Middleton digester using solar power to move manure fuel | Science & Environment


In a major new step in renewable energy, a Wisconsin company is using the sun’s energy to transport fuel made from cow manure.

Through a partnership with Peterbilt Motors and Maki Trucking, EnTech Solutions plans to use a battery-powered truck to transport methane from its Middleton biodigester to a pipeline injection port at the Dane County landfill.

Charged with energy from the digester’s solar panels, EnTech says the electric truck will reduce the environmental impact of the operation and make it more profitable.

Manure from area dairy farms is unloaded from a truck at the EnTech Solutions digester in Middleton, where microbes break down the waste to produce methane which is sold as fuel.


The Middleton digester converts manure from five nearby dairy farms into renewable natural gas that is interchangeable with natural gas mined from the earth.

Because the process captures methane – a heat-trapping gas much more potent than carbon dioxide – that would otherwise be released into the atmosphere, it qualifies for credits that can be sold to fossil fuel producers in California who must offset the greenhouse gas emissions of their products. The fewer greenhouse gases created during the manufacture of the gas, the more valuable the credits.

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The truck, one of about 50 electric models in service across the country, costs about three times as much as a comparable diesel model, said Matt Wetta, national account manager for Peterbilt’s alternative powertrain line.

Details of the partnership were not disclosed, but Maki Trucking owner Joel Maki expects to recoup the additional capital cost through fuel savings.

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Wetta said the 579EV, with a range of around 150 miles, isn’t practical for long-haul routes, but is great for short-haul applications like the digester, which typically requires three 40-mile round trips. per day.

The battery takes about three hours to fully charge or it can be topped up between deliveries with a charger connected to EnTech’s solar microgrid, which has a battery to store energy for recharging at night.

Maki said the electric model made “perfect sense” for the job.

“We have the electricity for the truck generated on site, we have the sustainably produced product to be transported, and we have the farmers to thank for their involvement,” Maki said. “This electric vehicle is the last link to close the loop.”

Entech biodigester

An electric truck like the one pictured here will haul renewable natural gas from a Middleton digester to a pipeline injection site at the Dane County landfill.


Entech estimates the truck will save up to 116 tons of carbon dioxide emissions per year, reducing the carbon intensity of the gas and giving it more value in the California carbon market.

“It’s a small but definitely noticeable improvement,” said Jacob Feutz, the company’s vice president of renewable fuels.

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Pilot Richard Harju delivered the first load of gasoline on Tuesday in a demo similar to the one Maki hopes to field by the end of the year.

After decades of driving diesel trucks, Harju said it was hard to get used to the smooth, quiet ride – with no clutches or gears to manage. “You almost have to roll the window down a bit to hear road noise,” he said.

Entech biodigester

Tanker trucks are loaded with pressurized methane produced from cow manure at EnTech Solutions’ Middleton Digester. The company plans to use an electric truck charged with solar energy transport the renewable gas to an injection site by pipeline.


Gundersen Health Systems of La Crosse built the $14 million digester in 2013 with approximately $5.8 million in federal and county support. It was originally designed to generate electricity but could not compete with increasingly cheap wind and solar power.

Manure from nearby farms is piped or trucked to the facility, where microbes in three sealed digestion tanks break down the waste to create methane. The remaining manure is separated into solids, which can be used as bedding, concentrated nutrients that are returned to farms as fertilizer, and purified water.

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EnTech Solutions took over the project in 2020 with the goal of producing renewable gas that could be delivered to an interstate pipeline through the county’s $28 million injection portal.

The Menasha-based company, a division of Faith Technologies Inc., added about 2.3 megawatts of solar panels to power the plant, reducing carbon intensity and improving the gas’s credit rating, Feutz said.

Entech biodigester

EnTech Solutions will use power from a 2.3 megawatt solar panel to charge a Peterbilt electric tractor used to transport renewable gas from the Middleton manure digester.


Feutz said the system was sized to handle electric transportation and that EnTech eventually plans to use electric vehicles for manure handling as well.

“We have a lot of excess power that’s currently being sent back to the utility,” Feutz said. “But we will find ways to use it locally here.”

Editor’s note: This story has been updated to clarify that EnTech Solutions is a division of Faith Technologies Inc.


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