Industrial production of charcoal, while far from being really clean, is still many times cleaner (and much more sustainable) than the traditional method. So remember, get the charcoal for your barbecue from an industrial source!
We will assume that all the wood used for this charcoal making is a by-product of other industries, or materials that would otherwise be discarded anyway (like coconut shells, briquettes of sawdust, etc.) Thus there is no entry for it in the "Uses" section, and a negative entry for "Recycled waste" in the "Produces" section.
The data for this section is taken from this paper. However, while the described twin-retort charcoal production system indeed seems very clean (compared to the traditional charcoal making), the actual numbers appear an too low. If you can help us with research in this section, please contact us!