City tests soil fabrication impact on methane at former landfill

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This article was published 06/12/2021 (1489 days ago), so information in it may no longer be current.

A byproduct of the sewage treatment process could now help cut the amount of polluting methane gas at one shuttered Winnipeg landfill.

For years, the city has been testing a landfill top cover at the former Summit dump site in northwest Winnipeg. The soil layer includes a mix of nutrient-rich biosolids (a byproduct of sewage treatment), woodchips and street sweepings.

The mixture is intended to help restore a native prairie landscape at the site, while keeping sewage byproducts from claiming ample space at the main Brady Road landfill.

In addition, officials are now testing how effective the “soil fabrication project” is at reducing methane, one of the most potent greenhouse gases.

“That top soil layer is pretty robust… (There is) bacteria within the soil that can feed on methane percolating through the soil. So we’re looking at, ‘Is our fabricated soil working in that way?’” Becky Raddatz, acting manager of the city’s office of sustainability, told council’s water, waste and environment committee Monday.

A public service report notes a carbon study is underway to determine how many greenhouse gas emissions are avoided by diverting the biosolids to Summit, instead of burying them at Brady. The study will also assess how much carbon can be sequestered in soil and how much emissions can be reduced at Summit itself.

“It sounds like, at Summit at least, this is the way to go, to try and tamp down the amount of GHG coming out… that must have been a big landfill in its day,” said Coun. Brian Mayes, committee chairman.

The report notes such “biocover” projects could be eligible for senior government funding to mitigate emissions in the future.

“Further study would be required to see if stabilized fabricated soil (and potentially native grasses/sod) could be transplanted to other closed landfill sites to act as a biocover,” writes Michael Gordichuk, Winnipeg manager of solid waste services.

The report does not offer an exact timeline for when the project will be completed.

The document doesn’t list other feasible options to capture or eliminate gas from closed landfills. While there are 33 former landfills in Winnipeg, 25 have already been reclaimed for other uses, such as sports fields, industrial sites and playgrounds, and aren’t available for methane capture, notes Gordichuk.

Of the remaining eight, only the Summit and Kilcona landfills produce enough emissions to meet a national pollution recording threshold. The report finds none of the closed landfill sites produces enough waste to install collection wells, which safely destroy gases at Brady Road landfill.

joyanne.pursaga@freepress.mb.ca

Twitter: @joyanne_pursaga