The decision to forge ahead will allow Montreal to say it's fulfilling a promise, but won't help reduce the city's ecological footprint, the research scientist warns.

Mayor Valérie Plante’s decision to forge ahead with a $175-million composting centre in St-Laurent borough will allow her administration to say it’s achieving a long-standing promise, but it demonstrates “a lack of serious environmental impact analysis” because the centre won’t help reduce the city’s ecological footprint, a leading Canadian clean energy research scientist warns.

“If you look only at the political angle, they’ll be building something that’s been delayed for a while and they’ll tell the public: ‘We achieved a promise of many years’. My response is that it’s not a sustainable environmental solution for the city of Montreal,” said Marzouk Benali.

Distroscale

Benali is manager of the R&D forest biorefinery program at the Varennes facility of CanmetENERGY, a federal research and technology organization that works in the field of clean energy and that’s attached to Natural Resources Canada.

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“The idea of building more composting centres is not environmentally sustainable because it’s not financially interesting and we’re not valourizing the organic material enough,” he said.

Plante’s Projet Montréal administration awarded the $175-million contract to design, build, operate and maintain the composting facility in late February, despite criticism that the price is more than triple the city’s initial estimate and that the project, the first of five organic waste treatment centres the city has planned for more than a decade across the island, is outdated.

Benali’s voice adds to those of other researchers who have in recent weeks criticized Montreal’s plan to build the large-capacity composting centre to treat food and yard waste collected from the West Island and west end of the city of Montreal. As some of the researchers explained, cities aren’t building large composting centres anymore.

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Under the plan first presented more than a decade ago by former mayor Gérald Tremblay, five organic waste treatment centres — including two composting centres, two biomethanation plants and one pretreatment centre — would be built in the north, east, south and west of Montreal Island to treat household organic material according to whether it’s collected in the eastern or western half of the island.

The Plante administration has said that it wants to move ahead with the St-Laurent composting plant and a biomethanation plant while delaying the other three facilities due to the costs.

The city is preparing to award the contract to design, build, operate and maintain a second facility, a 60,000-tonne per year biomethanation plant in Montréal-Est, in the coming weeks.

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The single bid the city received on that contract is also significantly above estimate.

However, coincidentally, the 50,000-tonne per year St-Laurent composting centre will cost about one-third more than the Montréal-Est biomethanation plant, for which the sole bid is around $130 million , sources say. The sole bidder on the biomethanation plant, Suez Canada Waste Services, was the winner of the St-Laurent composting centre contract.

The administration has justified building both the composting plant and the biomethanation plant despite the high prices because the city needs to expand organic waste collection and has targets to meet to divert organic waste from landfill.

However, Benali said a city’s goal should not only be to stop burying organic waste in landfills, where it produces harmful greenhouse gases in the absence of oxygen, but to transform as much of that waste as possible into alternatives to fossil fuels.

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The 50,000 tonnes of organic waste to be sent to the St-Laurent facility to create compost will be squandered, he said, because it could instead be easily transformed into renewable natural gas and other products that replace chemicals and fossil fuels in everything from fertilizers to fuel for vehicles. This is done in a biomethanation plant, not in a composting centre, where the resulting compost serves as a soil amendment spread on agricultural land, parks and gardens to help improve plant growth.

Organic waste should first and foremost be used to produce biomethane, a renewable form of natural gas, Benali said.

“The more you produce renewable natural gas, the more you eliminate fossil natural gas,” he said. By not producing renewable natural gas from the quantity of organic waste Montreal has access to, the city is in effect perpetuating society’s dependence on fossil fuel, he said.

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“Whatever goes to composting can go to biomethanation,” Benali said. And biomethanation doesn’t use much energy, he said.

“When you do the environmental review, it becomes interesting to have biomethanation.”

There’s a financial incentive for Montreal to transform organic waste into renewable natural gas at a biomethanation plant, Benali said. Énergir, formerly known as Gaz Metropolitain, buys biomethane from such plants to inject directly into its gas distribution network. Compost provides little or no revenue.

