The Danube River is famously blue, but after a recent toxic waste spill in Hungary, parts of it were flooded with a sickly red slurry. On Oct. 4, a reservoir wall had collapsed at an alumina plant near the village of Kolontar, releasing over 750 million litres of red mud—a byproduct of turning bauxite to alumina, which is needed for aluminum production. The disaster forced hundreds from their homes and left nine dead. The red mud was waist-deep in some places, locals reported; one witness said it smelled like blood.
A chemical soup of heavy metals and minerals (including iron oxide, hence its colour), red mud is highly corrosive; workers in Hungary measured the pH level and found that, in some places, it was as caustic as bleach. It can even be slightly radioactive. (Rio Tinto Alcan’s alumina processing plant in Quebec is the only one in Canada; it has withstood flooding and an earthquake without incident, a spokesman noted, adding that it’s “highly unlikely” such a spill could occur here.) We end up creating 63 million tonnes of red mud each year worldwide, but we still don’t know what to do with it: red mud is typically stored in reservoirs, dried out and buried, but it’s so chemically stable it won’t really break down. Marcel Schlaf, a chemistry professor at the University of Guelph, has a better idea. Red mud, he believes, could help transform bio oil derived from plant waste into fuel.
Bio oil is produced by pyrolysis, when biomass (organic waste, grass clippings, etc.) is rapidly heated in the absence of oxygen. Fossil fuels are created as “biomass is transformed over millions of years, deep in the Earth under high pressure,” says Franco Berruti, director of the University of Western Ontario’s Institute for Chemicals and Fuels from Alternative Resources. In the lab, “we do it in seconds. But we are not as good as nature.” Unlike fossil fuels, bio oil contains water and oxygen; it’s very acidic and hard to ignite, and if it’s overheated, it can solidify. What’s more, “it’s black, it’s viscous and it smells really bad, like concentrated barbecue sauce,” Berruti says.
About two years ago, Schlaf was teaching an undergraduate class about red mud, he says, when “a light went off.” He looked harder at the mud’s composition, and realized it might contain the right mix of metals to catalyze chemical reactions and upgrade bio oil, which he acquired from Berruti’s lab. (His findings were published in the journal Energy & Fuels earlier this year.) “The acidity of bio oil neutralizes the alkalinity of red mud,” he says, and “turns the bio oil into something usable.” It might turn red mud into something usable, too. After its transformation, “it’s no longer red; it’s grey and magnetic,” he says, and could be used to make anything from ceramics to cement.
Schlaf cautions that we won’t be running our cars on red-mud-treated bio oil any time soon; the research is in its early days. (He’s working with Murray Thomson, an engineer at the University of Toronto, to see how the upgraded oil works as a fuel.) Still, it’s an exciting idea, especially given our dwindling supply of fossil fuels. “The beautiful thing is that you’ve taken mining waste on one side, [agricultural waste] on the other,” and created a fuel, he says. With vats of red sludge just waiting to become landfill, it sounds almost too good to be true.