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The Australasian dairy industry is facing the dual challenges of increasing productivity, while also reducing its emissions of the greenhouse gases (GHG) methane and nitrous oxide. Following the COP21 Paris Agreement, all sectors of the economy will be expected to contribute to GHG abatement. Enteric methane is the major source of GHG emissions from dairy production systems (>70%), followed by nitrous oxide (13%) and methane (12%) from animal waste, with nitrogen (N)-fertiliser use contributing ~3.5% of total on-farm non-carbon dioxide equivalent (non-CO2e) emissions. Research on reducing methane emissions from dairy cattle has focussed on feeding dietary supplements (e.g. tannins, dietary oils and wheat), rumen modification (e.g. vaccine, inhibitors), breeding and animal management. Research on reducing nitrous oxide emissions has focussed on improving N fertiliser efficiency and reducing urinary N loss. Profitable options for significant abatement on farm are still limited, with the industry focusing instead on improving production efficiency, while reducing emission intensity (t CO2e/t product). Absolute emission reduction will become an imperative as the world moves towards carbon neutrality by 2050 and, thus, a priority for research. However, even with implementation of best-practice abatement, it is likely that some residual emissions will remain in the foreseeable future. The soil organic carbon content of dairy soils under well fertilised, high-rainfall or irrigated permanent pastures are already high, therefore limiting the potential for further soil carbon sequestration as an offset against these residual emissions. The Australasian dairy industry will, therefore, also need to consider how these residual emissions will be offset through carbon sequestration mainly in trees and, to a more limited extent, increasing soil organic carbon. The Australasian dairy industry is facing the challenge of increasing productivity while also reducing greenhouse gas (GHG) emissions. This paper reviews the most promising technologies, concluding that substantial GHG abatement is possible, but the industry will need to consider further offsets in trees to achieve carbon-neutral dairy farming in Australia and New Zealand. [ABSTRACT FROM AUTHOR]

The Australian red meat industry is an important contributor to the national economy and international markets. A focus on reducing greenhouse gas (GHG) emissions from this sector presents an important opportunity for the sustainability of the industry and to enable Australia to achieve its commitments set under the Paris climate agreement. Here we show that through changes in land management and application of technologies to reduce enteric methane emissions from grazing livestock it is possible for the Australian red meat industry to substantially reduce GHG emissions, and even become carbon neutral. We calculated baseline (2005) and current (2015) GHG emissions for the red meat sector, then examined the mitigation potential and costs of potential pathways to reduce and offset emissions. Emissions from the Australian red meat industry have decreased from 124.1 Mt CO 2 e in 2005 to 68.6 Mt CO 2 e in 2015, primarily through reductions in land clearing. Achieving carbon neutrality is possible with continued improvements in vegetation management combined with methods to reduce livestock emissions, sequester carbon, and maintain animal numbers. While possible, this ambitious target will require timely and substantial investment and policy support from private and government bodies. • Greenhouse gas emissions from the red meat sector have decreased since 2005. • The main sources of greenhouse gas emissions are land clearing and enteric methane. • Improved land and animal management are key to further reducing emissions. • Methods to reduce enteric methane must be applicable to extensive grazing systems. • Consistent and sustained policy support and incentives are required. [ABSTRACT FROM AUTHOR]

Simple Summary: Methane is a potent greenhouse gas. It is 80-times more effective at heating the earth than carbon dioxide over the first 20 years following release into the atmosphere. Ruminant animals have diverse microbial populations in their stomachs that employ anaerobic fermentation to digest feed. Methane is belched into the atmosphere as a by-product of the digestive process. This gut, or enteric methane, primarily from cattle, but also sheep and goats, contributes 30% of the methane released into the earth's atmosphere each day, and is more than any other single methane source. A major reduction in methane emissions from ruminants is crucial to preserve ecosystems on the planet. Various strategies to reduce enteric methane emissions in farm operations are reviewed to quantify their mitigation potential, determine their impact on animal productivity and likelihood of adoption. Two feed supplements, a commercial product, 3-NOP (Bovaer®), and the seaweed, Asparagopsis, can reduce methane emissions by 40+% and 90%, respectively, with associated increases in animal productivity and no adverse effects on animal health or product quality. The rumen microbial population can also be changed to provide long-term intergenerational reduction in methane emissions, if treated herds remain isolated from non-treated animals. Anthropomorphic greenhouse gases are raising the temperature of the earth and threatening ecosystems. Since 1950 atmospheric carbon dioxide has increased 28%, while methane has increased 70%. Methane, over the first 20 years after release, has 80-times more warming potential as a greenhouse gas than carbon dioxide. Enteric methane from microbial fermentation of plant material by ruminants contributes 30% of methane released into the atmosphere, which is more than any other single source. Numerous strategies were reviewed to quantify their methane mitigation potential, their impact on animal productivity and their likelihood of adoption. The supplements, 3-nitrooxypropanol and the seaweed, Asparagopsis, reduced methane emissions by 40+% and 90%, respectively, with increases in animal productivity and small effects on animal health or product quality. Manipulation of the rumen microbial population can potentially provide intergenerational reduction in methane emissions, if treated animals remain isolated. Genetic selection, vaccination, grape marc, nitrate or biochar reduced methane emissions by 10% or less. Best management practices and cattle browsing legumes, Desmanthus or Leucaena species, result in small levels of methane mitigation and improved animal productivity. Feeding large amounts daily of ground wheat reduced methane emissions by around 35% in dairy cows but was not sustained over time. [ABSTRACT FROM AUTHOR]