Anaerobic digester sought to help fill 'infrastructure gap'

Sedimentation tanks are shown at a waste-water treatment plant in France where anaerobic digestion is used to produce methane. A project is currently underway to attempt to bring a digester to Sarnia-Lambton. (AFP PHOTO / FREDERICK FLORINFREDERICK FLORIN/AFP/Getty Images)

Efforts are underway to attract an anaerobic digester to Sarnia to turn nutrient-rich industrial waste water from bio-chemical plants into renewable natural gas.

Sandy Marshall, executive director of Bioindustrial Innovation Canada, said the government-funded agency is working with Comet Biorefining on a proposal to see an anaerobic digester built and operated in Sarnia. Comet plans to build a bio-refinery in Sarnia to turn corn and wheat stalks into sugar.

Marshall said the digester project could cost in the range of $20 million to $30 million and a request for proposals has been released to identify a potential owner-operator.

The deadline for proposals is the end of June.

“We look forward to working with the successful company to have them build a successful anaerobic digestion business here,” Marshall said.

Sarnia-Lambton can offer access to steam, power, water and skilled trades to the bio-chemistry companies the agency works to attract and support but “one of the things we’re missing is the ability to treat these really rich organic steams that come from bio-plants,” he said.

“They’re too rich to go into a traditional waste water plant.”

The waste water needs to pre-treated in an anaerobic digester and the agency has been trying for some years now to fill that “infrastructure gap” so the community can continue to attract new bio-chemical companies, Marshall said.

“It’s just one more selling point for Sarnia-Lambton and the hybrid industry cluster.”

If an owner-operator for a digester can be found and a facility built, waste water from local bio-chemical plans would be pumped to the digester site and put into large tanks where bacteria breaks down the organics and turns them into methane, or renewable natural gas, Marshall said.

The digester could also take green bin material from municipal waste, as well as other sources of organic waste, to be ground up and all the non-organic material removed.

“And then, they basically make a very rich organic soup” which is fed into the tanks with the industrial waste water, Marshall said.

The renewable natural gas created is then purified so it can be delivered to customers such as Union Gas or TransAlta, and the “digestate” material left over can be used as “high-carbon fertilizer you can put back on farmland,” he said.

“This is the really cool part of the project.”

That material can return as fertilizer to farm fields where the process began when Comet used corn and wheat stalks as its feedstock, he said.

“It’s a great example of a circular economy,” Marshall said.

Sarnia Mayor Mike Bradley said the province is requiring some communities, including Sarnia, to begin green bin collection of organic waste in the coming years.

He said that when Sarnia looked at green bins a decade ago it found the system was “extremely expensive,” but the digester project could be an opportunity for the city.

“I think there’s an opportunity here for us to become directly part of the bio-fuels sector by being involved in something that gives us a benefit back,” Bradley said.

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