Hybrid electric vehicles (HEVs) are praised as being fuel efficient, and good for the environment. Most HEV owners will agree about the gas mileage: On average, HEVs get twice as many miles per gallon as conventional counterparts, data show. But the environmental impact of HEVs is harder to quantify, particularly since they are still relatively new to the automobile market.
One of the major negative effects of automobiles on the environment is smog-producing gases. Smog is particularly evident in large metropolitan areas, where many thousands of cars are concentrated. The gases that make up smog include nitrogen oxides, hydrocarbons, and other volatile organic compounds. Hybrid cars produce fewer gas emissions than conventional cars, but not as much less as you might think. Generally, the larger the car, the greater the difference in emissions between the hybrid and conventional versions. On average, compact hybrid cars produce 10% fewer smog-producing emissions than their conventional counterparts. Hybrid models of mid-size cars, mid-size sport-utility vehicles, and full-size SUVs reduce smog-producing gas emissions by 15%, 19% and 21%, respectively, over their conventional counterparts.
Emissions from Plug-in Hybrids
Plug-in hybrid cars (PHEVs) offer drivers the ability to charge their cars from a 120-volt power source, essentially creating a second fuel source. When fully charged, these cars primarily use their electric motors, with gasoline motors for backup only. The gasoline engine can be used as the primary engine if no electric power is available. These cars can get over 100 miles per gallon, and produce very few tailpipe emissions, the California Cars Initiative notes.
A negative impact of these cars on the environment depends upon the type of power plants that supply the electrical grids where they are charged. California, for instance, derives 80% of its cities' electric power from clean sources, such as hydroelectric plants. Charging PHEVs in California can thus be very good for the environment, since neither the cars nor the power plants produce harmful emissions. However, several states use mostly coal-burning power plants to produce electricity. In these cases, charging PHEVs produces power-plant emissions that can be just as harmful as tailpipe emissions, according to an Ohio State University study.
Nickel-Hydride and Lithium-Ion Batteries
Car batteries have always been a source of concern for environmentalists. Traditional lead-acid car batteries contain high amounts of toxic lead that can seep into the environment, the Hybrid Cars website reports, citing several studies. This can cause serious health problems, such as brain damage, kidney damage and hearing impairment. Hybrid vehicles do not use lead-acid batteries; as of 2010, many use nickel-hydride batteries, with an increasing shift toward lithium ion batteries as hybrid and electric car technology progresses.
A three-month research project conducted by Environmental Defense in 2005 compared the environmental effects related to the mining, manufacture, use, and disposal of the the three main battery types: lead, nickel and lithium. The study concluded that lead batteries are the worst for the environment, followed by nickel-hydride, then lithium-ion. The main threat posed by nickel-hydride batteries is that nickel appears to be a human carcinogen. Luckily, hybrid car manufacturers encourage consumers to return their cars' batteries for recycling, and even offer cash incentives for doing so.