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Comparing Green Cars with Those that Inhibit the Environment

written by: •edited by: Sarah Malburg•updated: 2/21/2011

At present the engines in some of our vehicles produce a high percentage of greenhouse gases. This is currently being addressed by the introduction of more energy efficient gas and diesel engines along with more use of alternative fuels. Modern hybrid and electric green cars also reduce emissions.

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    Introduction to Green VS Polluting cars

    Modern cars are becoming more efficient through the use of lighter materials and finely tuned gas and diesel engines which return much better MPG, resulting in less emissions of greenhouse gasses into the atmosphere.

    There has also been a lot of research and development into hybrid and electric cars which has made them more acceptable to the general public.

    However, there are still plenty of fuel guzzlers on our roads such as SUV’s, sports cars and badly maintained cars, which are emitting the harmful gases from their tailpipes.

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    Operation of Gas and Diesel Engines in Conventional Cars

    Gas Engines

    The gas engine works by supplying a combination of gasoline and air into the cylinders, where a spark plug ignites the mixture. This energy is transferred to the drive shafts which drive the wheels.

    To improve this engine's efficiency, modern engines are constructed from light alloys and a computer controls the injection of gasoline along with the minimum air required for combustion whilst monitoring the exhaust gasses.

    Diesel Engines

    These work by injecting diesel into the cylinder in a spray which ignites under a high compression without a spark. Diesel engines already give a higher MPG than an equivalent gas engine due to diesel oil having higher energy content than petroleum.

    Diesel engines can be made more efficient by increasing the engine compression, utilizing a turbo-blower (just a fan operated by the exhaust gases) along with a modern fuel rail system. Once again, the engine is computer controlled and monitored for optimum efficiency.

    Diesel engines produce less CO2 emissions than a gas engine but emit more noxious gases along with particulates; these cause the black smoke clouds evident when following an old diesel car, bus or truck.

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    Operation of Green Cars and Use of Alternative Fuels

    Green Cars

    Electric cars

    These cars are the most promising examples of the replacement of diesel and gas engines in our cars. They produce no emissions from the electric motor which drives the wheels and unlike hybrid cars; the modern electric car such as the Nissan Leaf does not have a gas or diesel engine. It depends solely on the batteries to power the electric motor drive.

    Regenerative braking which retrieves some of the energy used to slow the car down, adds to its overall efficiency. Many cities throughout the world are setting up recharging facilities where these cars can be plugged in while being parked in the street or a carpark.

    Modern electric cars can travel up to 100 miles on a full charge which takes 8 hours. This equates to $1 for 100 miles, even less if off-peak electricity is used at night. If your electricity provider is supplying electricity generated from renewable energy, zero or very low CO2 emissions are achieved.


    These are similar to electric cars, except that they have a small efficient engine for highway use and charging the batteries, the electric motor being used mostly in city traffic. Emission rates are low when using the electric drive, but still significant when using the internal combustion engine. Nonetheless, overall emissions are considerably reduced.

    Smart cars

    These were the forerunners of the hybrid and electric cars, and are still popular, especially for city driving as they are easily maneuvered and parked. Although they do not appeal to everyone, smart cars are very economical and efficient, having a highly tuned small 600cc engine, the diesel engine version returning 85MPG, considerably reducing its emissions into the atmosphere.

    Alternative Fuels

    Compressed Natural Gas (CNG)

    This is becoming more popular as an alternative fuel due to the rising costs of gas and diesel as CNG can cost up to 75% less than gasoline. Only gas-powered cars can run on CNG as it needs the spark to ignite the gas, but produces about 20% less CO2 than a gas engine with an 80% savings on diesel engine noxious gas emission.

    There are CNG supplies at some forecourt pumps, but a new innovation which enables household natural gas to be used in the car is currently under investigation.


    These are produced from plants and algae, so can be considered to be CO2 neutral, although so far they can only supplement diesel and gasoline fuels at around 20% mix ratio, however research into bio-fuels as a substitute for fossil fuels has been promising.

    Hydrogen Fuel Cells

    Fuel cells owe a lot of their technology to NASA as they adopted them for production of power in their spaceships; the Space Shuttle currently using hydrogen fuel cells for electric power and drinking water production.

    Fuel cells are becoming popular means of driving electric cars. Basically, the cell works by passing a mix of hydrogen fuel and oxygen over catalysts causing a chemical reaction. This chemical reaction produces electricity to drive an electric motor, water being the cells only emission into the atmosphere.

    Please read on to see the not so friendly cars...

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    A green car may be described as a car which emits little or zero greenhouse gasses into the atmosphere. It should be efficient in its use of fuels and manufactured from light, strong materials which should come from recycled or bio-materials as much as possible. A majority of Co2 emissions of cars, however, come from those such as SUV's and sports/high performance vehicles. You will learn more about the comparison between green cars and their emissions and how they are more beneficial to the environment.
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    Cars Not Helpful to the Environment

    • Sport Utility Vehicles (SUV)

    SUV’s have been in production from the early 1990’s and have proved popular because of their robustness and height, giving a feeling of safety. They are also roomy, taking a load of kids along with the week's groceries or five passengers in comfort with all their luggage.

    However, they are one of the worst polluters, some returning only 15MPG. On top of this, they pollute the atmosphere, emitting 30% more CO2 and 75% more noxious gases (NOx) than a normal family car, depending on the fuel used. This is due to the large, inefficient engine required to drive the very large, heavy body.

    • High Performance and Sports cars

    High performance and sports cars are built with three things in mind – speed, looks, and acceleration ability; with little consideration for fuel efficiency, emissions into the atmosphere, or comfort.

    They produce the most CO2 emissions of the cars examined in this article, and have a very low MPG.

    However, only the wealthy can afford to buy and run them, so there are not so many about. I really can't speak, as I was a speed fanatic in the sixties having owned various big motorcycle twins such as Triumph Thunderbird and Bonneville.

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    Effect of Car Exhaust Emissions on the Environment

    With the combustion of fossil derived fuels, our cars are responsible for large proportions of the emissions of greenhouse gases and other air pollutants that are so harmful to our environment, along with the production of city smog and low level ozone. This is formed by exhaust emissions of carbon monoxide, unburnt hydrocarbons, noxious gases and particulates in the presence of sunshine, which is why smog is so prevalent in sunny states.

    However, manufacturers still produce cars which are very harmful to the environment such as Sports Utility vehicles (SUV) and sports cars, these being the main culprits in my comparison of green cars and cars which do not help the environment.

    As well as mitigating the emission of CO2 and other harmful gases, manufacturers of green cars are using recycled materials in the construction of their cars.

    Car manufacturers are at last moving towards using 100% recyclable materials, helping the environment by reducing the recycled scrapped car components heading for landfills.

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    This article was written to compare green cars and cars that do not help the environment and hopefully will help folks decide if their next car should be a more eco-friendly one.

    I have included fuel efficient conventional cars, hybrids, electric and alternative fueled cars in the green car category, with Sports Utility Vehicles (SUV’s) and sport cars falling into the category which do not help the environment by emitting large volumes of CO2 and other noxious gases.

    To mitigate these emissions, car manufacturers have made their car engines much more efficient and have introduced alternative fuels such as compressed natural gas and bio-fuels. They have also developed hybrid cars and all electric drive cars which have zero CO2 emissions.

    I have constructed a table in the Image Section showing MPG figures for city and highway driving along with CO2 emissions in grams/kilometers, for the cars surveyed. This clearly shows how green cars help the environment, while gas guzzlers just pollute it.

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    Table showing CO2 emissions and MPG stats, and pictures of green and polluting cars

    TableNissan Leaf ( car( SUV(