The history of alternative transportation fuels is largely a history of failures. Niche fuels
such as liquefied petroleum gases (LPG) and compressed natural gas (CNG) have persisted here and there over the years, but never captured significant market penetration
for a sustained period. The two exceptions are ethanol in Brazil, made from sugar cane, and ethanol in the US, made from corn. For both these cases, the fuel was heavily
subsidized and protected for decades. They are now commercially successful, though at relatively small volumes, and will remain so as long as oil prices remain high. The real lesson is that success came only after decades of durable policy and subsidies, high oil prices and, in the case of Brazil, a committed automotive industry (first building
dedicated ethanol vehicles and then after their failure following a decade later with flexible fuel vehicles).