Capturing or offsetting carbon emissions: techno-economic evaluation of decarbonising industries with CO2-lean flue gas

Abstract

This work investigates the technical feasibility and costs of carbon capture from industrial emission sources with CO₂ concentrations of 0.5–4.0%. Three post-combustion capture schemes are considered: monoethanolamine absorption (MEA-ABS); alkali absorption combined with calcium looping (ALK-ABS); and temperature vacuum swing adsorption (TVSA), the latter two commonly investigated for direct air capture. Capture and avoidance costs are compared across industrial sectors, varying the flow rate and CO₂ concentration of the flue gas, and contrasted with the price of offsetting the emissions through purchases of carbon dioxide removal credits at current voluntary-market prices.

The results show that MEA-ABS has the lowest levelized cost of capture (LCOC) for flue gas streams with larger flow rates (>200 t/h) and CO₂ concentrations ≥1%. TVSA presents the lowest LCOC at lower flow rates (especially <100 t/h), while ALK-ABS has the lowest LCOC only within a small window of low CO₂ concentration (0.5–1%) and 100–200 t/h. Accounting for the carbon footprints of the input energy changes this picture: the carbon avoidance costs (assuming a transport and storage cost of 105 $/tCO₂) reach their lowest values with ALK-ABS, unless heat with a low carbon intensity is available for MEA-ABS. Comparing the cost of carbon avoidance with carbon dioxide removal credits on the voluntary market, it can be more economical for industries with flue gases with CO₂ concentrations <2.6% to offset their emissions through the purchase of such credits than to install any of the post-combustion capture technologies considered here.