Combustion, Not Belches to Blame
By
John Lindt
San Joaquin Valley - Vowing to cut smog in the Valley, regulators have targeted two reactive chemicals that when hit by sunlight, create ozone.
The two are nitrogen oxide (NOx) produced by combustion when you burn something and volatile organic compounds, and VOCs that create smog when combined with NOx emissions. VOCs occur both naturally and are manmade and vary widely by their reactive potential. The most common VOC is methane. Cows as well as wetlands supply plenty of that.
Cows make a lot of methane belching out fermented emissions from their rumen – their stomachs. “But methane is not a potent VOC,” says UC dairy researcher Frank Mitloehner. “It has very low reactivity.”
Trees supply a fair share of the emissions out there. “Over half the VOCs in the state occur from natural sources,” says Mitloehner.
There are so much naturally occurring VOCs in the atmospheric inventory that reducing the manmade portion to zero “still leaves plenty to react with NOX in the air to make smog.”
Nitrogen oxide emissions are largely from transportation – 70 percent mobile sources – with the largest stationary source the petroleum industry.
Still dairy industry critics, newspapers and the uninformed shout that cows create more smog than cars.
Mitloehner, who interacts with state and local regulators, says that those who enforce dairy regulations that have tightened over the past decade have “come around” to the latest science now.
Just a few years ago, the ARB used a 1938 study to guide policy that overstated the amount of VOCs produced by dairies by 50 percent.
He says in a recent paper that regulators used values 6 to 10 times too high, based on the reactive factor in order to estimate inventories used to make ozone attainment plans.
Two problems arise. Regulations cost the dairy industry lots of money driving the little guys out of the business, but it appears the tighter rules won't even make the difference in cleaning the air.
In a 2004 study, Mitloehner offered research that showed that rule makers were blaming the wrong end of the cow anyway – focusing on manure rather than cow belches as a major VOC source. Most significantly, the latest revelation is that reaching ozone attainment in the Valley requires the main focus ought to be strictly on nitrogen oxides.
By 2020, the Valley air district – seeking to get to an ozone level of 85 – which is attainment – could require a 50 percent cut in manmade VOCs and a 40 percent cut of nitrogen oxides from combustion.
In a modeling study, researchers realized
they could reach that same 85 ozone attainment level by requiring a zero
reduction in VOCs and a 47 percent cut in NOx.
The planning study focused on one of the smoggiest locations in the Valley
– Arvin – south of Bakersfield.
“It makes more sense to target
combustion – not VOCs,” says Mitloehner.
Confirming what amounts to a change in thinking by regulators is Valley
air district supervising engineer Sheraz Gill. “We did rely earlier
on the 1938 study but we revised the emission factor in 2005 based on
multiple studies. Now we have enough new information that we are looking
at revising that emission factor once again.”
“There is no doubt that in the long term we are a NOx-driven air
basin” and need to focus on reducing combustion to clean the air,
says Gill.
Offering a different emphasis, Lucinda Roth, supervisor in the district planning department says targeting VOCs in the earlier years of the plan – now for example – “makes sense but that in later years – from 2013 to 2020, the focus will be on NOx reduction.
“We have a problem since 80
percent of the NOx emissions are from out of our jurisdiction. At least
we have incentives” to cut combustion from mobile sources.
Perhaps a cynic might say – since you can't get to the cars, you
target the cows. This month in the UC ag publication California Agriculture,
Mitloehner offered recent research on dairy emissions both as smog precursors
and from a greenhouse gas perspective.
Here is another surprise. Rather than focus on either the front or back end of the cows – strategies should aim at dairy feed as a key source of emissions rather than manure or dairy lagoons.
“The big source is the stored
feed – the silage” that is fermenting. “Just smell it.”
Methane, while not a major problem with smog, is a potent greenhouse gas
implicated in global warming, says Mitloehner.
Strategies to cut methane include formula adjustment to feed and capture of the emissions to put them to good use. To reduce waste – what makes sense to Frank Mitloehner – is what they did in his parents' village in Germany.
The village of Juehnde built covered digesters for livestock waste and other biomass. Now the technology supplies enough power and heat for the entire village to go off the grid. Mitloehner says there is a tentative plan to do the same idea at UC Davis where he teaches – in the planned West Village campus subdivision that could get 2,000 students off the grid.
Turning a waste into a resource and helping restore the image of cows in the popular imagination as a sustainer of civilization may not be the goal of all this study. But with the public well detached from where their food comes and young people too often looking at dairies as the place where animal cruelty is
regularly practiced – where tons of polluting manure piles up – a new perspective is in order.
They ought to pay attention to where their protein comes from and the good that manure does making crops grow in the next field over.
There is no doubt methane is making
the world get warmer, however.
Mitloehner has calculated all the cattle in the world produce 614 billion
kg of methane and that requires 15 billion trees to soak that up.
“We had better get to planting,” says the researcher.
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of The Valley Voice Newspaper and may not be reprinted without explicit
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