An anaerobic co-digester operated by Vanguard Renewables in Vermont. The company has proposed constructing a digester in Waupaca County. (Todd Balfour | Vanguard Renewables)
On Dec. 4, residents of the rural town of Lind in Waupaca County packed the community’s small town hall, many of them wearing black baseball caps with blue brims, emblazoned with the phrase “No Digester.”
So many people showed up that the public hearing scheduled that day had to be canceled because attendance exceeded the capacity of the building.
At issue was a proposal to adjust the town’s zoning codes to allow for the construction of an anaerobic co-digester on Brooks Farms, a 600-cow dairy farm that has been operating in the town for 168 years. Brooks Farms is working with a national company, Vanguard Renewables, to construct the co-digester.
On many dairy farms, manure is collected in an open pit, or lagoon. In the lagoon, the organic matter breaks down without oxygen — anaerobically. That process of breaking down releases huge amounts of methane into the environment. Methane is a greenhouse gas that contributes to climate change, with livestock operations serving as a major source of that pollution.
In 2021, agriculture accounted for 10% of total greenhouse gas emissions in the U.S., according to the Environmental Protection Agency. Much of those emissions came from livestock and manure. The capture of that methane has become an important goal for mitigating the effects of climate change.
In addition to the methane emissions, most farms spread their manure on the land to use as fertilizer. However, overspreading is a risk and runoff from raw manure, which contains nutrients such as phosphorus and nitrogen, can harm local waterways.
A co-digester takes the manure produced on a farm and puts it into a tank with other organic waste such as food scraps and byproducts from industrial food processing. The temperature in the tank is increased and the organic matter is broken down, but instead of being released into the atmosphere, the methane is captured and turned into biogas, which can be used on the farm as an energy source or pumped into a local pipeline.
Proponents of the technology say it comes with hardly any downsides. In a place like Wisconsin, the manure and its resulting emissions already exist, so why not put it into a co-digester where the emissions can be contained, a largely renewable source of fuel can be created, the food waste can be kept out of landfills and the farmer can use the nutrient-rich discharge created at the back end of the process as a cleaner, cheaper fertilizer, all while reducing the odor that a dairy farm creates.
“Typically, why we implement anaerobic digesters as part of a technological solution is to help improve water, air and soil quality,” says Brian Langold, the director of biogas systems and research development at UW-Oshkosh. “For me if you look at the bigger picture, these are waste products that exist that we move around today: food waste, raw manure. Those wastes already exist but we can harness them for renewable energy, energy independence, and renewable fertilizer products. It really is promoting sustainability and renewable energy and clean air, water and soil.”
Yet critics say there are tradeoffs that proponents ignore.
The digestate created at the end of the process contains the same amount of nutrients as the raw manure that went in and whatever nutrients were added from the other food waste. The spreading of that digestate on the land can be just as harmful to local waterways if handled irresponsibly.
“At the tail end of the process, what are you doing to manage all of this? Do you have land to manage the extra nutrients that you took in at the front end?” says Jim Baumann, who spent nearly four decades working as a water quality engineer at the Wisconsin Department of Natural Resources (DNR). “These are questions that would need to be answered. So for example you have a dairy farm and they’re already challenged to have enough land to spread their manure and now you’re taking in an additional component of organic matter, now you have a bigger problem. That’s a question I would have in my mind.”
Ultimately, however, Baumann, who also works with the conservation group Wisconsin Green Fire, says co-digesters have a mostly neutral effect on local water quality.
“I don’t see digesters as this saving technology for water quality,” he says. “I don’t think they produce great water quality benefits and I don’t think they necessarily cause big problems either. But if we’re looking in terms of surface or groundwater, they don’t do much to change the pollutants much at all. In terms of pollutant control, it doesn’t provide a lot. Of course for greenhouse gas control, it provides something meaningful.”
A group of Democratic U.S. Senators has criticized the proliferation of digesters. In a letter to the U.S. Department of Agriculture written last year, Sens. Cory Booker, Kirsten Gillibrand, Bernie Sanders, Elizabeth Warren and Ed Markey warned about the use of federal dollars to subsidize digestion projects. They questioned the technology’s success in reducing emissions and creating renewable fuel. The senators also warned that the growth of the technology could encourage the further consolidation of the country’s agricultural systems, leading to fewer farms operating at massive scale, posing further threats to local water and the climate.
“To our knowledge, USDA has not yet produced evidence that subsidizing manure digesters will reduce absolute emissions from the agriculture sector, which is the top source of U.S. methane emissions,” the senators wrote. “Proliferation of methane digesters contributes to increased consolidation in the agrifood system. As consolidation and corporate power continue to shape the U.S. agrifood system, biogas is yet another global market that multinational agricultural and fossil fuel corporations are entering to further increase their economic power. To do so, companies could influence farmers, particularly hog and dairy, to increase farm herd size specifically for the concentrated manure — not more meat or milk.”
On Dec. 21, the local news outlet Tone Madison reported that in Wisconsin, digestion projects have received more federal subsidies in the last two years than solar projects have received in the last 12, raising concerns that the technology is crowding out other renewable sources of fuel.
In Lind, locals have raised these and other issues, including concerns about increased truck traffic bringing waste in and out and the effect that the co-digester will have on the local watershed, which includes a creek that feeds into the Fox River, which ultimately dumps into Lake Michigan.
Locals are worried that the source of the other organic waste that will go into the co-digester is still unclear, that PFAS could be introduced into the process and that the DNR considers the byproducts of the process “industrial waste.”
