CNET green car buying guide
Find the green car that is just right
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Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Should you buy green?
Investing in alternative fuel vehicles is not a no-brainer. The decision to buy a green car remains largely an ecological and political one, although there are some tangible advantages to do so.
The current popular and simplified reason to buy a car that emits less pollution is to prevent global climate change. However, efforts to clean up automotive emissions started as an attempt to address public health concerns by reducing smog. Gasoline-burning internal combustion engines release hydrocarbons, nitrogen oxide, carbon monoxide, and carbon dioxide into the atmosphere. Hydrocarbons and nitrogen oxide contributes to smog, while carbon monoxide is a poison in its own right. Most current automotive emissions controls are aimed at curbing these pollutants
Nitrogen oxide and carbon dioxide, specifically, contribute to global climate change. Currently, there are no laws limiting carbon dioxide emissions from cars, although California is attempting to implement regulations. For every gallon of gasoline burned, 19.6 pounds of carbon dioxide enter the atmosphere. Absent vehicle pollution controls, consumer choices are Americans' only tool for decreasing these automobile-generated carbon dioxide emissions.
For some, green cars offer another tangible benefit: lower costs at the pump. Because there is a direct relationship between fuel economy and carbon dioxide emissions, a car that produces less carbon dioxide will cost less to fill up, but the savings may not pan out over the lifetime of the car. Depending on the premium you pay for the green powertrain, you'll likely have to own your alternative fuel vehicle for many years to realize a cost saving. Depending on the cost of fuel, you may never see a fiscal advantage.
In this guide, we cover the current car options for people who want to reduce greenhouse gas and smog emissions. We also point out some future car technologies that may become viable in the next few years.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Hybrids
Hybrid cars have proven a popular green alternative. These cars have a battery pack that gets charged from excess engine energy and braking, and an electric powertrain alongside a traditional gas engine. When the car needs extra power, the electric powertrain draws on the batteries to help turn the wheels. Hybrid cars generally get better mileage, produce lower amounts of the regulated emissions than their gasoline counterparts, and are especially economical in traffic.
There are two main varieties of hybrids on the roads today, full hybrids and mild hybrids. A third type, plug-in hybrids, have generated interest, but are not in mass production.
Full hybrids
The most successful example of a car that uses a full hybrid powertrain is the Toyota Prius. Full hybrids use one to three electric motors that drive the car under full electric power. Typically, full hybrids run under electric power at low speeds, up to 25 mph. The electric motors also contribute power when the car accelerates, assisting the gas engine. A particular virtue of full hybrids in urban areas is that the engine shuts down when the car is stopped or creeping slowly in traffic, reducing all emissions to zero. The engine comes back on when the battery reserves run low or the driver requires more speed or acceleration. There is a wide array of full hybrid cars available today, from sedans to SUVs. Because of the extra equipment, especially the batteries, hybrids tend to cost more than their gas-only equivalents. On the plus side, many states let hybrids use car pool lanes no matter how many occupants are in the car. Here are two examples of full hybrids:
Mild hybrids
Honda pioneered the mild hybrid, and there are more recent examples from GM. Mild hybrid systems are less robust than full hybrid systems, differentiated by the fact that they don't run in an electric-only mode. They usually integrate one small electric motor with the gasoline powertrain. As in a full hybrid, regenerative braking charges the batteries. Mild hybrid systems can also shut down the engine when the car is stopped at a light or in traffic, but won't drive the car under electric power in slow traffic. Emissions will only drop to zero when the engine is stopped. Mild hybrids cost less than full hybrids, but don't deliver nearly the fuel savings and emissions reduction. Here are two examples of mild hybrids:
Plug-in hybrids
Tinkerers have found that recharging a full hybrid's batteries by plugging it in can yield 100 mpg. To convert a full hybrid into a plug-in, the car has to be modified, usually by changing the batteries from nickel metal hydride, used in current production full hybrids, to lithium ion, a battery type that better handles deep discharging. The power control software might also be modified to let the car run at higher speeds under electric power and, of course, a plug needs to be added. Plug-in hybrids offer all the benefits of a full hybrid, and they can keep the gas engine off for longer periods, ultimately releasing fewer greenhouse gases and other pollutants.Of course, the electricity from the grid used to recharge the batteries might come from power plants that produce greenhouse gases. However, advocates point out that, if the car is recharged overnight, there is surplus electricity available because of low demand. Also, power plants, because they are a large, single source, can be made more efficient and less polluting than thousands of cars on the road.
