialized microorganisms. Byproducts of fermentation are typically used as boiler fuel or in thermochemical conversion to other fuels and products (Williams, et al., 2003).
Aerobic – Aerobic conversion uses air or oxygen to induce the metabolism of aerobic microorganisms. Aerobic conversion operates at higher speeds than fermentation and anaerobic digestion; however, gas fuels are generally not produced from the process. Both composting and activated sludge wastewater treatment processes are examples of aerobic conversion.
2.1.3 Physico-chemical
The physico-chemical technology involves various processes to transform physical and chemical properties of solid waste. In the physicochemical conversion process fresh or used vegetable oils, animal fats, greases and other feedstocks are converted into liquid fuels or biodesiel. Similarly, the combustible fraction of the waste is converted into high-energy fuel and may be used in steam generation. This process results in products with lower ash and moisture contents and uniform size. Physicochemical conversion is both cost-effective, and environmentally friendly.
2.2 Factors affecting energy recovery
There are two important factors to consider when determining the potential of energy products from wastes. Both quantity and quality of waste are important factors in determining potential of useable products from waste. The following are parameters that determine both quality and quantity of wastes:
• Size of constituents
• Density
• Moisture content
• Volatile solids / Organic matter
• Fixed carbon 3.0 Agricultural Residue
3.1 Introduction to residue One of the greatest environmental threats of the 21st century is a continual reduction in global biodiversity. Coupled with concerns about the security and sustainability of fossil fuel and its uses, there is a renewed interest in crop residue as a biofuel to help meet our energy needs.
3.2 What is it Agricultural residue is a renewable, sustainable, and expandable resource capable of meeting the growing demand for Bioenergy and transportation fuel. It is derived from the fibrous, inedible portions of field crops that are left over after harvest. The most abundant and readily available primary agricultural crop residues are corn Stover (leaves, stalks and cobs) and wheat straw. Out of the 500 million tons of crop residues produced each year, there is a sustainable potential of 75 million dry tons of corn Stover and about 11 million dry tons of wheat straw. Corn tends to receive the most attention because it has a concentrated area of production and produces 1.7 times more residue than other leading cereals when based on current production levels (USDA, 2006). Other high residue crops include rice and sugarcane. While agricultural residues are used as feedstock for different uses, it primary purpose is the production of cellulosic ethanol. Cellulose is the core section in the cell wall of plants, and is the main structural material in the plants. This type of material is in general less expensive than corn (conventional ethanol) but is harder to convert to sugar. Ethanol, which is grain alcohol, is produced by fermenting and distilling simple sugars from biological sources. It is actually the same type of alcohol found in alcoholic beverages but commercial ethanol plants add about 2-5 % of poison to make it unfit for human consumption (Morris & Hill, 2006). Cellulose is chemically made up of a long chain of tightly bound sugar molecules. Although the refining process (converting to sugar) is more complex than traditional ethanol, cellulosic ethanol yields a greater net energy benefit and the production results in much lower greenhouse gas emissions. The conversion of cellulose to sugar will be explained in a later section.
3.3 Where is it produced Most residue recovery processes pick up residue left on the ground after the primary (edible) crops have been harvested. This process involves multiple passes of equipment over the fields and removes an average of 40% corn Stover and straw. Because agricultural residue is a byproduct of the harvesting of field crops, it will be concentrated in areas of high harvest. Because corn is the major contributor for residue, most of the Stover supply (62%) comes from the three major corn-producing states: Iowa, Minnesota, and Illinois (Graham, 2007). Supplies of Stover also come from Nebraska, which is another major producer of corn, but due to high wind erosion less residue is able to be collected. Areas suitable for the collection of large quantities of Stover collection include central Illinois and Indiana, northern Iowa, southern Minnesota, and along the Platte River in Nebraska (Graham, 2005). These areas are particularly suitable for residue removal because of high corn yields; the topography is flat, and irrigated. Conservation tillage, which is mulch, or no-till, is used in 22% of the central Illinois and Indiana land, 29% of the land in Iowa and Minnesota, and 61% in Nebraska (Graham, 2005). Once removed, agricultural residues are transported to ethanol production plants that convert the residue into cellulosic ethanol. As of 2001, there were over 60 ethanol production plants either in operation or under construction (Oak Ridge National Laboratory, 2001). These plants have the capacity to produce more than 2 billion gallons a year. They are located in 20 states concentrated within the Midwest. 22 of these plants were farm-owned facilities.

