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

Abstract

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.

Municipal Solid Waste Management in a Decentralized Composting Scenario: Assessment of the Process Reproducibility and Quality of the Obtained Composts

“…The final macronutrient concentrations were high in all the composts, the highest values for TN and K being found in Carrícola compost 6 (26.1 and 25.1 g kg −1 for TN and K respectively) (Table 6). Moreover, the values obtained are in line with those of other studies of biowaste composting [36][37][38].…”

“…Likewise, the values recorded exceeded those found in previous studies using different starting materials [17]. Furthermore, all the final composts showed an adequate degree of stability, according to the self-heating test of Brinton et al [22] and absence of phytotoxicity (GI > 50%) [21], with values similar or higher to those reported by Alves et al [36] during an experiment of community composting.…”

“…Although Storino et al [35] established that the addition of poultry manure to the co-composting of OFMSW with urban pruning waste did not increase the salinity of the final compost, in the present experiment, the addition of donkey manure to the mixture caused an increase in the EC of the final compost from 3.5, 5.3 and 5.3 to 5.3, 6.1 and 7.4 dS m −1 in the piles 4, 5 and 6 of Carrícola (Table 6), respectively. The final nutrient content of a mature compost defines its fertilizer capacity to improve agricultural crops and is determined by the heterogeneity of the starting materials [36]. Thus, it is important to avoid NPK losses in order to obtain a final product with high agronomic and economic value [17].…”