Indirect air CO2 capture and refinement based on OTEC seawater outgassing

Paul J T Straatman; Wilfried G J H M van Sark

doi:10.1016/j.isci.2021.102754

Indirect air CO₂ capture and refinement based on OTEC seawater outgassing

iScience. 2021 Jun 19;24(7):102754. doi: 10.1016/j.isci.2021.102754. eCollection 2021 Jul 23.

Authors

Paul J T Straatman¹, Wilfried G J H M van Sark²

Affiliations

¹ Indorama Ventures Europe B.V., Markweg 201, Harbour number 63473198, NB Europoort, the Netherlands.
² Utrecht University, Copernicus Institute of Sustainable Development, Princetonlaan 8a, 3584 CB Utrecht, the Netherlands.

Abstract

In this paper, we propose a low-cost method to capture and purify CO₂ from ocean water indirectly from the atmosphere. Atmospheric CO₂ dissolves in seawater following Henry's law. In open-cycle ocean thermal energy conversion (OC-OTEC), being a heat engine, large quantities of water are used to generate electricity from temperature differences in the ocean. CO₂ and other gases dissolved in seawater are extracted from seawater by a vacuum compressor, being essential for heat transfer in OC-OTEC. Non-condensable gases containing CO₂ from OC-OTEC are currently considered a waste gas stream. Based on literature, we calculate cold water non-condensables containing up to 14% CO₂. These non-condensables can be refined further to 80-90% purity with a water absorption process, inspired by those as used in the biogas industry. Levelized CO₂ capture and purification costs were estimated to be 15-35 euro per ton, as only refinement costs are allocated of a waste gas stream of OC-OTEC.

Keywords: Earth sciences; Energy engineering; Energy resources; Energy sustainability; Engineering.