Agenda - Council - 07/24/1984 - Laserfiche WebLink

Home

I I Page Seven Rese~ and c~mstratiom of bl,o!ogical treatment of ~lid w~te ~ve I i~r~ in r~t yea~ ~a~ (o~g~f~) ~eatment pr~uc~ metre ~ ~d a h~us like ~enal. Aer~m (o~ge~ri~) tr~tm~t I I I I I I I produces a sterilized humus llke m~terial or compost. These biological treatment methods can reduce the weight of solid waste by approximately 50%. Aerobic treatment or compasting can be applied to several kinds of solid waste including leaf waste and source separated organics such as food waste, and mixed municipal waste. Compastlng treatment of solid waste may be accomplished through windrow composting, aerobic chambers, or clay digesters. Windrow compasting is a biological process of composting, similar to bac~yard compasting 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 equipment designed specifically for turning compost windrows. Sewage sludge can be co-composted with mixed municipal waste in this method. A variety of aerobic chambers have been used in Europe to compost solid waste. While this compost technology is more capital intensive than windrowing~ . aerobic chambers speed up material processing because moisture~ oxygen~ and temperature levels cc~ be co~trolled. Sewage sludge c~ also be co- compasted in aerobic chambers with mixed municipal wastes. Clay ~gester is an experimental technology that is in many respects a nxxlified sanitary landfill operation to maximize biological activity, methane ganeration~ and rapid stabilization of the waste. In m~y respects a clay digester is very similar to the type of second generation landfill design that I was described in the County*s abatement report as an "accelerated decomposition landfill." (See Appendix 1V.) Solid ..v~t. e may also .be ~proc~ssed. to ..re~uce volume tl-~-ough combustio~ of I the sol,d waste matermls, This cambushon may take the form of incineration (simply the burning of the waste with no recovery of materials or energy) or i energy recovery (burning of the waste with the recovery of energy for space heating and/or process 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 ~ energy recovery rna), be I done through the mass burning in a large scale waste to energy facility such as proposed by Hennepin County or through the use of a number of smaller premanufoctured modular combustion units. Large scale mass burn facilities I and modular combustion units basically similar in that they burn are unprocessed waste and differ primarily only in terms of size. Modular combustion units normally are supplied in modules ranging in size from I$ - I 150 tons per clay and are available in approximately 25 - .50 ton increments. Primary combustion is usually followed by on 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 solid waste as m abatement strategy could be expected to accomplish approximately 70 - ~)% reduction of the sanitary landfill needs of Anoka County. (See Appendix III for costs.)