Agenda - Council - 06/24/1984 - Laserfiche WebLink

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I Page Seven I . . Rose.ch ~ demonst~ztlom of biological treatment of solid w~te hove lncre~ed ~n recent yeors...Anaerobic (oxygen-free) treatment produces I methane gas and a humus lIke material. Aerobic (oxygen-rich) treatment produces a sterilized humus like material or compost. These biological treatment methods can reduce the weight of solid waste by approximately I 50%. Aerobic treatment or composting can be applied to several kinds of solid w~ste including leaf waste and source separated organics such as food waste, and mixed municipal waste. Composting treatment of solid waste may i be occomplished through windrow aerobic charnbers, cJay composting, or digesters. Windrow composting is a biological process of cc)mpc=ting, similar to backyard composting only on a larger scale using heavy equipment. Windrowing involves an aerobic decomposition through frequent turning of long rows of organic material. Windrow turning can be accomplished through a variety of methods utilizing machinery such as front end loaders or I equipment designed specific-al Iy for turning compost windrows. Sewage sludge coo be co-composted with mixed municipal waste in this method. A variety of aerobic chambers have been used in Europe to compost solid waste. I While this compost technology is more capital intensive tl~3n windrowing~ - aerobic chambers speed up material processing because moisture~ oxygen~ and temperature levels can be controlled. Sewage sludge can also be co- l composted in aerobic chambers with mixed municipal wastes. ! Clay cllgester is an experimental technology that is in many respects a modified sanitary landfill operation to maximize biological octivity~ methane generatian~ and rapid stabilization of the waste. In many respects a clay digester is very similar to the type of second generation landfill design that wes described in the County's abaten?nt report as an "accelerated I decomposition landfill." (See AppendIx 1V.) i Solid waste may also be processed to reduce volume thr~ camlxation of the solid waste materials. This co.m. bustion may take the form of incineration (simply the burning of the waste w~th no recovery of materials or energy) or energy recovery (burning of the waste with the recovery of energy for space I heating ood/or energy). The only difference between the two concepts is the providing of equipment to recover the heat energy from the combustion chamber flue gases. Incineration and energy recovery may be I done through the m~ss burning in a large scale waste to facility such energy as proposed by Hennepin County or through the use of a number of anal ler premanufactured modular combustion units. Large scale mass burn facilities I and modular combustion units are bctsically similar in that they burn unprocessed waste and differ primarily only in terms of size. Modular combustion units normally are supplied in modules ranging in size from 15 - I IS0 tons per day and are available in approximately 25 - SO ton increments. Primary combustion is usually followed by an after burner section to assure complete combustion, which may or may not be followed by the recovery of I heat. If heat recovery is provided the concept would be referred to as waste to energy. If heat recovery is not provided and all of the heat energy is vented up the stack, the process would be referred to as incineration. The I combustion of sol id waste as an abatement strategy could be expected to accomplish approximately 70 - ~K)% reduction of the sanitary landfill needs of Anoka County. (See Appendix III for costs.)