Can we offset the methane emissions of cows by increasing soil carbon stocks?

Short answer: No.

Methane (CH₄) is the second most important anthropogenic greenhouse gas and has accumulated in the atmosphere over the course of several decades due to human activities. One such activity is livestock farming, particularly of ruminants, e.g. cattle, sheep and goats. These animals contribute between 114 and 124 teragrams of methane, accounting for around one third of anthropogenic CH₄ emissions (Saunois et al. 2025). These animals have the matchless capability to utilise cellulose-rich materials, such as grass, in their anaerobic digestive systems, which harbour methanogenic microorganisms (archaea). Ultimately, ruminants convert plant material that is not in direct competition for food into highly valuable products for human nutrition, such as milk and meat. Furthermore, many grassland biomes, which surpass the global cropland area by a factor of two, are not feasible for crop production due to climatic constraints, such as too short a vegetation season or being too dry. Despite these advantages, the methane issue is a major concern, prompting calls to curb these emissions by various means, mostly by reducing animal numbers. This brief discusses an alternative approach: offsetting emissions through soil carbon sequestration.

Pasture soils often store more soil organic carbon than croplands, and these stocks can be increased through targeted management techniques. However, even if sequestration were successful, would it compensate for the continuous release of methane by ruminants?

To answer this question, we first revisit how the climate impact of greenhouse gases (GHGs) is quantified. Global warming potentials (GWP) are most often used for this purpose. These are based on the comparison of the radiative forcing of a single pulse emission of one kilogram of a greenhouse gas (GHG), e.g. methane (CH₄), relative to a single pulse emission of one kilogram of carbon dioxide (CO₂), integrated over a period of one century (GWP₁₀₀). The GWP₁₀₀ of methane is approximately 27, typically expressed as CO₂ equivalents, meaning that, over one century, a single pulse emission of one kg of methane induces a radiative forcing (and thus warming; the relationship is slightly more complex, but let us simplify it for the sake of clarity) 27 times greater than releasing one kg of CO₂ as a pulse emission would. The underlying mechanics — namely, the radiative efficiency of a molecule in the atmosphere and the different lifetimes of various GHGs — can be combined into simplified Earth system models that provide radiative forcing and allow us to evaluate the potential of soil in the context of animal methane. The IPCC outlines this method in more detail here, and it has also been used by the author, e.g. here.

Let us now assume that one hectare of pastureland feeds one livestock unit (i.e. roughly one cow), which emits approximately 120 kg of methane per year (the average for cows in industrialized countries). We assume an annual net carbon uptake, i.e. sequestration, of 0.5 tonnes of carbon per hectare (not at the lower end of what is typically achieved), equaling 1.84 tonnes of CO₂ (1840 kg). However, mineral soils cannot sequester carbon indefinitely, but rather reach new, higher steady states over time. A realistic sequestration duration estimate is 30 years, i.e. a total carbon uptake of 15 tonnes as soil organic carbon. What impact does this have on the radiative forcing of such a grassland ecosystem? Simply by comparing annual fluxes and using the GWP for methane of 27, annual methane emissions of 120*27=3240 kg of CO₂-equivalent already override the soil’s sink by a factor of almost two. Misleadingly, sometimes the total soil carbon uptake of 1.84*30=55.2 t CO₂ (55200 kg) is compared to the annual CH₄ emission to cast the system in a favorable light.

These numbers are based on the GWP₁₀₀. A more realistic picture can be obtained by calculating radiative forcing dynamically, taking into account the emission rates and atmospheric stability of GHGs:

Figure showing annual (left) and cumulative (right) radiative forcing of one hectare of pasture sequestering 0.5 tonnes of carbon per year for 30 years, reaching a new, higher steady state thereafter. Curves below zero indicate cooling and curves above indicate warming. The land feeds one dairy cow, which emits 120 kg of methane per year. In the left panel the 30-year period of carbon uptake in the soil can be seen. This is followed by a relaxation of the negative forcing effect (i.e. cooling), which is not related to the release of carbon (the carbon is assumed to remain in the soil throughout the whole period), but rather to the global equilibration of the atmospheric CO₂ content. Calculations follow the mathematical approach cited in the text above.

As can be seen from the graphs, the annual radiative forcing (i.e. the warming induced by emitted methane) starts above zero because cows (and their ancestors) have lived on that pasture for a long time, resulting in a consistently higher level of methane in the atmosphere than would be the case without cows. This level is quickly reached and continues to contribute to global warming for as long as the CH₄ emission remains unchanged (i.e. as long as there are cows). Furthermore, regardless of how we examine the system (whether considering cumulative forcing, resembling the GWP approach, or instantaneous warming effects), the grassland soil carbon sink cannot offset the methane effect at any point in time. This topic has also been addressed on a global scale using the same methodology (Wang et al. 2023).

In summary, even with optimistic assumptions about the net uptake of CO₂ in soil organic matter and realistic assumptions about ruminants’ burps, it is very unlikely to expect to compensate for the methane released by these animals at any scale in time and space. As discussed at the outset, ruminants play an important role in human nutrition but both reducing and offsetting their emissions remains difficult. This finding should remind us, when it comes to mitigating climate change, it is not cows, but the CO₂ emissions from fossil fuels that pose the key, still unresolved challenge.