Life-cycle assessment of the intensity of production on the greenhouse gas emissions and economics of grass-based suckler beef production systems

In Ireland, the largest contributor of greenhouse gas (GHG) emissions is agriculture. The objective of the current study was to evaluate the impact of stocking intensities of beef cattle production systems on technical and economic performance and GHG emissions. A bioeconomic model of Irish suckler beef production systems was used to generate scenarios and to evaluate their technical and economic performance. To model the impact of each scenario onGHGemissions, the output of the bioeconomic model was used as an inventory analysis in a life-cycle assessment model and various GHG emission factors were integrated with the production profile. All the estimated GHG emissions were converted to their 100-year global warming potential carbon dioxide equivalent (CO(2)e). The scenarios modelled were bull/heifer and steer/heifer suckler beef production systems at varying stocking intensities. According to policy constraints, stocking intensities were based on the excretion of organic nitrogen (N), which varied depending on animal category. Stocking intensity was increased by increasing fertilizer N application rates. Carcass output and profitability increased with increasing stocking intensity. At a stocking intensity of 150 kg N/ha total emissions were lowest when expressed per kg of beef carcass (20.1 kg CO(2)e/kg beef) and per hectare (9.2 tCO(2)e/ha) in the bull/heifer system. Enteric fermentation was the greatest source of GHG emissions and ranged from 0.49 to 0.47 of total emissions with increasing stocking intensity for both production systems. The current study shows that increasing stocking intensity via increased fertilizer Napplication rates leads to increased profitability on beef farms with only modest increases in GHG emissions.