City trying to burn off less gas from all your garbage
Greenhouse gas emissions at the landfill are down — but at the sewage plant, they're up
The City of Ottawa has managed to dramatically reduce the greenhouse gases emitted from garbage at the Trail Road landfill in recent years, but it's still finding it a challenge to eliminate those emissions entirely.
Garbage gives off gases as it decomposes, roughly half methane and half carbon dioxide, explained Marilyn Journeaux, director of solid waste at the city.
The city has drilled more than 100 wells into the garbage to vacuum out those gases so they can be converted to electricity or flared off, said Journeaux.
As the garbage level increases, the city spends half a million dollars each year on drilling more wells and other infrastructure.
Our preference is obviously to generate electricity with the gas- Marilyn Journeaux, solid waste manager
Five generators at a centralized plant at the landfill started turning those gases into power to sell back into the electricity grid in 2007, and the city added a sixth one-megawatt generator a few years ago.
They produce enough electricity to operate 6,000 homes.
"Our preference is obviously to generate electricity with the gas, but there's a capacity of how much gas you can put in the generators," said Journeaux.
"So it's much better to flare that excess gas than to let it dissipate into the atmosphere."
Adding that sixth generator and upgrading the flaring system was the main reason for a 25 per cent drop in greenhouse gas emissions, according to a recent report measuring the city's progress at meeting its climate change reduction targets.
The rest was due to city buildings using electricity generated by cleaner sources, after the province closed its coal-fired power plants earlier this decade.
But the city is still burning off gas, something that immensely bothers Kevin Wylie, the city's general manager of public works and environmental service.
Wylie told CBC News the landfill flares off enough gas now to warrant a seventh generator.
"My understanding is the grid at this point doesn't need more electricity," he said.
"We're having trouble getting [a new generator] arranged, but we're still working on it."
City wants to take sewage plant off-grid
On the other side of the city, near the Ottawa River east of the Beacon Hill neighbourhood, Wylie is working to make the Robert O. Pickard wastewater treatment plant solely reliant on the energy it produces, rather than needing heat or power from the natural gas or electrical grids.
The sewage plant creates far fewer emissions than the landfill, but unlike the landfill, it saw emissions increase from 2012 to 2016.
The sewage treatment process turns waste into biogas to power half the plant, using four on-site generators.
The city is studying how to upgrade those engines, said Wylie, which could take the plant entirely off the grid within the next two to three years.
"We can make big differences on both [the landfill and sewage plant] fronts," said Wylie.