Cellulolytic activity in municipal solid waste composting

Abstract

A study was made of the open windrow method of municipal solid waste composting as related to those factors that might influence cellulose decomposition. Composting temperatures reached a maximum (55–65 °C) at 3 weeks and then gradually decreased during the rest of the 49-day process. The pH values of compost samples homogenized in distilled water decreased slightly during the initial stages of the process and then increased gradually to final values of 7.0–8.5. Clarified compost extracts were assayed for cellulase activity by measuring the hydrolysis rate of carboxymethylcellulose (CMC). Maximal cellulase activity occurred at 65 °C, pH 6.0, with a CMC concentration of 2.5%. The cellulase activity of compost increased 10-fold at a logarithmic rate while the cellulose content decreased 50%. In a preliminary search for microorganisms active in cellulose degradation during the composting process, three cellulolytic species were isolated; these were identified as Aspergillus fumigatus, a Bacillus species, and a Thermoactinomyces species of the Actinobifida group.