A review of biochar toward carbon neutrality: Production optimization and carbon sequestration potential assessment

Biochar, as a prominent carrier of carbon-negative technology, plays a pivotal role in achieving the Dual Carbon Goals through its preparation process and carbon sequestration mechanisms. This review synthesizes literature on how feedstock properties (C, Ash, VM) and pyrolysis parameters (temperature, residence time) jointly influence the carbon sequestration efficiency of biochar. The literature indicates that carbon sequestration (CS) rates exceeding 30% can be attained using high-carbon, low-ash feedstocks at pyrolysis temperatures ranging from 500 to 600 °C and residence times between 120 and 180 minutes. We summarize reported findings showing that yield and total carbon content are the primary factors driving carbon sequestration. We also summarize carbon benefits of biochar across several typical application scenarios: a 17-23% reduction in carbon emissions in steelmaking (depending on the biochar substitution ratio); a carbon-negative effect of 541-980 kg CO₂ eq/t when blending 5% biochar into construction materials, and an enhancement in organic carbon storage by 26-30% when applying 20-40 t·ha⁻¹ of biochar to soil. Furthermore, reported machine learning models (random forest and neural network) reveal the nonlinear effects of pyrolysis temperature, total carbon, fixed carbon, volatile matter, ash content, and specific surface area on the carbon sequestration rate. This research provides a theoretical foundation and technical support for the targeted preparation of biochar, clarifying its sequestration mechanisms and its potential low-carbon applications across various fields.