Annual production of corn Stover in the United States. Values were derived using 1995–2000 corn production statistics from USDA. (Graham, 2005) 3.4 What is role in environment
3.4.1 Environmental risks Agricultural residues provide a physical buffer for soil by protecting it from the direct impacts of rain, wind and sunlight. This leads to improved soil structure, reduced soil temperature and evaporation, increased infiltration, and reduced runoff and erosion. Crop residue also contributes to soil organic matter and nutrient increases, water retention, and microbial and Macroinvertebrates (USDA, 2006). The effects of which lead to improved plant growth and increased soil productivity and crop yield. The primary consideration for using the residues is maintaining the productivity of the soil where the crops are grown. Agricultural residue is managed using conservation tillage systems including, no-till, strip till, ridge till, mulch till, and other reduced tillage methods. A 30% covering of crop residue over soil after harvesting can reduce soil erosion from water and wind by 50-75% (Oregon’s Biomass Energy Resources, ).
The amount of residue needed for control of erosion it dependent on soil type and variations in slope length and steepness. Therefore the amount of agricultural residue available as a biomass energy resource will be limited to the amount of residue that is not needed to remain to maintain soil productivity. If no-till practices were universally accepted, the total amount of collectable residue supply could potentially increase to 101.2 million tons. Even with no tillage practices almost 50 % of agricultural residue would need to remain uncollected to conserve the health of the soil.
3.4.2 Health risks There are two potential risks to health: ethanol plant accidents like explosions and exposure to pollution. There is the potential for exposure to polluted water if the agricultural residue is over collected resulting in soil erosion allowing agriculture runoff to make it into nearby waterways.
3.5 Conversion of agricultural residue to energy
3.5.1 Process
The edible portions of corn and other grains are easily fermented into ethanol because there chemical makeup is abundant with starches (which are easily converted into sugar). Cellulosic matter, on the other hand, consists of hard fibrous cellulose and lignin (the skeleton of the plant) which must first be converted into starches before it can be fermented (converted to sugar). The cellulose goes through pretreatment methods to be broken down into its component sugar in two ways. Pretreatment refers to the solubilization and separation of one or more of the four major components of biomass: hemicelluloses, cellulose, lignin, and extractive. This pretreatment makes the remaining solid biomass more accessible to further chemical or biological treatment. The two pretreatment methods are:
1) Treat it with chemicals including dilute acid, alkaline, organic solvent, ammonia, sulfur dioxide, carbon dioxide or other chemicals to make the biomass more digestible by enzymes.
2) Treat it with enzymes. The enzymes work by breaking the chemical bonds between molecules. Once the molecules are separated into simple sugars they are more accessible to yeast and other microbes that then ferment the sugars to ethanol or other Bioenergy.

3.5.2 Risks As previously stated, the harvesting of cellulosic feedstock poses environmental challenges in the since that crop residue removal needs to be done carefully, leaving enough residues in place to reduce erosion and returning enough residues to the soil to maintain or improve organic matter content.
3.5.3 Benefits There are many benefits for converting agricultural residue into energy. These benefits include:
• The same residues that are being used for feedstock can often be burned to fuel the ethanol plant avoiding extra fuel expenses.
• The substitution of cellulosic ethanol for gasoline would result in a net greenhouse reduction of 86-128 %, compared to a 35% reduction if corn ethanol was substituted (Oak Ridge National Laboratory, 2001).
• Cellulosic feedstock prices have the potential to be more stable and less volatile than corn prices.
• Cellulosic ethanol plants can dispose of a wide variety of organic wastes.
• With fully developed biomass ethanol technology, Bioenergy from agriculture could displace 25 -30 % of U.S petroleum imports.