As there are currently no production plug-in hybrids, the only option is to buy a previously converted hybrid, or buy a hybrid and pay for the conversion. CalCars has a page on plug-in hybrids that lists some of the companies doing conversions and the costs, which range from $6,000 to $24,000. Major automakers, including Toyota and GM, have expressed interest in developing plug-in hybrids, but no prototypes have yet been shown.
For more information on plug-in hybrids, watch CNET's Green Mile: Plug in your hybrid.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
PZEVs and SULEVs
Partial Zero Emissions Vehicle and Super Low Emissions Vehicle are emissions ratings from the California Air Resources Board, which has strict regulations on vehicle emissions, classifying cars in a system that ranges from Low Emission Vehicle to Zero Emission Vehicle. Several states, including New York, Massachusetts, Connecticut, Vermont, Rhode Island, Maine, and New Jersey use the CARB emissions classifications, accounting for a large portion of cars sold in the United States. (Florida is in the process of implementing the CARB rules.)
Some hybrids qualify as Advanced Technology Partial Zero Emissions Vehicles because of their very low emissions and electric powertrains under CARB rules, but plenty of standard gas engine cars with similarly low emissions levels qualify as PZEVs and SULEVs. PZEV, SULEV, and AT-PZEV classified cars release only one pound of hydrocarbons into the atmosphere over 100,000 miles of driving. AT-PVEVs and PZEVs restrict pollution even more by emitting zero evaporative emissions. PZEV and SULEV-rated cars are almost as clean as hybrid AT-PZEVs, and usually less expensive.
While SULEV and PZEV cars limit the kinds of pollutants that lead to smog and all of its attendant health problems, they don't restrict carbon dioxide, a greenhouse gas. As carbon dioxide production relates directly to the amount of gas burned, higher mileage cars, such as hybrids, release less carbon dioxide. Also, cars that earn a SULEV or PZEV rating may be sold with different emissions systems in non-CARB states. The non-CARB versions will only meet Federal requirements, which aren't nearly as strict.
Volkswagen Jetta
Ford Focus
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Flexible fuel vehicles
GM markets many of its cars as flexible fuel vehicles, meaning they can run on a fuel mixture up to 85 percent ethanol and just 15 percent gasoline, referred to as E85. Ethanol is an alcohol commonly produced from corn in the United States and sugar cane in other parts of the world. Ethanol is also widely used as an additive to gasoline. E10 is a mix of 90 percent gasoline and 10 percent ethanol, while E100 is 100 percent ethanol. Most cars can run on E10, and many state governments have mandated its use, as the 10 percent ethanol works as an oxygenate, helping the fuel burn more completely and causing fewer emissions.
GM has 11 2008 models that can run on E85.
Burning ethanol as a fuel reduces carbon dioxide emissions by 21 percent over gasoline and releases no particulate matter. However, burning ethanol creates more ozone, leading to smog and potentially more respiratory health problems. Studies on ethanol emissions are ongoing. Ethanol also has less energy density than gasoline, so a car running on E85 gets worse mileage than the same car running on E10.
Another downside to ethanol is that, because the fuel is made from corn and other food crops, heavy demand for ethanol drives up food prices. Because global food prices are rising, the trade-off is problematic. Current research into cellulosic ethanol made of grasses or even trash seems poised to help ease this controversy.
