In the quest for a greener, renewable fuel source to power our cars, a number of alternatives are in use. In this column, I'm offering a quick take on each fuel and an invitation to put forth your arguments for your favorite option. In my last column, I wrote about my belief that hydrogen will be the next step. That column sparked a lot of solid arguments, mostly against hydrogen. In this column, I'm taking a step back, in both macro and temporal terms, to outline a range of fuel sources in use to varying degrees today. I'm still not convinced that hydrogen won't be a common fuel source for cars in the near future, say, within 20 years, but it's useful to look at all the options.
What's your favorite alternative fuel, and why do you think it's the best?
Popular among do-it-yourselfers, biodiesel can be burned in any diesel engine without modification. There is some preparation you can make to the fuel system to ensure problem-free driving, which I talk about in this feature, Get started with biodiesel. Biodiesel is made from vegetable oil that often has already been used in some sort of food preparation, from restaurants to potato chip factories. The vegetable oil is mixed with alcohol and a catalyst, which causes it to break down into glycerine and methyl esters, or biodiesel.
The fuel is renewable and, better yet, usually made from recycled vegetable oil, but it isn't zero emission. Its unburned hydrocarbon emissions are 67 percent less than petroleum diesel, with carbon monoxide and particulate matter both being about 48 percent less than petroleum diesel. Sulfur emissions are nearly zero from biodiesel.
For my two cents, I see biodiesel as having its best success in commercial trucking and industrial applications. Only about 3 percent of new cars sold in 2006 were diesels, although Mercedes-Benz predicted an increase to 10 percent by 2010. That still represents a lot of cars on the road that can't run on biodiesel. However, diesel engines are the standard in commercial trucking, so the conversion and the benefit would be more immediate. And although we certainly fry a lot of our food, I'm not sure we produce enough used vegetable oil to create biodiesel for all of our driving needs.
Straight vegetable oil
Another fuel source for diesel engines, straight vegetable oil (SVO) doesn't undergo the same refinement process as biodiesel. To get a diesel car to run on SVO, you need to install a special fuel system that will preheat the oil before it gets to the cylinders. You can either burn unused, fresh SVO or waste vegetable oil (WVO), which will need to be filtered. Although SVO and biodiesel have many similarities, such as emissions, SVO is easier to get. For biodiesel, you have to find a local supplier, but you can get SVO at any grocery store.
SVO has the same hurdles for widespread usage that biodiesel does. We would need to replace all of our unleaded cars with diesels, and I'm not sure if we have or could make enough of the stuff to replace unleaded gasoline. There is research into different types of plants for vegetable oil production that could increase the available amount. One interesting factoid I found, from the hemp lobby, is that it would only take six percent of U.S. land to grow enough hemp to convert into vegetable oil for all of our driving needs. Six percent doesn't sound like much, but I would rather see what percentage of land suitable for agricultural production would be required. And again, SVO still has a certain amount of emissions, even if they are fewer than with petroleum diesel.
A type of alcohol, ethanol is made by fermenting vegetable matter, such as sugar cane or corn. The sugars from these crops become ethanol and carbon dioxide during the fermentation process. Ethanol's big advantage is that it can be used in a gasoline engine with few modifications. It's also renewable, in the sense that you can grow more of whatever crop it comes from. Brazil serves as an example of an ethanol economy, using the country's large supply of sugar cane to provide cheap fuel for its cars.
Similar to biodiesel and vegetable oil, ethanol is not a zero-emission fuel. But, similar to those other two fuels, its emissions are significantly lower than that of gasoline. Ethanol delivers fewer miles per gallon than gasoline does, so we would either have to get used to shorter-range cars or incorporate bigger tanks. There have been studies that suggest we can't grow enough crops to supply all the ethanol we would need. Other critics point out that ethanol crop production would displace food crop production.
Personally, I see ethanol as a way of extending the gasoline supply, because it can be mixed in, but it's not a long-term solution. I tend to agree with the studies that say we can't produce enough ethanol for our fuel needs, as usable agricultural land is limited and, if it came down to a choice, I'd rather eat than drive.
Current gasoline-fueled cars can be converted to run on natural gas, either in compressed or liquefied form. Natural gas has been used successfully in fleets and shows a lot of advantages. Although not emission-free, it produces far fewer pollutants than gasoline does. Its carbon dioxide emissions are the least of any fossil fuel, and there is significant infrastructure already set up to distribute natural gas. Honda has even developed a system where you could fuel your vehicle from the natural gas lines going into your home.
The big problem with natural gas is that it's a fossil fuel, so it's not renewable (except on a geological time scale). Estimates of how much natural gas is available in the U.S. vary from around 1,000 Tcf to 1,800 Tcf (trillion cubic feet). The U.S. has three percent of the proven natural gas reserves in the world, Eurasia has 42 percent, and the Middle East has 34 percent. One of the main values I look for in an alternative fuel is nonreliance on foreign suppliers, and I don't see that being the case with natural gas. Eventually we'll face the same problems we are facing with gasoline.
Although not really a fuel, I'm including electricity in this roundup because it can serve the same function as all of the above: to turn your car's wheels. Electricity requires the most radically different vehicles from what we commonly drive. Although there are electric vehicles on the road today, they deliver inferior range to the fuels listed above. But there is a lot of research going into developing electric vehicles that will go further, either by getting electricity from fuel cells or from new battery types. Electricity's big advantage over the above fuels is no tailpipe emissions. We also already have a huge electricity distribution infrastructure. Electric motors also have fewer moving parts and are less complex than internal combustion engines, which should reduce maintenance and increase efficiency.
The big question about electricity is where to get it. There are myriad electricity generating sources in use today, some cleaner than others. But this is actually one advantage to electricity; an electric car doesn't depend on how the electricity was generated. It could come from a coal plant, a nuclear plant, or some future breakthrough means with no harmful side effects. You can even generate electricity from any of the fuels listed above.
I think electricity has the greatest chance of being a long-term solution to power our vehicles. It can be generated from renewable sources, and electric vehicles have zero emissions. Although generating it can cause pollution, it's easier to contain the pollution from one big plant as opposed to the pollution from thousands of cars.
There are lots of other alternative fuels under development, but the ones I've covered here represent the most common. Feel free to make a case for your favorite alternative fuel in our forums.