> Is the byproduct (not sure if it's purified gas or a solid compound) of any industrial or material use?
No. The byproduct is injected back into the ground to be remineralized, hopefully locked up to prevent its re-release into the atmosphere.
EDIT: If you used the byproduct in another process where it eventually would make its way back into the atmosphere, the process would no longer be carbon negative.
"This month, Climeworks installed a unit that captures carbon dioxide directly from the air and transfers it to CarbFix to inject underground. Because CarbFix has been monitoring the injection sites for the last three years, they can be sure there will be no leakage. And once mineralized, the CO2 will remain trapped for thousands or millions of years. This makes the Climeworks-CarbFix system the world’s first verified “negative emissions” plant."
Limestone (calcium carbonate) is even easy to make. You can make it "at home" by dissolving unslaked lime (calcium oxide) in water and blowing bubbles in it with a straw.
The real problem is that calcium oxide is usually converted from limestone via massive calcining, which releases... CO2.
I have seen some efforts at carbon negative cement; that might be an input that could accept this buuuuuut its most likely not as efficient as shoving the CO2 down into the ground with high speed pumps.
I don’t really understand the article cemenet manufacturing releases CO2 because the limestone (CaCO3) is calcinated and turned into lime (CaO) in the process of making cement.
The article says (2nd half the first half just describes a cemenet that isn’t made with limestone) that they capture the CO2 and make more limestone form it I’m guessing by sequestering it lime so in theory it can be carbon neutral (albeit I don’t know where they get the lime from without breaking limestone) but how does it become carbon negative?
No. The byproduct is injected back into the ground to be remineralized, hopefully locked up to prevent its re-release into the atmosphere.
EDIT: If you used the byproduct in another process where it eventually would make its way back into the atmosphere, the process would no longer be carbon negative.
"This month, Climeworks installed a unit that captures carbon dioxide directly from the air and transfers it to CarbFix to inject underground. Because CarbFix has been monitoring the injection sites for the last three years, they can be sure there will be no leakage. And once mineralized, the CO2 will remain trapped for thousands or millions of years. This makes the Climeworks-CarbFix system the world’s first verified “negative emissions” plant."