I learned that there are fireplaces that burn gel fuel and it does not require a chimney because the gel burns clean without toxic emissions. The gel is a bio-fuel: bio-methanol and bio-ethanol. The whole thing is a scam and who has no idea of chemistry might even believe it.
These bio-fuels contain the radicals -CH2-OH or -CH3-OH which through combustion they release oxide or dioxide of carbon. Besides, that bio linked to the radical also contains carbon, hydrogen, oxygen and other elements which through burning process form smoke.
Yet they are called bio-fuels because their provenience is the natural environment. Wood is a bio-fuel. Clothes made of synthetic material are just fuel, for example!