Greenhouse-gas abatement on Australian dairy farms: what are the options?

The Australian dairy industry contributes significantly to the rural economy, but must reduce its greenhouse-gas emissions to remain competitive in a global market that is starting to prioritise a low carbon footprint. Demand for improved environmental, social and governance performance from supply chains creates an imperative for research to deliver options for farmers to make reductions in their environmental footprint. Given the rapidly evolving nature of greenhouse-gas abatement research, this critical review provides an update on the state of the research relevant to Australian dairy systems and identifies research gaps that must be addressed if there is to be widespread on-farm adoption. Current research suggests that Australian dairy farms could theoretically abate enteric methane by 40-50%, with about another 5-10% reduction in whole-farm greenhouse-gas emissions being possible by flocculating or covering stored effluent. Fertiliser- and urine-patch management strategies could substantially reduce direct and indirect nitrous oxide emissions, but by variable amounts subject to local conditions. However, few abatement options are currently cost-effective for farmers. Significantly more research investment is required to facilitate the on-farm adoption of strategies, particularly to reduce enteric methane and improve the efficiency of nitrogen cycling. Improved understanding is required of the influences on each strategy's abatement potential and interactions with economically important traits in grazing systems, the effect of combining abatement strategies, and systems by which strategies can be implemented cost-effectively on farms. The challenge for research is to consider how the implementation of cost-effective abatement options can be refined for grazing dairy systems to maintain the position of Australian dairy in the global market.