Wet Coffee Grounds Converted to High-Grade Biofuel in 90 Seconds

Researchers at the Korea Institute of Geoscience and Mineral Resources (KIGAM) have developed a novel technology that rapidly converts wet spent coffee grounds into high-grade biochar. This process, named Flame Plasma Pyrolysis (FPP), bypasses the need for energy-intensive drying or oil removal, directly treating biomass with approximately 55% moisture under atmospheric-pressure plasma conditions.

Operating at temperatures between 800–900°C, the FPP system utilizes plasma flames generated from liquefied petroleum gas and compressed air. The intense heat rapidly vaporizes internal moisture, causing a 'popcorn effect' that enhances carbonization and creates a porous structure. The moisture itself acts as a steam-activation agent, accelerating reactions and improving the final product quality.

Under optimized conditions, the conversion process is completed in just 90 seconds, achieving an 83.3% mass reduction. The resulting biochar boasts a heating value of 29.0 MJ/kg, which is approximately 33% higher than the original coffee grounds and comparable to anthracite coal. This makes the biochar suitable as a renewable solid fuel and as a valuable carbon material for various industrial and environmental applications.

The FPP process significantly outperforms existing methods in terms of speed and energy efficiency. It is 40 to 240 times faster than hydrothermal carbonization and more than 20 times faster than torrefaction. Furthermore, by relying on combustion-generated plasma rather than electricity-intensive devices, the process lowers overall energy consumption. The ability to process wet feedstocks directly is highlighted as a major economic and environmental advantage, with potential applications for other high-moisture organic wastes like food waste, sewage sludge, and agricultural residues.