Animal feed top cause of San Joaquin ozone

While discussion of livestock's environmental impact has focused on methane emissions, researchers are now linking animal feed to excessive ozone, a greenhouse gas. While automobiles are the key generator of ozone in urban areas, rural ozone production has been linked to farming, Janet Raloff of ScienceNews reports. University of California-Davis researchers discovered "corn silage generated about 125 parts per billion ozone, alfalfa silage a little less, and mixed oat-wheat silage a whopping 210 ppb," Raloff writes. Silage grain has a particularly harmful role in producing ozone because it is deliberately fermented, meaning it has lots of alcohol, a "reactive organic gas that can drive the atmospheric chemistry responsible for making ozone," Raloff writes.

The study was conducted in the San Joaquin Valley in California, which produces almost a tenth of the nation’s total agricultural output and is "home to three of the nation’s six most ozone-ravaged counties," Raloff reports. Cody Howard, UC-Davis environmental engineer and researcher on the study, told Raloff the region's geography and agricultural intensity make it unique. "It’s completely surrounded by mountains," he said. "Anything emitted in the Valley typically stays there for a long time — which presents a problem when you’re talking about ozone formation." (Read more)