Evaluating negative emission technologies in a circular carbon economy: A holistic evaluation of direct air capture, bioenergy carbon capture and storage and biochar

The current study aims to develop an intelligent system incorporating various mitigation technologies. In this investigation, three technologies; Direct Air Capture (DAC), Bioenergy with Carbon Capture and Storage (BECCS), and Biochar production from pyrolysis are evaluated for their capacity to mitigate one million tonnes of CO₂. Process models are developed for each method, followed by techno-economic analyses and optimization to derive the most effective solution. The holistic approach considers objectives such as net energy gain, minimized water usage, and product sales. The results highlight BECCS as the most promising in terms of net energy gain, offering approximately 18.08 GJ, closely followed by Biochar, which offers about 15.08 GJ per 1 tonne of captured CO₂. Biochar stands out for its lower water consumption of 2.3 m³ compared to BECCS water consumption of 3.03 m³, while DAC exhibits higher water usage and demands extensive energy consumption of 11.95 GJ per 1 tonne of captured CO₂. Economic analysis reflects these scenarios, with Biochar, BECCS, and DAC presenting product sales of $756 million, $233 million, and $60 million, respectively. The optimization process revealed about 22 potential solutions based on energy, waste usage, and sales nexus. It suggests a system comprising 53% Biochar and 47% BECCS, considering the highest net energy gain, minimizedwater usage and cost and elevated technology maturity.