Microbial dynamics and enzyme activities during rapid composting of municipal solid waste – A compost maturity analysis perspective M.P. Raut, S.P.M. Prince William * , J.K. Bhattacharyya, T. Chakrabarti, S. Devotta Solid Waste Management Unit, National Environmental Engineering Research Institute, Nehrumarg, Nagpur 440 020, India Received 30 July 2007; received in revised form 12 November 2007; accepted 12 November 2007 Available online 26 December 2007 Abstract An investigation was carried out in the laboratory to find out the microbial dynamics and enzyme activities during rapid composting of municipal solid waste (MSW). Various treatments such as aeration (A), addition of chemical agents (glucose (G) and acetic acid (AA) and application of cellulolytic microbial (M) inoculum (Phanerochaete chrysosporium and Trichoderma reesei) were used to facilitate the decomposition of MSW. The result of the present investigation revealed that the degradation of organic substrates were quick (within 9– 12 days) in case of rapid composting as indicated by the reduction (below 20) in C/N ratio. Whereas, normal composting took more than 20 days to attain C/N ratio of below 20. Estimation of selected enzymes (amylase, protease, phosphatase and cellulase) provided infor- mation on the substrate specific degradation profiles of various labile substrates contained in organic waste. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Facilitated aeration; Enzyme activities; Municipal solid waste; Microbial biomass; Compost 1. Introduction In recent times, much importance is given to the compo- sting of municipal solid wastes because of its eco-compati- bility and easy operational procedures. Successful conversion of organic matter into simpler units of organic carbon and nitrogen is the basic functional process of com- posting. Composting helps in managing large quantities of organic wastes in a sustainable manner. It is one of the technologies of integrated waste management strategies, used for the recycling of organic materials into a useful product (Giglotti et al., 2005). In India, composting of bio-degradable wastes has been made compulsory by the Supreme Court considering the recommendations made by the Burman Committee report in 1999 and the consequent MSW handling rules (2000) (CPCB, 2002). Composting, undoubtfully, an efficient way of managing municipal solid wastes; however, disad- vantages such as time and space requirement and the need for manpower are the blocking stumps for this eco-friendly technology. Shortening of composting period with consid- erable reduction in the C/N ratio is one of the options con- sidered for making the composting business lucrative one. Another intricacy in composting technology is the assess- ment of compost maturity. Many parameters to evaluate the maturity of compost from food wastes or city refuse, such as the change of physico-chemical properties (Mathur et al., 1993; Jiminez and Garcia, 1992), calorimetric and spectroscopic methods (De Oliveira et al., 2002), germina- tion tests (Zucconi et al., 1985) enzymatic activity (Vuori- nen, 2000) have been reported. Hue and Liu (1995) suggested using the water soluble organic-C/total organic nitrogen ratio as a suitable parameter for assessing com- post maturity. He also proposed a value of <0.70 as a new index of compost stability. However, the abundance of chemical and biological changes that occur during the composting process and the number of methods that have been used to monitor these parameters (Melis and Castaldi, 2004; Castaldi 0960-8524/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.11.030 * Corresponding author. Tel./fax: +91 0712 2249752. E-mail address: prince14271@yahoo.com (S.P.M. Prince William). Available online at www.sciencedirect.com Bioresource Technology 99 (2008) 6512–6519