Toronto organics processing facility to convert food waste to RNG

Source: Ellen Cools | CANADIAN BIOMASS MAGAZINE | May 26, 2020

RNG infrastructure at the Dufferin Solid Waste Management Facility. Photo courtesy City of Toronto.

Ever wondered where your leftover food ends up? Well, in Toronto, that food waste will soon be turned into renewable natural gas (RNG).

The City of Toronto, in collaboration with Enbridge Gas Inc., is installing equipment at its Dufferin Solid Waste Management Facility, which will upgrade the biogas produced from processing food waste into RNG. Through its partnership with Enbridge, the city will be able to inject the RNG into the natural gas distribution grid and potentially use it to power its waste collection trucks, among others, as well as heat city buildings and facilities.

“It’s one of the first of its kind in North America and will allow the city to reduce its carbon footprint,” says Carlyle Khan, director of infrastructure and resources management, solid waste management services, for the City of Toronto.

The driving force behind this project? The city recognized that the Dufferin Solid Waste Management Facility was producing a waste stream, which was managed by flaring biogas. “We basically had a watershed moment where we said there has to be a better way (to manage our biogas) than flaring,” Khan says.

“Flaring is the everyday accepted common practice in terms of destroying biogas,” he continues. “But we asked ourselves, is there a way to take the biogas and convert it into something that is a more valuable and useful commodity?”

The idea to convert organic waste into RNG was first put forward in early 2014. The construction phase of the project began two to three years ago after the city spoke with Enbridge to ensure the project’s viability.

The collaboration with Enbridge was an obvious choice, Khan says.

“When we said, ‘OK, we can convert our biogas into renewable natural gas,’ the question, ‘Then what?’ was posed. The easiest way to use the RNG was to get it into the pipeline. So, that triggered us asking, ‘Who owns and who controls the pipeline and distribution grid?’ That was Enbridge,” he explains.

Enbridge is designing and installing the biogas upgrading infrastructure next to the Dufferin Organics Processing Facility (OPF), along with an injection station. Construction of the facility started in 2018 and will be complete by the third quarter of 2020. Enbridge will operate and maintain the facility for the next 15 years on behalf of the City of Toronto.

The Process

On a high level, the process for turning food waste into RNG is fairly simple.

Material from Toronto’s green bin program – separated organics – is taken to the Dufferin OPF, where it is pre-processed to remove contaminants and prepare it for the next step, Khan explains. It is then fed into anaerobic digestors where, in the absence of oxygen, it breaks down and produces biogas, which is made up of approximately 60 per cent methane.

“Once the facility is up and running, the biogas collected will be sent to a biomethanization unit, where it will be cleaned and conditioned and then injected into the distribution grid as RNG,” he says.