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A new closed loop heating system for composting of green and food wastes
- Pandey, Pramod K., Cao, Wenlong, Biswas, Sagor, Vaddella, Venkata
- Journal of cleaner production 2016 v.133 pp. 1252-1259
- Escherichia coli, Salmonella, air, carbon nitrogen ratio, composting, copper, environmental factors, feedstocks, food waste, green waste, heat exchangers, nutrient content, pH, pathogens, plowing, soil amendments, temperature, urban areas, water content
- Excessive amount of foodwaste in global food supply chain is a serious issue, and additional controlling measures are needed to prevent wastages of food. In our approach to tackle this global problem, we developed an improved composting system, which can be used as a small decentralized unit for treating food and green wastes in urban environment. A new closed loop heating system was developed to enhance the temperature of compost piles, and accelerate the inactivation of pathogens during the process. The system involved a heated bath circulator, an air injector, and a system of copper piping used as heat exchangers in bins. The system was tested under aerated, static, and plowed composting conditions. To test the pathogen inactivation in the composting, the concentrations of Salmonella and Escherichia coli in compost were measured. In addition, the changes in C:N ratio, pH, and moisture content were observed to understand the quality of the compost in terms of nutrient concentrations. Results showed that the Salmonella levels reached to non-detectable limit in 34, 5, and 34 days of composting in aerated, static, and plowed composting system, respectively. The E. coli levels were detectable till day 70 indicating longer survival of E. coli cells compared to Salmonella under composting environment. In the current system, feedstock C:N ratio was reduced by 71, 70, and 62% in static, plowed, and aerated composting, respectively. We anticipate that the proposed system will yield a new composting design with less dependency on environmental conditions. The proposed design can be used for developing an in-door composting system to convert food and green wastes into pathogen free soil amendment.