Algebraic and Automated Targeting Techniques Based on Marginal Abatement Cost for Carbon Dioxide Removal

Negative emission technologies (NETs) have now become necessary in global decarbonization strategies, particularly, in reaching net-zero emissions. The marginal abatement cost (MAC) curve that graphs decarbonization strategies according to increasing cost-effectiveness has been used in net-zero emissions planning using NETs. However, the net-zero emissions targeting and the calculation of the total system cost are done manually in the graphical approach, which is cumbersome and inaccurate. To address these limitations, this work presents two alternative approaches based on MAC curves in net-zero emissions planning. The first approach is net-zero emissions planning by algebraic targeting (NEPAT). NEPAT involves the use of a cascade table to determine the negative emissions deficit, which is then followed by technology capacity adjustments to reach net-zero emissions. Although NEPAT improves the laboriousness and inaccuracy issues of the graphical technique in calculating the total system cost, targeting and optimization are done repeatedly and manually. To further improve the algebraic approach, the automated marginal abatement cost (AMAC) model is proposed, where mathematical programming is used to automatically target net-zero emissions based on user-defined objective functions and constraints. Both approaches enable the automatic calculation of costs, which is a limitation of the traditional MAC curve. The two approaches are demonstrated in a system of CO₂-emitting sources and NETs. NEPAT has the advantage of increased interactivity with the model, while the AMAC has the advantage of optimization and ease of use. Both techniques contribute to decarbonization planning to reach net-zero emissions.