John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Researchers have extracted a substance from coffee grounds that they claim is cheaper and cleaner than diesel fuel.
To Cincinnati residents who've noticed people rooting around in Starbucks dumpsters, shoveling wet, smelly coffee grounds into buckets, don't worry – there's not a new breed of caffeine super-tweaker on the loose. It was just local researchers who are trying to achieve the extraordinary in coffee-based alchemy: transforming the stuff we drink in the morning into cheap, clean fuel to power our vehicles.
There is in fact a car that's been running for years on clumps of dried-out coffee. What environmental engineers at the University of Cincinnati are doing is a little different. They are extracting the oil from used-up coffee and then filtering it back through the grounds to remove impurities, in effect setting up a manufacturing process that uses every single part of the bean.
Coffee grounds are a surprisingly rich source of oil, with up to 20 percent of their mass potentially coming from triglycerides. Factor that in with the 1 million-plus tons of waste coffee that Americans throw out each year, and it's easy to get excited about a potential new source of green energy – and one that's unlikely to run out soon, according to the university:
The researchers say the method they're exploring to produce biodiesel would not only open landfill space, but it also holds promise in creating biodiesel from a natural product that's not also in high demand as a food source, such as corn and soybean crops that are used to manufacture biodiesel.
The engineering team, fronted by Yang Liu, Qingshi Tu, and Mingming Lu, are pumped enough about "coffee oil" that they've been dumpster-diving for three years to obtain the experiment's base material. They have reached the point where their biodiesel meets national testing standards and is cleaner-burning than petroleum diesel. The efficiency of their coffee-grounds filters, which remove unwanted gunk like methanol and glycerin, is less than typical biodiesel filters. But that problem is offset by the cheapness of the ingredients, with spent grounds being much more affordable than current purification materials.
The researchers claim they even can burn their filters as biomass when they're done with them, creating another source of earth-friendly energy. Coffee fuel: Just another example of how the caffeinated miracle drink is bettering the world, from de-smelling sewers to helping people with Parkinson's to providing an interesting kind of booze.
Top image: dyobmit / Flickr