Environmental, economic, and social trade-offs in biochar and biosurfactant-based soil remediation: A critical review based on mass flow analysis

Biochar and biosurfactants are emerging bio-based materials for remediating contaminated soils. While their pollutant removal mechanisms are well studied, broader environmental, economic, and social implications remain underexplored. Existing studies often rely on a 1 kg functional unit, limiting direct comparisons. This critical review evaluates and quantifies the multidimensional sustainability trade-offs of using biochar and biosurfactants to remediate one hectare of contaminated land, based on real-world applications. Use of common functional unit (1 hectare of land treatment) enables direct, meaningful comparison. Material flow analysis reveals biochar's superior energy efficiency (net output for the grid similar to 290 GJ/ha) and economic returns, despite higher production emissions (100 kg CH4, 55 kg N2O, 38 kg PM10, and 1.7 kg PAHs/ha). In contrast, biosurfactants emit negligible direct pollutants but demand significantly more energy (2340 GJ/ha). Both materials offer social benefits, such as enhanced rural livelihoods and health, yet face challenges like land use conflicts and patent barriers. Policy measures are proposed to mitigate these issues. Finally, the synergistic use of biochar and biosurfactants is highlighted as a promising avenue for future research in sustainable soil remediation.