Environmental fate studies of CO₂ capture solvents toward risk assessment

The main objective of the SOLVfate project is to investigate the environmental fate of possible degradation products from amine-based post-combustion CO₂ capture (PCCC). In the project, a group of nine nitrosamine and nitramine, identified as possible process degradation products of amine mixtures monoethanolamine (MEA) and piperazine, were selected for investigation in a number of environmental fate studies. Due to the risk associated with nitrosamines, very low levels of accepted occurrence in the environment have been established. The studies examined degradation and other processes in the atmosphere, aquatic and terrestrial matrices.

The atmospheric chemistry work establishes a reliable method for determining air and ground concentration levels together with dry and wet deposition of these amine chemicals over time near a PCCC plant, as well as for evaluating environmental and health hazards. In aquatic environments, nitrosamines and nitramines will not undergo hydrolysis, but where sunlight is present, nitrosamines will degrade rapidly by photolysis, while nitramines will be persistent. In the absence of light, microbiological degradation becomes an important process of fate, although it is considerably slower than photodegradation, and depends on the special properties of the individual compounds. Nitrosamines and nitramines will not be easily adsorbed to terrestrial soils, indicating that transport to groundwater or surrounding natural water is likely. Nitramines seem to be more of a concern than nitrosamines due to their greater resistance to environmental degradation processes. Based on their high water solubility, nitrosamines and nitramines are not expected to bioaccumulate in organisms, but will most likely concentrate in aquatic systems.

Acceptable levels of nitrosamines and nitramines in various matrices (eg atmosphere and natural water or drinking water) were identified from available literature. The project sought to establish an “Environmental Impact Factor (EIF)” of nitrosamines and nitramines, but a lack of available emission data prevented this. To perform such detailed risk assessments, emission data must be provided and used in combination with fate data in atmospheric, aquatic and terrestrial model tools. The new knowledge generated in the SOLVfate project has significantly improved our understanding of the environmental fate of amine-based CO₂ capture degradation products. The project was completed in July 2014.

Publications:

Lisbet Sørensen, Eirik Falck da Silva, Odd Gunnar Brakstad, Kolbjørn Zahlsen, Andy Booth, Preliminary Studies into the Environmental Fate of Nitrosamine and Nitramine Compounds in Aquatic Systems, Energy Procedia, Volume 37, 2013, Pages 683-690, ISSN 1876

Sørensen, L., Zahlsen, K., Hyldbakk, A., da Silva, E.F. and Booth, A.M. (2014). Photodegradation in Natural Waters of Nitrosamines and Nitramines Derived from CO Capture Plant Operation. International Journal of Greenhouse Gas Control (submitted).