Grass-based beef cattle production systems are generally perceived as beneficial to the environment. However, the climate impact of grass-based systems compared to systems based on energy-dense feeds remains controversial. While grass-based systems require less feed from crops, the production of which emits carbon dioxide and nitrous oxide, they generate more enteric methane emissions. Here, we provide a meta-analysis of cradle-to-farm-gate life cycle assessments of beef cattle production systems to estimate the effect of cattle diet on the carbon footprint of beef. Panel regressions indicate that every 10-percentage-point increase in grazing (resp. hay intake) at the expense of concentrates in cattle diets, based on dry matter intake, increases the carbon footprint of beef by 0.9 ± 0.35 (resp. 1.1 ± 0.5) kg CO2e per kg live weight. Lower feed efficiency and higher slaughter age are determinants of this effect. The findings highlight potential trade-offs between climate goals and other sustainability objectives (e.g., biodiversity, animal welfare).
Keywords: Life cycle assessments, beef cattle, GHG emissions, meta-analysis, grazing.
