Life Cycle Assessment of the Potential Carbon Credit from No- and Reduced-Tillage Winter Wheat in the U.S. Pacific Northwest

Decisions about reducing agricultural land tillage to offset global warming potential (GWP) are based on the evaluation of the agricultural eco-system and the profitability to local farms. Carbon sequestration and nitrous oxide emissions from winter wheat (WW) cropping were evaluated by modeling typical dryland cropping systems in eastern Washington. Variations in rainfall, tillage intensity and crop rotation were considered. System boundaries were expanded to consider fertilizer production and use of machinery in a standard life cycle assessment (LCA) study. GWP was evaluated both for WW crop alone and also for the entire crop rotation. Potential earnings from carbon credits obtained by converting to reduced and no-till scenarios were evaluated and compared with conventional tillage farm budgets. Assuming equivalent yields across tillage regimes, tillage reduction is economically feasible in high rainfall zones. In lower rainfall zones, reduced tillage systems are less profitable than the conventional tillage systems, assuming equivalent yields. In addition, less carbon sequestration occurs when tillage is reduced in this region, which reduces potential earnings from carbon credits.