Effect of natural and regulatory conditions on the environmental impacts of pig slurry acidification across different regions in Europe: A life cycle assessment

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Animal manure handling is an essential but challenging part of Europe's intensive agriculture. To safeguard the environment and facilitate sustainable livestock production, lower-impact manure management technologies need to be identified, evaluated and implemented. Slurry acidification has been developed to address some of the environmental challenges faced by pig farmers, such as methane and ammonia emissions, that contribute to environmental impacts such as climate change, terrestrial acidification and air fine particulate matter formation. However, the efficiency of this technology has been found to depend on local environmental and regulatory conditions. The current study compared two slurry treatment options (no treatment versus slurry acidification in storage tanks) under the climatic, agronomic and legislative conditions found in Denmark, the Netherlands and Spain using Life Cycle Assessment (LCA). Data for the LCA model was collected from various sources and emissions following field application and crop yields were simulated over a 100-year period using the Daisy agricultural model. To address the uncertainty in LCA modelling, parameter analyses and Monte Carlo simulations with 1000 iterations were conducted followed by pairwise statistical tests. The results indicated that slurry acidification reduces the impact in all countries in impact categories mostly related to direct emissions from agriculture, such as methane and ammonia. For impact categories related to the provision of materials and energy to the farm, acidification increased the impacts in some cases. Additional requirements for lime application to counteract potential soil acidification did not result in significant changes in the performance of slurry acidification. The sulphur in the applied acid as an alternative to mineral S fertiliser can in some cases reduce the environmental impact of slurry acidification, but should not be advertised as doing so per se. Introducing stricter P application limits would seem to be the preferred option compared with slurry acidification in the Netherlands, while the opposite appeared true for Denmark.