Use of monoethanolamine (MEA) for CO 2 capture in a global scenario: Consequences and alternatives

Recent research on CO2 capture is focusing on the optimization of CO2 absorption using amines (mainly monoethanolamine—MEA) in order to minimize the energy consumption of this very energy-intensive process and improve the absorption efficiency. Process optimization is always required and this research is worth and necessary. However, the main concern arises when thinking of the overall process: solvent production, solvent use and regeneration, and environmental effects related to its use/emissions. The production of MEA from ammonia involves important CO2 emissions during the Haber–Bosch process. The regeneration of the solvent after the absorption is also an indirect source of CO2 related to the use of fuels (i.e., combustion processes for energy supply). Thus, the evaluation of the overall balance of CO2 emitted and captured is essential to determine the efficiency of the process. In addition, other environmental impacts associated to the toxicity and environmental fate of the solvent have to be considered. The use of MEA and other amines in CO2 capture is a point of concern and a global application does not seem to be the best strategy. This review aims at giving an overview of the main implications of using MEA as absorption solvent for CO2 capture together with the last advances in research to improve the conventional absorption process. Furthermore, alternatives of using other solvents and/or using other technology and their advantages and weak points will be briefly provided. An approach oriented to produce CO2-based products with economic value that can be re-integrated in a closed carbon loop, reducing the use of fresh materials and decreasing the production cost, should be the final objective of current research on CO2 capture.