Probably more like trace amounts of heavy metals and other things like benzene or residue from other substances from the vessels. Stuff that would be awful to c

Probably more like trace amounts of heavy metals and other things like benzene or residue from other substances from the vessels. Stuff that would be awful to consume but likely won't make much of a difference in fuel. Like with anything else, the price will increase for how ever pure you need the substance to be. Using alcohol as a solvent doesn't require much purity, any other alcohols in the mix will still do the job. If you want to be able to drink it, then the alcohol needs to be as pure as possible.