# Why not use sodium hydroxide to reduce carbon dioxide emissions?

The products of the reaction are useful. Renewables like solar power can be used for the electrolysis of brine.

I don't understand why petrochemical companies are not using it as a scrubber?

• What are the products? What are the products useful for? If the products are used, will that use, release the exact same amount of CO2? Please add these details.
– AJN
Jan 22 at 16:28
• Have you considered the energy and CO2 does it take to produce NaOH to begin with? I know you said "Renewables like solar power can be used for the electrolysis of brine." but you have to get that sodium from somewhere and renewables probably can't do that job. Jan 22 at 17:47

This is because the manufacture of NaOH requires energy, and if that energy comes from fossil fuels, then the net gain of the overall process is either zero or less than zero.

Net-positive CO2 sequestration requires finding a natural source of the chemical reactant. One such source is the found in the rock formation called an ophiolite (specifically, the component peridotite), which naturally pulls CO2 out of the air as it weathers and decomposes.

Ophiolite is normally found deep in the earth's crust but there happens to be a very large deposit of it on the surface in the country Oman. It may be possible to mine the peridotite out of it and use that to offset CO2 production from burning fossil fuels.

• I was curious for more details and found this article, if others are interested. nytimes.com/interactive/2018/04/26/climate/oman-rocks.html Jan 22 at 23:42
• Mining & processing the peridotite without emitting CO2 would be critical otherwise your logic for not using NaOH also applies to peridotite. Some things are just not easily achieved :-(.
– Fred
Jan 23 at 2:11
• Best guess currently for making that work is in-situ, where you deeply frack the rock and pipe the co2 down the well. Jan 23 at 2:37

Total worldwide demand for sodium carbonate is about $$0.6\,\mathsf{Tmol}/\,\mathsf{y}$$. Total worldwide carbon dioxide emissions from fossil-fuel burning and cement production are about $$800\,\mathsf{Tmol}/\,\mathsf{y}$$. So either this approach would have a negligible effect on carbon dioxide emissions, or it would leave you with a lot of unwanted sodium carbonate to dispose of.

MEA is the most common scrubber solution the remove CO2, its been used for many decades. Calcium hydroxide is also common, but then there is solid calcium carbonate waste. Long ago, before I retired, there was more sulfur in flue gas so the carbonate was contaminated with calcium sulfate. I am not up to date on current technology but I am sure you can find information looking at "flue gas scrubbing"; it has been used a hundred years for various purposes in various industries. As has been pointed out, it does cost money.