Frank Mitloehner: A rethinking of CH4 associated with animal agriculture is needed

Reports from the World Nutrition Forum in Cancun Mexico

19-May-2023 - Last updated on 19-May-2023 at 15:02 GMT

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Frank Mitloehner, professor and air quality specialist, Director, CLEAR Center, Department of Animal Science, University of California, Davis, was speaking at dsm-firmenich's World Nutrition Forum (WNF), May 8-10, which was held in Cancun, Mexico.

We caught up with him following on from that presentation.

Feed additives offer great promise for sector-wide methane reductions and could be feasibly implemented at existing operations in the US.

But current US Food and Drug administration (FDA) policy is hampering feed innovation in this respect, said Mitloehner.

Feed additives require approval under the Federal Food, Drug, and Cosmetic Act (FD&C Act) and any manufacturer claiming a product reduces enteric emissions must be backed by results obtained from long term, controlled studies. Such barriers are preventing expedited market availability and widespread adoption of feed additives designed to block methane emissions, he said.

The methane reductions from programs in place today, from the dairy sector alone, if coupled with a feed additive strategy, would help the state of California achives its methane reduction targets by 2030, commented the UC Davis professor.

So far, California dairy digesters have reduced 2.3 MMT of CO2e – achieving 30% of the sector's methane emissions reduction goal, added Mitloehner.

California is the only state in the US to have a methane law which insists on a 40% reduction of methane by agriculture and other sectors by 2030.

Methane is a powerful GHG, the emissions of which are responsible for about 20% of the global warming now driving climate change, according to the California Air Resources Board.

"Over half of the methane emissions in California come from dairy and livestock manure and enteric fermentation (the latter mostly from burping). The remaining methane is from landfilled organic waste streams and fugitive emissions from oil production, processing, and storage; the gas pipeline system; and industrial operations. California can reduce methane emissions 40% by 2030 through capturing or avoiding methane from manure at dairies, reducing methane from enteric fermentation, reducing disposal of organics at landfills, and reducing fugitive methane emissions."

Mitloehner also stressed, during his presentation, that a rethinking of CH4 associated with animal agriculture is needed "to clarify long-standing misunderstandings and uncover the potential role of animal agriculture in fighting climate change."

His talk considered two climate metrics, the standard Global Warming Potential (GWP100), and the more recently proposed, GWP*, which was developed at the University of Oxford, and which assesses how an emission of a short-lived greenhouse gas (GHG) affects temperature. GWP* not only accounts for methane's short lifespan, but also its atmospheric removal, he argued.

Methane is not simply a stronger version of carbon dioxide, as GWP100 suggests. It is an altogether separate animal, and it behaves differently in the atmosphere, commented the academic. GWP* should be a go-to metric for assessing the warming impact of methane as it is more accurate than GWP100 when considering methane, accounting for the process whereby methane from animal agriculture warms in the atmosphere for approximately 10 years before it is naturally broken down, he explained.

"GWP100 overestimates methane's warming impact by a factor of three to four," said Mitloehner.

An Intergovernmental Panel on Climate Change (IPCC) report​​ confirmed that GWP100, by simply expressing methane emissions as CO2 equivalents, overstated the effect of methane warming, he said.

In our audio interview, the academic also responds to criticism by non-profits​​ of the research undertaken by the UC Davis CLEAR Center.

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