Seafloor alkalinity generation: opportunities and threats

Sebastiaan van de Velde^1,2

¹ Geobiology Research Group, University of Antwerp, Antwerp, Belgium

² Operational Directorate Natural Environment, Royal Belgian Institute of Natural Sciences, Brussels, Belgium

With global carbon emissions continuing to increase, the need for a variety of carbon dioxide removal (CDR) technologies is rapidly rising. One particularly promising ocean-based CDR is ocean alkalinization, where atmospheric CO2 is removed by increasing ocean alkalinity. Currently, the coastal seafloor is a natural source of alkalinity that generates ~20 Teq alkalinity yr-1 globally, equivalent to the uptake of ~730 Tg CO2 yr-1 from the atmosphere. The seafloor essentially functions as a natural biogeochemical reactor and presents many opportunities to enhance ocean alkalinity. In contrast, several economic activities in coastal zones, such as bottom trawl fishing and dredging, can inhibit the natural functioning of the seafloor, thereby limiting natural alkalinity generation.

Here, I will present our ongoing research into coastal ocean alkalinity enhancement using the seafloor as a natural biogeochemical reactor. I will focus on enhanced silicate weathering and carbonate dissolution. Additionally, I will discuss the potential impact of bottom trawl fishing and continuous dredging on the natural seafloor alkalinity source.