Cattle Carbon Footprint

Published on Tue, 06/15/2010 - 1:56pm

In 2006, a report by the United Nation’s Food and Agriculture Organization claimed domesticated livestock produces 18% of the world’s anthropogenic greenhouse gas emissions. Animal scientists—and the FAO itself—have been trying to clean up the damage ever since.

That wasn’t the only critical interpretation of the meat and poultry sectors in the 400-page report, which was entitled Livestock's Long Shadow. It also blamed runoff from pastures for “dead zones” in the sea, where aquatic life is choked out when unicellular organisms bloom from the added nutrients, die and decompose. It said drinking water is contaminated by antibiotics and hormones excreted by the livestock, and called overgrazing is "the major driver" turning a fifth of the world’s pastures and ranges into deserts.
But it was the greenhouse gas estimate that garnered the most controversy; the authors said 9% of the world’s carbon dioxide emissions are produced from fossil fuels burned to grow animal feed, and to process and transport meat; one third of emissions of methane—thought to be a far greater contributor per unit to the global warming phenomenon—are generated by decomposition of manure and from cattle flatulence and eructations.
But there’s a major problem with the report: it’s not accurate. The authors sought to cast blame on the industry for every emission indirectly associated with animal agriculture, and then drew the conclusion livestock produce more greenhouse gases than do all modes of motorized transport—without applying the same standards to its transportation calculations. It fell to Frank Mitloehner, a professor of animal science at the University of California-Davis, to conduct his own study demonstrating the inequities in the analyses, and present it at last year’s annual meeting of the American Chemical Society. FAO agreed with Mitloehner, and will revisit its report; an FAO policy officer says a more detailed analysis of food production emissions is due to be available by the end of the year.
But Mitloehner says damage has already been done. “No matter where you go,” he says, “people now think that consuming animal product will have a greater carbon footprint than their driving habits or their heating habits or other habits that they have, and it has really blown things out of proportion.”
It’s important to point out the FAO’s estimate, regardless of where it eventually settles, is for all of the world’s livestock; the greenhouse gas impact of herds and flocks in developed nations is far less. According to a 2009 study by EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks:1990-2007, emissions from the entire agriculture sector in 2007 represented 5.77% of total greenhouse gas emissions in the U.S. The entire livestock sector’s estimated contribution was 2.8%; emissions from manure management were 0.8%. Mitloehner pegs the contribution from the beef cattle sector at about 1%. “If you consider that the official number that was used by the FAO globally is 18%,” he says, “then these are huge differences that certainly do not warrant discussions of ‘Meatless Mondays,’ and so on.” (A group from Johns Hopkins University’s Center for a Livable Future encourages schools to adopt meat-free Monday menus, offering among other reasons the opportunity to “reduce your carbon footprint”. The largest school district to adopt the policy is that of the city of Baltimore, Md.)
Mitloehner says the U.S. industry could reduce its carbon footprint further by making better use of livestock waste, which is typically stored on the farm and then applied to crops. “One could do more things with waste,” he says. “For example, generate electricity from it.” But other than that, Mitloehner says livestock in industrialized nations are already managed so efficiently there’s little opportunity for further savings. “Doing what we do right now is really what should be done worldwide,” he says. 
A recent study by Australia’s University of New South Wales Water Research Center would seem to bear that out. Most of Australia’s cattle are finished on grass, but lead author Matthias Schulz says grass-fed beef produces more 38% more methane per pound than beef from cattle fed out on grain. This is because grain is more digestible; cattle farmers have long taken advantage of the abundance of inexpensive grass and the capabilities of the ruminant’s four stomachs, but the animal produces more enteric gas from forage. Schulz noted while cattle on a feedlot produce more emissions per day, they spend much less time on feed when finished on grain rather than grass, so the net emissions from feedlot animals are less.
Schulz’ study was commissioned by Meat and Livestock Australia, an industry-funded promotional body. Mitloehner also received a $25,000 grant from the U.S. beef promotion and research checkoff, but he bristles at the suggestion his data is somehow tainted, and points out his research gets $6 million a year from all sources. “My total support from agriculture is 5% of my total funding,” he says. “If somebody provides you with $25,000 to support one graduate student to do some literature research and you call that being in the pocket, it’s really bordering to libel. It’s actually laughable at this point.”
The contribution of livestock to emissions is “a really important issue at the moment,” says another researcher, Jude Capper. That’s why she’s spent the last four years working on it. Capper, an assistant professor of dairy sciences at Washington State University, was a post-doctorate student at Cornell when she began looking at the emissions impact of the dairy industry. But Capper’s focus is not on total, quantitative emissions; she calculates how much the emissions are being reduced per unit of production due to scientific advances.
“If we improve productivity, i.e. milk yield per cow, we cut our total carbon footprint,” Capper says. “So, if we compare it to the 1940s, our milk yield per cow has gone from 5,000 lbs/year to over 20,000 lbs/year. That means per gallon of milk, our carbon footprint has actually come down by 63%.” She’s wrapping up a similar study on beef cattle, to be published later this summer. “As with the dairy projects that we’ve done,” she says, “if we improve productivity, which in this case means beef yield per population, we are going to see a total cut in the carbon footprint and environmental impact.” 
Capper says most of the emissions impacts from the beef and dairy cattle sectors are similar as well. “The main greenhouse gases would be methane, which comes from the cows themselves plus the waste, and nitrous oxide, which comes from the cows, the waste and the fertilizers,” she says. The 2009 EPA study found nitrous oxide emissions from agricultural soil management on croplands and grasslands in 2007 accounted for 2.9% of total greenhouse gas emissions; nitrous oxide emissions resulting from manure management accounted for only 0.2%.
30-50% of the beef cattle emissions come from the previously noted eructation and flatulence, which are typically described in somewhat cruder terms. Capper’s findings are similar to what Mitloehner and Schulz said about efficiency; you can manipulate cattle’s diets to reduce their emissions, but if you do that, you tend to reduce their performance, thereby raising and not lowering the emissions per pound of beef produced. Similarly, Capper says, while waste can’t be captured as efficiently from a pasture as it can from a feedlot, the emissions themselves are different, balancing the effect.
The 2006 FAO report warned the environmental impact is expected to increase dramatically by the year 2050, by which time world demand for meat is expected to have more than doubled. That, said Capper, is precisely why the industry needs to continue improving its production efficiency, and reducing its emissions of greenhouse gases per pound of meat or gallon of milk produced. “By the year 2050 we’re anticipated to have a global population of over 9 billion people, which is a 50% increase,” she says. “To feed those people, we’re going to need 100% more food, partly because they’re going to be more affluent and because of that, they will want more milk and meat and eggs. So to improve the environmental impact of that increased food need, we’re absolutely going to have to improve productivity. Otherwise, we’re going to have a huge issue.”
But Capper is confident in the industry’s ability to continue to improve its productivity. “Absolutely, we can expect this to continue. The average milk yield per cow back in the 40s was about 5,000 lbs; the average yield now is over 20,000 lbs. We have whole herds with an average of 34,000 lbs, and we have individual cows with an average of 40,000 lbs. So, we can absolutely continue to make improvements over the next 20, and 30 and 40 years.”
And the issue facing livestock producers is whether the headlong rush to address greenhouse gas emissions via regulation or legislation will take into account the virtues of their production techniques as well. Frank Mitloehner thinks the government is paying attention. “I’ve had a lot of interaction with the EPA and others,” he says. “I think it probably has an impact.”