Dryland soils offer untapped potential for long-term carbon sequestration, mainly through sustainable bioenergy systems. This study assessed the role of biochar derived from elephant grass, biomass sorghum, and sweet sorghum in enhancing soil organic carbon (SOC), priming effects in SOC turnover and estimated the area needed to offset regional greenhouse gas emissions under biochar application strategies in two contrasting semi-arid soils in Brazil: a Sodic Gleysol (clay) and a Quartzarenic Neosol (sandy). A modified RothC model integrated with a biochar sub-model and priming effect dynamics simulated SOC over 20 years under four scenarios: 0 %, 25 %, 35 %, and 40 % of crop residues converted to biochar. Results showed that SOC accumulation was greater in clayey soils than in sandy soils following biochar application. Among the bioenergy crops evaluated for their soil carbon sequestration potential, elephant grass, applied either as raw residue or combined with biochar, showed the highest potential for SOC enhancement. Sweet sorghum caused SOC losses under no-biochar scenarios, highlighting its vulnerability to positive priming. Even under high priming (91 %), biochar reduced CO2 losses by up to 21.8 %, confirming its effectiveness in stabilizing SOC. At the regional scale, elephant grass with 40 % biochar reduced the required planted area to offset Rio Grande do Norte's annual (2022) CO2 emissions by 53 % in clay soils and 63 % in sandy soils, highlighting the potential of biochar to enhance land-use efficiency in carbon sequestration strategies. Our findings underscore biochar's potential as a low-cost, scalable negative emissions strategy for semi-arid regions. By combining high-yield biomass crops with optimized biochar rates, land-use efficiency improves while contributing to multiple Sustainable Development Goals (SDGs). Elephant grass combined with moderate biochar application maximizes SOC gains, minimizes land use, and offers a practical pathway for soil-based carbon removal in dryland ecosystems.