Research Article: Survival of Culturable Bacteria during Co-composting of Institutional, Agricultural, and Municipal Solid Wastes

Abstract

Cooperation among waste generators to co-compost institutional, agricultural, and municipal solid waste can balance carbon:nitrogen ratios, yield a value-added product, and ultimately reduce solid waste disposal nationally. A study was conducted to determine concentrations of indicator bacteria and other bacteria in compost components, immature compost, and cured compost. Compost components included pulped institutional food waste, newsprint, farm animal waste, and municipal landscape waste. Carbon:nitrogen ratios were balanced (mean = 30:1) through cooperative co-composting of institutional and agricultural waste with municipal landscape waste. Compost windrows were mechanically turned an average of 15 times during 60-days of composting, reaching highest internal mean temperatures of 62° C. Raw food waste, animal waste, immature and cured compost samples were collected aseptically and analyzed for total and fecal coliform, Enterococci, Staphylococci, and heterotrophic bacteria using standard culturing techniques. Initial indicator bacterial concentrations of 4–8 log₁₀ colony forming units (cfu) per milliliter (ml⁻¹) or gram (g⁻¹) dry weight recovered from animal waste and 2–3 log₁₀ cfu g⁻¹ dry weight recovered from raw food waste were reduced to below the detection limit of approximately 20 cfu g⁻¹ dry weight in all compost samples analyzed. Staphylococci and heterotrophic bacteria concentrations recovered from immature compost samples were also reduced in cured compost. Results indicated that cooperative waste composting reduced culturable indicator bacteria concentrations in compost samples analyzed. Results suggested that cooperative solid waste composting may reduce environmental health concerns associated with institutional, agricultural, and municipal wastes, while generating a value-added soil amendment and reducing solid waste volume.