From Coffee Grounds to Fuel in 90 Seconds: The Trick is Plasma Pyrolysis
From Coffee Grounds to Fuel in 90 Seconds: The Trick is Plasma Pyrolysis
A group from KIGAM, the Korean Institute of Geosciences and Mineral Resources, has developed a process that converts wet exhausted coffee grounds into biochar comparable to anthracite in 90 seconds, entirely skipping the pre-drying phase that burdens competing technologies. The method, named Flame Plasma Pyrolysis (FPP), works directly with biomass that has about 55% moisture without any preliminary treatment, and is described in a study published on June 1, 2026, in the Chemical Engineering Journal by Elsevier.
What makes this approach interesting is the speed combined with the quality of the product. The resultant biochar has a calorific value of 29.0 MJ/kg, about 33% more than the starting coffee grounds (21.8 MJ/kg) and close to that of anthracite. The fixed carbon content nearly triples, rising from 15.6% to 46.2%, while the overall mass decreases by 83.3%.
How It Works: Combustion Plasma and the Popcorn Effect
The system generates plasma flames at about 800-900 °C by burning liquefied petroleum gas (LPG) and compressed air at atmospheric pressure. The plasma is generated from combustion rather than from high-intensity electrical devices, which reduces the overall energy consumption of the treatment.
The carbonization mechanism turns the moisture problem into an ally. The intense heat quickly vaporizes the water trapped in the biomass particles, and the resulting pressure triggers internal micro-explosions, the so-called popcorn effect. These micro-explosions increase the material's porosity and accelerate carbonization. This is measured by the specific surface area, which increases from 1.5 to 115.4 m²/g: a leap that makes the product a possible precursor to activated carbon or adsorbent material, in addition to being a fuel.
Comparison with Alternatives and Environmental Profile
On the timing front, the margin is wide. The FPP is 40 to 240 times faster than hydrothermal carbonization, which takes from one to six hours, and more than 20 times faster than roasting, which requires at least thirty minutes.
The process also completely eliminates sulfur compounds, preventing emissions of sulfur oxides (SOx) during the combustion of the product, and generates minimal amounts of secondary pollutants such as smoke and tar compared to conventional technologies. According to the institute's press release on the FPP technology, its compact design and quick treatment would make it suitable for decentralized waste energy recovery plants directly on site.
The study is primarily authored by Dr. Taejun Park of KIGAM, in collaboration with GodTech Co., Ltd. The technology is, in principle, extendable to other organic waste with high moisture content, from food waste to sewage sludge to agricultural residues. "This technology introduces a new paradigm in which waste is no longer seen as a disposal problem but as a valuable energy resource," said Park. "We intend to extend the technology to various types of high-moisture organic waste and further optimize the process with a view towards industrial scale commercialization." The transition from laboratory scale to industrial scale remains to be demonstrated. The amount of exhausted coffee grounds in the world is over 10 million tons annually.