Burning gasoline and diesel in cars is the second-largest cause of U.S. greenhouse gas emissions (after buildings and homes). About 70% of oil is imported, which, in turn, exports hundreds of billions of dollars and adds little value to the U.S. economy. In terms of pollution, cost and supply security, reducing automotive petroleum use is generally good for both the country and the planet. Can biofuels be a major factor in improving supply reliability, reducing pollution and even reducing costs?
As with all energy questions, the first supply source should always be higher efficiency. Reducing the average weight of a car by 20% to 40% by using lighter materials and choosing smaller vehicles would dramatically reduce oil use. A Toyota Camry weighs 3,500 lbs and a Corolla weighs 2,600 lbs. This 900-lb difference provides an 18% gain in fuel efficiency by dropping one vehicle size. In the next couple of vehicle-design cycles, we can expect significantly lower weights as new materials like composites and aluminum substitute for steel and heavier plastics. Even relatively small changes in weight across the U.S. fleet would reduce oil use far more than any current targets likely to come from a switch to using ethanol.
After efficiency, the next step is to look at fuel choice. Nearly all U.S. cars and light trucks use gasoline. The United States recently introduced low-sulfur diesel, already available in Europe for a number of years. Diesel cars use 20% to 30% less fuel. In Europe, just about every model can be purchased with a clean-diesel engine, including small vehicles like the Toyota Yaris, and sporty ones like the BMW 7 series and the Mercedes S Class. Even the humble Ford Focus has three diesel engine choices. In a recent fuel economy race, the diesel Yaris exceeded 70 mpg. A Corolla with a clean-diesel engine has fuel efficiency similar to a Prius. The same car would be 40% more fuel efficient than a gasoline Camry.
More than 60% of new cars sold in Europe are clean diesels. Probably the next logical step for the United States government would be to encourage a switch to clean diesels, because every manufacturer, including Ford and GM, already has them; they simply don’t sell them here.
Biofuels are being proposed as a partial alternative. Ethanol has less energy than gasoline on a volume basis, so more is needed to cover the same distance. In the United States, bio-ethanol is typically mixed at 85% with gasoline, and engines require some redesign to handle the fuel. U.S. bio-ethanol mostly is made from corn, which uses energy for planting, fertilizing, harvesting and refining. Even more energy is needed to transport it for sale. By some estimates, it takes at least 80% more energy to make the ethanol than it provides to drive the car. Thus, the overall environmental gain is very small, the avoided imports negligible, and the costs are high. Also, corn is the base ingredient of a lot of food products, including meat, so the diversion to ethanol pushed up food prices.
Biodiesel, on the other hand, can be refined from many sources, including used cooking oil and even agricultural waste. Oil seeds grow easily on poor land and need little fertilizer. Diesel engines need little alteration to use biodiesel, even at 100%.
Algae are attracting a lot of attention as a source of biofuel. Where large amounts of mid- to low-grade heat are available, it’s possible to grow algae with very high natural oil content that can be refined into a diesel fuel with good calorific value.
As with any biological product, energy is needed to sustain algae growth, so it’s essential to find sources of heat that are cheap, readily available and low in environmental side-effects. Two hold out great promise: sunlight and heat recovered from large-scale electricity generation. Heat recovery is the largest immediately available U.S. energy source, if we can work out how to use it. Growing algae to make biodiesel might be one such use, with the added advantage that the algae need carbon dioxide to thrive, and fossil-based power plants make plenty of it.
The next step up the efficiency ladder will be diesel-electric hybrids. The first ones are expected in the market in 2010 from Peugeot and Volkswagen. These will reach yet another level of efficiency of 60 mpg to 70 mpg in a vehicle about the size of a Corolla. Powered with biodiesel, this will be much less polluting than any other immediately available car technology, at a fairly reasonable cost.
Whether it’s from plants or algae, biodiesel is likely to be more useful than bio-ethanol refined from foodstuffs in terms of being a practical, efficient and environmentally less damaging substitute for fossil oil-based transport fuels.
Peter Garforth is principal of Garforth International LLC, Toledo, Ohio. E-mail him at [email protected].