Backyard biodiesel

Vegetable oil is often confused with biodiesel because some people manufacture biodiesel at home. And like home winemaking, to make an acceptable product takes care, skill, and some specialized equipment.

To "crack" the cooking-oil triglycerides into an acceptable diesel fuel, the most common home process uses methanol as a solvent and lye as a catalyst. Lye and methanol are both highly toxic, however, and should be used with great care. The main byproduct of the refining process is glycerin, which you can compost or use to make your own soap.

One of the concerns with homemade biodiesel, and indeed with any biodiesel, is that if it can still contain methanol traces. Methanol is a solvent that attacks rubber aggressively, so it can eat its way through any rubber hoses or seals in a car's fuel system. Fortunately, most modern diesels already use nonrubber synthetic fuel-system parts. Otherwise, those parts can be replaced with readily available synthetic materials that are immune to methanol's predations.

The proportions of catalyst and solvent needed to make biodiesel will vary depending on the source of the feedstock used, so the recipe will differ with every batch. The whole process of mixing, pouring, settling, and then separating the liquids and solids produced can take anywhere from a day up to a week. For that reason we conclude that moonshine biodiesel is best left to a dedicated hobbyist with experience and a focus on safety.