Targeted technologies for nitrous oxide abatement from animal agriculture

Nitrous oxide (N2O) emissions account for similar to 10% of global greenhouse gas (GHG) emissions, with most of these emissions (similar to 90%) deriving from agricultural practices. Animal agriculture potentially contributes up to 50% of total agricultural N2O emissions. In intensive animal agriculture, high N2O emission rates generally coincide with anaerobic soil conditions and high soil NO3-, primarily from animal urine patches. This paper provides an overview of animal, feed-based and soil or management abatement technologies for ruminant animal agriculture targeted at reducing the size of the soil NO3- pool or improving soil aeration. Direct measurements of N2O emissions from potential animal and feed-based intervention technologies are scarce. However, studies have shown that they have the potential to reduce urinary N excretion by 3-60% and thus reduce associated N2O emissions. Research on the effect of soil and water management interventions is generally further advanced and N2O reduction potentials of up to 90% have been measured in some instances. Of the currently available technologies, nitrification inhibitors, managing animal diets and fertiliser management show the best potential for reducing emissions in the short-term. However, strategies should always be evaluated in a whole-system context, to ensure that reductions in one part of the system do not stimulate higher emissions elsewhere. Current technologies reviewed here could deliver up to 50% reduction from an animal housing system, but only up to 15% from a grazing-based system. However, given that enteric methane emissions form the majority of emissions from grazing systems, a 15% abatement of N2O is likely to translate to a 2-4% decrease in total GHG emissions at a farm scale. Clearly, further research is needed to develop technologies for improving N cycling and reducing N2O emissions from grazing-based animal production systems.