Direct Ocean Capture vs. Ocean Alkalinity Enhancement for Scalable Ocean Carbon Dioxide Removal

Jiawen Yu

doi:10.54097/5zh22n06

Authors

Jiawen Yu

DOI:

https://doi.org/10.54097/5zh22n06

Keywords:

Bipolar membrane electrodialysis (BPMED); carbon dioxide removal (CDR); direct ocean capture (DOC); ocean alkalinity enhancement (OAE); ocean-based negative emission technology (ONET).

Abstract

This paper explores various ocean-based negative emission technologies (ONETs) for carbon dioxide removal: direct ocean capture (DOC) using bipolar membrane electrodialysis (BPMED) and hollow fiber membrane contactors (HFMCs); ocean alkalinity enhancement (OAE) using olivine addition and BPMED alkaline stream return. In DOC, BPMED separates seawater into acidified and basified streams to concentrate CO₂, while HFMC removes CO₂ from the acidified stream. For OAE, traditional mineral addition methods using olivine increase seawater alkalinity through natural mineral weathering, while electrochemical BPMED allows controlled alkalinity manipulation. For comparative purposes, key performance vectors, including energy consumption, cost, geographical locality, scalability, and environmental impacts, were evaluated. Results indicate that DOC has more potential in integration with renewable energy, while OAE is fitted for larger-scale deployment. Both technologies present environmental considerations, such as concerns with drastic ocean chemistry changes and possible environmental and social impacts from mineral additions. To advise future research and pilot-scale implementation, DOC and OAE together highlight complementary pathways for ONETs, offering insights into technical feasibility, cost-effectiveness, environmental trade-offs, and potential integration with renewable energy.

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