Potential for Soil Carbon Sequestration with Livestock Systems

Best management practices reduce greenhouse gas emissions and improve beef cattle productivity and profitability.

Livestock production systems emit 26% of the methane and more than 50% of the nitrous oxide, contributing significantly to greenhouse gas emissions. In fact, these emissions represent about 15% of the U.S. total CO2 emissions equivalent (U.S. EPA, 2002). However, livestock systems also have potential for emission offsets or sequestration.

The potential of U.S. grazing land to sequester C has been estimated at 119 billion lbs C per year (Follett et al., 2001a). This is approximately 5% of U.S. CO2-C emissions. A spreadsheet model developed at Colorado State University evaluates "whole-farm" greenhouse gas emissions from several beef production scenarios. Results indicate that pasture management and feed consumption can significantly impact the amount of C sequestered or emitted.

Land use by simulated U.S. beef production systems, representing needs of the cow-calf through feedlot, vary from 3.0 to 18.5 acres per cow unit. If median sequestration responses from best management practices (BMP's) to pasture, range and hay land of 357, 45 and 178 lbs C/acre/year are applied to these hectares, the estimated C sequestration potential ranges from 46 to 94 tons C/yr for 100 cow production systems (Table 2). Recent measurements by colleagues (Conant et al., 2001, unpublished) support annual C-sequestrations of approximately 357 lbs/acre in response to intensive, rotational grazing management of pastures in the southeastern U.S. However, such increases in soil C are not likely in areas with less than moderate rainfall. Several other factors must also be considered when evaluating the imposition of BMP's such as, changes in yield and quality of forage, fertilizer inputs, or animal response. One simulation projected 357 lbs of C-sequestration/acre/yr in response to intensive rotational grazing. Other changes triggered by intensive grazing included forage yield increases (+ 50%), increased fertilizer inputs/ha (+20%), modest forage digestibility and protein content increases, faster animal growth, and lower land requirements. The increased C-sequestration for the herd in this case was estimated to be 50 tons/yr, representing approximately 30% of the total greenhouse gas (CO2 equivalent) emissions (Johnson et al., 2001).

It is likely that some sequestration of C is being realized under current pasture/forage management practices. Additionally, the application of BMP's to the grain cropping inputs into these production systems, primarily the feedlot, can provide additional C-sequestrations of 6 or more tons/yr. While it is not likely that sequestration will offset all livestock system emissions, the overall potential of more than 1/2 ton of C sequestered annually per mature cow projects significant advantages. These strategies will reduce greenhouse gas emissions, improve soil tilth and improve beef cattle productivity, potentially improving profitability.

Don Johnson, Professor,
Animal Sciences;
Hope Phetteplace, Post-doctoral Research Associate, Animal Sciences;
and Andy Seidl, Assistant Professor
and Extension Policy Specialist,
Agric. & Resource Economics