“We’re never told specifically who’s going to be bringing what from where to come to this site,” says Laurie Knutzen, a resident who has been active in opposing the project. “We’re not directing our focus on the farm, per se, our focus is the co-digester and what it will mean for the people who live around it and in our township.”
Knutzen, and fellow resident Victoria Gehrke say they’re opposed to industrial agriculture operating at the expense of human health and natural resources and they believe the co-digester gives the farm an incentive to grow.
“Industrial agriculture incentivizes, again with our tax dollars, for farmers to go big,” Knutzen says. “So they increase their herd size … and one of the bigger outcomes is the massive amounts of manure. And then the farm wants to say that ‘well, we have a solution to that, and that’s the digester.’ So then, they tried to bring us on board, who are not part of the problem, as including us into the solution statement by saying ‘this is going to be better for you as a townsperson or as a community member if you let us put in this digester.’”
Once the farm gets a digester, Knutzen says, there’s an incentive to grow. “So then we’re going to bring more cows, utilize more water, and we’re going to feed the digester more and then we’re just continuing this vicious cycle and the problem is all at the expense of our human health and our natural resources.”
Langold, the UW-Oshkosh researcher, says he hasn’t seen any evidence that digesters drive farm expansion.
“I have run a digester that’s on a farm that has 200 cows and been at one that has 6,000 cows,” he says. “We have 1.3 million dairy cows, roughly [in Wisconsin], but only 50 digesters currently. There’s a lot of raw manure being spread, which is a worse thing to be doing. I haven’t seen any evidence to convince me it incentivizes growing the farm size.”
Dr. Rebecca Larson, a professor at UW-Madison’s Nelson Institute for Environmental Studies who focuses on issues including manure management, says she understands the concerns of the locals and would have many of the same questions if it were her community, but that ultimately a co-digester can serve to make local air and water cleaner. She also added that the DNR classification of the byproduct as “industrial waste” could be better for the local environment because the agency regulates industrial waste more strictly than agricultural operations.
“Being someone who knows a ton about the technology, if I lived in a community with a livestock facility, if the choice was between manure going through a digester or not, I would choose the digester,” Larson says. “I would have concerns about how much truck traffic is that going to cause, how much [byproduct] operationally is that going to cause and do you have the land base to handle that on the backside? Those kinds of things locally are things that have to be discussed and would be a great topic for a community meeting. I know the citizens are concerned and there are important things they should be asking.”
John Hanselman, Chief Strategy Officer for Vanguard Renewables, says the company is taking the local concerns seriously and that they want to be a “good neighbor” — which he says would be accomplished by building the co-digester.
Hanselman says the company never uses human waste in its digesters, which is how PFAS would enter the equation and that the sources of the other organic food waste would likely be byproducts from dairy processing and beer brewing.
“I fully understand neighbors have the right to ask the hard questions, and they should,” he said. “I think what’s critical from our side is that we help them understand that we’ve never had detectable PFAS in any of our digestate ever and it’s in our permit that we cannot take human waste at the site.”
Sydney Howard, the assistant herd manager at the farm and a member of the family that has owned the farm for six generations, says the project is meant to make the family’s farm a better steward of its resources.
“The technology is a climate-smart step forward for how we handle manure on our farm and how we handle food waste on a national level,” Howard says. “We live in this community, too. We have been farming this land and protecting our water resources for 168 years. Right now, through our DNR permitting and our nutrient management plan we follow, we are spreading raw manure on our fields and the co-digester will do a better job to protect our water and land than spreading raw manure on our field. We want to be better stewards.”
Hanselman adds that he shares people’s concerns about local water, but that the co-digester would be the best thing that could happen for the local environment.
“It’s hard for us to understand. Emotionally, clean water is the thing that we all live for. And in a community I also would be very, very concerned about any new process coming in that might affect the groundwater,” he says. “We are probably the best thing that can happen to the farm. You know, we’re collecting all that manure. We’re taking all of that odor. We’re taking all the methane out of the environment, out of the atmosphere, and we’re making clean natural gas and organic fertilizer. So I fully understand the concern. But it’s not based in science.”
The process Vanguard’s co-digesters use to clean the digestate on the back end, Hanselman says, allows for nutrients to be removed and taken away. That allows the farm to limit the amount of phosphorus and nitrogen that is spread on the farm’s land. He noted that at the company’s first project in Vermont, they’re removing 12 tons of phosphorus per day from the environment.
Howard says that using the digestate as fertilizer will allow the farm to be much more precise about which nutrients get spread and when, instead of the more random process of spreading raw manure — which comes with the added risk of running off into local waterways.
“We are able to spread the right amount of nutrients at the right time on the right amount of land. This gives us more control of the nutrients and what the land needs,” she says. “We’re able to handle the nutrients instead of handling the manure. We’re able to treat this as a nutrient coming out of the co-digester instead of treating it as waste. That is crucial for how Mother Nature works.”
Hanselman also laid out the company’s process for managing truck traffic, which the farm operators say will remain largely the same as it is now because the co-digester will eliminate the need for delivery trucks to bring products such as fertilizer and sand to the farm as well as cut the 1,000 annual tanker truck trips that occur when the farm spreads its raw manure twice a year.
“We know every truck that goes in or out of the system,” Hanselman says. “If there’s any vehicle that exceeds the speed limit, that has any kind of issues with the neighbors, that vehicle is flagged instantly and then put it on to our hotlist where either they rectify the issue or they’re not allowed into the facility ever again.”
The company is being so careful it’s “a little bit crazy,” Hanselman adds, since “the digester is there for 20 years and so if we’re not a good neighbor, that is not going to work for anybody.”
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