The Maturity and CH4, N2O, NH3 Emissions from Vermicomposting with Agricultural Waste

ABSTRACT This study investigated the maturity and gaseous emissions from vermicomposing with agricultural waste. A vermicomposting treatment (inoculated Eisenia fetida) was conducted over a 50-day period, taking tomato stems as the processing object and using cow dung as the nutrient substrate. A thermophilic composting treatment without earthworm inoculation was operated as a control treatment. During the experiment, maturity indexes such as temperature, pH, C/N ratio, and germination index (GI) were determined and continuous measurements of earthworm biomass and CH4, N2O, and NH3 emissions were carried out. The results showed that the temperature during vermicomposting was suitable for earthworm survival, and the earthworm biomass increased from 10.0 to 63.1 kg m−3. Vermicomposting took less time on average to reach the compost maturity standard (GI 80%), and reached a higher GI (132%) in the compost product compared with the thermophilic composting treatment. Moreover, the decrease of the C/N ratio in vermicompost indicated stabilization of the waste. The activities of earthworms played a positive role in reducing gaseous emissions in vermicompost, resulting in less emissions of NH3 (12.3% NH3-N of initial nitrogen) and total greenhouse gases (8.1 kg CO2-eq/t DM) than those from thermophilic compost (24.9% NH3-N of initial nitrogen, 22.8 kg CO2-eq/t DM). Therefore, it can be concluded that vermicomposting can shorten the period required to reach compost maturity, can obtain better maturity compost, and at the same time reduce gaseous emissions. As an added advantage, the earthworms after processing could have commercial uses.