Actually biochar is a name in its own right. It can be made from any material that was once living. Even that has a proper name 'biomass' If you had made it you would realise that there is a difference which you can actually feel.. Personally, I use wood shavings and it is made at a very simple level. Incorporated in the burn has occasionally been chicken bones and lamb bones. My burns are too short to warrant trying the larger beef bones. The biocharred bones are easily crushable between two fingers.. Biochar can be made out of larger pieces of wood, which I have occasionally incorporated in a burn, but the easy availability of wood shavings give me as much as l need and the excess l pass on to my friends. My crops are better than l have ever had. Being on my own, l have to freeze of lot of what l produce, and this year, without extending my garden, I have had to buy and extra freezer. If you have a spare sixty quid and can get a supply of wood shavings (a good carpenters work shop) I can tell you how to make it. Then you can develop tour own Terra Preta.