A new review in the journal Biochar compares two ways to make biochar from waste biomass like crop leftovers and sewage sludge. Conventional pyrolysis heats biomass from the outside in, which takes longer and creates uneven pores. Microwave-assisted pyrolysis heats the material from the inside using electromagnetic radiation, producing biochar with more surface area and better pore structure. The review finds that microwave-made biochar adsorbs heavy metals like lead and cadmium more effectively, and also captures organic pollutants such as pesticides, pharmaceuticals, and PFAS. The process also locks carbon into a stable form, which could help with carbon sequestration. The main question is whether the energy cost of microwave pyrolysis scales well enough for commercial use.
