What is the evidence it is feasible to reverse ocean acidification by adding large quantities of a base (bicarb soda)?

Question

A commenter made the following reflection:

Ocean acidification is different than sea level rise and global warming, however. With ocean acidification, we're making an excursion unlike anything the planet has seen in 300 million years. There's simply no precedent that allows us to say "yeah, it's gonna hurt, but the world has already shown that it can cope with this kind of thing". It hasn't. As far as we know, this level of OA could produce a full trophic collapse -- and that isn't something that even I can't be cavalier about, as it would certainly be a civilisation-limiting (and possibly complex-life-limiting) event. Until we know for certain that the impacts of OA will be less severe than this, we should be doing everything we can to stop and reverse it.

I did High School chemistry. To me it seems that if you have something that is too acidic, then you change the pH by adding a basic (base) solution. (Albeit the reaction may cause some warmth).

But this feels like it is missing something that smarter people than me have spent time thinking through.

My question is: What is the evidence it is feasible to reverse ocean acidification by adding large quantities of a base (bicarb soda)?

Answer 1

Instead of using sodium bicarbonate why not use limestone instead? Limestone is already used on an industrial scale to neutralise acids and acidic solutions. Also, sodium bicarbonate needs to be manufactured, whereas limestone just needs to be dug up. The manufacturing of sodium bicarbonate would unnecessarily use energy and potentially create more carbon dioxide if it were to be used to neutralise the worlds oceans.

Danny Harvey of the University of Toronto has already looked into this. His solution is to deposit 4 Gt/a of limestone into the oceans. To put this in perspective, global coal production in 2013 was nearly double this at 7.823 Gt and it is more than global iron ore production in 2014 of 3.22 Gt.

The mining of so much limestone would be a massive and expensive undertaking. Then there are the added costs of grinding the limestone to $40 \mu m$, as specified by Danny Harvey. Added to this would be the cost of depositing the finely ground limestone to the oceans. Because the limestone could not be expected to be dumped at one coastal location and then disperse globally, this would require a fleet of ships to deposit the limestone all over the oceans.

The other things to consider include:

• Are there sufficient quantities of easily obtainable limestone to do this?
• What would such a use of limestone do to the supply and cost of cement, used for construction, etc.?
• What impact would such a huge annual deposition of limestone have of ocean life forms and biodiversity?

The other thing that Danny Harvey states in his document is that 4 Gt of limestone would need to be deposited in the oceans annually for at least 200 years for "a modest additional benefit".