So as far as powering Cars and other Vehicles, we have settled on Alcohol as the means of our emergency fuel supply.
Its espcially good if you can find a cheap supply of things to ferment - leavings from a Molasses plant, the leftover mash from a local brew-pub, crop leavings etc.
To do this legally you must apply for a
Federal Permit - there is a lot of information to be had
here Alcohol was was Farmers regularily used before Gasoline. The Model A originally had a level to switch it between the two fuels. It is true that many fermentables (like corn) require more energy to produce than you et out of the Alcohol. However, if you need a liquid fuel to make your car go and don't want to do a Steam engine conversion and burn wood or coal, well, you need to spend the energy to get something you can use. Second, there are many crops where this is not the case. IF advances in enzymes make celluose fermatation viable - this will become an excellent large scale solution, as corn stalks, cattails, grass clipping etc all become viable feed stock. You probably won't be doing that on your own however.
Converting Fuel injected engines is really just a matter of boring out the injectors so the computer thinks it puts in A, but its really putting in AX 1.5 or whatever ratio is needed. A number of people also sell
conversion kits for various vehicles.. most newer vehicles already have Alcohol resistent parts because of the Govt mandated ethanol content of regular gasoline... and some already have E85 as a listed fuel - if yours does, you can run on 100% alcohol.
Solutions run from this full
backyard plant to
moonshine stills - and there are a lot of project examples of "home-brew" (pun intended) solutions. If you really going to do this for a fuel supply you should look into vacuum stills as they require less energy- and you MUST have a readily available fermentation stock. I won't have that at my place ( juniper berries will be my best source) so we have a moonshine still from Milehi distilling and its for emergency use only-- we really have to make a trip and that s the only way to get there.
Bio diesel is a perfectly good option, if you can get the right ingredients, but it requires a larger investment.