Process characterization, and stability and maturity testing of forced air, static pile processed food scrap and wood chip compost

Forced air, static pile, food scrap and wood chip composting in an enclosed facility followed by open windrow curing of the screened compost was studied to assess site layout and processing factors leading to odor generation and leachate, stabilization of the degrading food scraps, and maturation of the finished compost.; Pile temperature and moisture content were monitored, and dissection of several piles at different retention times helped to determine that retention could be shortened from 8 wk to 5 wk, increasing the facility capacity by 40%.; Successive compost piles in the same bay were intensively monitored through four cycles. Screened composts at 0, 4, and 12 wk of curing were tested for stability (CO2 trap respiration) and maturity (24 hr cress seed germination and young root growth). Temperature monitoring at numerous points within the pile showed that the core and back of the pile were more dependent on aeration for biologically induced temperature increases, and that the exposed sides heated rapidly, probably due to the higher oxygen content of air near the surface as it diffused toward the pile center. Piles developed peak temperatures between 65°C and 71°C, even with cold ambient temperatures. Respiration in the stability test dropped from 20 mg CO2- carbon/g volatile solids/day to 6 mg after 4 wk of curing, but did not drop much further after 12 wk. The maturity test showed the freshly screened compost stimulated cress seed germination, but inhibited radicle growth. Results were not necessarily improved after 4 wk of subsequent curing.; Additional important management factors were noted throughout the study. Site inspections showed that accumulation of organics and weather exposure made the screening operation the critical odor source. Continued monitoring showed that seasonably cold conditions had more effect on how equipment functioned than on the compostability of the food scraps. Leachate occurred with mixes having >60% %M, which could be controlled by adding the appropriate amount of mix chips. In addition to laboratory tests on curing and curing methods, limited testing of the finished product in a greenhouse and an open flower bed were successfully conducted.