Why do you want to lock up carbon?
That’s the whole point behind sequestering carbon.
The massive burning of fossil fuels is adding a lot of carbon to the atmosphere and the level of CO2 is going up remarkably fast. You can argue about what that means for the atmosphere and the climate, etc., but you can’t argue that it isn’t happening.
So a bunch of people are trying to figure out how to capture carbon in the exhaust of power plants and such and keep it out of the atmosphere, reducing the rate of increase of concentrations of CO2. This is called sequestering and usually involves pumping it underground beneath a supposedly impermeable rock layer.
My point was that wood materials that are kept from decaying or burning are just as effective a method of sequestering carbon as pumping it underground.