Harnessing phytoremediation capabilities of nonedible energy plants for Cr6+ remediation and green energy perspectives: a review

Hexavalent chromium (Cr⁶⁺) pollution is a significant environmental and health risk. Phytoremediation, using green plants as solar-powered bioreactors, offers a sustainable reclamation method. However, managing the biomass generated post-remediation remains a challenge. To address this, bioenergy crops, known for their high biomass and biofuel potential, are increasingly used in phytoremediation. This research evaluates 13 non-edible bioenergy crops for their Cr⁶⁺ remediation efficacy, mechanisms, and post-remediation biomass management. These crops, including Jatropha curcas, Pongamia pinnata, and Ricinus communis, produce biodiesel from seeds, while others like Salix viminalis and Arundo donax yield bioethanol from biomass. Biodiesel yields from J. curcas, P. pinnata, M. ferrea, R. communis, E. camaldulensis, C. flexuosus, and J. gossypiifolia range from 23.9% to 75%. Bioethanol yields from S. viminalis, A. donax, T. domingensis, T. angustifolia, and T. latifolia vary from 3.19 to 51 g/L. These plants demonstrate significant Cr⁶⁺ uptake and detoxification through phytoremediation mechanisms such as phytoextraction, rhizofiltration, and phytostabilization, offering an eco-friendly alternative to conventional methods. Simultaneously, their biomass serves as feedstock for biodiesel, bioethanol, and bio-oil production, contributing to renewable energy systems. This synergy reduces risks of secondary pollution and aligns with global sustainability goals. The study emphasizes optimizing biomass conversion techniques, managing post-remediation residues, and leveraging genetic engineering to enhance plant efficacy. Future directions include scaling integrated phytoremediation-bioenergy systems and evaluating environmental, economic, and social impacts through life cycle assessments.

Graphical Abstract