Hybrid electric vehicles (HEVs) represent the latest in automotive technology, and are among the cleanest cars ever to be offered to consumers. The twin goals of hybrid manufacturers are to reduce greenhouse gas emissions and to increase fuel efficiency. The power source for all hybrid vehicles is a combination of an ultra-efficient internal combustion engine and a high-output electric motor.
Unlike electric vehicles (EVs), HEVs never need to be plugged into an electrical outlet. When needed, the battery that powers the electric motor is charged primarily through the gasoline engine and through regenerative braking. The gasoline engine is turned off when not needed - sitting at a stoplight, braking, or descending a hill. Other technological advancements include utilization of low rolling resistance tires, advanced catalytic converters, low aerodynamic drag, and weight savings. Although the Honda Hybrid Civic and the Toyota Prius are currently the only hybrids available to consumers, all of the leading car manufactures are researching and developing hybrids.
There are over 240 million motor vehicles on the road in the U.S. today, nearly 10 million of which are in public and private fleets (BTS, 2006; CTA, 2006a). Internal combustion engines drive most fleet vehicles and produce detrimental environmental impacts on a local, regional, and global scale. On the local and regional level, nitrogen oxide and sulfur dioxide emissions cause acid rain that causes damage to trees, crops, and water ecosystems. On a global level, motor vehicles are a major source of global warming pollutants. (Information in this section is from www.responsiblepurchasing.org ).
Energy - Over 95 percent of the fuel used by motor vehicles in the U.S. is petroleum-based (CTA, 2006b). As a result, motor vehicles emit close to one-third of our country's total annual carbon dioxide emissions (DOE, 2006). These motor vehicles emit more carbon dioxide than the total national emissions from any country other than China and Russia (EPA, 2006d; Marland, 2006). Carbon dioxide emissions contribute to global climate change, which results in a warmer atmosphere and impacts such as extreme summertime heat, rising sea levels, more intense hurricanes, shifting rainfall patterns, migrating disease vectors such as malaria and West Nile virus, bleaching of coral reefs, and species extinction. These changes are likely to affect agriculture and fisheries, will result in increased prevalence of extreme weather events including floods and droughts, and could lead to the displacement of hundreds of millions of people around the world.
Air Quality - The three most prevalent local air pollutants from vehicles are carbon monoxide, particulate matter, and nitrogen oxides. In addition, vehicles also emit small amounts of volatile organic compounds and sulfur dioxide.
Carbon Monoxide (CO) - is an odorless and colorless gas with high toxicity. Combustion of gasoline in vehicle engines is a primary source of CO in most cities today (ALA, 2000). When CO is inhaled, it enters the blood stream and inhibits the blood's ability to carry oxygen to the body's cells. In extreme cases, CO exposure can quickly cause death. Effects under lower concentrations include fatigue, dizziness, headaches, and nausea as well as long term lung and heart disease. In the last twenty years, CO emissions in the U.S. have dropped by over fifty percent due to vehicle engine improvements such as catalytic converters. Nevertheless, road vehicles are still responsible for nearly half of the CO emissions in the U.S. each year (EPA, 2005).
Particulate Matter (PM) - consists of small particles and liquid droplets that result from fuel combustion and industrial activities (EPA, 2003). Road vehicles are responsible for four percent of particulate emissions in the U.S., over half of which are from heavy-duty diesel vehicles (EPA, 2005). The health impact of PM is related to the size of the particle; with small particles (less than 2.5 micrometers in diameter) having greater health risk since they are able to penetrate deeply into lung tissue and in some cases enter the bloodstream (EPA, 2006a). Immediate effects of PM exposure include shortness of breath, coughing, and wheezing. Dozens of peer-reviewed studies link prolonged PM exposure to human health problems including respiratory disease, heart disease, and birth defects (HEI, 2003). Since 2002, PM emissions from heavy-duty diesel vehicles have declined by over fifty percent thanks to cleaner engines and fuels as well as particulate filters on exhaust pipes. PM emissions from diesel vehicles should decrease even more thanks to new EPA fuel standards. PM emissions from light-duty vehicles have remained constant over the past decade.
Nitrogen Oxides (NOx) - are a highly reactive class of gases that form when nitrogen and oxygen bind together during fuel combustion. Motor vehicles are responsible for over one-third of NOx emissions in the U.S., particularly in metropolitan areas with high population densities (EPA, 2005). Ground level ozone, commonly referred to as "smog," is created when NOx mixes with volatile organic compounds (VOCs) and becomes exposed to intense sunlight. NOx can also produce acid rain and other toxic pollutants in the air and water (EPA, 2006b). Smog reduces lung function in exposed people and leads to long-term damage to the respiratory system. Acid rain can harm exposed people's respiratory system (EPA, 2006c). Thanks to improved engine technologies, improved fuel blends, and advanced catalytic converters, NOx emissions from light duty cars have fallen by over 1/3 during the past decade (EPA, 1994; EPA, 2005). However, light duty gas trucks and heavy-duty diesel vehicles have emitted constant levels of NOx during the same time period (EPA, 2005).
Water - Motor vehicles cause water pollution when detergents used for vehicle cleaning are washed into sewers, engine fluids leak from vehicles or are disposed of carelessly, vehicle residues such as oil, gasoline, and wiper fluids are washed from roadways by rainfall, and air pollutants from vehicles are absorbed into rain. Environmental impacts of water pollution caused by vehicles (and other point and non-point sources) include algae blooms that reduce oxygen supplies in water and lead to fish kills, outbreaks of pathogens and other pests in degraded water, and drinking water supply contamination. In some cases, water bodies become so contaminated with pollutants that they can no longer support life.
The two main benefits of hybrids are increased fuel economy and reduced overall tailpipe emissions. On average, hybrids achieve double the fuel efficiency of the average car (50 mpg for hybrid, 25 mpg for conventional). Because hybrids use less gas per mile than the conventional car, hybrids will increase national security by reducing the U.S. dependence on foreign oil.
Similarly, significant environmental benefits have also been realized through the introduction of hybrids. Because less gas is used per mile, HEV's emit less carbon monoxide (CO), non-methane organic gas (NMOG), nitrogen oxides (NOx), and carbon dioxide (CO 2) than conventional cars. Reduced tailpipe emissions have also been linked to a decrease in the rate of respiratory illnesses, including bronchitis, emphysema, pulmonary fibrosis, and asthma.
By using a more efficient gasoline engine, HEVs can go 7,500 miles or six months in between regular maintenance service. Both the Civic Hybrid and the Prius come with three-year warranties, and all of the hybrid components are covered for eight years.
- Environmental Protection Agency - http://www.epa.gov/fueleconomy/
- Car comparison for Fuel Economy - http://www.fueleconomy.gov/feg/findacar.htm
- Responsible Purchasing Network- www.responsiblepurchasing.org
- Alternative Transportation Website, Commonwealth of Massachusetts Energy and Environmental Affairs - www.mass.gov/eea/energy-utilities-clean-tech/alternative-transportation