Higher efficiency and lower environmental impact of membrane separation for carbon dioxide capture in coal power plants

Global warming may be slowed down by carbon capture and storage systems that allow to sequester carbon dioxide from large fixed point sources such as power plants or industrial facilities that use fossil fuels or biomass as fuel. Nonetheless, these processes often consume a lot of energy and materials, and they emit pollutants. In particular, monoethanolamine regeneration after carbon dioxide absorption is energy-intensive. Alternatively, membrane separation presumably consumes less energy than absorption, yet there is no reported quantitative comparison. Here we compared monoethanolamine absorption and two-stage membrane separation for carbon dioxide separation in a supercritical pulverized coal power plant, using life cycle assessment. We considered 13 midpoint impact categories including global warming, ozone depletion, freshwater eutrophication, marine eutrophication, terrestrial acidification, fossil resource depletion, water resource depletion, metal depletion, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, human toxicity and particulate matter formation. Results show that membrane separation is 5% more efficient and requires 11.6% less energy than monoethanolamine absorption. Membrane separation has also lower environmental impact scores versus monoethanolamine absorption, such as 0.495 versus 0.546 for global warming, 0.219 versus 0.243 for human toxicity and 0.284 versus 0.318 for fossil depletion. Overall, the two-stage membrane separation should induce less damage to ecosystems, human health and resources.