ANH CHU - The Globe and Mail
In Calgary's Shepard landfill, the seagulls squawk like a dissenting mob amid the drone of heavy machinery flattening trash. But one hectare of land sits with no apparent activity above ground. Below the surface lies the potential to transform the way cities manage their solid waste.
This site is home to the Biocell, a pilot project whose premise – garbage as a renewable resource – sounds more like wishful thinking than reality.
“Landfills are garbage graveyards, or perpetual storage,” says Patrick Hettiaratchi, biocell research lead at the University of Calgary's Schulich School of Engineering. Unexpected finds have been unearthed from old landfills, where even organic waste such as yard clippings and kitchen scraps are slow to biodegrade in the dry, tomb-like conditions.
“It's quite easy to read a newspaper from the 1970s,” says Corey Colbran, landfill operations leader at the City of Calgary.
Conventional sanitary landfills try to minimize the two common hazards of trash: leachate (toxic garbage juice) and methane (a major contributor to greenhouse gases). The biocell is a sustainable, closed-loop system in which the negative byproducts of garbage become advantages.
Leachate is collected at the bottom of the cell and recirculated through a network of pipes – meaning the toxic soup doesn't need to burden wastewater treatment plants. The moisture from the leachate speeds up the degradation of the garbage, and because no oxygen is present, the anaerobic environment accelerates the production of methane. The research team at the Schulich School of Engineering is finding ways to augment the leachate to degrade tough materials.
Normally, more methane is not a desirable outcome. But within the biocell, the gas is collected and converted into electricity. From 2007 to 2009, more than 800,000 cubic metres were converted into electricity, which then helped power Calgary’s light-rail transit system.
The production of methane for electricity is not new, but the landfill biocell is unique. A two-day workshop of international engineering consultants provided the genesis for the pilot project in 2003. “People have tried gas extraction before. People have tried landfill mining. We said, ‘Why don't we combine these ideas?’” explains Dr. Hettiaratchi.
Methane production is the first of three stages. “The first stage is an anaerobic reactor, where we get the gas out. For the second stage, we put air into the system and make it aerobic, so it becomes like composting,” says Dr. Hettiaratchi. About 70 per cent of the waste in Calgary's landfills is organic.
Once methane production slows, phase two begins and air is dispersed throughout the cell to mimic the aerobic biodegradation that occurs during composting. The resulting compost-like material should be stable enough to use in the city's parks.
In the third and last phase, the area will be mined for non-biodegradable materials. “Dirty plastics could be used to manufacture things like park benches,” Dr. Hettiaratchi explains.
Calgary has about 30 to 40 years of landfill space left, and a biocell could extend that to 100 years. It would also be cost-effective. “The landfill becomes a cheap processing facility,” says Dr. Hettiaratchi. Researchers picture biocells processing landfill waste in networks of 10 cells – with eight in operation concurrently, one in the filling stage and one in the excavating stage.
The project is as collaborative as the techniques suggest. In addition to the university, the City of Calgary works with consulting engineering firm Stantec for design and construction, and CH2M Hill for operations.
The pilot has yet to be completed and its results analyzed, but the bottom line is the biocell must prove itself as a financially viable option for cities.
“The focus is on making sure all the technology works” before applying for patents for particular components, says Dr. Hettiaratchi, noting that any experiment may have unexpected results.
“Our initial research estimate, as far as construction was concerned, was that the biocell would cost 50 per cent more than the typical landfill,” he says, estimating that Calgary has spent about $2-million to $3-million so far in the biocell's construction, not including operations and management.
“Regardless of what methods a municipality chooses to manage its organic waste, there will still be landfills of some description, because some materials are just not recyclable or reusable,” says Stantec's Don Davies.
The biocell can generate energy, create compost, recover other resources and reduce the amount of leachate and greenhouse gas emissions produced, but the biggest advantage could come in a finite resource that all burgeoning cities face: space.
“Space is at a premium at landfill sites, so excavating the site is critical because you're then able to reuse that area,” says Mr. Colbran.
The biocell project has already garnered awards for innovation in engineering. If the results remain as promising as they have been in Calgary's dry and wintry climes, which prolong the process, the benefits are far-reaching. In fact, a waste management company from Mumbai has already discussed adopting the technology.
Mr. Davies speaks best to the necessity of innovative thinking when it comes to garbage: “Whether it's the biocell concept or some other method of processing organic waste, this is the future.”
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