This review discusses methods to enhance biochar properties in sewage sludge, indicating its potential for recovery and pollution control.
The uptake of biochar from sewage sludge has developed into a critical avenue for resource reclamation whilst solving waste disposal concerns. However, despite the latter side in environmental palliative, the use of this biochar for remediation, recovery of nutrients, or adsorption of pollutants is often suboptimal due to poor surface area, high percentage of ash and functional group scarcity. Sewage sludge-derived biochar (SSB) has emerged as a promising material for resource recovery, environmental remediation, and sustainable waste management.This review paper scopes out the recent developments in the field of sludge derived biochar and focuses on the advances in hydrothermal carbonization biochar and its modified forms. Pretreatment methods such as hydrothermal carbonization, enzymatic treatment, ultrasonic, and acid/base wash are looked into in order to improve the purity and the characteristics of the feedstock. Post the structural adjustments some of the molecular modification methods are implemented using KOH, ZnCl2 and H3PO4 for chemical activation, doping with Fe/Mn or Mg, and thermal and microwave processes which are aimed at increasing porosity, adsorption and catalytic activity. The review also evaluates the combination of various methods to fabricate multifunctional biochar for applications such as phosphate recycling, heavy metals and carbon absorption and utilization, as well as the application of biochar as catalysts in advanced oxidation processes.
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Tanwar et al. (2025) studied this question.