Abstract:
Thermophilic composting produces a significant amount of greenhouse gases. The objectives of this
study were (i) to evaluate the effectiveness of vermicomposting to reduce nitrogen losses and greenhouse gases emissions compared to thermophilic composting, and (ii) to determine the effect of different
variables (i.e. carbon:nitrogen ratio, earthworm density, moisture content and carbon quality) on
greenhouse gases emissions and earthworm growth during vermicomposting. The results showed that
vermicomposting significantly reduced nitrogen loss by 10e20% compared to thermophilic composting.
Vermicomposting decreased nitrous oxide emissions by 25e36% and methane emissions by 22e26%. A
higher earthworm density increased carbon dioxide emissions by 3e14%, but decreased methane
emissions by 10e35%. Earthworm density had a marginal effect on nitrous oxide emissions. Vermicomposting decreased nitrous oxide emissions by 40% with higher moisture and by 23% with lower
moisture. Vermicomposting also decreased methane emissions by 32% and 16% with higher and lower
moistures respectively. This study showed that the addition of labile carbon sources increased carbon
dioxide and methane emissions and earthworm growth, but did not affect nitrous oxide emissions. In
conclusion, vermicomposting is effective at reducing nitrogen losses and greenhouse gas emissions from
composting. Therefore, vermicomposting could represent an option for reducing greenhouse gas emissions from composting, particularly in developing countries where the existing technical solutions are
expensive and difficult to implement.
