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

Abstract

Background Organic solid waste management is a major challenge in high population density areas like apartments, educational institutions, hospitals, etc., as their disposal with other wastes could not only lead to issues like vector menace, odour generation but also would lead to loss of resources that could be reused such as nutrients which will benefit soil. In places like educational institutions, the major portion of waste generated is organic waste, especially food waste and yard waste from the campus, apart from paper waste. Composting is an organic waste treatment method that is cost effective and leads to resource recovery. In this study, the characteristics of composting of yard waste and co-composting of yard waste with wastes generated in an institution (university campuses of Anna University, Chennai, India) are examined. The composts were characterized in terms of total solids, volatile solids, pH, electrical conductivity, carbon: nitrogen (C:N) ratio and total Kjeldahl nitrogen. The stability index and germination index of the compost were assessed. Results The C:N ratio of all the different composts (except the one generated from yard with canteen waste consisting of vegetable waste) produced in this study has a value less than 30:1, which satisfies the basic requirements for the compost. It was also observed that the mature compost from these feedstocks did not have heavy metals at toxic levels. Conclusion This study demonstrated that the co-composting of yard wastes with paper and canteen wastes (fruit, coffee grounds, tea leaf waste) could produce value-added products. In addition to that, kinetic models were developed to predict the decomposition rate constant of the process.

Comparison of three systems of decomposition of agricultural residues for the production of organic fertilizers

“…In VC and CP the Nt increased at 68 DAE (1.76 ± 0.05% and 1.71 ± 0.13%, respectively), while in SC an increase in Nt was observed at 35 DAE (1.70 ± 0.02%). In all three treatments Nt had increased by 183 DAE, which coincides with Sangamithirai et al (2015) who found an increase in Nt at the end of the SC process with OW from garden and tea leaves, as well as with Fornes et al (2012) who recorded increases of Nt in VC and CP.…”

“…In VC the percentage of OC dropped sharply by 68 DAE and the subsequent decrease was gradual, which coincides with Garg and Gupta (2011) for the transformation of plant residues and cow manure with E. fetida. The gradual degradation of OC in SC coincides with that mentioned by Sangamithirai et al (2015), when studying gardening and paper residues.…”

“…The GI presented a similar gradual decrease for SC and CP; however, for VC an increase of the GI was observed towards 169 DAE (132.78 ± 5.46%), followed by a subsequent decrease at 189 DAE (100.26 ± 9.34%). Sangamithirai et al (2015) reported that the GI of different mixtures of OW transformed under SC during 90 d was less than 80%, and therefore considered that their direct application to the crops could be phytotoxic.…”

Enriched cocoa pod composts and their fertilizing effects on hybrid cocoa seedlings

“…C/N ratio has been used as an indicator of the potential of compost stability. A mature compost should have an C/N ratio B25 (Sangamithirai et al 2015). The C/N ratio of the final composts was also lower than 12 (Table 3).…”

In-vessel co-composting of yard waste and food waste: an approach for sustainable waste management in Cameron Highlands, Malaysia

“…Riffaldi et al (1986) studied GI of garden cress and reported that compost is certainly not phytotoxic to plants when GI is more than 80%. Similar to garden cress seeds, germination indexes of at least 80% in radish seeds (Mitelut and Popa 2011) and cucumber seeds (Sangamithirai et al 2015) indicated production of compost which is not phytotoxic. Investigated compost samples in this study recorded germination index higher than those achieved by Kumar et al (2010) during co-composting of green waste and food waste at low C/N ratio using an invessel lab-scale reactor.…”