Scientists have demonstrated a new plasma-based process that converts wet coffee waste into high-performance biochar without any pre-drying treatment. The technology could address one of the biggest challenges in biomass recycling while creating a valuable source of renewable fuel.

Developed by researchers at the Korea Institute of Geoscience and Mineral Resources (KIGAM), the system converts moisture-rich coffee grounds into carbon-rich biochar in less than two minutes. The resulting material delivers an energy content comparable to anthracite coal, offering a potential pathway for turning difficult waste streams into useful resources. Researchers believe the technology could help reduce waste disposal costs while expanding opportunities for decentralized waste-to-energy systems.

Moisture becomes an asset

High moisture content has long complicated efforts to recover energy from organic waste. Most biomass conversion technologies require a separate drying stage before processing, increasing costs and energy use.

The KIGAM team designed its Flame Plasma Pyrolysis system to eliminate that requirement. The process uses plasma flames generated through the combustion of liquefied petroleum gas and compressed air. Those flames reach temperatures between approximately 1,470°F and 1,650°F, allowing the system to process wet biomass directly.

Instead of hindering conversion, moisture helps drive the process. As water trapped inside coffee particles rapidly turns into steam, pressure builds and creates microscopic explosions. Researchers describe the phenomenon as a “popcorn effect.” The bursts break apart the biomass structure, increase porosity, and accelerate carbonization. Under optimized conditions, the system achieved complete conversion in just 90 seconds.

Fuel performance rivals coal

The resulting biochar delivered a heating value of 29.0 MJ/kg, roughly 33% higher than untreated coffee grounds. Researchers said the material performs similarly to anthracite coal. The treatment also nearly tripled fixed carbon content, increasing it from 15.6% to 46.2%. At the same time, it completely removed sulfur compounds, helping prevent sulfur dioxide emissions during combustion.

Researchers observed another significant improvement in the material’s structure. Its specific surface area increased dramatically, creating a highly porous carbon product. Those characteristics could make the biochar useful beyond fuel applications. Potential uses include activated carbon production, filtration systems, and industrial adsorption materials. The process also generated minimal smoke and tar compared with conventional biomass treatment methods.

Faster route to resource recovery

Speed is one of the technology’s key advantages. Hydrothermal carbonization systems often require one to six hours to process biomass, while torrefaction can take 30 minutes or longer. Flame Plasma Pyrolysis completes the conversion in less than two minutes. Researchers said the system also reduces energy demand by using combustion-generated plasma rather than electricity-intensive plasma devices.

Although the study focused on spent coffee grounds, the team believes the technology could process other high-moisture waste streams, including food waste, sewage sludge, and agricultural residues. Lead author Dr. Taejun Park said the technology offers a new way to view organic waste. Instead of treating it as a disposal problem, industries could use it as a source of energy and valuable carbon materials. The team plans to expand the process to additional waste types and continue optimizing it for commercial-scale deployment.

The study is published in the journal Chemical Engineering Journal.

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