From feedstock to remediation: biochar’s potential in soil restoration

Abstract

ABSTRACT Biochar has emerged as a promising soil amendment for the remediation of acidified and contaminated soils, owing to its capacity to modify key physical, chemical, and biological soil properties. This review synthesises current knowledge on how feedstock type and pyrolysis temperature determine biochar characteristics and, consequently, its performance in soil remediation. Evidence indicates that biochar can increase soil pH, enhance cation exchange capacity, improve porosity, promote soil organic carbon accumulation, reduce metal mobility, and support crop productivity. However, these responses are highly context-dependent and are strongly influenced by soil properties, biochar characteristics, application rate, and experimental conditions. While high-temperature biochars generally show greater liming capacity, low-temperature biochars may provide advantages related to nutrient availability and cation exchange, depending on the target application. This review also critically discusses situations in which biochar provides limited or no agronomic benefits, compares its performance with conventional amendments for acid soil remediation, and highlights the importance of long-term field validation together with economic and social considerations for large-scale adoption. Overall, biochar should be regarded as a context-specific management strategy rather than a universal solution for soil restoration.