Cotton doesn't come to many people's minds as a food product. The main use of cotton in the modern world, after all, is as a fiber for cloth. But the oil from cotton seeds is a light, neutral-flavored vegetable oil that has been used for cooking in America since the 1860s [source: NCPA]. Cottonseed has also been used as animal feed, although using too much of it can lead to nutritional problems with livestock [source: Osborne].
Cottonseed oil's use as a biofuel makes sense: According to some analysts, there's more oil available per acre from cotton than from corn or soy, two of the most popular biofuel sources [source: Journey]. But cottonseed oil does have one drawback that, as with many other biofuels, presents a nagging engineering challenge.
Cottonseed oil begins to solidify in cold temperatures. A vehicle run on pure cottonseed oil would be unusable in winter unless it contained some type of oil-heating system that kept the biofuel above its gel point. More popular biofuels, such as soy biodiesel, encounter this problem, too. But while soy biodiesel gels at about -16 degrees Celsius, cottonseed oil gels at only -1 degree Celsius. Much of the world encounters colder temperatures on a regular basis, making pure cottonseed oil less than optimal for widespread use as a biofuel.