Smart Pasturing Can Reduce Emissions from U.S. Beef Industry

U.S. beef cattle are responsible for 160 million metric tons of global warming emissions every year–equivalent to the annual emissions from 24 million cars and light trucks. But unlike American drivers, farmers who raise beef on pasture can reduce global warming emissions by storing, or sequestering, carbon in pasture soils, according to a report released today by the Union of Concerned Scientists (UCS).

“Given the threat that climate change poses, all sectors of our economy–including agriculture–have to do their part,” said UCS Senior Scientist Doug Gurian-Sherman, the author of the report. “There is a range of affordable ways beef producers, especially those who raise beef on pasture, can significantly reduce their impact by cutting emissions and capturing more carbon in soil.”

The report, “Raising the Steaks: Global Warming and Pasture-Raised Beef Production in the United States,” concluded that U.S. pasture beef producers could reduce their annual global warming impacts by as much as 140 million metric tons, the equivalent of taking 21 million cars and light trucks off the road.

Carbon sequestration, the report found, has the most potential for mitigating pasture beef’s climate impact. Such practical methods as preventing overgrazing, increasing pasture crop productivity with a mix of crops, and adding adequate amounts of nutrients from manure, legume crops or fertilizers, could capture significant carbon dioxide (CO2) emissions from a variety of sources.

Pasture beef farmers also can adopt practices to cut emissions. Pasture beef cattle emit the three major heat-trapping gases–methane, nitrous oxide and CO2–but the amount of CO2 is such a small percentage of total U.S. global warming emissions that the report did not include it. Per ton, methane and nitrous oxide are much more damaging to the climate than CO2. Methane has 23 times the warming effect of CO2, and nitrous oxide is nearly 300 times worse.

The 35 million head of cattle the U.S. beef industry raises annually release more than 103 million metric tons of the CO2 equivalent of methane into the atmosphere. Meanwhile, crop and pasture sources of nitrogen–such as manure and fertilize –generate 57 million metric tons of the CO2 equivalent of nitrous oxide.

All beef cattle spend their first months–and sometimes more than a year–on pasture or rangeland, grazing on grass, alfalfa or other forage crops because feeding cattle grain their entire lives would cause life-threatening illnesses. Some beef cattle live on pasture until slaughter, but most U.S. beef cattle are fattened, or “finished,” for several months in CAFOs (confined animal feeding operations) on corn and other grains. 

The UCS report recommended a number of approaches that would reduce the impact of pasture-raised beef. Most of them are more suitable for the finishing stage of fully pasture-raised cattle systems–which have environmental and nutritional advantages over CAFOs–but they also could apply to the many months CAFO-bound cattle spend grazing on rangeland.

One key is to improve cattle’s diet, which, in some tests, reduced methane production of pasture-raised cattle by 15% to 30%. More research is needed to accurately estimate its potential to reduce cattle emissions nationally. Animals fed on rapidly growing or more nutritious types of grasses and other pasture plants, which are more easily digested, produce less methane than cattle eating older or otherwise less nutritious pasture plants. On this more climate-friendly diet, the animals also grow faster, need less food, and therefore produce fewer emissions.

Gurian-Sherman examined dozens of peer-reviewed studies and found that cattle fed a mixture of high-quality grasses and legumes such as alfalfa produced less global warming emissions than animals fed on grasses alone. One particularly promising legume is a plant known as birdsfoot trefoil. Like all legumes, it adds nitrogen to the soil, which improves the productivity of pasture grasses. But unlike most other legumes, it contains natural chemicals known as condensed tannins, which reduce methane production during digestion.

There are also ways to reduce nitrous oxide, which is produced by the action of soil microbes on nitrogen in industrial fertilizers and manure and crop residues. The report recommends that farmers use only enough nitrogen to produce adequate pasture crop productivity because excess use results in especially high rates of nitrous oxide. It also recommends that farmers spread cattle more evenly around a pasture to minimize manure buildup in particular spots. That allows more nitrogen to be absorbed by pasture plants, leaving less for soil microbes to turn into nitrous oxide.

Some studies have found that CAFO systems produce less heat-trapping emissions than pasture systems, but those studies relied on data that assumed low pasture nutritional quality. The scientific literature documents that planting higher quality pasture crops, using adequate fertilizer, and managing grazing “intensity” would substantially reduce the disparity between CAFO and pasture systems. 

Smart pasture operations also have other advantages. Pasture-raised cattle require far fewer antibiotics than CAFO-raised cattle, resulting in fewer harmful antibiotic-resistant pathogens, such as Salmonella and E. coli. And pasture-raised beef contains healthier fats.

“The Department of Agriculture has a role to play here, too,” Gurian-Sherman said. “It should sponsor more research to improve pasture crop quality and productivity, and provide incentives to help farmers adopt climate-friendly pasture practices.”

The report has implications beyond U.S. beef production, Gurian-Sherman added. Worldwide, beef contributes a substantially greater proportion of total climate change emissions than it does in the United States, so adopting these approaches internationally would have a significant impact. Moreover, beef production is only one facet of animal agriculture. According to a 2006 report by the U.N. Food and Agriculture Organization, livestock farming worldwide generates nearly 20% of all global warming emissions.

The report is available at the link below.