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Tracy Material Recovery and Transfer Station—Compost Facility <br /> Alternative Compost Technologies <br /> As described in the Project Description, the compost feedstocks will include co-collected food <br /> waste and green waste that could contain up to 20% food waste and food scraps from <br /> residential customers. The co-collected yard waste and food waste could either be composted <br /> in a windrow composting system or in an aerated static pile system. <br /> Food waste from commercial sources may be mixed with green waste to achieve an optimum <br /> ratio of carbon to nitrogen. Materials containing food waste will be composted utilizing a <br /> covered aerated static pile system, and could include compost feedstocks containing as much <br /> as 50%food waste. <br /> TRACY MRF/TS & CF proposes to cover actively composting material with food waste content <br /> above 20% using forced aeration with either an impermeable cover with aeration openings or <br /> with a minimum six-inch thick layer of finished compost, as described in the Project Description. <br /> When the impermeable cover is used, the only option is that the forced aeration be under <br /> negative pressure, with the exhaust gas passing through a biofilter before discharge. In the <br /> case of a layer of finished compost, the forced aeration can be either positive or negative. In <br /> the case of positive aeration, the layer of finished compost serves as the biofilter; however, <br /> there is not as much data demonstrating the degree of emissions control with positive aeration <br /> through a finished compost layer as there is with a constructed biofilter. <br /> Finished Compost Layer Emission Control Efficiency <br /> Two studies have been done on compost windrow emission control using a layer of finished <br /> compost. <br /> CalRecycle Study <br /> Emissions testing of volatile organic compounds was done at a compost facility in Modesto, <br /> sponsored by CalRecycle (CalRecycle, 2008). A layer of finished compost was placed over a test <br /> windrow; however, the windrow was managed as an open windrow without forced aeration. <br /> Nonetheless, the approximately six inch layer of finished compost reduced emissions over the <br /> first 7 days of the trial by 82% relative to the control. When averaged over the first 14 days, the <br /> measured emission reduction was 75%. The image below (Figure 1) is a front loader placing the <br /> finished compost cover on a windrow. <br />