Beef cattle have been identified as the largest livestock-sector contributor to greenhouse gas (GHG) emissions, suggesting the importance of and opportunity for reducing emissions from this source. Using life cycle analysis (LCA), several studies have concluded that grass-finished beef systems have greater GHG intensities than feedlot-finished (FL) beef systems. However, these studies evaluated only one grazing management system – continuous grazing – and assumed steady-state soil carbon (C), to model the grass-finishing environmental impact. Alternatively, adaptive multi-paddock (AMP) grazing, which involves managing for more optimal forage growth and recovery, can improve animal and forage productivity, and potentially sequester more soil organic carbon (SOC) than continuous grazing. Understanding the possible impacts of improved grazing management is critical, as such systems may also help to support livelihoods and additional ecosystem services, such as clean water, soil health, and biodiversity.
To examine impacts of AMP grazing and related SOC sequestration on net GHG emissions, we conducted a comparative LCA of two beef finishing systems in the Upper Midwest, USA: AMP grazing and FL. We used on-farm data collected from the Michigan State University (MSU) Lake City AgBioResearch Center and MSU Beef Center for the AMP grazing and FL systems, respectively. Impact scope included GHG emissions from enteric methane, feed production and mineral supplement manufacture, manure, and on-farm energy use and transportation, as well as the potential C sink arising from SOC sequestration.
Results/Conclusions
Prior to inclusion of SOC data, estimated GHG emissions associated with FL and AMP finishing were 6.09 and 9.62 kg CO2-e kg CW-1, respectively. Across-farm SOC data showed a 4-year C sequestration rate of 3.59 Mg C ha-1 yr-1 in AMP grazed pastures. After including SOC in the GHG footprint estimates, finishing emissions from the AMP system were reduced from 9.62 to -6.65 kg CO2-e kg carcass weight (CW)-1, whereas FL emissions increased slightly from 6.09 to 6.12 kg CO2-e kg CW-1 due to soil erosion.
Our findings indicate that AMP grazing has the potential to offset GHG emissions through sufficient soil C sequestration such that the finishing phase could be a net C sink. However, FL production produced 120% more beef ha-1. This research suggests that AMP grazing can mitigate agricultural greenhouse gas emissions through SOC sequestration and challenges previous conclusions that only feedlot-intensification reduces the overall beef GHG footprint through greater productivity.