Metro sells bottom ash from trash for cash at energy plant
An advertisement about collecting ash from Metro Vancouver’s waste-to-energy plant captures a tidy snapshot of the recycling and money generation that goes on at the south Burnaby facility.
Three firms have bid on purchasing what’s known as “bottom ash” — gravel-like chunks, as opposed to fly ash that is fine and rises — and repurpose it, most likely as a component in cement and concrete or as aggregate material for building foundation.
“As a region, we recycle 64 per cent of the waste that’s generated,” said Paul Henderson, general manager of solid waste services with Metro Vancouver. “That is North American-leading.
“After all the recycling, there is roughly 900,000 to a million tonnes a year of garbage that requires disposal.”
About a quarter of that total, roughly a quarter-million tonnes, is dealt with at the waste management facility, where it’s turned into energy, metal and about 43,000 tonnes of bottom ash a year.
The bottom ash is the non-combustible material left after slag, ceramic, glass, ferrous and non-ferrous metals are burned to power a boiler, which in turn generates electricity that’s sold to B.C. Hydro.
Historically, bottom ash from the waste- to- energy facility has been sent to the Vancouver landfill or, more recently, used during construction at the new Coquitlam transfer station as aggregate.
The waste-to-energy facility was built in 1988, and a more recent five-storey tower houses an electromagnetic machine that separates metals.
Metro Vancouver earns $8 million a year selling electricity to B.C. Hydro that’s produced burning the waste. That electricity powers 16,000 homes a year.
“It generates a lot of electricity, over 20 megawatts of electricity, continuously throughout the year,” Henderson said. “What’s left over is this approximately 43,000 tonnes of bottom ash.
“There have been lots of pilots projects, we’ve done pilots with paving stones, etc., but to our knowledge, on a full-scale where you’re taking all the bottom ash from a waste-to-energy facility, we’re not aware of any other similar initiative in North America.”
Over the 32 years the facility has been operating, Henderson said it has performed considerably better than the required regulatory emissions standards. Those same health standards will go into selecting the successful tender for the bottom ash, he said.
A grapple picks up waste three tonnes at a time and drops 11 tonnes an hour into each of three chutes, kept full so they continue to burn and keep the boiler going to make steam to produce electricity.
A lime-and-carbon injection reactor treats the flue gas to reduce acid and mercury, while hoppers collect fly ash which is then stored in a silo.
About 9,000 tonnes of ferrous metal is collected every year and sold as scrap, generating $2 million in annual revenue. Since 2018, 500 tonnes a year of non-ferrous metals such as aluminum and copper has been extracted and sold for about $300,000 a year.