In the United States, Ford, GM, Chrysler, Mercedes-Benz, Mazda, and Nissan sell cars that can run on ethanol mixes up to E85. The National Ethanol Vehicle Coalition hosts a map on its Web site showing the locations of E85 stations around the country.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Natural gas vehicles
Natural gas is commonly used in the United States to heat homes and water, and fuel ovens and stoves. It can also fuel internal combustion engines, usually as compressed natural gas. Vehicles using CNG produce 15 percent to 20 percent less carbon dioxide than gasoline cars, although they release a lesser amount of methane, another greenhouse gas. Of the regulated emissions, CNG cars produce substantially less carbon monoxide and nitrogen oxide than similar gasoline cars. The California Air Resource Board classifies the Honda's Civic GX as an Advanced Technology Partial Zero Emissions Vehicle, which means it has extraordinarily low smog-causing emissions.
One reason for CNG's reduced carbon dioxide output over gasoline is that it has the highest ratio of energy over carbon content of any fossil fuel. On the downside, because it's a gas, CNG requires more space for a quantity equivalent to a gallon of gasoline, resulting in larger tanks. Natural gas is currently cheaper than gasoline, and mostly produced domestically, but finding a filling station can be difficult. Honda showed off a home filling station, which taps natural gas lines that are part of public utilities infrastructure, at recent auto shows. Other natural gas filling stations appropriate for vehicles can be found on the Department of Energy's Alternative Fuel Locator Web site.
Because of the few natural gas refilling stations, most natural gas vehicles are in fleets, both private and government. Few car companies make a production model for the United States market, so most are conversions. To get a CNG-powered car, buyers can either get the Honda Civic GX or look for a used car from a fleet.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Electric cars
Of the various green car choices, electric cars are the greenest. They produce no emissions, neither smog producing gases nor greenhouse gases, and qualify as Zero Emissions Vehicles. However, unless the electricity used to charge up the car's batteries comes from a clean source, such as water, wind, or solar, a power plant somewhere created emissions associated with running the car. However, it's easier to monitor and control one power plant's emissions than those of thousands of gas-powered cars on the road.
The major drawback of current electric cars is that they don't offer the performance of gas-powered cars, most notably in range. Current production and research electric cars can travel from 40 miles to 100 miles. Proponents argue that the average commute is less than 20 miles each way, making electric cars work well as everyday vehicles.
No major automaker currently sells a production electric car, although Subaru and Mitsubishi have announced research projects into small, urban-oriented cars. Some notable small manufacturers, such as Tesla, Phoenix, and ZENN offer electric vehicles.
Neighborhood electric vehicles fill one electric car niche left by the major automakers. NEVs are basically golf carts approved for use on roads with a speed limit of 35 mph. GEM produces a large number of these types of vehicles.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Series hybrids and fuel cells
GM made big news when it showed off the Chevrolet Volt concept car at the 2007 Detroit auto show. The Volt is an electric car with an onboard electricity generator designed to improve its driving range, otherwise known as a range extender vehicle. Ford has also developed an REV platform called Hy-Series, and has shown it off in concepts at auto shows. REVs have a full electric powertrain, with one or more electric motors driving the wheels and drawing power from a battery. An onboard generator, such as a small gas engine or a hydrogen fuel cell, generates electricity to recharge the battery as needed. REVs are also designed with plug-in capability to minimize the use of the onboard generator, thereby reducing emissions.
REVs are sometimes called series hybrids, as the various power sources run in a line from the electric motor to the range extending device. Current hybrids on the road today are referred to as parallel hybrids, as both the electric motor and gas engine can send power to the wheels. Public interest in the Volt led GM to promise a production model sometime about 2010.
Fuel cell vehicles are another form of the electric car. Because standard electric cars have such short range, carmakers have researched using fuel cells to generate extra electricity from hydrogen. Fuel cells draw electricity from the reaction when hydrogen combines with oxygen to form water, making water the only emission from a fuel cell vehicle. Almost every major automaker has a fuel cell research program, which has led to good gasoline-equivalent performance from the prototypes, with ranges in excess of 300 miles.
