161 Use of life cycle assessments for carbon monitoring in beef cattle systems.

Abstract Life cycle assessment (LCA) is a standardized approach for assessing the life cycle environmental impacts of goods and services over their product life cycle. Carbon monitoring is the tracking of carbon storage and fluxes over time, including CO2 and CH4. The power of LCA is in its ability to integrate these and other short- and long-lived climate pollutants into an estimate of the cumulative impact of beef production systems—from cow-calf production through finishing, processing, consumption, and waste. To this end, LCA can be used to evaluate both carbon and climate neutrality of livestock systems. There are several metrics used to estimate climate impact: global warming potential (GWP, also referred to as carbon footprint), global warming potential* (GWP*), and global temperature change potential (GTP), though GWP is by far the most used metric to date. Where measured carbon emissions data are not available for integration into LCA (i.e., from eddy covariance towers, SF6 tracers, respiration chambers, or commercially available monitoring technology), modeling approaches may be used. Modeling approaches range from static (i.e., use of IPCC emission factors) to mechanistic (i.e., use of process models that simulate CH4 production as a function of diet composition and rumen microbial activity). Of particular interest in carbon monitoring of beef systems is the potential for soil carbon sequestration to mitigate climate impacts. Some evidence suggests that grazing management can contribute to soil carbon sequestration, though the magnitude and persistence of the sequestration is context dependent. Critical to the inclusion of soil carbon data in LCA for this purpose is a study design with a non-grazed control, a robust soil sampling protocol (addressing change over time, spatial variability in soil properties, land management history, and carbon fractionation), and inclusion of uncertainty analyses. Though infrequently reported to date, uncertainty analysis is critical to be able to make definitive conclusions about soil carbon contributions to carbon and/or climate neutrality in beef systems. A final consideration for the use of LCA for carbon monitoring in beef systems is the potential for technological interventions to stimulate rebound effects. Capturing rebound effects in LCA methodology has not yet been widely adopted, but is critical to a complete picture of the impacts of management and climate mitigation technologies on the climate impact of beef.