The Capital Regional District could save $5.4 million a year on fuel costs by processing biogas from sewage treatment.

By 2015, the digestion of sludge would generate approximately 10,700 cubic metres of biogas per day – enough to fuel up to 65 natural gas-powered transit buses, according to CRD discussion papers on resource recovery.

Biogas trumped electricity production when it came to salvaging resources from the proposed $1.2 billion sewage treatment system, primarily because B.C.’s hydro is already cheap and green, said Dwayne Kalynchuk, CRD general manager of environmental services.

“The fundamental point is you have to look at your own economic model,” he said. “That is why what would be a priority in North America may be different than Sweden, because the utility costs are different.”

The district would capitalize on greenhouse gas credits as well, he added.

During the CRD’s fact-finding trip to Sweden, district members found that larger cities, such as Goteborg and Stockholm, use biogas to fuel buses. As well, a European program called BiogasMax aims to run 25 to 35 per cent of vehicles on natural gas derived from sewage sludge.

Biogas could also be integrated with natural gas pipe networks, Kalynchuk said.

Since 1985, King County in Washington state has pumped biogas created from its two major sewage treatment plants in Renton and West Point into the grid system.

Combined, the plants service 1.4 million people living in a 675-square kilometre area, said Annie Kolb-Nelson, King County’s wastewater treatment division’s spokesperson.

The plants produce 5.3 million therms of natural gas annually, enough to heat more than 16,500 homes in a year. The gas is sold to Puget Sound Energy.

“Technology has given us the opportunity to be able to create resources from what at one time was considered waste,” Kolb-Nelson said. “So a wastewater treatment plant is in essence kind of like a large recycling plant.”

The production of biogas through sewage sludge digestion is more efficient in a large plant rather than a series of small plants, Kalynchuk noted.

“You need a certain mass,” he said. “That is why within our framework we are still saying that the solids should be managed at one or two locations, because that is your best opportunity to generate (resources).”

Victoria engineer Stephen Salter said the region needs to integrate organic food waste composting with sewage sludge digestion as a way of generating even more biogas.

An industrial ecologist who co-authored the report “Resource from Waste,” Salter said the region creates enough organic waste and wastewater to supply three treatment plants.

“The main thing is you get the best results if you integrate your plants,” he said. “It is common to digest biosolid in a digester to get biogas, but if you look at the city as a whole, there is about five times more energy available in food waste.”

raldous@vicnews.com