Biofuels is a diverse subject. Based on their usage, they could belong in Food Processing and Preservation; Heating, Ventilation, and Cooling; Transprt, Hauling, and Movement; or here in Home Workshop. Courses exclusively concerned with their use, say Cooking with an Alcohol Stove, will be found in the approprate category. The production of the raw material will be covered in the appropiate Permaculture Husbandry category. Courses in this category are primarily concerned with the processing of biofuels, but other issues like storage may also be addressed.