There are a lot of things wrong with this idea. - Shallow burying the wood would not stop emissions from escaping into the atmosphere. Doing so would deprive

There are a lot of things wrong with this idea. - Shallow burying the wood would not stop emissions from escaping into the atmosphere. Doing so would deprive it of oxygen which would cause the production of methane which is even worse than co2 - Wood is way less dense than coal so even if the idea worked you would only be able to store a fraction of the amount of co2 - Its hard to imagine the sheer scale of collecting all the wood to ship back to the mines. As mentioned wood is much less dense than coal so the effort to ship the wood to coal mines would be much more difficult than shipping the coal out of the mines. Not to mention that the wood would be coming from a much wider area. There are ideas about burning wood to produce electricity, capturing the CO2 exhaust and pumping that deep underground. The concept is called Bio-Energy with Carbon Capture and Storage (BECCS).