Marine biodegradability and ecotoxicity of solvents for CO2-capture of natural gas

In post combustion CO2 capture, the large scale use of solvents could lead to environmental effects through the emission of chemicals. Finding solvents which have low or no negative environmental effect and determining acceptable emission levels is important for implementing the technology globally. In this work 43 compounds including known solvents for CO2-capture such as MEA, AMP and MDEA as well as new possible solvents have been tested with two standardized screening tests for the marine environment: A marine phytoplankton test and a marine biodegradation test. The results show a wide variability, with biodegradability ranging from <1% to 100% (median 30.0% biodegradability), and Skeletonema EC50 ranging from 1.84 to >10,000 mg/l (median 198 mg/l). Most of the compounds tested had low acute toxicity, with only five compounds having EC-50-values below 10 mg/l. However out of the 43 tested compounds, 20 had biodegradability under the recommended value of 20%, and most of the compounds with biodegradability above were natural compounds. Known solvents such as AMP, piperazine and MDEA, were shown to have low biodegradability and preventing release of such compounds will be important to avoid environmental impact. The fate estimation model EPI Suite™ [US EPA, Washington, DC, USA] has also been used to estimate the biodegradation and toxicity of the chemicals and was not found suitable as a screening tool.

► Marine ecotoxicity and biodegradability tested for CO2 capture solvents.
► 43 compounds tested, showing wide variability.
► Most compounds have EC-50 values above 10 mg/l.
► Half of compounds have biodegradability below 20%.
► EPISuite™ not found suitable as a screening tool.