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Of Cows and Climate

CALS researchers are leading a far-reaching effort to gather information about greenhouse gases related to dairy—and to give farmers and other industry professionals the tools they need to reduce them.

Living in Wisconsin, you can’t help but absorb a few things about dairy, beyond the calcium. You likely know that Wisconsin is America’s historic creamery. You also probably know that dairy farms are getting bigger, while other states are challenging Wisconsin’s historic primacy. And chances are you also have your own opinions about the advisability of wearing a large wedge of dimpled yellow foam on your head.

But did you know that cows belch, and it’s a problem? Cows are ruminants, which means they regurgitate and re-chew their food. Combined with microbial action in multiple stomachs, they can break down fiber to get more nutrition out of plants. But these microbes also create methane, the primary component of natural gas.

In the last decade scientists have become increasingly concerned because methane has more than 20 times the global warming impact of carbon dioxide. New research suggests that livestock sources of methane have been undercounted by as much as half. Overall, agriculture creates 36 percent of human-related methane emissions, followed by natural gas systems (23 percent) and landfills (18 percent), according to a report, “Climate Action Plan: Strategy to Reduce Methane Emissions,” released by the White House in March.

Methane isn’t the only challenge. Another gas, nitrous oxide, is generated by nitrogen reactions in the soil and by the breakdown of manure. There is less of it, but nitrous oxide has 314 times the warming impact of carbon dioxide.

When this issue first surfaced around the turn of the century, the dairy industry was perplexed. Ruminants have been chewing their cud for millions of years, so wouldn’t their impact already have been rolled into natural systems? But as human population has grown, so has the cultivation of animals to feed them. Examining the initial evidence, rough calculations and trends, the dairy industry had to acknowledge that methane and nitrous oxide from agriculture was a real, if poorly quantified, threat.

The industry responded by taking environmental stock. They surveyed 540 farms across the country, scores of processors, and 20 percent of the milk transportation system. Overall, dairy was responsible for 2 percent of total U.S. greenhouse gas emissions. It wasn’t a massive number, but then that’s the challenge of greenhouse gases: because practically every human activity contributes to the problem, solutions need to be found everywhere.