Community composting strategies for biowaste treatment: methodology, bulking agent and compost quality

The European Union’s commitment to increase recycling and recovery rates of municipal solid waste requires significant changes in current waste management. Local governments are developing various strategies for treating the organic fraction of municipal waste (biowaste) via composting. Community composting centres (CCC), green waste collection, treatment points and community gardens are some of these new approaches. Population density and spatial distribution, together with the existence of community green areas, determine the location of the various infrastructures for recycling local biowaste. The composting process consumes high amounts of bulking agent (BA) necessary to provide the structure that allows, amongst other uses, biowaste aeration and microbial surface colonisation. Shredded green waste from parks, gardens and households can be used as BA in community composting and home composting. In this study, a total of 46 compost samples obtained from CCC with two types of handling were analysed: 22 samples treated by vertical flow (VF) and 24 samples treated by horizontal flow (HF). The HF model allowed better use of the volume of modular composting units and the VF model required less effort and time for the CCC operator. Mature, stable and high-nutrient-content composts were obtained with both models. These composts met the legal requirements to be used as an organic amendment, and they can be delivered to the participants or used in community gardens in the municipality.