Edmonton’s Utility Services Branch is about to take another big step towards diverting 90% of the city’s waste from landfill.
This year at the Edmonton Waste Management Centre (EWMC), construction will begin on an anaerobic digester – a building which will act like a giant ‘stomach’, digesting up to 48,000 tonnes of organic waste a year.
The Anaerobic Digestion Facility will be the second of its kind in Canada, says Christian Felske, the branch’s general supervisor of engineering innovation.
In addition to increasing by almost a third our ability to process organic waste into fertilizer, the facility will be even more environmentally friendly than the City’s current method of composting organics.
Right now, the City separates the organic portion of the waste collected from residents and some businesses and composts it indoors at the Edmonton Composting Facility.
Edmontonians generate about 125,000 tonnes of organic waste each year, and the current system can handle that amount, but only if the supply of organics is steady – which it’s not.
“There’s a large spike in organic waste in spring and summer, when people are gardening and cutting grass,” says Christian. “During those seasons, we receive so much more organic matter that our capacity is temporarily exceeded,” says Christian.
Initially, the anaerobic digester will enable the City to handle the summer spike. Over time, it will also help to cope with the demands of a growing city.
The digester involves a building 75 meters square and 10 metres high containing several long, narrow airtight boxes. After organics are ground up, they’ll be loaded into the boxes. Doors will close, and all the oxygen will be consumed by bacteria.
“We’ll spray water on top, let it percolate through the piles, collect it at the bottom and recycle it. Anaerobic bacteria – bacteria that thrive in oxygen-free environments – will begin breaking down the organics,” says Christian.
The bacteria will produce energy rich methane gas, which will be tapped off and used to power a combined heating and electrical generation plant.
After 28 days, the material will be moved into other aeration boxes where it will spend a week with air being pumped up through it from the floor. That will provide the necessary oxygen for composting to start and to partially dry the material out.
The system has many advantages, says Christian:
Because it’s so environmentally friendly through the reduction of greenhouse gas emissions, the facility received a $10 million grant from the Alberta Climate Change Emissions Management Corporation. The University of Alberta, which will provide 1,500 tonnes of organic waste annually from all of their campuses is a partner with the City on this project.
For more information on the City’s organics processing program or information about the open house please visit Edmonton.ca/OrganicsProcessing