Potential GHG emission benefits of Asparagopsis taxiformis feed supplement in Australian beef cattle feedlots

Abstract

The red macroalgae Asparagopsis taxiformis has been identified as a promising feed supplement to inhibit enteric methane formation during ruminant livestock production and thereby contribute to GHG emissions reduction. Some studies also suggest improvements to animal weight gain through enhanced feed conversion efficiency. In this study, the potential GHG emissions reduction benefits were assessed from a life cycle perspective and in an actual industry context – the large Australian beef cattle sector, where feed supplementation occurred during feedlot finishing, when farmers have greatest control over animal diets. Seven adoption scenarios were compared to a baseline emissions inventory that was extrapolated to 2030. Feed supplementation with A. taxiformis had the potential to reduce the sector's carbon footprint by 1–4% in 2030, which due to the scale of the industry is a relevant emissions reduction (0.6–2.0 Mt CO2e), but modest in relation to the industry's goal of carbon neutrality by 2030. When emissions were assessed using alternative climate metrics that are more sensitive to changes in the rate of methane emission than the GWP100 climate metric (i.e. GWP*, radiative forcing climate footprint), larger potential benefits were found. Considering only the feedlot subsector, the radiative forcing climate footprint reached a plateau under most scenarios, indicating that climate neutrality is realistically achievable for the feedlot subsector within 5 years. That said, concurrent action on CO2 and N2O emissions will be needed, as even steep reductions in methane emissions at the expense of additional long-lived emissions will only achieve a short-term climate benefit and will make long-term climate stabilization more difficult.