Work

Alkalinity enhancement with sodium hydroxide in coastal ocean waters

Year: 2025

Type: article

Abstract: Carbon Dioxide Removal (CDR) is increasingly recognised as essential for achieving net zero emissions to limit the impacts of climate change. Ocean Alkalinity Enhancement (OAE) presents a potentially scalable marine CDR (mCDR) technique. Here we report on the first OAE field trial in Australia, conducted at a coastal site in Tasmania using continuous addition of aqueous sodium hydroxide (NaOH). The resulting plume of modified seawater was effectively tracked, and changes in surface carbonate chemistry were quantified using a containerised laboratory. At the point of NaOH release, partial pressure of CO[Formula: see text] (pCO[Formula: see text]) decreased by up to 370 μatm with alkalinity increasing by approximately 545 μmol kg[Formula: see text]. Maximum downstream decreases in pCO[Formula: see text] ranged from 22 to 77 μatm, corresponding to signal strengths of < 1 - 5%. This small-scale field trial confirmed that the dispersion of a plume of modified seawater occurs rapidly and within meters of the site of addition, and that with appropriate tools, these changes can be measured directly in a coastal ocean location. These results suggest that the deployment of shore-based OAE, in combination with local coastal infrastructure and regional models, have potential as an mCDR approach.

Source: Scientific Reports

DOI: 10.1038/s41598-025-31606-w