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Seniors in Michael Twedt’s Renewable Energy Systems class got a close look at what it takes to bring renewable natural gas to a viable market during a tour of NorthWestern Energy’s renewable natural gas receipt facility at the north edge of Brookings Nov. 19.

The 24 mechanical engineering majors got an opportunity to “see the working systems that we discuss in class,” Twedt said. That included monitoring equipment to ensure the methane that originates at area diaries has been processed to pipeline quality and odorizing equipment to give odorless gas its rotten egg smell.

The class got a look at the facility in fall 2023 when it was still under construction, and Twedt brought a new class back to see the finished product.

NorthWestern Energy constructed four renewable natural gas facilities in South ��ֱ���� in 2024 with a fifth site at Bryant to come online before the end of the year. The others are at Milbank, Parker and Estelline.

Class member Matthew Anderson said, “It was interesting to see how they combine multiple drop-off points into one main pipeline connection. It was also cool to see the engineering behind everything; how they have been constantly improving on previous designs and projects.”

The Brookings station is unique to NorthWestern Energy because it is fed from four separate farms with room to expand to eight. A renewable natural gas developer constructed digesters and filtration equipment at each  farm. The developer compresses the cleaned gas and loads it on a truck, which carries it to Brookings. 

At the Brookings facility, the gas is unloaded, brought to pipeline pressure and passed to NorthWestern Energy’s equipment for quality checks and injection into the natural gas grid. This arrangement keeps connection point costs down for the renewable natural gas vendor  and  equipment in the field in one location for NorthWestern Energy. 

While the students had been briefed in class about the facility, they said the tour still proved eye opening.

“It definitely exceeded my expectations,” Ryan Olson said. “Getting to see just the quantity of gas that is being moved at any given time is shocking.” Production began in March, and NorthWestern Energy expects to receive and distribute about 700,000 dekatherms of renewable natural gas annually, which would serve roughly 10,000 residential customers annually.

However, the facility at Western Avenue and the U.S. Highway 14 Bypass is strategically located between two major industrial customers — the Valero ethanol plant in Aurora and the South ��ֱ���� Soybean Processors plant in Volga.

Olson added, “What’s being done here is important because it really illustrates the necessity for a variety of different energy sources. There’s no one good answer to providing energy, so having a variety is really helpful.”

“Renewable natural gas contributes to a sustainable future, and provides opportunities for local agriculture businesses,” said NorthWestern Energy President and CEO Brian Bird. In addition to NorthWestern Energy’s five South ��ֱ���� sites, three more are planned for the Rushmore State as well as one each in Nebraska and Montana, according to Allison Snyder, a 2018 SDSU mechanical engineering graduate who now is a business development engineer with NorthWestern Energy in Aberdeen.

The Brooking’s facility, built on the site of an existing NorthWestern Energy regulation site, cost around $1 million to construct. 

However, when including manure tanks, pipelines, injectors and processing facilities, the total cost hits $150 million. That is borne by third-party developers who partner with NorthWestern Energy.

The project proves to be a winner for dairy operators, who gain income from the sale of what otherwise would have been a waste product.

It’s also a winner for the mechanical engineering students.
Twedt said, “The students who toured it last year commented that it was one of the highlights of the class.” He expects the same response when this year’s seniors evaluate the class.