• In combination with better vehicle efficiency, smart-growth urban planning, and biofuel, the U.S demand for gasoline could be practically eliminated.
• Ethanol production from corn stover could result in $8.9 billion in industrial output and $3.8 billion in value added. It could also create about 76,000 permanent jobs (Oak Ridge National Laboratory, 2001).
• According to a USDA study, a 100 million gallons/year ethanol production facility would create 2250 local jobs for a single community (Oak Ridge National Laboratory, 2001).
• Substituting biofuels for one gallon of gasoline/diesel saves 20lbs of carbon dioxide emissions to the atmosphere (Oak Ridge National Laboratory, 2001).

3.5.4 Future as energy source While agricultural residue as a feedstock will not be able to completely replace fossils fuels for transportation and electricity, the diversity of this feedstock will allow the U.S to increase its energy independence. The U.S is making great strides toward that goal. In 2007, the DOE announced that it would invest up to $385 million for six biorefinery projects over the course of four years. Once these biorefineries are fully operational, they will be expected to produce more than 130 million gallons of cellulosic ethanol per year (DOE, 2007). Former President Bush’s announced a goal of making cellulosic ethanol cost-competitive with gasoline by 2012, and along with increased automobile fuel efficiency, reducing America’s gasoline consumption by 20% in ten years (DOE, 2007). Former President Bush’s Twenty in Ten Initiative aims to increase the use of renewable and alternative fuels in the transportation sector to the equivalent of 35 billion gallons of ethanol a year by 2017. Funding for these projects will lead to the wide-scale use of non-food based biomass, like agricultural residue, in the production of transportation fuels, electricity, and other products (DOE 2007).

4.0 Animal Waste
4.1 Introduction to animal waste Animal wastes includes livestock and poultry manure, bedding and liter, dairy parlor waste water, feedlot runoff, silage juices from trench silos, and wasted feed. (Hammond, 1994) The waste also comes from water that has contacted animal manure, litter, or bedding; water from washing, flushing, or cleaning animal pens; and liquid or solid waste from pens used at kennels, animal hospitals, poultry processing facilities, dairies or rendering plants. . (www.trinity-trudy.org/coolstuff/vocab.htm) Approximately two trillion pounds of animal waste are produced per year nationally. Common animal waste treatment practices used in agriculture and farming are often inadequate to protect the environment producing a major pollution problems in the nation. This large volume of waste cannot be assimilated by natural processes so treatment is required. Waste is pumped into open air pits called lagoons then the liquid manure is sprayed onto fields at volumes that exceed what the crops can take up, leaving a large amount to be released into the air or runoff into surface waters. (Scorecard, 2005) Emerging technologies have since been developed to combat these pollution problems. Transformation of waste to energy is one of the best options to make use of waste and to get rid of waste. Modern methods of purification means there is no emission of toxic waste. (Alvarez, 2008.) The process of using anaerobic digesters to breakdown animal waste for energy will be discussed in detail in section 4.5. The first farm based digesters were introduced in the US in the 1970’s. A major problem getting started was the need for large capital investment. Energy prices at that time were down so the technology to turn animal waste into useable energy was not pursued by many farmers. Today the technology is funded through state grant money and renewable energy credits in the private market. (Bogo, 2009)
4.2 What is animal waste comprised of? Animal waste is made up of nutrients such as Nitrogen and Phosphorus, organic matter, pathogens, heavy metals, hormones, antibiotics, and ammonia. (EPA, 2009)
Animal waste can effect water, soil, and air quality if not properly handled and treated. The waste can be a valuable resource for farmers and the environment if managed correctly. It could reduce the need for commercial fertilizers, improve soil tilth, and supply power to run the farms. (Hammond, 1994)
4.3 Where is it produced?
Animal waste is produced on dairy farms, pig farms, poultry farms, raw and composted feed lots, sheep farms, and cattle ranches across the nation. The majority of waste is produced in the central portion of the United States from Texas to Minnesota and also includes California and North Carolina (See Figure 2.0 ) (Scorecard, 2005)
Figure 2.0 Animal Waste Levels Among States

