Spatially and temporally explicit life cycle global warming, eutrophication, and acidification impacts from corn production in the U.S. Midwest

The demand for biobased products, such as food, fuel, and chemicals, has been continuously increasing. Meanwhile, agricultural production, serving as the primary stage of biobased products, is one of the largest contributors to greenhouse gas (GHG) emissions and nutrient releases. Environmental impacts of agricultural production influenced by farming practices, soil properties, and climate conditions, are often site-specific and time dependent. Although assessing spatially and temporally explicit environmental releases and impacts are required to inform a sustainable trajectory for agricultural production, such analyses are largely lacking. This study provides site-specific analysis of on-farm and supply chain emissions from corn production to demonstrate the spatio-temporal variability of environmental impacts in the U.S. Midwest states. Using process-based life cycle assessment (LCA) and the physically-based Environmental Policy Integrated Climate (EPIC) agroecosystem model, we estimated county-level life cycle environmental release inventories from corn production in 12 U.S. Midwest states for the period of 2000–2008. Based on the Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (TRACI) impact assessment model, we quantified the corresponding life cycle global warming (GW), eutrophication (EU) and acidification (AD) impacts of corn. The results show that life cycle GW, EU and AD of corn production varied by factors of 4.2, 83.7 and 10.6, respectively, across the Midwest counties over the nine-year span (2000–2008). Life cycle GW impacts of producing 1 kg of corn ranged from −6.4 in Franklin County, Illinois to 20.2 kg CO₂-eq. in Perkins County, South Dakota. The life cycle EU impacts also spanned over a wide range of 0.99 g in Morton County, Kansas to 82.9 g N-eq. in Leelanau County, Michigan, whereas life cycle AD impacts ranged from 1.3 in Clermont County, Ohio to 100.7 g SO₂-eq. in Perkins County, South Dakota. Moreover, trade-offs existed among life cycle GW, EU and AD impact categories for corn production. The spatial variation analyses showed that key contributors were the different soil types, precipitation, elevation and the amounts of fertilizers applied. These findings provided critical insight into spatio-temporal variations of life cycle environmental impacts of corn production and identified spatial hotspots and top contributors for improving environmental performances of corn production.