A combined assessment of the energy, economic and environmental issues associated with on-farm manure composting processes: Two case studies in South of Italy

Livestock effluents “surplus” is a very sensitive issue for farmers who have several difficulties to manage them and ensure their safe disposal. In this regard, composting is a very strategic way to break down environmental impacts associated with manure management. This study was aimed at assessing the production sustainability of one ton of compost from dairy cattle/buffalo manure in two on-farm facilities operating in Southern Italy and using different bulking agents (wood chip from Short Rotation Forestry, straw and pruning residues). A combined assessment approach was used in 2013 to investigate all the aspects of the composting processes studied, to identify strengths and weaknesses and then optimize the operative steps. Particularly, Life Cycle Assessment, Energy Analysis and Life Cycle Costing were used to calculate environmental impacts, the involved energy and the cost of the production of 1 ton of compost, respectively, and to compare the various composting scenarios. Regardless of the type of composting scenarios, one ton of on-farm compost caused essentially ecotoxicity potential and abiotic depletion and its cost ranged from 10 to 31 euro. Compost production required from 233 to 756 MJ of energy. Particularly, the lesser impacts and the lesser energy and cost requirements occurred when maize straw or pruning residues were used as bulking agents. The proposed study, which linked together the three above mentioned methodologies, is unusual within the available literature on dairy cattle/buffalo manure composting. This combined approach allowed to define a complete landscape of sustainable possibilities in managing organic residues (especially manure) at the farm level giving useful information to promote the diffusion of these low technology composting processes and the agronomic use of compost thus obtained. All this to ensure sustainable resource use alleviating stress on the environment as claimed by the Europe’s Bioeconomy Strategy.