New study blames dairy farms for much of LA’s smog

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Dairy cows may be a bigger contributor to smog in the Los Angeles area than many people thought, according to a new study.

The study, conducted by scientists from the University of Colorado and the National Oceanographic and Atmospheric Administration and published in Geophysical Research Letters, found that dairy farms and motor vehicles are about equally responsible for a sizeable fraction of the smog over LA, says this article in Ars Technica.

A large portion of the smog is ammonium nitrate, consisting of small particles from the interaction of ammonia and nitrogen oxide gas. Both cows and automobiles are responsible for ammonia, but it’s the automobiles that produce nitrogen oxide.     

Data gathered in and around the Los Angeles basin in May 2010 suggest that the region’s 9.9 million autos generate about 62 metric tons of ammonia each day, according to this article from Reuters. Ammonia emissions from dairy farms in the eastern portion of the basin ― home to about 298,000 cattle ― range between 33 and 176 metric tons per day, the article says.  

Yet, many of the dairy farms east of Los Angeles ― particularly those around Chino ― are no longer in business.

“There are not many dairies left in Southern Cal, and I am surprised to hear that these few dairies would have a major effect. The ammonia that they have measured does not come from the San Joaquin Valley with all its dairies,” says Frank Mitloehner, air-quality specialist in the Department of Animal Science at the University of California-Davis.

“I disagree with the notion that cows produce more smog than cars,” Mitloehner says. “Both contribute pollutants that need to mix to form PM2.5 (fine particulate matter). It is as if you were to say ‘flour is more important than the egg when baking a cake.’ You need both!”

The study appears to overstate the number of cows in the area.

There are about 100,000 mature cows -- milking and dry -- on about 110 facilities in Chino, Ontario and San Jacinto, according to Rob Vandenheuvel, general manager of the Milk Producers Council in Ontario, Calif. 

Ying Wang, director of Life Cycle Assessment research for the Innovation Center for U.S. Dairy, issued the following response to the study:

“We believe the ammonia emissions estimate of California dairy farms from the study published in Geophysical Research Letters is more than 50 percent higher than other research that we have reviewed,” Wang said.

For instance, the National Air Emissions Monitoring Study (NAEMS) study, which the National Milk Producers Federation commissioned with the U.S. Environmental Protection Agency, came up with significantly different findings, Wang said.  

“NAEMS was conducted from 2007 to 2009 at seven different dairy production facilities located in New York, Indiana, Texas, Wisconsin, California and Washington. The study is a credible representation of ammonia emissions from U.S. dairy farms,” Wang said.

According to the NAEMS study, the average ammonia emissions per cow per day are approximately 60.9 grams. To convert this to metric tons and compare it to the Geophysical Research Letters study:

  •   60.9 grams per cow per day multiplied by the 298,000 cows referenced in Geophysical Research Letters article equals 18,148,200 grams per day, which is about 18 metric tons per day. This is significantly less than the 33 to 176 metric tons per day range cited in that study.  
  • And, if there are only 100,000 cows, the final number would be one-third of that, or 6 metric tons.



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Smog City  |  May, 07, 2012 at 03:07 PM

Wow, ever been to Juarez, Mexico there is a lot of smog there and no cows go figure...Some studies I feel are done with the intent to hurt industries. Drink milk, eat cheese! (If you were starving you wouldn't pass a piece of steak no matter how "vegan" you were.)

Charlie Peters    
May, 08, 2012 at 02:12 AM

Bill Clinton, Al Gore & Senator Obama supported the California 2006 Prop. 87, a GMO corn ethanol welfare program. Bill, Al, have changed opinion on the ethanol mandate, I wonder if Obama will make this the time for CHANGE? I support a waiver of the ethanol mandate, voluntary use of ethanol in my gas. Federal ethanol policy increases Government motors oil use and Big oil profit. It is reported that today California is using Brazil sugar cane ethanol at $0.16 per gal increase over using GMO corn fuel ethanol. In this game the cars and trucks get to pay and Big oil profits are the result that may be ready for change. We do NOT support AB 523 or SB 1396 unless the ethanol mandate is changed to voluntary ethanol in our gas. Folks that pay more at the pump for less from Cars, trucks, food, water & air need better, it is time. The car tax of AB 118 Nunez is just a simple Big oil welfare program, AAA questioned the policy and some folks still agree. AB 523 & SB 1326 are just a short put (waiver) from better results. GOOGLE: Prop 87 (510) 537-1796

Robert Hagevoort    
New Mexico  |  May, 08, 2012 at 09:00 AM

Anybody that has ever lived in the IE (Inland Empire), which is anything east of LA, knows that prevalent winds in the LA basin are westerly, and the smog from LA moves into the IE and clouds the sky. Much less today as maybe 10-20 yrs ago, but nevertheless! The only days this is reversed is when Santa Ana winds blow from east to west and clear out the basin. If you happen to be fishing that day at Catalina Island: you're in the smog! To suggest that cows are a major contributor is just as fine a piece of research as the FAO's infamous "Long Shadow": extrapolation beyond the scope of the research which makes it worth just as much: a bunch of hot air (dirty that is)!l

Dairy supporter    
CA  |  May, 08, 2012 at 02:32 PM

As I have heard stated before..."I'd rather be trapped in a garage with a bunch of cows rather than ONE running car!"....

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