A life cycle assessment model of Irish grain cropping systems focused on carbon footprint

Abstract

Life cycle assessment (LCA) models are used to determine the carbon footprint of grain. Few have been adapted for Irish conditions. We developed an LCA for Irish grain that computed greenhouse gas emissions from cradle to farm-gate. It utilised national research to determine agricultural emissions and carbon sequestration in CO2 equivalents (CO2e). Gross and net emissions were quantified based on inputs levels and related to crop yield at standard moisture levels to derive carbon footprints. The model was applied to a random sample of large-scale Tirlán growers (n = 48). Approximately 95% of their output in 2022 was accounted for by six crops: winter wheat (WW), winter barley (WB), spring malting barley (SMB), winter oats (WO), winter oilseed rape (WOSR) and spring feed barley (SFB). In gross terms, WO, WW, WB and WOSR had mean carbon footprints of 207, 217, 229 and 384 kg CO2e/t, respectively. Spring crops’ mean gross carbon footprints ranged from 207 kg CO2/t for oats to 238 kg CO2/t for SFB. Average gross carbon footprints for these large-scale growers were in the lower end of international estimates. Mean footprints for OSR were significantly greater than cereals or beans. However, in energy terms, net carbon footprint for OSR did not differ from other crops (excluding oats), which underscores the importance of footprint units. Net footprints were lower than gross footprints for oats, barley and OSR due to straw incorporation and were near net zero for WO. Further enhancing sequestration through management change will support the sector achieve net zero.