The Plante administration refused to provide the city internal evaluations of how much revenue could be generated by the composting facility or the Montréal-Est biomethanation plant. The Montreal Gazette has filed an access-to-information request seeking that information.

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However, Montreal has said in previously released information that it anticipates the Montréal-Est biomethanation plant will have a capacity to produce four million cubic metres per year of biomethane.

Given that Enérgir pays $9 to $22 per gigajoule to buy renewable natural gas, the plant’s production capacity can be expected to yield $1.4 million to $3.3 million in revenue for the city each year. However, the contract specifications for the project call for the city to split any revenue from the plant with the future contractor.

A biomethanation centre in the west end could also generate additional revenue with the recovery of nutrients in the digestate that will be produced by the plant. Nutrients such as phosphorus can be sold for use in bio-fertilizers.

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Other researchers agree with Benali on the benefits of biomethanation over a composting centre.

“I have difficulty seeing the interest in a composting centre,” said Évelyne Thiffault, who teaches in the department of wood and forest sciences at the Université Laval.

“I don’t see why you’ll have a composting centre as well as a biomethanation plant.”

Biomethane can be used for heating and electricity, and it can be transformed into liquid fuel for cars, she said.

“Worldwide, the strong trend is for the production of biomethane to replace fossil natural gas,” Thiffault,said.

“So on a worldwide scale, it’s very high on everybody’s agenda to develop the capacity to produce biomethane to replace natural gas. That’s the interest in biomethanation.”

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As one of the few urban centres in the province, Montreal has the population and the quantities of organic waste to generate renewable natural gas, she said.

“In the fight against climate change, energy transition (towards renewable energy) is essential and it requires biomethanation projects. So I understand there’s a question of cost. But when you take the macro view, the view of trying to save the planet, we want to see big cities like Montreal or Quebec City have biomethanation projects.”

Critics have also argued that the 50,000 tonnes of organic waste going to the St-Laurent facility will create more compost than can be used in parks and gardens on Montreal Island, so it will wind up being transported off-island to farms on trucks that emit greenhouse gases.

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As well, the east-end biomethanation plant will produce a digestate that will need to be composted, but Montreal didn’t plan for a composting operation at the biomethanation plant. Other municipal biomethanation projects in Quebec provide for composting of digestate on site. So the digestate from the Montréal-Est plant can be expected to be trucked 28 kilometres to the St-Laurent composting facility.

Organic waste such as food and municipal sludge are ideal feedstock to feed a biomethanation plant, Benali said.

And yet Montreal doesn’t have plans to send the sludge produced at the island’s massive waste water treatment plant in Rivière-des-Prairies to the future biomethanation plant in Montréal-Est.

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Montreal incinerates 267,000 tonnes of sewage sludge each year. What remains is 45,000 tonnes of ashes, most of which is transported for burial in a landfill where it releases dangerous greenhouse gases into the atmosphere. In fact, the waste water treatment plant’s incinerator produces a quarter of all greenhouse gases emitted by city operations, Projet Montréal said in 2015, while it was in the opposition at city hall.

At the time, Projet Montréal was calling for a public consultation to discuss ways to reuse waste water treatment sludge because the incinerator will come to the end of its useful life in 2020.

In 2018, just 14 per cent of ashes produced from incinerating the waste water sludge was recovered for use on agricultural land. The rest would have been landfilled.

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What’s more, the city is going ahead with the composting facility and the biomethanation plant without a pre-processing plant where non-organics would be removed from the waste before treatment.

Benali said a facility to handle pre-treatment of organic material should logically precede the treatment facilities.

“Absolutely,” he said. “You need the pre-treatment centre first.” During the pre-treatment phase, items like steel wiring are mechanically or magnetically removed from the organic material.

In fact, the correct approach is to have an integrated sorting centre for different waste streams, he said.