That’s the point, we are stores of carbon until the bacteria eats us. Trees are only a store of carbon until there’s a massive wildfire.
Underground geological formations have been proven stores for carbon for millions of years, far more permanent than trees or people.
As for the difference between carbon, hydrocarbons, and carbon dioxide, they’re all really the same when it comes to the CO2 emitted, so that’s where I was going with that. You are of course correct that people and fossil fuels are not yet carbon dioxide.
In your picture you are missing the part where CO2 is the fundamental compound to create life on earth, as it is the source of carbon to “create” all living beings, as well as fuel and oxygen source needed for many of them to live.
Carbon capture is extremely expensive and inefficient, because it is thermodynamically disfavored. In the big picture ineffective, because we need to transform CO2, we don’t need to bury it. The solution is to reduce the amount of excess of CO2 released, and increase the processes that transform CO2