4.4 What is its role in environment?
4.4.1 Environmental risks
One of the biggest water quality problems today is from non point source pollution. Point source pollution is any pollution that is discharged from the end of a pipe (i.e., factories and sewage treatment plants); non point source (NPS) pollution is any pollution that does not come from the end of a pipe (i.e., agricultural runoff, fertilizer runoff from lawns, and construction site runoff). Current farming practices often result in the release of sediment, fertilizers, pesticides and animal waste into local water bodies. (Scorecard, 2005) The added nutrients from the waste (nitrogen and phosphorus) produce excessive algal blooms causing an unpleasant taste and odor. (Hammond, 1997) When the algae die off the bacteria responsible for decomposition consumes all the dissolved oxygen in the water resulting in there not being enough oxygen left for fish, crabs and other aquatic life to breathe. (Scorecard, 2005)
Another environmental risk caused by animal waste is an increase in greenhouse gases into the atmosphere. Animal manure produces naturally occurring methane that if not captured is released into the air. (Hammond, 1997) Livestock produces 9 percent of human-induced carbon dioxide (CO2); 37 percent of all human-induced methane (CH4); and 64 percent of ammonia, which is tied to acid rain. It also generates 65 percent of human-induced nitrous oxide (N20), which the FAO says has 296 times the global warming potential of CO2. (Oliver, 2008)
Animal waste also has a negative affect on soil. The manure increases the soils pH making it difficult to produce a decent crop yield. A waste management and nutrient management plan is needed as part of the total soil and water conservation plans for farms producing livestock and poultry. Soil and waste testing is done in order to match the crop needs to the nutrients available. (Hammond, 1997)
4.4.2 Health risks
Improper collection and disposal of untreated animal waste can harm groundwater and human health. Nutrients and bacteria from animal waste can cause contamination of drinking water supplies; fish kills; and harm shellfish in contaminated water bodies. (Hammond, 1997) Dangerous and offensive odors and other air pollutants are emitted making air quality harmful for neighbors especially the very young and the elderly. Antibiotics used on factory farms to compensate for unsanitary growing conditions and promote slightly faster livestock growth develop into an antibiotic resistant strain of bacteria in animal waste. (Scorecard, 2005)
4.5 Conversion of animal waste to energy
4.5.1 Process
The featured processes being tested and used to convert animal waste into useable energy are anaerobic digestion and thermo chemical conversion technology [combustion, gasification, and pyrolysis].
Anaerobic digestion is the most widely used technology to convert animal waste to energy. Farms in Pennsylvania (PA), Nebraska (NE), Wisconsin (WI), Vermont (VT), California (CA), Texas (TX), and Oklahoma (OK), just to name a few have begun to use this technology. (Stevanus, 1998) Anaerobic digesters transform more than 8 million gallons for manure and waste water into electricity, bedding, fertilizer, and heating fuel each year. (Bogo, 2009) A good example of how anaerobic digestion works is at a farm in Rockwall, PA. On the farm sits an outbuilding, inside the outbuilding there is a 19,000 gallon holding tank that mixes cow manure and wastewater slurry. Manure is low energy since it already has been digested once by the cows so high energy food waste is added to the mix to help aid the process. The slurry goes into the digester where anaerobic bacteria breakdown organic matter producing Biogas consisting of approximately 65% methane. The gas fills a 12 inch air space and is piped into a 40 ft diameter (17,000 cu ft capacity) rubberized bladder which then is feed into a natural gas caterpillar engine that runs a 130 kilowatt generator. The system is capable of producing 1.2 million kilowatt-hours (kwh) of electricity. This is enough power to supply heat and hot water to the farm and nearby homes generating a savings of more then $60,000 yearly. The unused energy is sold to the local utility at 2.3 cents per kwh. (Bogo, 2009)
On the same lines as anaerobic digestion is the use of thermochemical conversion technology which can be used to generate bioenergy from manure.
