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of methane, about 50 percent. To capture this biogao the process must be in a <br />closed vessel. <br />When anaerobic digestion is applied to the organic fraction ofMS\N, the primary <br />purpose of the facility shifts from landfill diversion to biogas production. There are <br />many anaerobic digestion plants both in use today and historically that have been <br />installed to produce and utilize biogasaswell as manage a waste. However, most of <br />these facilities utilize sewage sludge, animal manures and other homogenous wastes <br />as feedstock. Very few utilize »4SVVasafeedstock. <br />It has long been o/rnrnon pnadjoa in Europe to use anaerobic digestion at waste <br />water treatment plants to treat sewage sludge. It has been less common over the <br />same period to use anaerobic digestion to treat industrial effluents and agricultural <br />sludges, although there are a number of examples dating back to the 1950s. In the <br />last ten years or so in Europe, because ofthe introduction of requirement, that the <br />separated organic fraction of MSVV be treated before landfill disposal, anaerobic <br />digestion has been adopted for this purpose. Anaerobic digestion has long been <br />popular in India where a large number of anna|| and simple plants are in use <br />processing farm wastes. Currently, a number ofvendors are offering farm-based <br />systems in both Europe and the United States. <br />The process of producing biogasfnorn y4SVV by anaerobic digestion has similar steps <br />to the production of liquid biofue| discussed above. - [haprooessindudes: <br />1. A"pretnaatnment" phase to make the organic material more available for <br />digestion by size reduction and to remove recyclable materials and <br />contaminates; <br />3. Digestion of the organic material in closed vessel by microorganisms; <br />3. Treatment of the biogas to remove water, compress the gas, and other <br />processes depending on the end use; and <br />4. Curing of the solid residue from the digestion to produce a compost product <br />which may bemarketable. <br />The longest established anaerobic treatment processes include: <br />° Anaerobic suspended growth, <br />° Upflmw and down-flow anaerobic attached growth, <br />° <br />Fluidized-bed attached growth, <br />° UoMow anaerobic sludge blanket (uaob), <br />° <br />Covered anaerobic lagoons, <br />° <br />Membrane separation anaerobic processes, and <br />° <br />Dry process anaerobic digestion ofMSVV. <br />The above emerge in process designs, when developed and offered by the <br />technology providers, which are either optimized to: <br />1. Efficiently remove material (mostly organic) from liquid streams topermit <br />discharge of a treated effluent to a specified water quality standard, and <br />biogas production may be just incidental; or <br />2' To provide treatment ofa waste material, including plSVV, to make it suitable <br />for diversion away from landfill, with biogas generation optimized for revenue <br />creation, and potential sales of fibrous and liquid fertilizer by-products. <br />[]88/C08027-01 B-18 August 15,2OO8 <br />