Digesters produce renewable energy from manure, but face obstacles – InForum

A Danish company’s plans to turn cow manure into renewable energy in Minnesota and Wisconsin’s dairy region have failed, at least for now.

Nature Energy planned to build several large-scale anaerobic digesters that would harvest methane from animal waste to produce biogas. The company was considering three locations in dairy-rich Stearns County, as well as Lewiston in southeastern Minnesota and Benson in western Minnesota.

But in August, British oil and gas giant Shell announced that its subsidiary Nature Energy was “strategically suspending” all its projects in the United States.

Shell’s abrupt change of course is a disappointment to project backers in communities such as Paynesville, where Nature Energy had proposed building its first plant in Minnesota. They believed this would harness a local waste stream to benefit farmers and the climate.

“He looks forward to helping protect the environment and really bringing a new type of energy development to the region and the country,” Paynesville Mayor Shawn Reinke said in July.

Shell’s withdrawal also indicates that promising biogas technology still faces obstacles – including high costs, regulations, market forces and local opposition – to becoming a major energy source in the United States.

But some energy experts say it makes sense to turn the methane in manure from a liability into a commodity, especially in Minnesota, home to about 9 million pigs and nearly half a million cows. dairy industries, which produce between 50 and 100 million tonnes. of manure per year.

“It’s a lot, and right now a lot of it isn’t really being used,” said Roger Ruan, director of the University of Minnesota Biorefinery Center. “There is a lot of potential here in using manure to generate electricity. »

When manure or other organic matter decomposes, it releases methane, a greenhouse gas more than 25 times more potent than carbon dioxide. Livestock are a major source of methane emissions.

Anaerobic digesters heat manure to approximately 125 degrees, creating an environment conducive to the growth of microorganisms. The bacteria break down the manure and produce biogas, made up of methane, carbon dioxide and other gases.

Biogas can be used to replace traditional natural gas to produce electricity, for heating and cooking, or to power vehicles. What’s left is called digestate, a nutrient-rich material that can be used to fertilize agricultural fields.

Anaerobic digesters are not new. Some farmers have used them for decades to harness energy from livestock manure, mostly on a small scale. The first in Minnesota was Dennis Haubenschild, who began using methane to

make electricity

on his Princeton dairy farm in 1999.

But Nature Energy’s plans were different: It proposed building larger, commercial-scale plants that would collect manure from farmers within a 20- to 30-mile radius.

The company collects manure from small farms once a week and several times a day from larger farms, Jesper Nielsen, vice president of U.S. business development, said in an interview in late July.

“Basically, Nature Energy borrows the manure from the farmer and brings back a better product,” Nielsen said.

Most pathogens and some nutrients such as phosphorus are removed, reducing the risk of pollution of local rivers and streams, said Bob Lefebvre, former executive director of the Minnesota Milk Producers Association. He was hired by Nature Energy in 2022 as vice president of business development at the farm.

Lefebvre said he saw the projects as an opportunity to help even small dairy farms meet the industry’s goal of being carbon neutral by 2050.

“Virtually all dairy farmers now have the opportunity to reduce their carbon footprint through methane reduction by partnering with Nature Energy,” he said in July. “This is something no other anaerobic digestion or biogas company can do.”

Nature Energy also touted its enclosed facilities as clean and odor-free. Several Minnesota city officials traveled to Denmark last March to tour one of the company’s plants.

Paynesville City Administrator Tariq Al-Rifai was among them and left with a favorable impression.

“One of the concerns people had was, ‘Well, they’re going to have all these trucks coming and going, and you’re going to see a lot of dirt and mud and other things everywhere.'” he said. ” We did not do it. It was actually very, very clean.

But local residents have opposed Nature Energy’s plans in some communities, including Paynesville. They expressed concerns about potential odors, safety concerns and truck traffic.

Barbara Schmit, a 47-year-old resident of neighboring Paynesville Township, said she worries about the impact on the town and the nearby Crow River if a spill or explosion occurs.

“What about the rest of the city if something catastrophic happens?” » » asked Schmit. “They may say, ‘Well, we’ve never had an incident.’ OK, that’s good. But accidents happen.

Some environmental groups also oppose large-scale methane digesters, calling them “greenwashing,” fearing they will encourage the expansion of large industrial farms that have negative impacts on air and water quality. the water.

There are methane digesters that have been working for years. The University of Wisconsin-Oshkosh biogas program developed three anaerobic digesters as learning laboratories and continues to operate two of them, said Brian Langolf, program director.

About 2,300 digesters are operating in the United States, but the industry still has plenty of room to grow, Langolf said. By comparison, Germany has around 10,000.

As the focus turns to energy independence, methane digesters offer a solution that uses an existing waste stream, Langolf said. And they can operate 24/7, even when the weather isn’t nice or the wind isn’t blowing.

“The good thing about digesters is that they can treat waste. They can produce renewable energy,” he said. “But they can also help purify the air, water and soil and then make a renewable fertilizer.”

Manure digesters could also help reduce Minnesota farmers’ need to rely on a volatile international supply chain for fertilizer, whose prices have soared since Russia’s invasion of Ukraine, a Langolf said.

Minnesota’s climate action plan specifically calls for anaerobic digestion as a method of reducing greenhouse gas emissions from agriculture, said Megan Lennon, who directs the Department of Agriculture’s energy and environment section. Minnesota.

“The manure lying around in the lagoons is constantly releasing methane,” Lennon said. “This is one of the reasons why livestock production has a high carbon footprint. »

Capturing that methane and converting it into renewable natural gas allows it to be used for a variety of other purposes, she said.

But keeping small digesters running smoothly requires maintenance and a constant flow of manure, which can be a lot of extra work for already busy farmers.

“You deal with it every day,” Lennon said. This may be why some digesters installed on farms 20 years ago no longer work, she said.

So there’s a lot of interest in finding places in Minnesota where there is enough biomass to support a larger digester, Lennon said. This could include not only livestock manure, but also food scraps or food processing waste, she said.

A 2021 report from the U.S. Environmental Protection Agency finds that each year, carbon dioxide emissions from food waste are the equivalent of 42 coal-fired power plants.

When it comes to biogas development, Europe is ahead of the United States, in part due to stricter regulations on the treatment of waste streams and stricter decarbonization targets, said Alex Klaessig, Senior Director of the Hydrogen and Renewable Gas Forum at S&P Global.

Some states, including California, offer incentives to build digesters that capture methane and convert it to biogas. The state’s low-carbon fuel standard gives digester owners carbon credits, which they can sell or use to offset their greenhouse gas emissions.

Klaessig said these types of incentives have fueled double-digit growth in U.S. biomethane production in recent years, and it will likely continue to grow.

“Transportation is the tip of the spear,” he said. “Natural gas utilities also see renewable natural gas as a way for them to pursue their future in a low-carbon world. »