AN INVESTMENT OVERDUE
Edmonton's faulty compost digester needs $6.7 million to fix quality, stop plastic littering: City reportLauren Boothby - Yesterday -
Edmonton’s long-fraught digester facility needs millions of dollars in investment to keep poor-quality compost out of the landfill and from littering the environment with plastic.
Digestate produced by the high solids anaerobic digester when it arrives at the compost cure site.
© Source: City of Edmonton business case for digester upgrades
The high solids anaerobic digester, which fully opened just last year, needs up to $6.7 million more to build two screens and two mixers to filter out garbage and remove moisture, according to a staff report heading to city council Sept. 12. The original facility was budgeted for $30 million in 2013 but costs grew to $42 million by 2018 .
The facility uses microorganisms to degrade waste without oxygen and produces “digestate” and biogas. Digestate is put into aeration boxes to create compost. It was designed to process up to 40,000 tonnes of waste a year.
But a business case recommending the new upgrades paints a damning picture of what the long-awaited facility is producing.
The digester was designed to work in tandem with the Edmonton Composting Facility (ECF). ECF was shut down in 2019 for safety issues — it partially closed after a roof collapsed the year prior and had known structural issues since at least 2017. The previous city council voted in private last August not to build a replacement.
But without the screening provided at ECF, the digestate now arrives at the curing site full of garbage, littering the Edmonton Waste Management Centre (EWMC) site and the adjacent wetlands, the business case states. The compost quality is so poor it’s sent to line the dump.
“Status quo or doing nothing is not a practical option as continued cure site littering is considered a significant environmental problem that can’t be ignored,” the business case states.
“The compost is currently only being used as alternative daily cover for landfilling because it does not reach the quality level to have other uses. This compost usage results in a cost to waste services for disposal.”
In addition to limiting litter that blows off the cure site, upgrades promise to mix woodchips more effectively with digestate so it can be recycled instead of the city paying to dispose of it, and create a more marketable compost, a staff report states.
Digestate that’s been screened and cured at the Edmonton waste campus.
The high solids anaerobic digester, which fully opened just last year, needs up to $6.7 million more to build two screens and two mixers to filter out garbage and remove moisture, according to a staff report heading to city council Sept. 12. The original facility was budgeted for $30 million in 2013 but costs grew to $42 million by 2018 .
The facility uses microorganisms to degrade waste without oxygen and produces “digestate” and biogas. Digestate is put into aeration boxes to create compost. It was designed to process up to 40,000 tonnes of waste a year.
But a business case recommending the new upgrades paints a damning picture of what the long-awaited facility is producing.
The digester was designed to work in tandem with the Edmonton Composting Facility (ECF). ECF was shut down in 2019 for safety issues — it partially closed after a roof collapsed the year prior and had known structural issues since at least 2017. The previous city council voted in private last August not to build a replacement.
But without the screening provided at ECF, the digestate now arrives at the curing site full of garbage, littering the Edmonton Waste Management Centre (EWMC) site and the adjacent wetlands, the business case states. The compost quality is so poor it’s sent to line the dump.
“Status quo or doing nothing is not a practical option as continued cure site littering is considered a significant environmental problem that can’t be ignored,” the business case states.
“The compost is currently only being used as alternative daily cover for landfilling because it does not reach the quality level to have other uses. This compost usage results in a cost to waste services for disposal.”
In addition to limiting litter that blows off the cure site, upgrades promise to mix woodchips more effectively with digestate so it can be recycled instead of the city paying to dispose of it, and create a more marketable compost, a staff report states.
Digestate that’s been screened and cured at the Edmonton waste campus.
© Source: City of Edmonton, business case to upgrade anaerobic site
Compost from garbage
Neil Kjelland, director of sustainable waste processing with the city, said the compost from the anaerobic digester is poor quality because it’s made from organic waste extracted from the garbage stream.
The city sells other high-quality compost in bulk made from organics collected with seasonal yard waste which is far less contaminated, he said.
“As a compost suitable for all applications, we also provide limited quantities of this compost back to Edmontonians for free at Eco Stations,” he said in an email statement Friday. “In addition, the organics collected in green carts is also processed into good-quality compost, because it contains much less contamination.”
Kjelland said the new mixers will improve how all organics are processed.
“It will help screen contaminants (plastics, etc.) from the organics. It will also be used to pre-process organic waste that will be sent to processing partners, to help ensure they are receiving organic waste that is free of contaminants.”
The 2017 business case for three-stream source separation said organics from green bins would be processed at the anaerobic digestion site.
Last year, an estimated 40 per cent of waste was not diverted from the landfill.
Wood chips and plastic can’t be separated at the anaerobic digestion facility. This means these items go to the landfill, together, although wood chips can be recycled.
© Source: City of Edmonton, business case for digester upgrade
Plan was to make a profit
Producing something the city can sell for profit was part of the original plan when the anaerobic digester was first funded by council in 2013.
The digester captures methane gas which can be burned to produce heat elsewhere on the waste management campus, create electricity and be sold.
Whether or not the digester is meeting expectations is unclear from documents available on the city’s website. Answers provided by the city did not clarify the situation.
“Some gas has been used to generate electricity that has been used at our facility, put back into the grid or sold. The subject-matter expert who can provide revenue information is not available until next week,” Kjelland stated.
The 2021-2022 annual business plan shows an intention to do grading to better understand “the waste’s biomethane potential” which will create “expected electricity cogeneration key performance indicators.”
So far the city has made $235,000 from bulk compost sales this year, Kjelland said.
The digester site was built by Maple Reinders using BioFerm technology and is operated by Veolia, previously known as Suez.
Maple Reinders’ project website said the site can process 48,000 tonnes of waste although the city says its capacity is 40,000.
lboothby@postmedia.com
@laurby
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