Pig manure treatment with housefly (Musca domestica) rearing – an environmental life cycle assessment

Abstract

The largest portion of a product’s environmental impacts and costs of manufacturing and use results from decisions taken in the conceptual design phase long before its market entry. To foster sustainable production patterns, applying life cycle assessment in the early product development stage is gaining importance. Following recent scientific studies on using dipteran fly species for waste management, this paper presents an assessment of two insect-based manure treatment systems. Considering the necessity of manure treatment in regions with concentrated animal operations, reducing excess manure volumes with the means of insects presents a potentially convenient method to combine waste reduction and nutrient recovery. An analytical comparison of rearing houseflies on fresh and pre-treated pig manure is reported with reference to agricultural land occupation, water and fossil depletion potential. Based on ex-ante modelled industrial scale rearing systems, the driving factors of performance and environmentally sensitive aspects of the rearing process have been assessed. Expressed per kg manure dry matter reduction, the estimated agricultural land occupation varied between 1.4 and 2.7 m2yr, fossil depletion potential ranged from 1.9 to 3.4 kgoil eq and the obtained water depletion potential was calculated from 36.4 to 65.6 m3. System improvement potential was identified for heating related energy usage and water consumption. The geographical context and the utility of the co-products, i.e. residue substrates and insect products, were determined as influential variables to the application potential of this novel manure treatment concept. The results of this study, applied at the earliest stages of the design of the process, assist evaluation of the feasibility of such a system and provide guidance for future research and development activities.