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of methane, about 50 percent. To capture this bkogas the process must be in a closed vessel. When anaerobic digestion is applied to the organic fraction of MSW, the primary purpose- ofthefac|ity shifts from landfill diversion tobiogasproduction. There are | nt� both in, h�torca||ythat have been rnanyana�nobicdiges�|on p� . plants --- ' ' �� Hoxvev�r, most of installed produce and u�|i�� biogas as well aornanegea waste. , ^-- these facilities utilize sewage sludge, anima| manures and other homogenous wastes as feedstock. Very few utilize MSVVasafeedstock. It has long been common practice in Europe to use anaerobic digestion at waste water treatment plants to treat sewage sludge. It has been less common over the sane period to use anaarobio digestion to tat industrial effluents and agricultural sludges, although there are a number of ��anp| �� dating back to the 1950s . In the last ten 'years or so in Europe, because of the introduction of requirement that the separated organic fraction of »By be treated before landfill disposal, anaerobic digestion has been adopted for this'urpooe. Anaerobic digestion has long been popular in India where a large number of small and simple plants are in use offering fa bas�d s� processing farm wastes. Currently, a nunnberofvendors are o rng rnm- aternsin both Europe and the United States. The process ofproducing biogasfionm y4S\N bv anaerobic digestion has similar steps to the production of liquid b|ofue| discussed above. Tha process includes: 1 - A"pretreatn)ent" phase to make the organic material more available for digestion bv size reduction and to remove recyclable materials and contaminates; 2 Digestion of the organic material in a closed vessel by microorganisms; 3. Treatment of the biogas to remove water, compress the gas, and other pro o' processes on u�' and 4. Curing of the solid residue from the digestion to produce a compost product which may be marketable. The longest established anaerobic treatment processes include: ° Anaerobic pendadgroxvth' • U''mw and down-flow anaerobic attached growth, • Fluidized-bed attached growth, • UoOovv anaerobic sludge blanket (uaeb), • Covered anaerobic lagoons, � Membrane separation anaerobic processes, and ° Dry process anaerobic digestion ofMSVV' The above emerge in process designs/ when developed and offered by the technology providers, which are either optimized to: 1 ' Efficiently remove material (mostly organic) from liquid streams to discharge treated effluent to specified water quality standard, and biogas production may / just incidental; or 2' To provide treatment ofa waste material, /n duding4By / to make itsuitable for diversion away from landfill, with biogas generation optimized for revenue creation, and potential sales of fibrous and liquid fertilizer by-products. GBB/CO8027-01 I B-18 August 15, 2008