Carbon footprints of greenhouse gas mitigation measures for a grass-based beef cattle finishing system in the UK

Purpose: Agri-food systems across the globe are faced with the challenge of reducing their supply-chain emissions of greenhouse gases (GHGs) such as nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4). For instance, 10% of the UK’s GHG emissions are generated by agriculture, and ~56% of these are generated by livestock production. Numerous mitigation measures are being proposed to reduce GHG emissions from ruminants (representing 70 to 80% of total livestock emissions), particularly from beef cattle (presenting 30-40% of total livestock emissions). Methods: To explore such potential, first, a business-as-usual (BAU) partial cradle-to-finishing farmgate scale modelling framework was developed. The BAU systems (i.e., steady-state productivity based on primary data from the North Wyke Farm Platform) were built using ensemble modelling wherein the RothC process-based soil organic carbon (SOC) model was integrated into the Life Cycle Assessment (LCA) framework to conduct a trade-off analysis related to mitigation measures applicable to the study system. Potential mitigation measures were applied to the BAU scenario. The interventions assessed included: (i) extensification; (ii) adopting anaerobic digestion technology, and; (iii) the use of the nitrification inhibitor DCD, and substitution of fertiliser nitrogen with symbiotically fixed nitrogen from legumes. Results: The partial carbon footprint for 1 kg of beef liveweight gain leaving the farmgate could be reduced by 7.5%, 12%, or 26% by adopting nitrification inhibitors, white clover introduction (pending establishment success), and anaerobic digestion for manure management, respectively. Conclusions: The findings highlight the importance of including emissions beyond the farmgate level to analyse the carbon footprint of different management scenarios in order to assess the sustainability of agri-food production systems.