The life cycle impacts of feed for modern grow-finish Northern Great Plains US swine production

A life cycle assessment (LCA) model was developed to analyze the environmental impacts per head of swine for typical feed rations of Northern Great Plains (NGP) US grow-finish swine production. The all-inclusive ‘field to gate’ approach incorporated steps ranging from corn and soybean production to shipping the market weight pig to a slaughtering facility. Feed production scenarios included: (1) a standard feed diet of 72% corn and 28% soymeal using 100% synthetic fertilizer; (2) standard feed diet using 40% manure as fertilizer; (3) modified feed diet using dry distillers gains with solubles (DDGS), with 100% DDGS allocation towards ethanol production; and (4) modified feed diet with 50% DDGS allocation towards ethanol production. For the standard NGP feed diet, enteric emissions and feed production were the two largest contributors towards climate change impacts, while feed production further resulted in significant contributions towards human health damage (44.6%), ecosystem diversity (67.4%), and resource availability (75.0%). DDGS incorporation assuming 100% allocation reduced corn and soymeal inputs considerably, resulting in overall decrease in impacts associated with climate change (−2.7%), terrestrial acidification (−7.1%), and both marine (−14.6%) and freshwater eutrophication (−22.7%); however terrestrial ecotoxicity increased (+22.9%) due to natural gas drying. 50% DDGS allocation increased all impact categories, with the greatest change found for terrestrial ecotoxicity (48.4%). The study results highlight the significant LCA impact contributions associated with feed during grow-finish swine production, and the benefits associated with DDGS incorporation; however, LCA benefits were realized only if 100% DDGS allocation was applied towards ethanol production.