9 Is a Climate Neutral Animal Agriculture Possible?

Abstract

Animal agriculture contributed 4% to the total greenhouse gas (GHG) emission from the US in 2019. Most of the climate impact from animal production are due to emissions of methane, which contributed about 70% of all livestock GHG emissions. Methane lasts in the atmosphere for around a decade. However, its warming potential over a 20-year period is up to 84 times compared to CO2. The impact on warming from methane is not gradual build-up over time but from relatively recent years. Therefore, reducing methane emissions is one the most effective ways to slow down the rate of climate warming. By some estimates, reducing methane by just 0.3% per year will result in no more warming from methane. Scaling it up further, may even reverse global warming. There are several mitigation options that can help achieve methane reduction in the short term. These can be broadly categorized into dietary and rumen manipulation. Dietary manipulation methods include increasing feed digestibility, such as concentrate to forage ratio, or increasing fats and oils, which are associated with lower methane emissions. These methods can potentially reduce methane emissions by up to 30%. Rumen manipulation through feed additives can be through either modifying the rumen environment, which indirectly affect emissions or directly inhibiting methanogenesis. The rumen environment modifiers include plant bioactive compounds such as essential oils and tannins, and nitrate rich feeds. Their effectiveness ranges between 10 to 30%. The inhibitor category include 3-nitroxypropanol (3-NOP) and seaweeds containing halogenated compounds. 3-NOP reduces enteric methane emissions by over 30% and has been approved for use in certain countries. Seaweed, in particular Asparagopsis spp., reduce emissions by over 90% in beef cattle. The combination of dietary and rumen manipulation options, including feed additives, is expected to reduce enteric methane emissions by over 30% in the next decade and help move the livestock industry closer to climate neutrality.