In a deep article about the use of butanol for ICE (internal combustion engines) published by Consumer, a magazine created by a chain of Spanish supermarkets, there is an interesting section about the origin of butanol.
Before World War I, several scientists worked on systems with bacteria that could result in industrial applications (hey, there isn't much new under the sun). One of this scientists was Chaim Weizmann (who would later become Israel's first president) who in 1916 used a bacteria called Clostridium actobutylicum to produce acetone, which was then used for the manufacturing of explosives. This process, called Acetobutilic Fermentation (ABE), gave two interesting byproducts: ethanol and butanol.
The process was used in several countries until the 1950s, when new systems to obtain acetone from oil were discovered. It's making a comeback.