DH spent all last weekend making charcoal. He has been obsessed with it for ages but usually we end up with a pile of ash, This time however we have a huge sack of charcoal. Made in this way charcoal is carbon neutral in that it is made from a sustainable source (trees) rahter than a fossil fuel. However I am assuming that a lot of charcoal is made using dodgy forrestly methods and releasing toxic gases. So best to buy local ethical stuff but it can get very expensive.
The best BBQ I've come across is the cobb BBQ as you get 3 hours cooking time from 7-8 lumps of charcoal. Its quite small though.