Valorization of banana peel as biochar and assessment of its effect in biochar-assisted phytoremediation of cadmium-contaminated soil by using the Taguchi method

In the present study, effects of banana peel biochar on the phytoremediation of Cd-contaminated soil and enzymatic activity of soil were evaluated using the design of experiments (Taguchi’s method). An L9 orthogonal array having nine experimental runs was performed for two factors, i.e., metal and biochar concentrations at their three levels (0, 5, and 20 mg/kg for metals and 0, 100, and 200 mg/kg for biochar). To identify the most significant factor influencing the phytoremediation and soil enzyme activity, the analysis of variance was also performed. The results of this study suggested that for the increase in stem height, root length, urease, and dehydrogenase enzymes, biochar concentration contributed more than metal concentration. On the other hand, chlorophyll content, proline, alkaline phosphatase, Cd uptake, and accumulation in root and shoot were majorly affected by the metal concentration in comparison to biochar concentration. Metal concentration significantly (p < 0.05) contributed to Cd uptake in the shoot (99.31%), Cd uptake in the root (99.24%), Cd accumulation in the shoot (94.66%), and root (88.22%). On the other hand, though the contribution of biochar addition was less than metal, the banana peel biochar augmentation increased the metal uptake in Bidens pilosa. It is concluded that the combined use of banana peel biochar with heavy metal accumulator plants can be a viable option for the increased phytoremediation of heavy metal–contaminated soil. The use of banana peels as biochar in phytoremediation also provides an alternative option for the waste management of banana peels.