The City of Vancouver is setting out on a plan to repurpose Vancouver biosolids that are currently being produced by five wastewater treatment plants. This is in anticipation of population growth and the changing needs of the community.
The region’s five wastewater treatment plants have processed more than 450 billion litres of sewage and generated 55,000 tonnes of treated sewage sludge, or biosolids last year alone. It is projected that this number will rise to more than 90,000 tonnes of biosolids by 2021 and more than 150,000 per year by 2050.
Vancouver biosolids have primarily been used for land application. As much as 98% are converted into Nutrifor topsoil for landscaping purposes. It is also being utilised for reclaiming mine sites and gravel pits, as a top cover for landfills to absorb methane, and for fertilizing range and agricultural land in the Interior. But it is unlikely that they could sustain this arrangement because of growing public concern and changes in market demand.
Lillian Zaremba, a program manager with Metro Vancouver’s liquid waste services department, says that this exploration into new uses for Vancouver biosolids is innovative, new and works on proven technology. “This is exciting because it’s different uses than we’ve had in the past, so a diversity of options.”
Treatment plants are producing so much more biosolids than they can make use of which usually ends up being sent out to landfills outside of British Columbia. “That’s why we want to beneficially use as much as we can,” said Zaremba.
One possible solution is to dry biosolids using natural gas and biogas from the plant. The resulting pellets could be used as a coal replacement in cement kilns or be added into fertilizers. It is theorised that those two market segments could each utilise 75,000 tonnes of dried biosolids annually. Zaremba says that “It just adds versatility and diversity by opening up that fuel option.”
Although developing a drying facility would cost around $197 million to build, the costs would eventually decrease in the long term compared to land applications or landfill disposal.
Richmond Coun. Harold Steves, himself a farmer, is receptive to the use of Vancouver biosolids for these new purposes, but he still advocates for the continued use of biosolids in soil. “The problem we have worldwide is we’ve depleted our soils — 68 per cent of the world’s soils are depleted of organic materials,” Steves said.
Another alternative use for Vancouver biosolids is its conversion into oil. A $9-million pilot hydrothermal processing facility is being built to turn sewage sludge into biocrude using up to 25,000 tonnes of undried biosolids that could be burned at Metro’s waste-to-energy facility in Burnaby. Annacis Island wastewater treatment plant is also working on producing low-carbon fuels from biosolids.
“The hydrothermal processing is exciting,” said Zaremba. “I would say it’s further out in the future for full-scale implementation.”
The Ministry of Environment is currently looking at changing its regulations on the use of biosolids for land application. They are looking into policies that would increase public transparency and information sharing. This includes working with First Nations and local governments. Future changes to the Organic Matter Recycling Regulation are also expected to be implemented in the coming year.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.