Combustion is a subset of thermochemical conversion technology and is used to convert poultry waste into useable energy. Fibrominn, a power plant in Benson, Minnesota is currently using this technology to provide power the plant and approximately 50,000 homes. The waste used is from Confined Animal Feeding Operations (CAFOs), turkey farms in Minnesota. 1.7 million tons of turkey litter is produced annually. Its traditional use was for fertilizers for fields and crops. An alternative solution for disposing the waste is to turn it into power. Half a million tons of poultry waste is combusted annually to produced 55 mega watts of renewable energy. 3,000 tons of turkey waste is trucked daily to a storage facility for the plant, which can hold up to 10,000 tons at one time. The smell is intense, causes your eyes to burn, and can remain in clothing for several days so the building is kept at negative pressure (a sort of vacuum state) trapping the odor inside so not to offend the nearby community. The Biomass travels on a conveyor belt to the boiler building. It is combusted at >1500ºF which heats water in the boiler that produces steam to turn a turbine connected to a generator that produces the electricity. (See figure 3.0) (Discovery Channel videos, n.d.)
Figure 3.0 Boiler/Turbine Configurations

4.5.2 Risks and Challenges
The main current hurdle for biogas production is economic feasibility. The capital costs of large-scale anaerobic digester plants are very high and may range from a few hundred thousand to a few million dollars, depending on the size of the plant. Other key challenges are a lack of infrastructure and technological limitations related to efficient large-scale production and use of biogas. Developing a large centralized digester would also require major infrastructure and logistical frameworks to bring manure to one place, handle digestate and manage numerous other requirements. (Farming for Tomorrow, 2007)
4.5.3 Benefits
Environmental benefits of using anaerobic digestion to convert animal waste into energy:
• One billion tons of manure is produced in the U.S. annually. This amount of waste has the potential to generate 88 billion kwh of electricity, approximately 2.4% of the annual consumption in the U.S. and can eliminate 99 million metric tons of greenhouse gases.
• Waste heat from the digester engines saves fuel oil by heating the milking parlor and water for the farm. The water the runs through the pipes inside the digester maintain a temperature of 105º F.
• Wastewater goes to an auger style compressor that separates the liquids from the solids producing and “earthy” smelling soft bedding for the cows replacing the traditional green sawdust now in use. The new bedding contains less harmful bacteria.
• Microbes in the digester convert volatile fatty acids to odorless methane producing a liquid byproduct that is less potent to be used as fertilizer on the fields. Crops can take up the ammonia nitrogen quicker then the organic nitrogen in straight manure. (Bogo, 2009)
Environmental benefits of converting turkey waste into energy:
• Little to no pollution is generated by this process because of the advanced emission/pollution control equipment used at the power plant by Fibrominn. Only water vapor and minimal amounts of CO2 is emitted from the smoke stacks.
• This process does create large quantities of ash, but the ash is recoverable because it is rich in nutrients and can be used in fertilizers. (Discovery Channel videos, n.d.)
4.5.3 Future as Energy source
The U.S.-based Sierra Club is still very skeptical about the success of biomass as an energy source. It believes that anaeorbically digested manure has limited potential in the U.S., pointing out that even if all the 7,000 farms in the U.S. cited by the EPA as "good candidates" for anaerobic digestion technology was used, they could only produce 0.0002 percent of all energy consumed in the country today.
Proponents of biogas say that using waste products is far more preferable than biofuel since it steers clear of the "food crops v. fuel crops" dilemma. They also favor the fact that biogas negates the need for chemical fertilizers, since natural fertilizer is a by-product of the AD process, which means even more benefit in terms of greenhouse gas emissions. (Oliver, 2008)
5.0 Processes/Regulations/Technology
5.1 Regulation, Expenses, and Practicality
The availability of waste to energy facilities is steadily increasing. As of 2000, approximately 102 facilities implemented thermochemical, biochemical, or physiochemical processes to convert wastes to energy (Recovered Energy, Inc.). Currently, W2E plants process 14% of solid waste produced in the United States, over 30 million tons each year (Recovered Energy, Inc.). Facilities can reduce over 90% of the volume of waste while meeting regulatory standards in place by federal, state, and local governments. Although ash is still a byproduct from W2E processes, modern facilities and technology have determined alternative uses for ash.