But the hydrogen car is also imperfect. Although hydrogen is one of the most abundant elements, it's generally not found in pure form and it takes energy to separate it from other elements to which it has bonded. Currently, generating pure hydrogen uses more energy than that contained in the hydrogen, although there is a benefit to having a transportable fuel. Research into more efficient ways of generating hydrogen is ongoing. There is also very little hydrogen infrastructure, as filling stations exist in only a few locations to support research vehicles.
Most automakers have put working fuel cell vehicles in the hands of various government or scholarly bodies so they can get some real-world testing. Both GM and Honda have gone even further, putting their fuel cell cars in the hands of consumers. GM has placed 100 Chevrolet Equinox fuel cell cars with consumers as part of its Project Driveway test, while Honda is leasing its Clarity fuel cell vehicle to a select set of consumers. Both of these programs are confined to specific geographic areas, and the automakers choose the participants.
Find the green car that is just right
Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.
Diesel and bio-diesel
Diesel cars may seem like an odd choice for a green car-buying guide, but the truth is that modern diesels run cleaner than equivalent gas engine cars. Because diesel engines get 20 percent to 30 percent better mileage than gas engines, they produce 20 percent to 30 percent less carbon dioxide, the major automotive emission classified as a greenhouse gas. Diesel engines produce almost no carbon monoxide, but in the past, nitrogen oxide and particulate emissions caused diesel passenger cars to virtually disappear from U.S. roads.
New emissions systems from both German and Asian automakers substantially clean up the worst components of diesel emissions and have lead to the reintroduction of this type of car to the United States. The new generation of diesels use varying methods to clean up nitrogen oxide emissions, letting them pass emissions tests in all states that follow California Air Resources Board regulations. Mercedes-Benz has been particularly aggressive about getting new diesels on the market, while Honda is also poised to offer diesel versions of its cars. Other automakers, such as Volkswagen, BMW, Mitsubishi, and Nissan also have diesel cars they would like to sell in the U.S.
Here are two diesels from Mercedes-Benz:
Biodiesel
Biodiesel is available in blends, going all the way from B5, or five percent biodiesel and 95 percent petroleum diesel, up to B100, or 100 percent biodiesel. No major automaker sells a biodiesel car and most will void the warranty if any blend greater than B5 is used. However, many individuals have used biodiesel blends, and even B100, in standard diesel cars without problems. Biodiesel filling stations can be found on the Department of Energy's Alternative Fuel Locator Web site.
Using biodiesel in a diesel car reduces some emissions significantly. Although carbon dioxide production is the same as with petroleum diesel, proponents point out that this carbon dioxide would be released into the atmosphere anyway. If the organic material used to create biodiesel were allowed to decompose naturally or was used in some other fashion, it would still release carbon dioxide. Carbon dioxide released from organic materials is part of a natural and stable cycle that has been going on for millennia. Burning petroleum diesel, or gasoline, for that matter, releases carbon dioxide that had been trapped, leading to our current problem of global warming.
As for other emissions, biodiesel produces 50 percent fewer hydrocarbons than petroleum diesel, according to EPA certification tests. Nitrogen oxide emissions theoretically go up about 10 percent over petroleum diesel, although those emissions have been shown to clean up considerably when passed through emissions control systems such as a catalytic converter.
See the CNET Insider Secret on using biodiesel for more information.
Straight vegetable oil
Where biodiesel is refined from vegetable oil, some people have converted their cars to run on straight vegetable oil, because it can often be obtained for free, and emissions similar to biodiesel. Like biodiesel, SVO can be used to fuel diesel engine cars. However, because SVO has a tendency to gel, SVO-fueled cars need a separate tank for the SVO, and a preheater to keep it in liquid form. While SVO can often be obtained for free from restaurants that use it for frying foods, it must be filtered to remove any solids before it is put in the tank.
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