Dairy cows’ feed exacerbates air pollution in central California

Although it has a relatively low population density, California’s San Joaquin Valley has some of the worst air pollution in the nation, especially when it comes to ozone (O3), a gas that can cause respiratory and cardiac problems. To counteract the air pollution, California and San Joaquin Valley regulators have taken significant actions, but results to date have been disappointing. It seems that the people who estimate the pollutant emissions from transportation, industry  and agriculture missed something. The San Joaquin Valley is home to much of California’s dairy industry, so it has been suggested that the masses of manure or perhaps the cows themselves were a big source of air pollution.

A new study comes to a somewhat surprising conclusion: cattle feed is a previously unnoticed source of ozone precursors, possibly being responsible for more ozone formation than light-duty cars and trucks in the valley. Basically, as the cattle feed ferments in huge covered piles, all sorts of alcohols, aldehydes and other reactive gases are formed and can react with oxides of nitrogen to form ozone after being released.  The biggest contributor is corn silage because of its popularity among dairy farmers (10 million metric tons feeding 1.9 million cows in a recent year), possibly leading one to remark something like “Corn, is there anything you can’t screw up?”  However, other types of feed also emit ozone precursors, so it’s conceivable that switching from corn silage to alfalfa or oat silage could have a similar impact (the articles, however, are not clear on how switching feeds would change things). To reduce this source of pollution, farmers will need to change the way they feed their cows so that or the way that they store silage — the articles are short on specifics.  Dairy farmers in other concentrated dairy areas probably don’t need to rush out and change their practices, as the geography of the San Joaquin Valley makes it a place that is uniquely susceptible to air pollution. (Fresno Bee; Green at the New York Times; Science News;  the full article is in Environmental Science and Technology, subscription only, but might be available for free via EurekAlert!)

7 Responsesto “Dairy cows’ feed exacerbates air pollution in central California”

  1. Blame game is so easily manipulated. The UN blamed cows for being more polluting than cars. But with cows they included too much and with cars too little. Turns out they’re now back tracking:

    A 2006 United Nations study claiming livestock production emits more carbon dioxide emissions than transportation overstates the impact of livestock production on global warming, one of the authors has admitted.
    Dr. Frank Mitloehner, an associate professor at the University of California at Davis, has acknowledged the UN study calculated livestock carbon dioxide emissions more liberally than it calculated transportation emissions.
    Authors of the UN study included in their livestock emissions calculations not only the carbon dioxide directly emitted by livestock, but also the carbon dioxide emitted as a result of land clearance, fertilizer production, and vehicle use associated with livestock production. On the other hand, the UN study did not include similar related emissions in its assessment of transportation.
    “I must say honestly that he [Mitloehner] has a point – we factored in everything for meat emissions, and we didn’t do the same thing with transport,” Pierre Gerber, a policy officer with the UN Food and Agriculture Organization, told the BBC News.
    Gerber, nevertheless, said the flaw in calculating relative carbon dioxide emissions does not call the rest of the study into question.
    The UN study, Livestock’s Long Shadow, asserts livestock production is one of most environmentally damaging activities on the planet. The study claims “the livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global.”
    “At virtually each step of the livestock production process substances contributing to climate change or air pollution are emitted into the atmosphere, or their sequestration in other reservoirs is hampered,” argues the study.
    Environmental activists and anti-meat groups have seized upon these claims to advocate restrictions on livestock production and meat consumption.
    The message here is that we need to be very careful taking these studies at face value. Question them. Think about who is presenting them and who benefits.

  2. This is not the “blame game,” it’s using good science to find out why the San Joaquin Valley can’t solve its air pollution problem.  Recall that the initial theory was that the cows themselves or their wastes was the air pollution source, but thanks to the research reported in the article, we know that the real answer is the feed, which is something that the dairy industry can deal with a lot easier than, say, if the issue was the animals themselves or their waste. If you know of any credible complaints about the methods used in the study, please pass them along.

    You’re right about paying attention to who is doing and funding the research, and perhaps the Ethicurean should make a point of noting funding sources when writing about research.  In the case of the cows and ozone study (which was focused on near-field lung-burning, asthma-inducing air pollution, the kind of pollution that chains kids to inhalers, and puts elderly people in the hospital, not climate change), the research was performed by staff from the Department of Civil and Environmental Engineering, Crocker Nuclear Laboratory, and Department of Animal Science in the  University of California at Davis.  Interestingly, one of the paper’s co-authors is Dr. Frank Mitloehner, who is quoted in your comment. The research in the digest was funded by USDA Grant TM No. 2004-06138 with additional funding provided by the California Air Resources Board and the San JoaquinValleywide Air Pollution Study Agency under contract 2000-05PM.

