greenhouse gas


UC Scientist: Don’t Blame the Cows

Cody Sheehy is a rangeland ecologist and independent documentary producer.

87736822By Cody Sheehy

A couple of months ago, nearly lost amid the “Hopenhagen” hype,  the University of California, Davis (UCD) put out a press release with an admonition: “Don’t Blame Cows for Climate Change.” The release was a first look at some work conducted by UCD Associate Professor and Air Quality Specialist Frank Mitloehner. His study examines the greenhouse gases, or GHGs, emitted by the livestock sector.  As California’s air regulators turn more attention toward methane in particular, the report remains timely.

Mitloehner’s paper is entitled: “Clearing the Air: Livestock’s Contributions to Climate Change,” and was published in the peer-reviewed journal Advances in Agronomy. The paper is a synthesis of current science on the cattle-climate connection. Mitloehner has been updating some of that science in recent years.

In 2008, I stopped by his cluster of “bio bubbles;” airtight domes that serve as high-tech stables for cows. Inside, Mitloehner had set up simulated dairy operations, measuring GHGs emitted by the cows’ digestive process and decomposition of the manure. The numbers then in common use had been generated in the 1930s.

Research "bio-bubbles" at UC Davis. Photo: Cody Sheehy

Research "bio-bubbles" at UC Davis. Photo: Cody Sheehy

Mitloehner says cattle gets a bum rap in the media, and points to some examples, including a 2007 story in Time magazine, which included assertions like: “Which is responsible for more global warming: your BMW or your Big Mac? Believe it or not, it’s your Big Mac,” and “A 16-oz T-bone is like a hummer on a plate . . ”

In many cases, Mitloehner says the statements are crafted from an influnencial 2006 United Nations report entitled: “Livestock’s Long Shadow.”  According to the executive summary, “The livestock sector is a major player, responsible for 18 percent of greenhouse gas emissions measured in CO2 equivalent. This is a higher share than transport.”

But Mitloehner points to a quote deeper in the report:

“The respiration of livestock makes up only a very small part of the net release of carbon that can be attributed to the livestock sector. Much more is released indirectly by other channels, including: the burning of fossil fuel to produce mineral fertilizers used in feed production, methane release from the breakdown of fertilizers and from animal manure, land-use changes for feed production and for grazing, land degradation, fossil fuel use during feed and animal production and fossil fuel use in production and transport of processed and refrigerated animal products.”

Mitloehner cautions that the transportation number they use only accounts for tailpipe emissions. To be even-handed, he says, the authors should’ve incorporated emissions from the entire oil industry, including refinement of the oil and production of cars. In the UCD release, Mitloehner calls it a “lopsided ‘analysis” and “a classical apples-and-oranges analogy that truly confused the issue.”

Meanwhile, the Bio-bubbles have been generating some interesting numbers. Mitloehner found that the amount of methane the cows respire (belch) and how much is released in the breakdown of animal manure is quite different from what previous research had calculated. In combination, these two sources represent the most direct GHGs from the livestock industry, even if they’re not the largest GHG emitter associated with the industry. They’re also the most out of date.

Emission factors used in “Livestock’s Long Shadow” provide an estimate of methane respiration of about 86 million tonnes (metric tons) of methane (CH4) and 17.5 million tonnes of CH4 annually from manure decomposition. In the annex of the UN report, the authors write: “Obviously, great improvements to the estimates of emission factors could be made if more data on nutrition and production were available.” And so it is that inside his bio-bubbles, Mitloehner has come up with numbers much lower than those that represented the conventional wisdom since 1938.

All in all, we’ve got a discussion about comparing apples and oranges (more appealing than manure, granted) and some updated numbers that lower the emissions of livestock in one category. As with any scientific paper, there will probably be debate on both of these points and new ones, but let’s look at the broader consequences. Will industry look at this study and see an incentive to update and revise carbon emission numbers all across the board?

According to Emilo Laca, an agricultural ecologist at U. C. Davis, some of these questions will be fodder for policy debates that lie outside the realm of science. He says “The real question is, ‘How are we going to split this up?'” Laca used a hypothetical problem to explain: Let’s say that a certain livestock industry consumed 30% of soybean production as a food source. Livestock producers might concede that they should be accountable for 30% of carbon emissions related to soybeans. It makes sense. It’s what the numbers say. Others might counter that without this certain livestock industry, the soybean market would behave differently and some amount–lets guess 70%–wouldn’t need to be planted. Therefore, the livestock industry in this example is responsible for 70% of the emissions, not 30%. Science can support both interpretations. As Laca says, the decision is how to “split” things up. And ultimately, those decisions may fall to policy wonks.

Bay Area Greenhouse Gases on the Rise

trafficjam_sm.jpgThe Bay Area Air Quality Management District has issued a new inventory of greenhouse gas sources, updating a report issued last year, for “base year 2002.” (Yes, the 2006 report was for 2002–let me know if that’s not confusing enough).

If you thought the heavy hitters were those half-dozen or so big, smelly oil refineries strung out between Richmond and Antioch, guess again. If you’re going for your climate geek merit badge, you’ll know that here in California, at least, the transportation sector is the reigning CO2 champ.

According to the updated report, transportation accounts for about 40% of emissions. Non-farm industrial & commercial emissions (from stationary sources) weigh in at 34%. Amaze your friends! If you take that transportation sector and break it down further, it turns out that cars and light-duty trucks account for almost 64% of those mobile emissions.

Okay, so you know all that. But what jumps out of the report are the projections of emissions through 2029, which the Air District arrived at by blending current levels with projected population and economic growth. The trend is not only upward but steeply upward, from 104 million metric tons (CO2 equivalent) to 128 million by 2020 and 150 million by 2029, an increase of 44% in two decades.

But good gravy, how can that be? Isn’t California “leading the way” in greenhouse gas reductions? Well, yes and no. Henry Hilken, Director of Planning and Research for the district, explained that because most of the state’s aggressive mitigation programs are not yet in place, his number crunchers did not take them into account in their calculations. In other words AB-32, cap-and-trade, the so-called Pavley regulations on tailpipe emissions, the low-carbon fuel standard–none of it is actually happening yet. The projections represent a future based on “business-as-usual.”

That’s likely to change, however. State regulators have been virtually assured that they’ll get the required EPA waiver to put stricter tailpipe regulations in place, shortly after President-elect Obama takes office, to use just one example. For more on this issue, listen to Sasha Khokha’s feature from The California Report, earlier this week. On the other side of the ledger, full implementation of AB-32 remains in question, as the funding mechanism is not fully in place.

How much would the picture change with all those–or even some of those measures in place? Hilken says he hasn’t attempted those calculations. It’s also likely that a long, deep recession could put a kink in the emissions trend. So while you can argue that the numbers in the inventory are a weak predictor of things to come, they are a useful snapshot of where we are–and a sobering assessment of where we’ll end up without an aggressive climate policy.

The Air District report tracks two types of carbon dioxide (CO2), along with methane (CH4), nitrous oxide (N2O) and a handful of lesser-known gases. The non-CO2 emissions are converted mathematically to “CO2-equivalent” values.