Biochar in Sustainable Agriculture: A Comprehensive Review of Soil Health, Crop Productivity and Carbon Sequestration

Abstract

Soil degradation, nutrient depletion and climate change continue to challenge agricultural sustainability and food security. Biochar, a stable, carbon-rich material produced through the thermochemical conversion of biomass under oxygen-limited conditions, has received increasing attention as a soil amendment within sustainable and climate-smart agriculture. This review synthesises published evidence on biochar production technologies, feedstock-dependent properties and the mechanisms through which biochar influences soil health, crop productivity and carbon sequestration. The review indicates that biochar can improve soil physical conditions by reducing bulk density, enhancing aggregation and increasing water-holding capacity, especially in coarse-textured and degraded soils. It also contributes to chemical fertility by improving nutrient retention, moderating soil acidity, influencing phosphorus availability and reducing nutrient losses. In biological terms, biochar provides microhabitats and nutrient-rich surfaces that can support microbial biomass, soil enzyme activity and mycorrhizal associations. These changes may enhance crop performance, particularly where productivity is constrained by acidity, low nutrient retention, drought stress, salinity or contaminant bioavailability. Biochar also contributes to climate change mitigation because its aromatic carbon structure can persist in soils over long periods and because its application may reduce nitrous oxide and methane emissions under suitable soil and management conditions. However, the magnitude and consistency of benefits depend strongly on feedstock type, pyrolysis conditions, soil properties, crop species and management practices. Adoption is further constrained by production costs, logistical requirements, feedstock variability, possible ecotoxicological risks and insufficient standardisation. Long-term field studies, quality-assurance systems and soil-specific biochar products are needed to support safe, effective and economically feasible use in sustainable agriculture.