A systematic literature review of Life Cycle Assessments on primary pig production: Impacts, comparisons, and mitigation areas

This paper presents a comprehensive systematic literature review of life cycle assessment publications performed on primary pig production, defining their functional unit as "mass of pig live-weight". After the initial search in Scopus and Web of Science, a four-step screening process for eliminating results out of scope was applied, resulting in a total of seventy-four (74) studies. The publication years ranged between the years 2005 and 2023, with assessments conducted across twenty-seven (27) countries. Reported impact potentials for climate change, acidification, eutrophication, land-, water-, and energy use are presented and discussed in individual sections. Contribution to climate change was primarily attributed to feed production, animal housing and manure management. Climate change impacts ranged from-0.02 to 11.2 kg CO2-eq per kg pig live weight excluding land use changes. Inclusion of direct land use change was reported to increase the climate change impact up to 470 %. Substantial differences of climate change impacts were observed in studies including production from multiple countries. A reduction of 31-37 % of the climate change impact per kg of pig live weight was reported on national levels over the last two decades. Feed changes resulted in reductions of up to 35 % to the climate change impacts, although more commonly below 20 %. Manure management systems and housing of animals were commonly compared in conjunction with multiple systematic changes in conventional and organic production. Incorporation of anaerobic digestion and biogas production was consistently reported beneficial, achieving reduction in climate change impacts of up to 64 % through substitution of energy or natural gas. Substantial impact mitigation will most likely be achieved through a wide selection of improvements including breed selection, animal feed, animal housing and manure management system changes. Issues relating to assessment approach/method and modelling choices are discussed, as their heterogeneity presents a limitation in terms of comparability of assessment results.