New Process Rapidly Converts Wet Coffee Grounds into Biochar

At a Glance (China Coffee Network): Scientists in South Korea have developed a new process that converts wet coffee grounds directly into high-quality biochar within 90 seconds, skipping drying and de-oiling entirely—a fast, energy-efficient route to turn high-moisture waste into fuel and carbon materials.

Scientists at the Korea Institute of Geoscience and Mineral Resources have developed a new process that converts wet coffee grounds directly into high-quality biochar within 90 seconds, completely eliminating the drying and de-oiling steps. This achievement opens a fast and energy-efficient new pathway for converting high-moisture organic waste into valuable fuel and carbon materials. The related paper was published in the latest issue of the Chemical Engineering Journal.

More than 10 million tonnes of coffee grounds are generated globally each year, most of which end up landfilled or incinerated. Coffee grounds have extremely high water content, and converting them into fuel or carbon products typically requires an energy-intensive pre-drying process, making large-scale resource recovery economically difficult.

To solve this problem, the team developed flame plasma pyrolysis (FPP) technology, which burns liquefied petroleum gas and compressed air to produce a plasma flame at about 800–900°C, capable of directly treating biomass with about 55% moisture content under atmospheric-pressure plasma conditions.

FPP completely eliminates pre-drying. During heating, moisture inside the biomass particles evaporates rapidly, and the resulting pressure buildup triggers micro-scale explosions—the “popcorn effect.” This effect both enhances carbonization and shapes a highly porous structure. Moisture thus becomes not an obstacle but a steam activator, accelerating the reaction and improving product quality.

Under optimized conditions, the team converted wet coffee grounds completely into solid biochar in just 90 seconds. Its calorific value reaches 29 MJ/kg, about 33% higher than the original coffee grounds (21.8 MJ/kg), on par with anthracite. In addition, sulfur compounds are completely removed in the process, eliminating sulfur-oxide emissions during combustion; the specific surface area soars from 1.5 m²/g to 115.4 m²/g, meaning it has great potential in the field of activated-carbon precursors or adsorbent materials. These characteristics make the resulting biochar usable both as a renewable solid fuel and as a high-value carbon material for environmental and industrial applications.