Garbage-to-energy demonstration plant struggles to reduce the pollutants in its emissions
By Kate Jaimet, The Ottawa CitizenMay 25, 2010
The Plasco garbage-to-energy demonstration plant -- promoted by Ottawa Mayor Larry O'Brien as a solution to Ottawa's waste-disposal problems -- is struggling with smog-causing emissions, and has not yet proven it can be successful, according to the Ontario Ministry of the Environment.
Plasco CEO Rod Bryden said he's confident the company can solve its pollution problems -- and it won't sign a contract with the city for a full-scale plant until it does.
"It has been clear that we and the city would only sign that contract when the Ministry of the Environment can confirm that the plant is operating and meets all the (environmental) requirements under its certificate of approval," Bryden said Monday.
Data from the ministry show that the demonstration plant's five engines -- which are fuelled by the gas formed from vapourized garbage -- have chalked up a total running time of only 85 hours since operations began in January 2008.
The engines have been shut down frequently, and for extended periods of time, because the company hasn't been able to keep the level of pollutants in the exhaust below the regulatory limits, said ministry spokeswoman Kate Jordan.
"There were concerns with their emissions, which is why they're required to stop and re-assess," Jordan said. "They have some kinks and technologies to iron out in terms of emissions controls."
Jordan added that frequent shut-downs are normal for a demonstration plant for an experimental new technology.
"It's still in the process of study. It's really too early to make any kind of judgment or conclusion on the success of the project," she said.
The city is negotiating a contract for Plasco to build a commercial-sized plant that would process 400 tonnes of garbage a day, and produce 20 megawatts of energy, enough to power about 7,200 houses. The city would pay Plasco tipping fees of about $8 million a year to accept the garbage.
The city, which partnered with Plasco for the demonstration plant, stands to receive royalties of up to $3.5 million a year if other Plasco plants are built elsewhere in North America.
The Plasco demonstration plant on Trail Road uses high temperatures to vapourize garbage into a gas, which is initially a dirty, impure substance, but is passed through a series of cleaning mechanisms to remove impurities. Finally, the gas is fed into an engine, which uses it to generate electricity.
The problem is that the exhaust from those engines contains levels of smog-causing organic compounds and nitrogen oxides (NOx) that exceed regulatory limits.
To reduce the level of pollutants, Plasco is now experimenting with running the exhaust through a flare before releasing it to the atmosphere.
However, Bryden said the company does not view flaring as a long-term solution, because it is inefficient: the flare requires gas to burn, which could be better used to power the energy-producing engines.
Bryden said the company plans to install technology, similar to catalytic converters in cars, to deal with the NOx.
The smog-causing organic compounds pose a more complex problem.
Bryden said the bulk of the organic emissions are composed of unburnt methane gas. He said that other waste-to-energy operations, such as those that capture landfill gases and burn them in engines, release far more methane into the atmosphere than Plasco, but are regulated differently.
"It's already a small fraction of what comes out of every landfill gas engine in the world," he said. He's asking the ministry to ease up on Plasco's regulatory limit, as it relates to methane.
However, Bryden acknowledged there could be other potentially more harmful organic compounds "hiding in the gas behind the methane." And until the ministry knows exactly what they are, it wants to keep a tight limit on the total emission of organic compounds.
Although methane is a greenhouse gas and does contribute to smog, it is more innocuous than other organic pollutants, known as volatile organic compounds, said Carleton University professor Matthew Johnson, Canada Research Chair in Energy and Combustion Generated Pollutant Emissions and a member of Plasco's public advisory committee.
"Volatile organic compounds are not so nice. They contribute to smog and have some toxicity in their own right. Ontario just puts them into one big group (of organic emissions). It could be the more innocuous hydrocarbons or it could be the VOCs," Johnson said. "Ontario has crappy regulations. Although it's so bloody complex, it may be possible to excuse them."
Bryden said the company has commissioned independent labs to test the organic compounds in Plasco's emissions, and they indicate that the organics, apart from methane, occur at concentrations of less than 10 parts per million. However, there's an issue as to whether the tests are sufficiently precise.
"It appears to us that we may be able to maintain testing that will clearly identify how much of the organics coming out of the exhaust are methane and how much is everything else, and what else," he said. "The discussion is going on, but the ministry has been extraordinarily responsive with Plasco."