    Similarly, one needs to be wary of skeptics:  who is funding them and their motivation. The research from Dr. Mitloehner’s that you cite above was funded by a $26,000 grant from the Beef Checkoff program (according a UC Davis press release about the article).   Over at the Livable Future blog at Johns Hopkins, there was some back and forth about Mitloehner’s work, the UN reports and the popular press’s misinterpretation of them, including comments from Mitloehner himself.  Part 1 and Part 2.

    In addition, the Heartland Institute, who you cite, won’t reveal who pays their bills. Why not?  In recent years, they have received funding from a number of fossil-fuel-industry connected foundations, like the Scaife Foundations and the Koch Family Foundations, and a small amount from oil companies.  A full list of contributors before they started hiding who pays their bills is at SourceWatch.   Heartland is also no friend of organic, small-scale farming, and is happy to distort research to further its Big Ag agenda, as a 2007 post by Bonnie pointed out. 

    As for the UN report, I’m glad they are reviewing it, that’s something should be doing every year and subjecting to it wide-spread review. It’s no easy task to estimate the emissions from the livestock industry (and the related industries that support it, like feed production and transport).  It will be interesting to see what they come up with. I suspect the contribution will be somewhat lower but still quite significant.

  3. My, my, so defensive. I’m getting tired of people citing the UN study. It was poorly done, is really about CAFOs not pastured livestock and completely fails to take into account the full load of pollution caused by transportation and other sources of pollution. The result is the vegan evangelists have been having a field day citing the UN study to justify their call for everyone should convert to their credence of not eating meat. They completely fail to understand or discuss the destruction caused by vegetable and fruit farming and the fact that pastured livestock can convert marginal land into high quality proteins.

    So relax, Marc.

  4. Very Closely Related:

    “Study Says Vegetarians Hurt Environment More Than Meat-Eaters”
    A study commissioned by the World Wildlife Fund and conducted by the UK’s Cranfield University examined how vegetarian and carnivorous diets affect the environment. Researchers found that overall, meat-eaters produce less of a carbon footprint than those who only consume meat-free products. The study counters the recently popular claim that adopting a vegetarian diet decreases greenhouse gas emissions.


  5. Note that I’m not promoting a “Eat Meat Only Diet”. Unlike the vegan evangelists I don’t really care what people eat. That is their business. What would be a far better study that looks at local food, pastured for the meat, low fossil fuel inputs for both meat and veggies. It can be done and on a scale that would feed the world. Far better to have 10,000,000 small farmers. That’s food security.

  6. Walter — Although I’m unable to find the actual report, the Telegraph article linked to in the change.org piece seems to indicate that the study is more of an indictment of highly processed foods made from raw materials grown far away than vegetarianism in general. Food is far too complicated to be able to say that ovo-lacto vegetarian, vegan, or non-vegetarian is worse than the others in the abstract. It’s easy to come up with a diet from any of the categories that has less or more impact than the others. E.g., a meat eater who only eats animals raised on pasture, local fruits and vegetables vs. a vegan with a diet heavy in processed soy and imported nuts, fruits and vegetables. Personally, in the last few years I’ve come to see the value of choosing protein sources like locally raised pastured pork, local dairy (Straus), local beans (like Rancho Gordo), and pastured chickens (Soul Food Farm) over tofu and other processed vegetarian staples from factories in other states.  It would be interesting to see what you propose, the study of a local “food shed” that includes the impacts of pasture (e.g., carbon storage, water filtration).

    Getting back to your favorite subject, the UN report, although I’d need to study the UN report to see how they counted animals and whether they were actually considering CAFOs only, I think it’s likely the case that they completely ignored the “power of pasture” in their estimates. This is a serious oversight, as well-managed grasslands have a significant ability to store carbon. And this carbon storage also has plenty of other benefits as I described in the post about the Marin Carbon Project (who you might want to contact to exchange ideas). Pasture can have also have much more biodiversity than a monocultured soybean or corn field.

  7. Veg diets are not practical year round in our northern climate.
    Veg diets require shipping foods from far away.
    Veg diets for the masses uses lots petroleum.
    Veg diets for the masses require special land that is tillable – rare here.
    Livestock raised on pasture use virtually no petroleum, don’t eat grain, can use pastures not suitable for growing crops and are sustainable in our northern climate.
    A veg diet is a lot more destructive of the land and world than vegs like to admit.
    An appropriate local omnivore diet is better. Fit in with your climate.
    The veg evangelists are getting annoying with their lies. The fact that the UN is now headed by one is sad.