Pyrolysis of Biomass Wastes into Carbon Materials

This study presents the results of the biomass pyrolysis process focusing on biochar production and its potential energetic (as solid fuel) and material (as adsorbent) applications. Three kinds of biomass waste were investigated: wheat straw, spent coffee grounds, and brewery grains. The pyrolysis process was carried out under nitrogen atmosphere at 400 and 500 degrees C (residence time of 20 min). A significant increase in the carbon content was observed in the biochars, e.g., from 45% to 73% (at 400 degrees C) and 77% (at 500 degrees C) for spent coffee grounds. In addition, the structure and morphology were investigated using scanning electron microscopy. Thermal properties were studied using a simultaneous thermal analysis under an oxidising atmosphere. The chemical activation was completed using KOH. The sorption properties of the obtained biochars were tested using chromium ion (Cr3+) adsorption from liquid solution. The specific surface area and average pore diameter of each sample were determined using the BET method. Finally, it was found that selected biochars can be applied as adsorbent or a fuel. In detail, brewery grains-activated carbon had the highest surface area, wheat straw-activated carbon adsorbed the highest amount of Cr3+, and wheat straw chars presented the best combustion properties.

Automated summary

This study investigates the production and potential applications of biochar in the biomass pyrolysis process. Three types of biomass waste, wheat straw, spent coffee grounds, and brewery grains, were studied. The carbon content in the biochars increased significantly, with the highest increase observed in spent coffee grounds. The structure and thermal properties of the biochars were characterized, and their adsorption properties were tested using chromium ion adsorption. It was found that the selected biochars can be applied as adsorbents or fuels, with different materials exhibiting different properties.