Interesting bar chart, thank you.
I did my own cost comparison calcs back during Covid and I spent quite a lot of time researching the cost per kWh in the various fuels. Wood was the most difficult to pin down. I can't remember my methodology for the wood but it was based on the price of a cubic metre of kiln-dried oak, including delivery to me and the cost I came up with was 7p per kWh. Solid fuel was 8p per kWh.
Quite a difference from the bar chart above but mine was for the total calorific value of the fuel, not the 'useful' calorific value which strikes me as a matter of opinion!