Method of making propanol and ethanol from plant material by biological conversion and gasification

A method for producing propanol and ethanol from a material, wherein the material comprises plant material or plant material that has been subject to pretreatment or saccharification, and wherein less than 75% by weight of the carbon-containing compounds in the material are carbohydrate substances, the method comprising:

• i) converting the material into at least a first intermediate and a second intermediate,
• wherein the first intermediate is produced by a biological conversion process and comprises propionic acid, a propionate ester, a propionate salt, acetic acid, an acetate ester, an acetate salt, or a mixture thereof, and
• wherein the second intermediate is produced by gasification and comprises a reductant;
• and
• ii) reacting the reductant and the propionic acid, propionate ester, propionate salt, acetic acid, acetate ester, acetate salt, or a mixture thereof by hydrogenation to produce propanol and ethanol,
• wherein the chemical energy efficiency of the method is greater than the chemical energy efficiency of i) a method in which the material is converted into propanol and ethanol using only a biological conversion process;
• and ii) a method in which all of the material is initially subjected to a thermochemical conversion step as part of the process to produce propanol and ethanol.