Experts say that the growing utilization of biogas could help lower greenhouse gas emissions from some of the toughest sectors to decarbonize — transportation, industry, and heating buildings — even as it reduces heat-trapping methane emissions, keeps organic waste out of landfills, and prevents manure runoff into rivers and water supplies. Through anaerobic digestion, biogas can be made from any organic material — food scraps, agricultural residues, even the sludge left over from brewing beer. These materials are fed as a slurry into tanks where microbes feast on them in the absence of oxygen, destroying pathogens, producing methane and other gases, and leaving a nutrient-rich fertilizer as a byproduct.
In the field of renewable natural gas, the U.S. is playing catch up with Europe, which has more than 17,400 biogas plants and accounts for two-thirds of the world’s 15 gigawatts of biogas electricity capacity. Denmark alone, a country of 5.8 million people, has more than 160 biogas systems. For a period last summer, 18 percent of the gas consumed in Denmark came from RNG produced by its anaerobic digesters. Flush with their success, Danish bioenergy firms estimate it will be feasible to fully replace the country’s natural gas with renewable natural gas within 20 years.
The former manager of the EPA’s anaerobic digestion programs, Chris Voell, was so impressed with Denmark’s biogas operations — which are highly engineered to digest a mix of household food scraps, residuals from food processing businesses, and livestock manure — that he now works for the Danish Trade Council to introduce Danish digester technology and business models to the U.S market.
As with most climate initiatives, California is leading biogas efforts in the U.S. The state’s Low Carbon Fuel Standard (LCFS) — which provides incentives for fuel producers to increase the amount of low-carbon or renewable fuels they supply and sell — is a key component of the state’s ambitious climate plan and has catalyzed the rapid growth of a new, lucrative market for RNG as a vehicle fuel.
A growing crop of specialized firms builds, owns, and operates anaerobic digesters in the U.S.
Companies like Maas Energy Works and California Bioenergy have responded to these incentives by installing digesters at California’s dairy farms at a rapid clip. Maas has built 17 so far, with 12 more under construction and 32 others in development, according to its website. Both companies are racing to take advantage of valuable LCFS incentives.
And both are among a growing crop of specialized, investor-backed firms that build, own, and operate anaerobic digesters in the U.S. “With every day the industry is gaining more credibility,” Voell says. “We’re seeing more professional third-party companies. And in order to see this scale, it takes those professionals to come in and build 10, 20, 50 projects, and access a lot of equity investors. They want a portfolio of projects to invest in, not just one.”
In North Carolina, the abundant feedstock is hog manure. And the latest entrant in the RNG race is Smithfield, the world’s biggest grower of hogs. North Carolina is the second-largest pork-producing state (after Iowa). Each day, more than 2,000 of its hog farms flush manure from 9 million pigs into vast lagoons, which emit equally vast quantities of methane. Ninety percent of those farms are contract growers for Smithfield.
Late last year, Smithfield launched a joint venture, Align RNG, with a Virginia-based utility, Dominion Energy, to invest $250 million in covering lagoons and installing anaerobic digesters at nearly all of its hog finishing farms in North Carolina, Utah, and Missouri over the next 10 years. Construction is already underway on four projects that will produce enough RNG to power 14,000 homes and businesses.
A covered lagoon manure digester on Van Warmerdam Dairy in Galt, California. MAAS ENERGY WORKS
These systems will all be modeled on Optima KV, a biogas project in Kenansville, North Carolina, in the heart of hog country. Last year, Optima KV became the first project in the state to produce and inject RNG into an existing natural gas pipeline.
The factors that made Optima KV possible — along with the waste from 60,000 pigs on five nearby farms, and a centralized system to clean and upgrade the gas — include a state renewable energy portfolio standard law signed in 2007. That law contained a requirement that utilities source at least 0.2 percent of their electricity from swine and poultry waste by 2020. That mandate helped push Duke Energy, one of the biggest utilities in the U.S., to sign a 15-year agreement to purchase 80,000 million BTUs of RNG from Optima KV. That biogas will directly displace the use of fossil natural gas and generate 11,000 megawatt-hours of power in two of Duke’s power plants.
Vanguard’s new operation in Vermont represents an alternative model for scaling up RNG production. The company’s digesters are more complex and expensive — engineered to produce a consistent output of gas even as feedstocks and other conditions change — than the systems being built in California. The California systems basically cover huge dairy waste lagoons with plastic membranes and then extract, refine, and pipe the gas to customers.
“We take a more high-tech approach primarily because we need to produce a lot more gas from a much smaller footprint,” Hanselman says. “We don’t have the luxury of a 10,000-cow dairy.”
RNG has flourished in Europe because of generous subsidy programs that are lacking in the U.S.
Along with the daily stream of 100 tons of manure from the Goodrich farm’s 900 cows, and 165 tons of food waste, a number of factors have come together to make Vanguard’s Vermont project possible. In Middlebury College, Vanguard found a large customer eager to slash its carbon footprint. A new law about to take effect in Vermont will ban food waste from landfills starting in 2020, forcing grocery stores and food processors to find new places to send their waste.
And Goodrich Farm will get free heat, monthly lease payments for hosting the system, and bedding for its cows from the leftover digested solids — cost savings that can offer a lifeline for dairy farmers in a period of disastrously low milk prices.
Hanselman, Vanguard’s CEO, says that a key element to expanding RNG is taking the burden of running the system off of farmers. Hanselman encountered many irate farmers who had negative experiences with a previous generation of digesters that had been sold to them as a low-maintenance, low-cost solution to their nutrient management problems. In fact, digesters are finicky machines, sensitive to changes in temperature and the variability of organic material in feedstocks. Says Hanselman, “We tell our farmers, ‘Your job is to make milk, healthy cows, and take care of your fields and soils. Let us run these machines.’”