Dairy's Methane Impacts Re-examined
Fri December 6, 2013
Is Livestock’s Contribution to Climate Change Still Being Overestimated?
In a 1,000 year old village in Germany (Juehnde), methane is not a dirty word. The recovered methane from a manure-fueled bioreactor feeds the burners that heat water for every household in the village. The same hot water provides heating. These households benefit from living adjacent to a livestock economy whose manure was once just a smelly nuisance. The manure is transported by truck to an enclosed bioreactor, thereby reducing odor and feeding a system that powers an entire community. Frank Mitloehneronce called this village home. Now a professor and air quality UC Cooperative Extension specialist in the Department of Animal Science at UC Davis, Mitloehner thinks that if this village can do it, so can California.
It is easy to see how Mitloehner was inspired to study ways that California can take advantage of its plentiful supplies of animal methane. In eight bovine bio-bubbles that function as airtight barns, he captures and measures every emission from his resident livestock in order to understand how methane emissions vary with feed and herd management.
Mitloehner recently hosted a seminar for the Western Center for Agricultural Health and Safety at Davis. He is a member of the FAO committee that produced the 2006 report, Livestock’s Long Shadow. Before joining the committee, he challenged two misleading sentences in their report. The report compared the contribution of livestock emissions to that of transportation. By saying the contributions to climate change were similar, the report led many environmental advocates to the conclusion that eating less meat was the equivalent of taking cars off the road, setting up a meat vs. miles tradeoff that exaggerated the methane contributions of livestock everywhere.
Mitloehner’s response was the publication Clearing the Air, Livestock’s Contribution to Climate Change, his science-based estimate that livestock’s contribution is 3.4 percent of U.S. emissions. Globally, 18 percent of warming was estimated to be livestock related. This estimate included livestock in the broadest sense - changes in land use, deforestation and desertification in developing countries.
Why is the U.S. so low? Mitloehner shared a few facts that help explain the phenomena:
- The U.S. has fewer dairy cows. Today’s 9 million dairy cows supply 60 percent more milk than the 16 million cows in production in 1950. That means there is increased efficiency per cow for the same methane produced.
- Thirty percent of the methane in dairy production is from manure in ponds. There is the potential for recovery on the approximately 1,500 California farms, where the average herd size is 1,100 head.
- Methane has 20 times the warming potential of carbon dioxide, but when burned to heat water or to generate power, its warming potential is reduced by a factor of 20.
- The more fiber in the feed, the more methane is released by the rumen of the animal. One dairy cow in the U.S. produces an average of 20,000 lbs of milk per cow annually, the same amount of milk as five cows in Mexico, or up to 100 cows in India for the same, or less methane per cow. Reasons: low fiber diet, fewer parasites and less disease result in large differences in production per cow.
In reality, California has been exporting surplus dairy products to growing populations since the 1890s and that won’t change soon. Those markets do more to keep dairies profitable than my weekly milk and yogurt purchase. Lactose for pharmaceuticals and whey proteins for infant formulas are shipped internationally from several of California’s mammoth cheese factories, sometimes worth more the cheese itself.
Mitloehner believes that “sustainable efficiency” is the solution to keeping local dairies viable. He believes that science will provide the path to better regulation. His Mitloehner's leadership keeps methane bioreactors on the agenda.