Global Warming and Pasture-Raised Beef Production in the U.S. (2011)
Agriculture accounts for about 6 percent of total heat-trapping emissions in the United States, and beef production alone accounts for 2.2 percent of the total—roughly the equivalent of the annual emissions of 24 million cars or light trucks, or 33 average-sized coal-fired power plants. So while the emissions contribution of beef production may sound small, it is not an insignificant part of the problem.
The good news is that beef production can also be part of the solution. A February 2011 Union of Concerned Scientists report, Raising the Steaks: Global Warming and Pasture-Raised Beef Production in the United States, looks at ways pasture-based beef producers could lower their climate emissions and take greater advantage of pastures’ capacity to remove heat-trapping carbon from the atmosphere and store it in soil.
The problem: methane and nitrous oxide
Cattle produce large quantities of methane, a potent heat-trapping gas, in their digestive tracts; manure also emits small quantities of methane. Emissions of another heat-trapping gas, nitrous oxide, are produced by manure and by nitrogen fertilizer applied to soil. On the positive side of the ledger, pasture plants are much better than grain crops such as corn when it comes to removing carbon dioxide from the atmosphere and storing—or sequestering—it in soil.
Climate-friendly beef production practices reduce methane and nitrous oxide emissions while increasing carbon sequestration.
Reducing methane emissions
One way to reduce methane emissions is to increase the nutritional quality and digestibility of forage—the plants cattle eat while on pasture. The report suggests several strategies to improve forage quality:
- Increase the percentage of legumes in forage mixtures
- Avoid the use of low-quality, mature pasture crops for grazing
- Breed better pasture species to improve nutritional quality
- Plant birdsfoot trefoil (a legume that produces condensed tannins, which can reduce both emissions and disease risk)
Climate-friendly pasture management
The way pastures are managed can play an important role in mitigating climate impact. The report offers some suggestions for climate-friendly pasture management:
- Avoid excessive use of nitrogen fertilizer to curb nitrous oxide emissions
- Use moderate stocking densities (number of cattle per acre) to avoid excessive manure buildup and allow pastures to recover from grazing
- Prevent overgrazing to increase carbon sequestration
- Move water and shelter sources to ensure that manure is spread more evenly
- Use nitrification inhibitors—chemicals that prevent the microbial processes that change ammonia to nitrous oxide—to reduce nitrous oxide emissions on urine patches
Pasture finishing vs. CAFOs: It’s complicated
Research shows that pasture finishing has nutritional advantages, and that CAFOs (confined animal feeding operations) come with serious environmental costs. But is pasture more climate-friendly? The answer, according to the report, is “it depends.”
The grain-based feeds used in CAFOs produce more rapid weight gain than pasture forage, with fewer calories lost to methane emissions. However, high-quality forage—especially when grown on high-quality land—can minimize the climate emissions advantage of grain. And pasture finishing has other climate advantages, including the ability to sequester more carbon than grain crops.
Toward better beef: recommendations
Public investment in improved practices can reduce the climate impact of beef production. The report suggests a three-pronged approach:
- The U.S. Department of Agriculture (USDA) should expand its research on global warming emissions from pasture beef production.
- The USDA’s Natural Resources Conservation Service (NRCS) should provide financial incentives and technical assistance to beef producers who want to adopt improved practices.
- University extension services should advise and train beef producers on climate-friendly practices.