Biofuel Production from Phytoremediated Biomass via Various Conversion Routes: A Review

Phytoremediation is recognized as a highly cost-effective technique for remediating soils contaminated with heavy metals (HMs). Biomass residues from these remediated plants constitute a significant resource with considerable potential for biofuel conversion. However, the potential of these residues for biofuel production has not been extensively reviewed. This review aims to comprehensively review the recent progress in converting phytoremediated biomass into biofuels via various pathways. Methods for the disposal and biofuel conversion of residual phytoremediated biomass are summarized. The advantages and limitations of the different techniques are discussed and compared. These residues can be converted into gaseous (biogas/methane), liquid (biodiesel, bioethanol, and bio-oil), or solid energy forms (biochar, hydrochar). The conversion methods reviewed include anaerobic digestion, nanomaterial synthesis, incineration, gasification, and pyrolysis. HMs such as copper, cadmium, and zinc significantly influence these processes, enhancing them at lower concentrations but inhibiting them at higher concentrations. However, these conversion routes often involve high costs and complex operational conditions, and are typically limited to laboratory-scale, short-term trials. Therefore, there is an urgent need for multi-objective strategies that consider economic factors, viability, scalability, and environmental sustainability through sustainable pathways. Proper treatment of phytoremediated biomass with energy recovery presents an economically viable and environmentally sustainable solution.