“She’s from the Bronx,” said Walleser, 23, of De Soto, referring to Alexandria Ocasio-Cortez, U.S. representative for New York’s 14th congressional district and one of the authors behind the Green New Deal.
McClelland, 51, of Viroqua was concerned. Of the eight dairy farms he had passed on his 10-minute drive into town, his was the only one still in business, he said. “The people that are making decisions don’t have a clue about farming. We can’t play a guessing game because they want to do something that messes with people’s livelihoods.”
As they wrapped up their meal, Dale Torgerson, 43, of Viroqua wondered how much milk he’d have to produce to match the price of the milk he’d ordered with his meal. He had paid $1.75, a 22-fold markup compared to the $15.40 per hundred pound milk price.
Given the economic challenges dairy farmers face, there’s a certain wariness toward the Green New Deal, a nonbinding resolution that pushes for a rapid and fair transition to a carbon-neutral economy. The resolution contains a 60-word bullet point on its vision for agriculture but doesn’t offer specifics for how to get there.
Agriculture makes up 9% of all U.S. greenhouse gas emissions, according to the U.S. Environmental Protection Agency. However, farmers receive a disproportionate amount of attention because the heat-trapping emissions from agriculture are primarily due to methane, said Horacio Aguirre-Villegas, a scientist at the University of Wisconsin-Madison biological systems engineering program.
Although methane accounts for 10% of U.S. greenhouse gases, about 36% of that methane comes from livestock. One kilogram of methane equals 28 to 34 kilograms of carbon dioxide on a 100-year timescale. Methane is even more damaging in the short term, with a global warming potential 84 to 87 times that of carbon dioxide over 20 years.
“It’s way more potent than carbon dioxide, so we need to find ways to reduce methane emissions,” Aguirre-Villegas said.
Since the bulk of dairy’s carbon footprint come from the cows themselves, growing crops for feed and handling manure — and a potential silver bullet to neutralize cow burps is still in research and development — experts say that producing milk more efficiently and using technology to capture emissions from manure for energy are two key strategies for reducing dairy’s carbon footprint.
And just as investments in renewable energy should match where wind or solar are most reliable, carbon-reducing policies and solutions need to be be farm-specific, Aguirre-Villegas said.
This is especially true in Wisconsin, where about 7,800 dairies large and small dot the landscape, each shaped and constrained by their terrain.
Chasing efficiencies
Milk is one of the most carbon-intensive foods after meat, cheese, poultry and eggs. It takes the equivalent of four kilograms of carbon dioxide to produce one gallon of milk.
And cows are gassy creatures, thanks to methane-releasing microbes in the rumen, the first of four compartments in a cow’s stomach.
Frank Mitloehner, professor and air-quality extension specialist at the University of California-Davis, compares the rumen to a 50-gallon bathtub where fibers are fermented into nutrients, with methane as a byproduct. About 95% of this methane escapes the cow through belches and breaths; the rest is passed from behind.
Modern dairy cows, depending on their genetics and diet, expel up to 1.4 pounds of methane each day. Add up the cows and their methane represents up to 50% of on-farm methane emissions.
Since cows emit methane no matter what, it makes sense from a climate and economic standpoint to optimize milk production from your cows, Mitloehner said.
Efficiencies are something every farmer understands. Dairy farmers Walleser, McClelland and Torgerson use nutritionists to help develop diets that get the most milk from their cows.
Mitloehner compared a very productive milk cow with two mediocre milk cows that together, produced the same amount of milk as the single cow. Even though the better milk cow emits more methane on a per-cow basis because it eats more feed, it has a lower carbon footprint than the two cows when you measure emissions by pounds of milk produced, Mitloehner said.
As a general rule, cows eat forage such as grass, small grains, winter wheat, baled or chopped-up corn stalks, and alfalfa hay supplemented with high-energy, high-starch, easily digestible grains including corn kernels to make milk.
Fiber is necessary for healthy rumen function, but when cows eat too much fiber, they get full faster on fewer nutrients. This not only reduces milk production, it also increases methane gas because more fiber means more food for the methane-releasing microbes. Meanwhile, additives including corn grain help cows produce more milk.
In other words, a 100% pasture-grazed system might not be as environmentally friendly and milk from conventional farms might not be as bad for the environment as popular wisdom suggests, Mitloehner said. It depends on each farm’s life-cycle assessment, a complete look at milk production from cow to feed to manure storage to fertilizers and farming practices used for feed production.
It’s common for farmers to scrape or flush manure out of barns into watery lagoons, especially on confined dairies where cows eat, sleep and poop in the same general area.
This storage environment, like the rumen, encourages methane-producing microbes in cow feces to continue breaking down manure and results in higher methane emissions. Smaller farms where manure is shoveled out and stacked or applied onto the field daily have lower methane emissions from manure. When manure is exposed to air, methane-producing microbes can’t thrive in oxygenated environments, though there are still emissions from fertilizer application in the form of nitrous oxide.
UW-Madison researchers modeled greenhouse gas emissions from Wisconsin-style dairies with different grazing regimens, feed-producing systems, and manure management practices to see how grazing systems compared with confined feedlots.
Their models showed that pastured cows can become more efficient milk producers with lower carbon footprints per pound of milk when feed from grazing is optimally supplemented with corn grain for milk production.
And confined dairies with no pasture time could have the lowest overall greenhouse gas emissions per pound of milk produced, despite significantly higher methane emissions from storing manure in lagoons, if they added a costly but effective extra step to treat their waste.
Methane-making machines
Anaerobic digesters, essentially large oxygen-free fermentation tanks that decompose manure and capture methane as biogas, are that costly but effective extra step.
According to one of their models, adding a digester to manure management can cut greenhouse gas emissions from milk production by 18%, said Rebecca Larson, professor of biological systems engineering at the University of Wisconsin-Madison.
The problem is that digesters are expensive. “For a thousand cow-dairy, we’re talking about millions of dollars,” Larson said.
And digesters require a lot of manure. The EPA recommends at least 500 cows to make the captured methane, which can be used to fuel cars or combusted to make electricity, worthwhile.
That’s why although Wisconsin leads the country with dairy digesters, it’s California, which passed legislation to decrease methane emissions from all sectors by 40% relative to its 2013 emissions, that’s investing most heavily in anaerobic digesters that produce biogas from manure.
It’s a tough sell for Wisconsin farmers to keep embracing anaerobic digesters without programs that make the technology more economically viable for smaller or mid-sized farms.
Nobody wants to be the first to take the risk when the industry is in survival mode, Walleser said. “They can’t take away from the profitability of the farm, because there’s no profits to take.”
Wisconsin has a program that offers grants for feasibility studies and small to mid-sized farms can apply for up to $500,000 in funds for anaerobic digester projects. But without guaranteed higher buyback rates from utilities for the electricity produced, there’s less incentive to install a digester.
Digesters break even when they sell electricity for about $0.08 a kilowatt hour, Larson said.
Green New Deal-style investments in digesters for smaller and mid-sized dairies could be a good place to start, Aguirre-Villegas said. He and other UW researchers are looking at areas where it makes sense to put centralized digesters where a cluster of dairy farmers could bring their manure, he said.
That would be a double win, because you’re not only limiting greenhouse gases from the agricultural sector, you’re using it to make renewable energy that replaces greenhouse gases that would have been emitted from burning fossil fuels, Aguirre-Villegas said. “You have the manure available right there, so it makes sense to use it.”