Poultry litter stabilization by two-stage composting-vermicomposting process: Environmental, energetic and economic performance

Abstract

Poultry litter (PL) is a heterogeneous mixture that contains bedding materials, antibiotics, dead skin, feed scraps, water, feathers and the resulting microbiota from poultry production cycle. Although its treatment does not receive attention, it is an important organic resource generated in the north-east region of Santa Fe Province since animal primary production is one of the main economic activities there and in the whole country. The objective of this work was to analyse the economic and energy aspects and the environmental impact of two scenarios corresponding to treat two different mixtures of organic wastes: Eucalyptus sp. sawdust (ES), rice hulls (RH) and PL. PL was considered in two different volume proportions: 1RH:3 PL for scenario 1 and 0.5RH:1 ES:2 PL for scenario 2. The two-stage combined system of composting + vermicomposting was applied to both scenarios and compared; on one hand, the current regulated practice for waste final deposition (landfill) and on the other hand, a base line scenario, which describes the current situation, where the raw material is transported and spread over the field as fertilizer without previous stabilization. The scenario construction was based according to on-site data, lab-scale experiments previously published and software databases. The environmental study was carried out with life cycle assessment; and the energy study, using cumulative energy demand methodology and the energy balance. Based on the results, it was possible to affirm the importance of the integrated agricultural waste treatment to address environmental benefits, especially related to the base line scenario. Furthermore, there were no significant differences between the two proposed scenarios. Economic and environmental results were contradictory when no long-term socio-economic consequences are considered. Combined composting and vermicomposting strategy reduce the organic matter and nutrients content not only to avoid discharges into the environment, but also to replace the fossil fuels consumption during unsustainable techniques as sanitary landfill, producing improved substrates for agricultural use.