Expenses
Although calculation of the expenses of animal and agricultural waste to energy goes beyond the scope of this paper, the following tables present the potential for cost recovery when implementing waste to energy technologies. Carroll County, Maryland Estimates the following expenses and income:
Carroll County, Maryland: Expenses of Waste to Energy Table 1.0
Investment/Expenses/Income Est. 2012 Est. 2015
WTE Capital Cost 200 140 60
WTE Expenses 26.8 22.4 4.4
WTE Income 11.3 11.8 .5
(in millions)
Capital Cost: Investment in project
Expenses: Loan payment + Annual Operating Costs + Transportation Fees
Income: Electricity + Recovered Metals
(Carroll County Department of Public Works, 2008)

Table 2.0
WTE INCOME
- Electricity 9.5 10.0 .5
- Recovered Metals 1.8 1.8 0.0
Total Income 11.3 11.8 .5
(in millions)
(Carroll County Department of Public Works, 2008).
Table 1.0 represents the initial cost of the investment in the Waste to Energy facility, and the potential for income despite operating costs and transportation fees. Transportation fees are a potentially costly expense for Waste to Energy facilities, and consideration of this expense must be taken into account. The transportation of steam, fuels, and other recoverable materials to processing facilities must be considered in depth. Transferring these products over long distances and state lines determines costs and applicable permitting.
Table 2.0 identifies the potential for recoverable metals and electricity from waste to energy processing in Carroll County. Although this table may not represent applicable transportation and permitting fees, the potential for income recovery is great. This income can be used to fund projects for waste treatment facilities as well as technological advances in waste to energy facilities and continuing maintenance and meeting of regulatory requirements.
Regulation and Practicality
As seen in Table 1, implementing W2E strategies can be a great expenditure of funds up-front. However, over time, these funds are recoverable. Determining cost effective strategies and innovative strategies to meet regulatory standards can be a time consuming process. The following section outlines advantages and disadvantages of the implementation of a W2E facility:
Disadvantages:
• Cost of shipment of steam/fuel produced
• Permitting
• Costs of transportation of ash residue
• Emission of toxic gases and criteria air pollutants during combustion processes
• Potential of groundwater contamination due to ash production
• Waste to Energy facilities may reduce consciousness of source reduction and limits in production of waste. As technologies for waste management continue to evolve, waste producers may not recognize the potential impact of wastes on the environment and human health.
Advantages:
• Landfill volume is reduced
• Steam and fuel can be sold, increasing economic recovery as well as resource recovery at facilities
• W2E can be considered an environmentally responsible method of waste disposal (when in compliance with regulations.
• Clean, reliable, renewable energy sources with less environmental impact than other sources can be produced.
• Even ash residue can be reused as material for landfill construction, in asphalt mixtures and the production of cement blocks.
5.1 Regulations governing W2E
In implementing W2E facilities, it is important to consider all state, local, and federal regulatory requirements governing the production, transportation, and emissions produced by the facility. The use of advanced emissions control and monitoring technologies can ensure facilities meet federal state and local requirements in respect to the Clean Air Act. Careful consideration must also be used when determining methods for shipping and transporting fuels and other recoverable materials. Permitting may be necessary to move these items across state lines, or to other facilities. Maintaining proper management practices, and on going facility maintenance is necessary to stay up to date on regulatory guidelines while also maintaining an efficient process at the facility.

