Greetings from the Interior

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Scientists and dairymen get to know the cow’s digestive system with an eye to the future

By Nathan Gilles
Illustration by DMD

greetings from the interiorFor the dairy industry, methane is an environmental Achilles’ heel. Methane is second only to carbon dioxide as the leading cause of human-made climate change, accounting for 26.7 percent of emissions, according to the United Nations. And although methane can emanate from sources as varied as rice paddies and landfills, ruminant livestock—mostly sheep, cattle and dairy cows—are the planet’s largest single source of human-induced methane.

Concerned that the consumers who become aware of the milk-methane link might cut their dairy consumption, the U.S. dairy industry funded an ambitious study from 2009 to 2013 designed to track its environmental footprint from “grass to glass,” as one industry person puts it.

When methane and, to a lesser extent, nitrous oxide—which results from collecting manure—turned up as the biggest culprit, the dairy industry set itself the lofty goal of cutting back its carbon footprint by 25 percent by 2020.

Cows have become a central focus of this effort, and the consensus is that there are two major ways to mitigate a dairy cow’s methane emissions: control the animal’s burps and tackle the backlog of manure.

But it’s a dirty, mysterious business figuring out how to intervene in the gaseous work that converts grass and feed into milk. Researchers are just starting to grasp how complicated a task they have ahead of them.

It’s About the Burps

First off, we need to get something straight: Despite all the quips by headline writers, cow flatulence is not the problem.

“We are talking just about the front side, not the backside,” says University of California, Davis researcher Frank Mitloehner.

Mitloehner is one of the nation’s leading researchers on what are called “enteric methane emissions.” Basically, he measures cow “burps.” (Methane from manure is another story, but we’ll get to that.)

The reason burps are the focus, says Mitloehner, lies in the cow’s rumen. The rumen is the first chamber of a cow’s four-chambered stomach, and it’s—if you’ll pardon the alliteration— roomy.

To grasp just how spacious, Mitloehner says imagine your bathtub. The average tub holds about 40 to 50 gallons of water. A mature dairy cow’s rumen can carry about the same. She needs all this space, says Mitloehner, to convert the vast quantities of fibrous plants she eats—including grasses—into body mass, useable energy and milk. And although the cow does her part—she chews a lot and then chews her partially digested slop again after regurgitating it back into her mouth, aka “chewing her cud”—a dairy cow gets help from the rumen.

At 100 degrees, the rumen contains roughly 100 billion bacteria per milliliter. There are also fungi, protozoa, and archaea, each genetically distinct, that work together in a consortium with the bacteria to aid digestion.

“They all work together in a consortium,” explains researcher Karen Beauchemin. “Fiber is not easily digested, so it takes a whole host of organisms.”

Beauchemin works for Agri-Food Canada, Canada’s federal agriculture agency, and is a leading expert on efforts to fight methane emissions from cows and other domesticated ruminants.

She says of all the life in a cow’s gut, it’s a group of archaea, called methanogens, that’s largely responsible for burped methane. As the archaea break down the cell walls of feed, they make methane. Once formed, the methane is burped out of the cow and into the atmosphere. What Beauchemin and other scientists’ research have focused on is how to make this molecular process, called methanogenesis, stop generating so much gas. They have a lot of leads, but haven’t found a long-term solution yet.

Beauchemin’s preferred method is to head straight to the heart of the problem and alter the bovine’s microbiome. She says ideally ruminants could be fed a dietary supplement composed of non-methane emitting microbes able to battle with the archaea for control of the rumen—roughly the equivalent of eating, say, yogurt or something else with active cultures. But, although Beauchemin says unlocking the mystery of the ruminant microbiome undoubtedly holds the key to halting methanogenesis, and despite the fact that promising research has been done with certain strains of yeast, this is still largely science fiction.

In fact, many of the solutions scientists are working on involve countering the millions of years of evolution that created ruminants’ ability to digest fibrous plants—an approach that doesn’t make sense from either the whole systems or animal welfare perspectives.

Interestingly, study after study has shown pasturing cows burp more methane than animals fed highstarch diets rich in ingredients like corn, which act by, in effect, starving the methanogens. This has led to the seemingly counter-intuitive finding that cattle in feedlots belch less methane than pasturing cows.

In multiple studies, the dairy industry’s burps have outpaced that of the meat industry, with organic dairy— which is required to pasture its animals for at least 120 days out of the year— leading the band of belching bovines.

None of the scientists who spoke with Edible Portland for this story are suggesting we lock up our cows and feed them starchy foods—cows have evolved to digest vegetation that others, especially us voracious bipeds, cannot. And, unlike the exhaust that comes out of the backside of human industry, what comes out the front side of a cow is a natural process.

Also, any ostensible environmental gains to feeding ruminants high-starch diets over more natural high-fiber ones need to be balanced against the carbon cost of producing the feed itself. According to the U.S. dairy industry’s own numbers, feed production accounts for about 33 percent of the industry’s total carbon footprint, a significant amount even while it’s less than both burped methane (43%) and decaying manure (41%).

Beauchemin says the confounding problem for scientists set on reducing methane generated in the rumen is how to do it without hampering the ruminant’s ability to be, well, a ruminant.

Making Power from Poop

Cow methane issues don’t stop once the food has left the rumen, exited the back end of the cow and landed in a manure pile. When animals are crowded together and their waste is collected in one spot, because the manure isn’t entirely exposed to oxygen, anaerobic digestion and methane emissions start anew.

