Charcoal briquettes into biochar?

I know that BBQ charcoal briquettes aren't good for biochar because they aren't purely carbon. However, could they be put into a retort and have all the other stuff gassified out of them to then BECOME the perfect char for making into true biocha?

I see biochar’s value as utilizing and sequestering excessive ladder fuels from regrowing forests with the majority of trees destined to die young due to competition and forest succession. I would not pay for the material to make it, except for help with labor. Charcoal briquettes will likely lose much of their carbon and turn too much to ash in the process of burning off often toxic chemicals in them to make them viable in the garden or for filtration.

I wouldn't feel safe that 100% of the undesirable stuff would off-gas or burn off in the process.

If I had a bunch of extra briquettes around, I'd probably use them to fuel the retort to char some known clean inputs.

Yeah, too many unknowns. Not worth the hassle in my opinion. Better to start with clean biomass for peace of mind.

I agree with the above. Most areas have places where you can get wood to burn for free, like Chip drop, Facebook marketplace or craig's list.

It doesn't make sense to buy something contaminated when the real stuff is free.

John S
PDX OR

Commercial charcoal is made from coal dust compressed with some filler. I have read some reports of very good success using coal dust as a soil amendment. I have not yet tried it but may this year.

Thanks for all the responses.
I wasn't thinking of spending money to get briquettes to do this with, I was more thinking of if they were available as "unusable" because people had left them out in the weather or something like that.
I have plenty of available wood to make into char, but was hoping that maybe I could turn another (considered unuseable by others) source into usable char.

There are briquettes, pressed together from an unholy mixture that sometimes includes brown coal, starting fluid, sawdust etc. I would use this stuff as an emergency heat source but personally I don't think I would cook food on it. Therefore it wouldn't go in my garden.

Then there is pure lump hardwood charcoal (Kingsford is one I've seen). I *would* cook food on this, so I wouldn't hesitate to make biochar from it. But the cost is a killer! Woody biomass is free and (as noted above) you know exactly what you're getting.

(Edit: Even though I refreshed the page before replying, a lot of posts didn't show before I posted. Good comments all!)