Environmental impacts of pig production systems using European local breeds. The contribution of carbon sequestration and emissions from grazing

Environmental assessment of pig production systems using local breeds remains poorly documented in the literature. So far, studies did not account for specificities of outdoor rearing which is quite common in such systems. The present study aimed at evaluating the environmental impacts of pig production systems using local breeds in Europe, while accounting for emissions associated to consumption of grass and mitigation of impacts through soil-C sequestration. Environmental impacts were estimated for 48 farms using local pig breeds: 25 in France (Gascon breed), eight in Italy (Mora Romagnola breed) and 15 in Slovenia (Krškopolje breed). Assessment was performed with and without accounting for pasture-intake emissions and potential soil-C sequestration. The data were obtained from on-farm surveys. Systems with Gascon pigs had the lowest impacts per kg of live weight for global warming and cumulative energy demand, due to lower impacts of feeds. Acidification potential was higher for Krškopolje pigs due to high dietary crude protein content and high AP of feeds, while eutrophication potential was higher for Gascon pigs due to higher phosphorus content of feeds (28% higher than the mean of the other farms). When impacts were expressed per ha of land use, pig production in Gascon farms had the lowest impacts due to more available area per pig, except for eutrophication. Low contribution of soil-C sequestration to climate change mitigation was observed (4.7% on average). However, it may have a substantial contribution for the most extensive pig systems using large land surfaces. Emissions resulting from grazing had a rather low contribution to Global Warming Potential (4%) and Eutrophication (3%), but a substantial one to Acidification impact (9% on average). In the frame of our study, the contribution of emissions related to grazing is moderate because commercial feed supply for outdoor pigs was higher than in extensive systems studied in literature. This study highlighted that main hotspots include feed composition and supply and the origin of feed ingredients. It also suggests that future assessments of extensive pig systems relying on pig foraging on grasslands or rangelands should account for soil-C sequestration and emissions associated to grazing and foraging.