A considerable amount of pollutants released in the world are through vehicles, the two significant pollutants from vehicles being carbon dioxide and carbon monoxide, which are the major greenhouse gases. The European Environment Agency assesses that motor vehicles are accountable for approximately 14% of emissions in the European Union (Reducing CO2 emissions from cars, n.d.). Yet the number of cars in the world are increasing, accelerating the greenhouse effect. The question is how to apply the brakes to stop these emissions or at the least reduce them.
The Vehicle Certificate Agency (VCA) states that ‘for a given type of fuel the carbon dioxide emissions are directly proportional to the quantity of fuel consumed (Cars and Carbon Dioxide, n.d). So car manufacturers have invested large amounts of money into the research of lower fuel consumption and/or alternative fuel sources, particularly with the pressure of governments imposing restrictions on the amount of carbon dioxide emissions from a vehicle such as the Kyote Conference on Climate Change in 1997, followed by various other ‘agreements'.
However, one of the factors that car manufacturers are tackling is that as motor vehicles become more advanced, there are more stringent safety measures put across for vehicles such as airbags, crash tests, thus increasing the overall mass of the vehicles, taking into account additional features, for example power-assisted steering (Cars and Carbon Dioxide, n.d).
Having put an extensive magnitude of research to increase fuel efficiency, modern cars have in this respect improved vastly. In the US the average fuel consumption of cars were 19.6 miles per gallon in 2004 (note that this is US gallons, not UK gallons). Within a few years, the figures are now up in the low 20s (Moto Vehicles and Carbon Emissions - A General Overview, 2008). Consequently, one of ways to reduce carbon emissions is to purchase cars based on their fuel efficiency. This also depends on different fuel types. The Code of Federal Regulations (40 CFR 600.113) states the value for Petrol carbon content per gallon is 2421 grams and for Diesel it is 2778 grams (Emission Facts: Average Carbon Dioxide Emissions Resulting from Gasoline and Diesel Fuel, 2005). At the outset, it would seem for this reason petrol cars are more desirable, however diesel vehicles present a higher miles per gallon when compared to petrol variants, therefore an overall lower carbon dioxide output (Emissions and VED ratings, n.d). Additionally, diesel vehicles produce less carbon monoxide and hydrocarbons than petrol variants, while diesel vehicles produce more NOx and Particles (Cars and Fuel Options, 2009).
Although purchasing fuel efficient diesel cars might be a desirable option, the reduction in carbon emissions is not significant. Switching to alternative fuel sources such as Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG) offers a far more effective carbon emission reduction than both petrol and diesel or at least closer to diesel fuel consumption without the Local pollutants: CO, NOx, HC and Particles. Combined with the government legislations of reduced or exempting Vehicle Excise Duty (Road Tax) to encourage consumers to purchase cars such as these, consumers would be paying less overall, as running costs of the car are reduced (Emissions and VED ratings, n.d).
Hybrid vehicles such as the well known Toyota Prius use an internal combustion engine together with an electric motor and battery. These work in conjunction with each other in various ways for greatest efficiency such as the electric motor supplying power when under high load or accelerating and by transferring lost energy from braking into other useful forms (Cars and Fuels, 2009), for example electrical energy. Hybrid vehicles produce very little carbon dioxide emissions and other local pollutants, therefore is considered more helpful in reducing carbon emissions than petrol or diesel vehicles.
Using biodiesel as a fuel source is also less damaging to the environment because it is obtained from renewable energy sources such as rapeseed, sunflower or soybean. Any fuel consumed is ‘balanced by the absorption from the atmosphere during the fuel crop's growth states greencarsite.co.uk (Alternative Fuel Cars: Biodiesel, n.d). One of practicalities of biodiesel is that it can be used on most existing diesel cars from a blend of between 5 to 30% biodiesel while some newer cars can use 100% biodiesel. Biodiesel helps to lubricate the vehicle itself, decreasing engine wear, so is an added bonus for consumers. However, nothing is without its downfalls. Biodiesel increases the NOx pollutants as well as reducing engine power and causing failures of certain components of vehicles for instance the fuel pump seals (Hess, M. Scott, 2003).