From the earliest days of internal-combustion engines, technological visionaries dreamed that engines would run on fuel made from plants. Experiments conducted in the 19th century showed that it was possible, and both Henry Ford and Rudolf Diesel supported the notion. Interest has waxed and waned for decades. These days, it is running high once again, and the fuels have acquired a modern moniker: biofuels.
While the geopolitical and environmental risks of oil dependency may be obvious today, it was not always so. In the early days of motorized transport, fuels derived from plants lost out to fuels refined from crude oil, which could be obtained cheaply in many parts of the world just by poking holes in the ground. Not only were gasoline and diesel the cheapest fuels for many decades, but they are about as energy-dense as liquids can be, which makes them superb choices for carrying vehicles long distances. Replacing them will not be easy, and the struggle to do so has produced some of the most intense controversies of modern society.
In the search for replacements, biofuels have attained the greatest political momentum, in part because they promise lucrative new markets for farm products. In the United States, Congress had adopted extensive mandates and subsidies to get a biofuels industry off the ground, and other countries have also adopted renewable-fuel policies.
But first-generation biofuels — chiefly, ethanol made from corn or sugar cane, or biodiesel made from vegetable oil — have provoked intense backlash. They have been blamed for causing unintended environmental damage and for displacing production of food crops, which may have helped raise world food prices. Amid these attacks, the political momentum of biofuels has slowed in the last couple of years. In principle, biofuels offer a huge advantage over fossil fuels. The source plants absorb carbon dioxide from the air as they are growing, and consequently, the carbon dioxide that is released when biofuels are burned does not represent a net addition of that greenhouse gas to the atmosphere. In practice, some fossil fuels, especially natural gas, are consumed in refining today’s biofuels, one source of controversy about them.
Many scientists believe second-generation biofuels made from plant wastes, or from crops specially grown for the purpose on land not suitable for food production, offer greater promise than the biofuels being produced today. But the technology to make these newer fuels is in its infancy and the claims of its advocates have yet to be proved.