Disclosed is a method of making a combustible fuel which is a hydrocarbon, the method comprising converting a pretreated biomass feedstock which comprises contacting the feedstock with one or more cellulolytic enzymes and utilizing a microorganism which is a fungus or bacterium or yeast to produce the combustible fuel, wherein the converting comprises fermentation with the fungus or bacterium or yeast, wherein the feedstock has been pretreated by irradiating with electron beam radiation at a dose of between 10 Mrad and 150 Mrad； and wherein the biomass feedstock comprises a cellulosic and/or lignocellulosic material.
