How do you justify livestock methane emissions?

Methane (CH4) emissions are an incredibly urgent issue that we as a global society must find solutions to quickly, but global assessments often employ "a narrow focus on emissions efficiencies per animal or per unit of product, without assessing the system as a whole, including the potential for sequestration" (Scoones et al. 2022).

As with the study of all living systems it is imperative to take a holistic view due to the interconnected and dynamic nature of relationships (in this case between plants, animals, soil, and the atmosphere), and at the same time keep a broad perspective to ensure we are aiming our limited resources where they can have the greatest marginal reaction.

Savory's position

Savory's position is that well-managed grasslands with properly-functioning ecosystem processes effectively balance ruminant methane production and breakdown. While the scientific literature has not yet explored or quantified this exact scenario since studies on grazing and CH4 have only looked at continuous grazing schemes (not properly-managed grazing), our mechanistic understandings of methane-oxidizing bacteria in healthy soils and hydroxyl radicals in the vegetative zone surrounding plants support this position, and broader carbon sequestration research from well-managed grazing paints a clear picture of the role healthy grasslands and soils play in addressing the climate crisis.

Further, nearly all analyses of livestock and methane make no distinction between feedlots, continuous grazing, or well-managed grazing. As long espoused by the Savory Institute and more recently supported by those in academia (Stanley et al. 2024), to evaluate the ecological impact of livestock you must always distinguish between forms of grazing management to account for the high degrees of variability seen in their outcomes.

How much methane do livestock emit?

It is widely understood that livestock belch methane as a byproduct of the forage fermenting in their rumen. While it is often claimed that livestock emit 14.5% of global anthropogenic GHG emissions, the FAO's most recent analysis more accurately accounts livestock's proportion to be 11.1%. A new methodology for estimating methane's warming potential, known as GWP*, is becoming more widely accepted and lessens livestock's GHG proportion even further, but academic debates on the exact number are ongoing. Taking into consideration the effects of good grazing management, research has shown that improvements to forage quality, which we see with properly managed grasslands, can reduce enteric GHG emission by 30% (Wang et al. 2015).

Emissions, however, are just one side of the warming equation. To accurately evaluate methane's warming potential, we must take a systems view that looks at both sources and sinks.

Methane-oxidizing bacteria

Healthy, well-aerated soils are home to methanotrophs, methane-oxidizing bacteria commonly known to consume around 10% of atmospheric CH4 pools (Shashank et al. 2015), though some assessments show high variability of the fraction oxidized with a range of 11-89% (Chanton et al. 2009). Methanotrophic activity is known to be regulated by various soil conditions like bulk density, moisture, and temperature (Pan et al. 2021), and we know that the ideal conditions for methane oxidation (cool, moist, well-aerated soils) are a characteristic quality of grasslands under Holistic Planned Grazing. To that end, one could reasonably assume that methane oxidation in soils that have been managed holistically falls towards the higher end of the ranges previously studied.

Another factor that significantly reduces methanotroph activity is the application of inorganic nitrogen-based fertilizers, whereas organic nitrogen in the form of manure (Brady and Weil, 2016).

Methane oxidation in the troposphere & at vegetation interface

Most methane emitted is oxidized in the troposphere (0-10km above the Earth's surface) through interaction with hydroxyl radicals (OH) (Prinn et al. 2005). A whitepaper by Bruce-Iri et al. 2021 – which is worth reading in its entirety as it relates to this entire methane/livestock discussion – proposes another oxidation pathway closer to the source of emissions that has yet to be investigated in the literature: OH radicals that exist near the plant surface as a result of biological volatile organic compounds (BVOC's) expelled by a plant. While the oxidation potential has not yet been quantified at this vegetation interface, it would make intuitive sense given the co-evolution of grasslands and grazing herbivores for millennia.

Does replacing meat with plants reduce methane?

While calls for livestock reductions are commonplace, less common are analyses of the opportunity costs of replacing one source of food for another. In the 2021 US EPA Greenhouse Gas Inventory of Emissions and Sinks, agriculture's total emissions are shown to be 9.3%. Of that, 3.1% come from livestock enteric emissions while 4.5% come from cropland soil management. If one were to replace animal-source foods in their diet with plants, the enteric emissions of livestock are essentially being swapped for mismanaged cropland soils that have an even higher emission potential.

Does removing livestock from agricultural lands reduce methane?

Nearly 2/3 of global agriculture occurs on marginal land, i.e. land that is too rocky, hilly, dry and/or unproductive for arable farming (FAO, 1997). On these marginal lands, animal agriculture is not just the only viable form of food and fiber production, it is essential for maintaining the ecosystem function of these fragile grass-based biomes. The stimulus provided by livestock grazing, followed by appropriately-timed recovery periods, allows for actively-photosynthesizing vegetative growth during growing seasons and well-covered soils that are protected from erosion during dormant seasons. If livestock were removed from these lands due to their enteric methane emissions, the productivity of these landscapes would greatly diminish while carbon emissions would increase as a result of plant oxidation. While true that methane would not be emitted in this scenario as its production requires anaerobic conditions like those that occur in the rumen of an herbivore, in water-logged rice fields, and in landfills, a broader accounting of all GHG's would show a significant increase in CO2 emissions as a result of plant biomass oxidation. Again, eliminating livestock would be swapping one source of GHG for another.

Can soil carbon sequestration offset methane emissions?

In recent years there has been an abundance of research demonstrating the carbon sequestration potential of good grazing management. Most notably, a lifecycle analysis of greenhouse gases in an holistically managed grass-finished operation compared to a feedlot operation showed that for every kilogram of carcass weight produced, over six times that amount was reduced from the atmosphere in terms of carbon dioxide equivalence with all other production related gases accounted for, including enteric and manure emissions (Stanley et al. 2018). Other research has shown that "properly-managed grazing, if applied on 25% of our crop and grasslands, would mitigate the entire carbon footprint of North American agriculture" (Teague et al. 2016). Of course, carbon sequestration rates on a given landbase will be highly dependent on a variety of factors including soil type, moisture availability, and previous and current management practices, but the evidence appears to be stacking up in favor of Holistic Planned Grazing.

For a list of various carbon sequestration rates found in the peer-reviewed literature, please see Savory's post "Soil Carbon Sequestration with Holistic Planned Grazing: A Map of Published Rates." For a broader look at the various scientific literature supporting Holistic Management and Holistic Planned Grazing, please see Savory's Library.

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