Drive by a pulp and paper mill and one of the first things you’ll notice is the unmistakable smell. But give U of T engineering professor Grant Allen his way and you’ll be able to breathe easy the next time you pass a mill. Allen, director of U of T’s Pulp and Paper Centre, is researching biofiltration techniques that use bacteria to “eat” air-pollutant byproducts from the pulp process and thereby filter out the odour. “All industrial processes have air emissions, and in the case of pulp and paper mills, the smell can be quite overwhelming,” says Allen. “This biofilter operates like a mini-ecosystem. It’s a microbial community that degrades the pollutant and breaks down the compounds that cause the odour.” The filter – composed of materials such as wood chips or plastic spheres – is used at the end of the manufacturing process before sulphur compounds are released into the air. The compounds are food sources for the bacteria, and as the bacteria chomp away at them, they also eat the smell.