6.0 Recommendations 6.1 Policy recommendations/guidelines
The Federal government should:
• Provide long-term extension of tax incentives for renewable energy production and energy efficiency;
• Establish incentives for the construction and purchase of super fuel efficient
• autos such as plug-in electric hybrid vehicles;
• Set a national renewable electricity standard for utilities to produce a significant portion of their electricity from wind, solar, and geothermal energy. This should be at least 20% by 2020. It would reduce consumers' energy costs, energy price volatility and greenhouse gas emissions;
• Establish, enforce and update building code standards for energy efficiency in new and retrofitted buildings to save consumers money and reduce fossil fuel use;
• Provide incentives for efficiency related renovations Reduce building energy use by 50% by 2030;
• Put a price on carbon pollution, through a cap-and-trade program or other means;
• Modernize and expand the nation's electrical grid to make it smart and more secure, and capable of transferring or storing clean renewable energy in combination with electric vehicles, while providing greater access to such resources in an environmentally responsible way;
• Provide the technical and financial resources for a transition of states, like Nevada, and/or small countries around the world to be completely energy independent and carbon neutral to serve as an example of how these goals can be achieved;
• Act swiftly to increase the fuel efficiency of cars and trucks, and increase funding for private-public partnerships to build a transportation sector that uses far less or no oil;
• Buy, and give significant incentives to consumers and small businesses to buy, clean alternative fuel and plug-in hybrid vehicles. This should include natural gas heavy-duty fleet vehicles;
• Initiate electrification of our entire transportation sector so it uses only clean domestic energy soon;
• Fully fund and expand a green jobs/clean energy corps program to weatherize millions of homes, train workers for new energy technology application, build a smart grid, etc.;
• Provide incentives to states to decouple utility profits from electricity sales to encourage significant new investments in energy efficiency, and ensure net metering and “time of use” pricing/real time information is available;
• Create a Federal clean energy fund to invest in research, development and deployment of efficiency and renewable technologies;
• Encourage or direct utilities to organize the retrofitting of existing buildings to become significantly more energy efficient;
• Expedite identification and reservation of Federal public lands that have high potential for the environmentally responsible production of renewable electricity, and improving permitting processes for clean energy production on such lands;
• Vastly increase the budget for clean energy research, development and deployment, including greater emphasis on commercializing research funded by taxpayers;
• Greatly increase investments in public transit to make it more affordable and accessible;
• Fully fund and expand Low Income Home Energy Assistance Program (LIHEAP), low income weatherization and Energy & Environmental Block Grant programs;
• Reduce Federal government energy consumption by half within the next fifteen years;
• Fund research into carbon capture and storage technology that can dramatically reduce carbon dioxide emissions from coal fired power plants;
• Speed the transition from corn based ethanol to sustainable biofuels such as cellulosic ethanol made from wood chips, agriculture waste, and switch grass. This could include a joint US-Brazilian investment in sugar cane ethanol in the Caribbean, which would create jobs in this developing region;
• Convert solid waste landfills so that they produce waste heat, biofuels or fertilizer from methane emissions or organic materials; and
• Assist China and India and other developing nations with their adoption of clean energy technologies.
States Should Consider Policies to:
• Require all new state government buildings to be Leadership in Energy and Environmental Design (LEED) certified;
• Convert state vehicle fleets to clean alternative fuels;
• Create incentives for renewable energy by lowering property taxes for these facilities, and exempting them from sales tax; and
• Require that homeowner associations allow solar panels and other renewable technologies. 6.2 Future benefits
Digestion technology offers a lot of promise as way to power farms and small rural communities with a renewable and fossil-free energy, while also helping to manage the animal waste problems on farms. Farm runoff is an enormous environmental problem.
Anaerobic digestion protects surface streams from contamination because the process destroys some of harmful microorganisms that are carried in manure. In addition, digesters reduce the odor in manure, reduce the emission of greenhouses gases, and reduce dependence on fossil fuels. While the initial cost for a digester system is high, it does reduce fuel costs for a farm and even provides a small revenue source from selling electricity to the grid and selling the clean and digested manure.
Energy subsides are available as a form of tax credit for electricity generated form renewable sources including animal waste. To be eligible for the credit, the methane digester systems need to be capable of generating 150 kwh of electricity. (Clay, n.d.)

7.0 Conclusion
7.1 Summarize w2e: Movement of agricultural residue/animal waste from waste stream to energy, reduction of environmental/health risks. Future of w2e.

8.0 Works Cited

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