Valorization of biomass waste to engineered activated biochar by microwave pyrolysis: Progress, challenges, and future directions

•Key concepts, mode, operating parameters, and products of current pyrolysis applications are reviewed.•Heat transfer is more efficient in microwave pyrolysis of biomass waste.•Lack of top-tier reactor design blocks the commercialization of microwave pyrolysis.•Microwave pyrolysis produces engineered activated biochar with desirable properties.•Engineered activated biochar has wide application in pollution control, catalysis and energy storage.