There are a number of commercial schemes for carbon capture. Most seem to involve sequestering carbon dioxide (CO2) by either using the CO2 for some other purpose or storing it somewhere like disused oil and gas wells. Quite apart from the unanswered questions about whether that CO2 is actually locked away for the long term, there is a question of basic chemistry; Carbon dioxide is a gas that traps two oxygen atoms for every one carbon. In other words they are sequestering oxygen at twice the rate of carbon.
Fewer trees and other plant life mean less oxygen is being freed up for animals and humans to breath. What we need is a way of separating carbon from oxygen such that the carbon is in form that can be stored without danger of it re-uniting with oxygen and returning to the atmosphere.
All the CO2 and methane pumped into the air by human activity means all that oxygen is unavailable to animals and humans. It is burning or breakdown of hydrocarbons that is causing the issues of climate change we face today.
An alternative to burning hydrocarbon based fuels until they are reduced to ash is to use pyrolysis. Pyrolysis separates the volatile fraction of hydrocarbon based fuels in the absence of oxygen, leaving the carbon and a small amount of minerals (ash) locked up in a form that is stable at room temperature. By its very nature, cooking hydrocarbons to split carbon from hydrogen takes quite a bit of energy. To break wood and plant material down into carbon in the form of charcoal and drive off the volatile elements requires the material to be cooked at 300 to 600 degrees Celsius until all the volatiles have been driven off. While it would be possible to use alternative heat sources to achieve pyrolysis, the most practical solution is to use the volatile elements driven off the material to power the heating of the pyrolysis oven. The gasses given off by pyrolysis are mainly hydrogen, carbon monoxide, water and carbon dioxide. Burning the gasses in this way does produce water and carbon dioxide but critically, between 25% and 50% of the carbon is left intact as charcoal.
Thanks to pyrolysis we now have, perhaps, half the carbon from our feedstock in a form that does not bind to oxygen at normal temperatures. Yes, you can set fire to it to cook your burgers or make gunpowder for fireworks out of it but this would create CO2 and defeat the whole point of the exercise. So what can we do with the charcoal to protect it from being used as a fuel? Burying it in landfill simply risks someone mining it like coal in the future.
We need to examine the properties of charcoal to realise the potential benefits of having a supply of it as a commodity.
Charcoal is used in a number of products such as water purifiers. Since carbon is an anionic substance, many chemicals will bind tightly to the surface, which is why it is good at filtering out pollution. The large internal surface area also means that it can hold a lot of chemicals and water. Hydrophilic properties of the internal surface area mean that molecules are bonded closer to the surface than they would be to each other when free standing This means the amount of water held in the carbon is greater for a given volume than free standing water.