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Issue: 2015-04-16 PHOTO: Shannon Mallory
Shannon Mallory studied biogas in Sweden
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Issue: 2015-04-16 GRAPH: Shannon Mallory
The biogas process
If you’re unsure whether you consider Whitehorse a progressive city, here’s some fodder for the thought that it is: we’re one of a (growing) handful of municipalities across North America that is learning how to produce energy from our own waste.
It’s called biogas, and if you’ve heard of it, it’s probably because it’s an old technology. “In Canada you’ll see a lot of biogas on farms,” says Shannon Mallory, environmental coordinator at Yukon Energy. “In Chilliwack, for example, there’s a farmer who wanted biogas, so he produces it and feeds it into the city’s grid.”
It’s also normal to find biogas production on even smaller scales all over the world. “There are lots of farmers in rural areas in India, Bangladesh, China, that might have a barrel where they produce their own,” says Mallory. This is because it is such a simple technology — an earth-designed one.
Biogas is energy-rich methane and carbon dioxide. It’s a natural byproduct of anaerobic digestion — which literally means “living without air” — a process that occurs naturally in landfills, bogs, and in your own compost pile. We simply have to set up systems to capture the gas it produces. What makes the venture in Whitehorse progressive is it aims to create this system on the municipal level.
On and off since 2009, Yukon Energy, in collaboration with Cold Climate Innovations at the Yukon Research Centre, has been investigating just this possibility. Mallory brought the idea with her from Sweden, where she did her master’s thesis on biogas. “North America has much less biogas than Sweden,” says Mallory. “There’s around 150 plants there, maybe one in every municipality.” Denmark, Germany, and Austria are the same.
Yukon Energy’s end goal is a biogas power plant, one that works with the city’s well-established compost system. The plant would use the food and yard waste that comes from green bins, collect the energy rich biogas that is produced, and feed that energy into the city’s power grid.
It’s a project that works towards future sustainability using systems that are currently in place. “We’ve designed this project so it could easily fit in to what the city’s already doing,” Mallory says.
She stresses that it won’t interfere with normal compost production. Rather, it somewhat enhances it, reducing the time needed for the composting process, and making it easier for plants to uptake the nutrients. “Compost is such a good thing to have in the city, we don’t want to mess with that. We want to work with it.”
Here’s the system: you have a large oxygen-free tank with a front-end loader, through which food and yard waste is fed. The tank is heated to 36 degrees Celsius. At that temperature bacteria called methanogens start working on the compost, and through their “work’, biogas is produced. The tank is also a percolator, collecting the water that accumulates at the bottom and bringing it up to spray over top. The process can take two weeks to a month, with the compost continuing on its regular journey after it’s done in the tank.
Methods of collecting the biogas from the tank vary, but Yukon Energy has been looking at one that works a little like a giant lung, inhaling and exhaling. “The study is quite preliminary,” says Mallory. “We’re not sure who would own a plant like this in the end. We’re looking at getting it to a point where someone else could take this on, another organization, department, or company
. “We’re always trying to find the best project for the environment, for rate payers, to have good economics, to make it reliable — all those components are really important.”