At Lochmead Farms, which produces the milk used to make Lochmead’s dairy products just outside Junction City, the manure from roughly 1,140 bovines is “flushed” from the spaces they occupy down a small canal and into a 16-footdeep, 25-foot-square concrete pit outside the barn. Standing nearby in knee-high rubber boots on a recent day is 72-year-old farm co-owner Jock Gibson.

The odor is powerful. Gibson, who has been working the farm with his brother, Buzz, and the rest of the Gibson clan since the mid-1940s seems inured to the smell.

“When it gets up to [a] certain level,” says Gibson pointing at the lagoon, “then the pumps go on, and it goes to one of these tanks.”

He gestures toward three massive silo-shaped structures behind him: two large tanks, about three stories tall, 50 feet in diameter and capable of holding 480,000 gallons of manure, and a third smaller tank able to hold about half as much. Like the rumen, the tanks, or “digesters,” are where the anaerobic magic happens, with microbials inside the digesters feasting on scatological spread and forming methane in the process.

This methane, called “biogas,” is then pumped via a series of pipes into a small shed containing a converted diesel engine that burns the methane, significantly lessening its effect on our climate. In the process, it converts it into approximately 190 kilowatts of electricity per hour. The methane-produced electrons power the farm. The rest is sent to the grid.

Gibson isn’t, of course, the only person to get this idea. University of Arkansas Professor Greg Thoma, who was the lead scientist on the 2013 study that kicked off the U.S. dairy industry’s carbon mitigation efforts, says he sees digesters as one of the most effective ways for the industry to reach its 25 percent goal by 2020. Thoma’s research found that manure—which produces methane when decomposing, and later nitrous oxide when it’s applied to the field—makes up about 41 percent of dairy’s carbon footprint. Digesters would largely solve both the methane and nitrous oxide problem. But, where the cow burp problem is searching for a bio-technological fix, digesters need a political-economic one.

“It’s a hard landscape to get stuff done,” says Peter Weisberg, of the Climate Trust. Based in Portland, the trust helps fund renewable energy projects by acting as an environmental broker between investors and potential green projects. Weisberg helps make these deals happen, and lately, he says, renewables, especially dairy digesters, have been a hard sell.

“You have a situation where, compared to the past, the capital costs are now twice as expensive, and the energy… you now get half as much for it,” says Weisberg.

In Oregon, part of the rising cost is due to the recent expiration of the Business Energy Tax Credit program. Designed to encourage businesses to invest in alternative energy, the program sunset date was January 2013. Builders have until July 2014 to complete their renewable projects.

However, the less-than-favorable regulatory conditions aren’t the only reason dairy digesters aren’t popping up everywhere.

Natural gas accessed in previously untapped American reserves through hydraulic fracturing, or fracking, has made natural gas abundant and cheap. When it comes to cost per electron, biogas is more expensive and the result, says Weisberg, is that biogas projects are having a hard time attracting investors.

Still, biogas has potential, not only for large-scale operations of 1,000-plus cows where generating lots of poop isn’t a problem, but also smaller ones with less than 200 cows, for which systems built for their scale are just coming into existence. Oregon currently has just five dairy digesters, according to the Environmental Protection Agency. But a joint 2011 study by the Climate Trust and the Energy Trust of Oregon found the potential for 45 dairy digesters across the state.

National numbers tell a similar story. The American Biogas Council estimates the United States currently has about 2,000 biogas plants nationwide. Most of these treat municipal waste from wastewater to landfill gas. Only about 181 of these are anaerobic dairy digesters similar to those at Lochmead. Nonetheless, the council estimates there are 8,200 dairies nationwide that could add digesters.

To get these projects to pencil out, dairy operators are trying out a new strategy: adding food waste to their digesters. This approach could make the digesters useful to more businesses and improve how efficiently they produce energy.

“I will tell you, it’s going to take uncommon partnerships,” says Erin Fitzgerald, senior vice president for sustainability at the Innovation Center for U.S. Dairy, the industry-funded research center charged with getting dairy to its 2020 carbon goal.

Grassfed Dairy

Some in the dairy industry, especially organic milk producers, are placing their bets on pasturing to ameliorate the effects of methane while giving cows a healthier life.

“We feel that pasture is the key; it really kind of unifies the whole footprint of dairy,” says Jonathan Reinbold, sustainability program manager at the dairy-farmer-owned cooperative Organic Valley.

Currently the farmer-owned co-op, via Reinbold’s sustainability office, has been funding a Northwestern University program that’s examining how soil can sequester, or lock in, carbon emissions. At the moment, the science of carbon sequestering is relatively new. Even so, the 2009 to 2011 study funded by the U.S. dairy industry included sequestering in its life cycle analysis.

Adding fats to a cow’s diet—be it from flaxseed, linseed, rapeseed, canola or distillers grains—has a long history with farmers and is now gaining attention as a way to fight methane. Organic Valley is looking at feeding fats to its cows as a way to reduce emissions, and the organic yogurt producer Stonyfield Organic has already studied this approach.

Another part of the math here is that pastured cows produce virtually no methane emissions from their manure. The reason is that those microscopic organisms die once they are exposed to our planet’s oxygen-rich atmosphere.

Tackling cow emissions is a complicated calculus with no easy answer. But the potential payoff from a solution is huge: Methane is estimated to be about 21 times more potent at trapping heat in the atmosphere compared to carbon dioxide. But, unlike carbon dioxide, which can stay in the atmosphere for decades if not centuries, methane has a life span of only about one decade. This means cutting methane emissions could produce a quick turnaround for the climate, which many scientists warn is necessary if the planet is to avoid runaway climate change.

Nathan Gilles is a Portland-based freelance journalist. nathangilles.com

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