Evaluation of in-vessel co-composting of yard waste and development of kinetic models for co-composting

Background Organic solid waste management is a majorchallenge in high population density areas like apartments,educational institutions, hospitals, etc., as their disposalwith other wastes could not only lead to issues like vectormenace, odour generation but also would lead to loss ofresources that could be reused such as nutrients which willbenefit soil. In places like educational institutions, themajor portion of waste generated is organic waste, especiallyfood waste and yard waste from the campus, apartfrom paper waste. Composting is an organic waste treatmentmethod that is cost effective and leads to resourcerecovery. In this study, the characteristics of composting ofyard waste and co-composting of yard waste with wastesgenerated in an institution (university campuses of AnnaUniversity, Chennai, India) are examined. The compostswere characterized in terms of total solids, volatile solids,pH, electrical conductivity, carbon: nitrogen (C:N) ratioand total Kjeldahl nitrogen. The stability index and germinationindex of the compost were assessed.Results The C:N ratio of all the different composts (exceptthe one generated from yard with canteen wasteconsisting of vegetable waste) produced in this study has avalue less than 30:1, which satisfies the basic requirementsfor the compost. It was also observed that the maturecompost from these feedstocks did not have heavy metalsat toxic levels.Conclusion This study demonstrated that the co-compostingof yard wastes with paper and canteen wastes (fruit,coffee grounds, tea leaf waste) could produce value-addedproducts. In addition to that, kinetic models were developedto predict the decomposition rate constant of theprocess.