Simply put, motion requires energy. Automobiles’ energy generally comes from hydrocarbon-based fuel – for 100+ years mostly energy-rich and reasonably inexpensive gasoline and diesel. But alternative fuels are making headway.
The shift begun in the 1970s has accelerated, driven by: 1) the relatively high cost of gasoline, 2) most oil still comes from overseas, and 3) government regulations mandating higher fuel-economy and lower tailpipe emissions.
Steam and electricity predated petroleum power. Electric cars’ costliness, plus their limited range, led to their early phase-out. Despite steam’s efficiency, Henry Ford adopted the internal combustion engine (ICE) for the Model T. It was much cheaper than steamers, and when an electric starter motor was added, steam’s popularity dropped.
Inefficient gasoline combustion causes annoying and potentially damaging engine knock. Engineers knew early on that controlling knock would allow higher compression, better fuel efficiency and power. Automobile manufacturers found an inexpensive anti-knock agent early in the 1900s: ethyl alcohol (ethanol). But in 1921, a General Motors chemist discovered that tetraethyllead also worked. It was introduced in 1923 and aggressively marketed.
Eventually GM joined Standard Oil of New Jersey to create the Ethyl Gasoline Corp. Promoted for speed and power, lead-added Ethyl gasoline became ubiquitous despite evidence that its lead content was poisonous and lasted in the environment. Ethyl wasn’t banned until the 1970s when catalytic converters, which weren’t compatible with leaded gasoline, were introduced to reduce smog.
The government began requiring oxygenated gasoline in ozone-polluted areas – including Denver – in the early 1990s. The first additive, MTBE, polluted drinking water, and was replaced by ethanol. Cheap and mainly produced from corn, ethanol was popular with powerful U.S. agriculture. Most cars can run on E10 (10% ethanol/90% gasoline). In recent years, Flex Fuel vehicles have been developed that can run on E85. The Environmental Protection Agency has approved an E15 blend for vehicles 2001 and later. Ethanol produces lower emissions, higher octane and can be produced from plant waste. But it’s less fuel-efficienct, increases food prices, and production may actually lead to a net pollution increase.
Diesel – used widely in domestic trucks and in foreign markets – is catching on for automobiles. Refiners were required to remove polluting sulfur so diesel now burns cleanly, offering more torque and 30 percent better efficiency than gas. Renewable biodiesel produced from plant waste is available, although petroleum diesel is much more prevalent. Diesels cost more but generally hold value better and last longer than gas-powered vehicles.
Compressed natural gas (CNG) is cheaper and cleaner than gasoline with comparable power. Many buses and trucks run on CNG but it hasn’t yet caught on for American automotive use. Now the U.S. is a leader in producing natural gas, CNG automobiles may become more available.
Hybrid vehicles with gasoline engines, electric motors and battery packs have surged in America since the Prius was introduced in 2000. Hybrids are more fuel-efficient but also more expensive. Plug-in hybrids can operate for limited distances on stored electricity supplemented with gasoline for longer trips. They take time to recharge and also are more expensive. However, sales figures show that both hybrids and plug-in hybrids are increasingly popular. Most automakers offer at least one model. Diesel hybrids – on the horizon promise even more efficiency.
All-electric vehicles are the next step and a few are now available. They have no tailpipe emissions and cost-per-mile is low. However, drivers have to plan ahead to recharge and there’s still an argument over whether overall they pollute less since much electricity still comes from coal-powered plants.
Hydrogen fuel cell vehicles that emit only water vapor are the new fuel frontier. Several manufacturers promise fuel cell vehicles within the next few years but there is no fueling infrastructure in place and hydrogen fuel production is itself polluting.
There is no perfect solution to the efficiency-emissions-economics equation but huge progress is being made. The range of alternative-fuel options available at your local dealer is greater now than it’s ever been.