Gaseous Biomass Fuels
Animal Waste | Food Byproduct | Pulp & Paper | Human Waste | Landfill Gas | Links
Methane can be produced from animal wastes in a process known as anaerobic digestion. The process works best in an airtight container containing a mixture of bacteria normally present in animal wastes. The bacteria break down the waste, such as fat and protein, into simpler molecules. The final product is a biogas containing methane and carbon dioxide, which can be used for heating or electricity production in a modified internal combustion engine or an advanced gasification technique to fuel a gas turbine.
Animal manure was identified by the study, Animal Manure and Related Biomass Feedstock Market Assessment and Preliminary Feasibility Study for a Paper Mill Biomass/CoGen Facility produced by LINPAC, as the most available source of feedstock in the state, and though transfer costs might be high, changing regulation could make it more economical. The report lists, sector by sector, quantities of waste available. Anaerobic digestion was shown to be economically feasible and environmentally beneficial. LINPAC recommended using a gas combustion turbine/cogeneration system, and despite high capital costs, the system had a positive return on investment.
The South Carolina Energy Office hired Dr. Joe Flora from the University of South Carolina to identify the potential for using poultry litter as an energy resource in the report, Availability of Poultry Manure as a Potential Bio-Fuel Feedstock for Energy Production. The report identified between 650-700 tons of available poultry litter each year.
Facilities already exist in South Carolina to produce energy from poultry manure and litter, but the waste is burned. The Johnny Hite Farm in Batesburg uses a Hardy Furnace to heat the chicken house during colder months. Though the heater primarily burns wood, it has also been adapted to burn chicken litter, composed of a significant amount of wood chips. More information about the process can be found in the report, Case Studies of Biomass Energy Facilities in the Southeastern U.S., produced by the Meridian Corporation. Though energy can be produced by burning animal waste, it is far more beneficial to produce biogas such as methane.
Though information gaps exist for methane potential from animal residuals, food service byproducts, and food processing byproducts in South Carolina, they are readily available for electricity generation through anaerobic digestion. According to the report, Animal Manure and Related Biomass Feedstock Market Assessment and Preliminary Feasibility Study for a Paper Mill Biomass/CoGen Facility produced by LINPAC, approximately 169,000 tons of animal residual and food waste are generated each year in South Carolina. A small portion of these food service and processing byproducts are used as animal feed and fertilizers, but a significant portion is sent to landfills. More study is needed to understand the economic potential for these forms of green power in South Carolina. The new Animal Co-Products Research and Education Center at Clemson University will address these issues in the future.
The pulp and paper industry produce large amounts of wood residues as a result of logging and processing operations. Trees are composed of lignin, hemicellulose, and cellulose fiber and due to the chemical and physical properties of lignin, it breaks down easier than cellulose. Pulping separates the lignin and cellulose fibers to create paper. The leftover materials can be used to create energy for the paper mill. South Carolina produces approximately 250,000 tons of pulp and paper waste a year according to Animal Manure and Related Biomass Feedstock Market Assessment and Preliminary Feasibility Study for a Paper Mill Biomass/CoGen Facility produced by LINPAC. Due to its homogenous nature, cellulose is an excellent source of feedstock for anaerobic digestion in a biomass cogeneration facility. Care must be taken however to modify current plant wastewater treatment procedures as oftentimes biocides are used to prevent bacterial buildup in pipes which would alter the effectiveness of anaerobic digestion processes. Currently, the LINPAC Paper Plant in Cowpens is planning to install a biomass cogeneration facility to power the plant with pulp and paper residuals.
Sewage and human fecal waste have always been a contentious issue for city planners and finding an environmentally sound way to dispose of this waste has proven difficult. The anaerobic digestion of sewage sludge produces biogas similar to that produced by animal waste, with about 50-60 percent methane. Methane is compressed, purified and stored in a container known as a gasometer, and then transported to a gas engine to produce electricity. A study being conducted for the South Carolina Energy Office will examine the feasibility of extracting methane from sewage in South Carolina. Results should be available by September 2006. According to estimates by the SC Department of Health and Environmental Control, approximately 148,500 tons of human sewage are generated a year in the state.
Landfill gas accounts for almost all of the green power available to South Carolina households and businesses. Since 1999, the South Carolina Energy Office has partnered with the U.S. Environmental Protection Agency's Landfill Outreach Program (LMOP) in an effort to reclaim and use landfill gas in the state. Concentrated efforts on the Landfill Gas to Energy Program (LFGTE) projects have resulted in significant energy and environmental benefits to the state. Landfill gas is produced in a similar manner to anaerobic digestion. The anaerobic conditions within a landfill produce methane and other gases naturally, and these gases migrate to tubes deep within the landfill. The tubes transport the gas to collection stations on the surface, where it goes through a cleaning process to remove harmful and corrosive chemicals prior to electricity generation.
In 2001, Santee Cooper became the first electric utility in the state to generate and offer green power to its customers utilizing electricity from the 3.3 Mwh (megawatt hour) Horry County Landfill Generating Station near Conway, and expects to increase to 9 Mwh. The company opened its second green power facility in 2005 at Allied Waste's Lee County Landfill, generating 5.4 Mwh of electricity, expecting to increase to 21 Mwh. The largest LFGTE project, costing $12 million, became operational in 2003 at the Palmetto Landfill in Spartanburg County, and produces the equivalent of 10 Mwh of electricity and will upgrade to 12 Mwh. The majority of methane gas produced is piped 9.5 miles from the landfill to BMW's automotive manufacturing facility near Greer. The methane powers four turbines, generating enough electricity to supply 20 percent of the plants electrical needs and 80 percent of their thermal needs. BMW is upfitting the system and upon completion landfill gas will supply 40 percent of the plants electrical needs and 100 percent of thermal needs. Santee Cooper constructed two additional green power stations in 2006: 1) Anderson Regional Landfill, generating 5.5 Mwh now and increasing to 13 Mwh and 2) Screaming Eagle Landfill in Richland County, generating 5.5 Mwh and increasing to 11 Mwh.
These facilities bring Santee Cooper's total green power generation to 29.7 megawatts, and in the future 70 Mwh. Three upcoming Santee Cooper projects include the Richland Northeast Landfill (starting at 2 Mwh, and increase to 7 Mwh), Oak Ridge Landfill in Dorchester County (starting at 4 Mwh, expected to increase to 7 Mwh), and Hickory Hill Landfill in Jasper County (starting at 4 Mwh, expected to increase to 7 Mwh). The SC Energy Office expects by 2012 Santee Cooper will bring the total energy produced by landfill gas to 87 Mwh. The map below locates current landfill projects around the state.
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