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BSRNews » Reflections » Biomass Energy: programs; the U.S. Department of Energy (DOE) estimated that by 2010, 4% of U.S. transportation fuel could be made from biomass, and that energy crops and crop residue could supply 14% of domestic energy demand.

Reflections » Biomass EnergyFebruary 13, 2007
Topics » Alternative Energy, Biofuel, CO2 Emissions
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There are a number of renewable sources that can be used for energy production, and one of the most abundant sources is also one of the least popular commercially. Biomass, or waste materials ranging from sewage and manure to landfill garbage and agricultural waste, can be processed or burned to generate power, and the technology needed to do this is being developed and implemented in a variety of places and ways. Biomass is currently used to generate approximately 3% of the energy consumed in the U.S., according to the Energy Information Administration. Estimates of the potential energy that could be produced using biomass vary and depend on agricultural forecasts and industrial waste reduction programs; the U.S. Department of Energy (DOE) estimated that by 2010, 4% of U.S. transportation fuel could be made from biomass, and that energy crops and crop residue could supply 14% of domestic energy demand.
FuelWaste material is most commonly discussed as a source for cellulosic ethanol. Cellulose is a primary component of plant matter that is difficult to ferment directly. Therefore, ethanol is currently made from only the plant parts that contain simple sugars; in the U.S., corn kernels are used. Cellulosic ethanol is not yet commercially produced, but the technology to do so is being developed by a number of public and private organizations. A few companies, like Dyadic International, Inc., are developing enzymes and bacteria that will break down cellulose for fermentation into ethanol. When these techniques can be used economically on a commercial scale, corn stalks and waste plant material from the timber and agriculture industries could also be used to make ethanol.
Waste products can be used to make traditional ethanol as well, but this practice is not widely implemented because these waste sources are not found in large concentrations and don't lend themselves to commercial-scale conversion. Coors Brewing Company refines residuals from the beer brewing process into 3 million gallons of ethanol annually. North Carolina State University has been researching the possibility of converting pig waste to ethanol using steam gasification methods. A Wisconsin company has also recently found a method for converting cheese waste into ethanol. It is technically possible to convert just about any substance containing sugar into ethanol, but it is only economically feasible for companies like Coors that can make their operations self-sufficient.
Biodiesel is made from waste products more often than ethanol is, but like the production of ethanol from common waste sources, large-scale biodiesel production is hampered by the fact that waste sources are scattered and moving the different feedstocks to one place can be very expensive. Used cooking oil is the most popular waste source for biodiesel production; most recycled oil comes from restaurants, though other sources are available. Arizona-based Grecycle holds an annual "grease recycling drive" after Thanksgiving to collect used cooking oil from residences, and a Missouri-based diesel plant uses waste from a nearby turkey processing plant to manufacture biodiesel.
Methane, which can be combined with oil to produce biodiesel, can be found in greater quantities than used cooking oil and some of the other material used to make biodiesel. Methane can be derived from a variety of waste sources, with landfills the most popular. Methane makes up about 50% of the gas emitted from landfill sites as a natural by-product of the decomposition of organic material; extracting the gas involves drilling a series of wells within the landfill and constructing a vacuum system that captures the gas. Agriculture giant Cargill Incorporated plans to use this system to convert methane emissions from a landfill to biodiesel at a new plant in Iowa.
The use of landfill gas is beneficial in that it prevents methane, a powerful greenhouse gas, from entering the atmosphere; landfills account for 13% of the methane emitted worldwide. There are drawbacks to using landfill gas, one of which is the emission of nitrogen oxides that results from the combustion of landfill gas. The use of methane from landfills is not widely practiced, so regulations regarding its use are widely varied and very little governmental support is currently available.
Extracting methane is not the only way that waste products can be used to generate fuel. Japanese scientists at the Tokyo University of Agriculture and Technology have extracted gasoline from cow manure by subjecting the manure to high pressure and temperature while applying a catalyst; no details have been disclosed. This technology is expected to be introduced to the commercial market by 2011.
