Drying wet coffee grounds before turning them into fuel costs time and energy. Researchers at the Korea Institute of Geoscience and Mineral Resources (KIGAM) found they could skip that step entirely, and that the water inside the grounds helps the job along.
The product is biochar, which is charcoal made by heating organic waste in an environment without oxygen. It has two uses. Left alone, it locks away carbon dioxide for centuries, possibly millennia. Burned like coal, it gives off energy. The second route has been awkward, because making biochar normally eats so much energy that little is left over to sell.
The popcorn effect
The KIGAM team worked with damp coffee grounds and did not dry them first. Water trapped inside each particle flashes to steam. “As water trapped inside coffee particles rapidly turns into steam, pressure builds and creates microscopic explosions,” Interesting Engineering explained in an article on the work. The blasts break the biomass apart and leave a more porous structure, which speeds up carbonization. The researchers call it the “popcorn effect.”
Removing the drying stage saves time, energy and money. The biochar that comes out has three times the carbon content of typical biochar and about one-third more calorific value. It contains no sulfur, so it burns relatively cleanly. The whole process is also very fast.
“This study demonstrates that flame plasma pyrolysis provides a sustainable, energy-efficient, and ultra-fast pathway for waste-to-energy conversion, effectively turning the intrinsic moisture of biomass from a thermal burden into a functional activation agent,” the researchers wrote. Their open access paper appeared as a short communication earlier this month in the Science Engineering Journal.
Beyond the coffee cup
There is plenty of raw material. The world throws out more than 10 million tons of coffee waste each year. The team believes the method could work on other wet organic waste too, including food scraps, sewage sludge and agricultural residues, which would close a loop between waste disposal and power generation.
Energy demand is climbing, and the artificial intelligence boom is a big part of it. A June Business Insider report found that if all data centers permitted through 2025 come online, they will use between 224.3 terawatt-hours and 358.8 terawatt-hours of electricity annually, an increase of 50% over the previous year across the range. OilPrice.com, which reported the KIGAM work, noted that this is about what Mexico uses in a year.
Its verdict was measured: the biochar discovery is no silver bullet, though it could be one piece of a more varied energy supply.
