Emission of greenhouse gases (GHGs) during composting and vermicomposting: Measurement, mitigation, and perspectives

As the population grows, so does waste generation, which is a major concern, particularly in developing countries. Although composting and vermicomposting are environmentally friendly methods of managing organic waste, one of the major downsides is the release of greenhouse gases (GHGs). The most essential elements influencing GHG generation are aeration, C/N ratio, temperature, pH, bulking agent, and moisture content, all of which are thoroughly explained in this review. Vermicomposting emits less GHGs than composting in many cases mostly in reduction of methane (CH4) emissions; however, earthworms are also significant contributors to nitrous oxide (N2O) during vermicomposting, imposing the need to juxtapose both processes in context to GHGs emission (GHGsE). Effective GHGsE measuring methodologies allows for the calculation of emissions while also assisting in the identification of the critical elements relevant to GHGs emission reduction. Various methodology implemented for GHGs measurement and among them chamber method is the most common method used. Finally, the review also discussed the already existing mitigation measures as well as perspectives.