Livestock Greenhouse Gas Emissions

Greenhouse gas (GHG) emissions from cattle have been receiving increased attention recently. Cattle contribute to 14% of all GHG emissions and 17% of all methane emissions. Methane is a potent GHG 25 times more potent than CO2. Industrial agriculture proposes that increasing efficiency (faster rates of gain or more milk production with the use of higher energy diets, growth hormones, and other additives) is the solution for reducing GHG emissions for livestock production. A recent Cornell study funded by Monsanto (http://www.pnas.org/content/early/2008/06/27/0802446105.full.pdf) concluded that conventional dairies that use rBGH (recombinant bovine growth hormone) reduced the global warming potential of the dairy industry compared to conventional dairies that do not use rBGH and organic dairies. Numerous individuals have cited this study as flawed and biased, largely due to the claimed increases in milk production from the adoption of rBGH that have never been realized from the industry as a whole. U.S. milk production never significantly spiked during the years of reported widespread use of rBGH by dairy farmers.

Rather than looking towards new technologies to solve livestock GHG emissions, I believe the solution may lie in grazing grasslands. I would like to see a study comparing the net GHG emissions of a well managed rotationally grazed dairy or beef herd compared to a confinement dairy (with or without rBGH) or beef feedlot. I would hypothesis that with the carbon sink of a perennial pasture and the lower use of fossil fuels in production systems, grazing dairy and beef cattle (despite higher methane emissions due to lower milk production/gains per animal) would have net GHG emissions (CO2-C equivalent) significantly lower than confinement operations (with or without rBGH). There are very few studies I have found researching the GHG exchanges for grazed grasslands. Soussana et al. (Agriculture, Ecosystems and Environment 121 (2007) 121–134) studied 9 sites in Europe and concluded that even with accounting for the methane emissions of grazing ruminants, grasslands are still CO2-C equivalent sink.

The scientific community needs researched studies that will address best possible agricultural strategies for improving air quality and reducing contributions to global climate change. I have a bias towards grazing systems, believing not only in the numerous environmental benefits of well managed grazing systems, but also the possibility of an economically viable alternative to adopting the newest technologies of industrial agriculture. Unfortunately, grazing natural grasslands does not have the backing of industry dollars, reducing the potential of innovative research.