You can actually make biodiesel from butter. It’s about 80–82% fat, so first you clarify it to remove the water and milk solids, then react the fat with methanol and a catalyst like sodium hydroxide. That gives you fatty acid methyl esters (biodiesel) and glycerol as a byproduct.

In theory, a kilo of butter could yield around 0.9 litres of biodiesel. The main problem, apart from the ridiculous cost, is that butterfat has a lot of saturated fatty acids, so the resulting fuel has pretty terrible cold-weather properties.

Of course in this case i suspect it was probably not quite pure.