Can you eat charred wood

If by "you" you mean termites, i would say it depends on the thickness of the charring.

I have seen termites eat through timber that has been charred using a blowtorch and then coated with tar.

They ate through both layers to get to the wood underneath. I feel thicker charring would be effective once it has been impregnated with a substance that is toxic to them.

Simply charring by itself does not appear effective.