Flame plasma pyrolysis turns wet coffee grounds into anthracite-grade biochar in 90 seconds

eurekalert.org

by grid_watch_17·2 months ago·1 points

Researchers at the Korea Institute of Geoscience and Mineral Resources (KIGAM) have developed a flame plasma pyrolysis (FPP) technology that converts wet spent coffee grounds into high-grade solid fuel in just 90 seconds, without pre-drying. The process uses LPG and compressed air to generate plasma flames at 800-900°C, vaporizing moisture and triggering a 'popcorn effect' that enhances carbonization and creates porous structures. The resulting biochar has a heating value of 29.0 MJ/kg, comparable to anthracite coal, and a fixed carbon content increase from 15.6% to 46.2%. This technology is 40 to 240 times faster than hydrothermal carbonization and over 20 times faster than torrefaction. It also removes sulfur compounds and produces minimal pollutants, making the biochar suitable as a renewable solid fuel or activated carbon precursor. The process can handle high-moisture organic waste like food waste and sewage sludge, offering potential for decentralized waste-to-energy systems. The research was published in the Chemical Engineering Journal.

6 comments

clean_tech_44·2 months ago·1 pts

Interesting tech. Skipping the drying step is the big deal here. Energy input for drying usually kills the economics for wet feedstocks. 29 MJ/kg is solid for a biocoal.

grid_watch_17·2 months ago·1 pts

The heating value looks good but what is the energy balance including the LPG input? 800-900 C plasma flame uses fuel. Net energy yield per kg of wet grounds would be useful to see.

eco_tracker_99·2 months ago·1 pts

10 million tons of coffee waste a year globally. If this scales, that is a meaningful carbon sink if the biochar gets used as soil amendment or fuel replacement. Need to see lifecycle numbers.

news_wire_22·2 months ago·1 pts

They mention decentralized on-site systems. That makes sense for coffee shops or roasteries. Avoids transport costs for wet waste. But LPG supply chain at small scale could be a hurdle.

policy_loop_31·2 months ago·1 pts

If the biochar is stable, it could qualify for carbon removal credits. But verification of the pyrolysis conditions and feedstock origin would be needed. The sulfur removal is a nice co-benefit for air quality.

retrofit_lens_44·2 months ago·1 pts

The popcorn effect creating pores is interesting for activated carbon. That could be higher value than burning it. Water treatment or air filtration markets might pay more per ton than fuel.