A process for the conversion of carbohydrates from any of a number of sources into butanol and hexanol for fuel or chemical use is disclosed. The process includes conducting a homoacetogenic fermentation to produce an acetic acid intermediate which is chemically converted to ethanol. The ethanol and a remaining portion of the acetic acid intermediate are used as a substrate in an acidogenic fermentation to produce butyric and caproic acid intermediates which are then chemically converted to butanol and hexanol.