PowerMethane can also be refined into natural gas and used for other power applications, including electricity production. An increasingly popular source of methane for power generation is manure, most commonly from dairy cows; anaerobic digesters are used to break the manure down until methane is released. In Vermont, the Central Vermont Public Service's Cow Power program allows customers to purchase power generated using local farm waste. Pacific Gas & Electric Company, the utility subsidiary of PG&E Corporation (NYSE:PCG), plans to buy 8,000 Dth/d of natural gas produced from cow manure to fuel some of its power plants. And utility companies aren't the only ones using manure as a power source: methane from manure is being used by a growing number of industries to generate power. Ethanol plants being planned in Nebraska and Indiana will use cow manure to power the ethanol production. Feedlots will be included in the refinery complex so that transportation of the manure will be inexpensive; completing the cycle, cows in the feedlot will be fed a by-product of the ethanol production process.
Cows are not the only group providing power-generating manure; methane can be extracted from all kinds of manure. The Munich zoo uses waste from the animals to provide power to zoo facilities. Reynolds, Indiana, plans to remove itself from the power grid and use pig manure as a power source instead. There are a number of pig farms near Reynolds and each pig produces seven gallons of manure each day; this amount of manure could be used to produce about 3.2 MW of power, which is more than Reynolds consumes. Dogs are also making a contribution; a garbage company in San Francisco is testing the feasibility of using dog waste collected from area parks to generate power. Any place where manure is collected in large amounts can provide a renewable energy source.
According to Environmental Power Corporation (AMEX:EPG), a company that produces manure power, the potential U.S. market for manure gas is over 250 million BOE per year. EPG estimates that 875 cows produce enough methane to provide power to about 600 homes. The conversion process also produces useful by-products, including pathogen-free livestock bedding and seed-free fertilizer. Another benefit to using manure to generate power rather than letting it decompose in a heap lies in the fact that the methane released into the atmosphere as the manure breaks down is a greenhouse gas 21 times stronger than carbon dioxide. Capturing and burning the methane to generate power prevents its emission; as a result, some farmers who contribute manure to power generation have been able to increase their income by selling greenhouse gas emissions credits on voluntary greenhouse gas markets.
Opponents of manure power point out that it is only economically competitive with fossil fuels when the manure comes from very large, industrial farms, where the manure is stored in large piles or pools that can pollute ground water and streams. The United Nations Food and Agriculture Organization has said that large livestock operations create environmental and human health hazards that are not created by smaller farms, negating some of the environmental benefits of using the manure in the first place. However, transporting manure from a number of smaller farms to a centralized location for processing is not economically feasible. For this reason, manure power may remain a local supplement to the grid rather than a large-scale source of energy.
Another waste source of energy is industrial and agricultural waste, which can be burned directly to create heat or generate electricity. According to the Union of Concerned Scientists, biomass can replace up to 20% of the coal burned in boilers at coal-fired power plants; the process, called co-firing, reduces power plants' operating costs and emissions. Alliant Energy Corporation (NYSE:LNT) began testing the co-firing of switchgrass at its Iowa facility in 2005 with help from the DOE; the tests were so successful that Alliant built a permanent biomass processing facility at the site.
HeatAnimal waste can also be used to generate heat. The city of Oslo, Norway, uses raw sewage to heat some residences; a refrigerant sucks heat from the sewage and transfers it to a 250-mile network of hot water pipes that run under the city. Augmented by plants that burn industrial waste, the sewage raises the water temperature 38 degrees Celsius. Oslo's system illustrates the use of biomass power from a number of sources, rather than just one; while this increases complexity, it also increases the resilience of the system since it is no longer dependent on just one energy source.
ConclusionThe number of different waste materials that can be used to generate power seems endless, but the creation of biomass energy is not more widespread because the cost of transporting the waste to commercial production centers is often prohibitive. Biomass contains less energy per pound than fossil fuels, so shipping raw biomass more than 50 miles uses more energy than the biomass will provide. Biomass is best suited for small-scale, local power generation where the feedstock is essentially free and the cost of transporting it is negligible. While biomass energy may never be able to meet global energy demand, it can be used in a variety of ways to supplement the grid; in smaller communities, biomass power plants can be custom-designed to meet the area's energy demand in a self-sustaining manner with no concern that the input will run out. After all, waste is everywhere.
SourcesEnergy Information Administration. "U.S. Energy Consumption by Energy Source." Energy Information Administration. U.S. Department of Energy. Accessed 21 January 2007. http://www.eia.doe.gov