Posted on: 03/25/10

The question of petrol vs diesel and the environment is often debated. Honda's Graeme Seymour sheds his perspective on the issue.

The debate and media focus on the environment have increased markedly in the 18 months since Al Gore took to the world stage with his movie An Inconvenient Truth. And the UN convention on climate change has ended debate on whether it is or is not happening with an unequivocal statement on man’s effect on the environment.

Honda New Zealand Managing Director Graeme Seymour says: “There are many stories around emissions and these often focus on coal mining and electricity generation, aircraft and motor vehicles. When you understand the principles, it is interesting to see the misinformation being promoted. Recently, a new aircraft was promoted as carrying a passenger for less CO2 [carbon dioxide] output than a new car. They conveniently forgot to say that there were five seats in the car!”

DETAILS YOU NEED TO KNOW
CO2 is seen as the prime greenhouse gas and the main contributor to global warming. The primary environmental focus is, therefore, on CO2 emissions. Mr Seymour says: “This is because we have been digging up coal and oil [key repositories of historic carbon which combines with oxygen to form CO2] since the 1700s and burning it to create CO2. You are welcome to believe whether this makes an impact, or not.” When looking for ways to reduce CO2 outputs in cars, it makes sense to compare fuels such as petrol and diesel.

Burning one litre of petrol creates 2.3kg of CO2 versus 2.7kg for diesel. That’s 17 per cent less CO2 than diesel per litre. On the other hand, diesel engines may travel further on a litre and thus create less CO2 per kilometre if the economy improves by more than 17 per cent. But what about the other emission outputs from burning fuel? In the last issue of Eclipse, you would have seen the sobering photograph of Auckland’s beautiful skyline filled with deadly emissions. Approximately 40 per cent of air pollution in Auckland comes from motor vehicles and is made up of the following:

• Particulates (PM-10)
• Carbon monoxide (CO)
• Carbon dioxide (CO2)
• Nitrogen oxides (NOx)
• Sulphur dioxide
• Ozone
• Benzene
• Toxins including hydrocarbons (HC)
See www.arc.govt.nz/arc/environment/pollution

“In recent times diesel engines have been depicted as clean by holding a white handkerchief to the exhaust pipe of a diesel vehicle,” says Mr Seymour. “But due to the size of these noxious particles, to see them you would need to examine them under a microscope.” Hydrocarbons and nitrogen oxides are largely responsible for the  photochemical smog, which exacerbates asthma, irritates the eyes, nose and throat and causes coughing, chest pains and nausea. The illustration top shows the widespread presence of NOx (shown in red) across Auckland. While you may not live near Auckland’s main motorway corridors, you and your family can still be affected by the haze as it spreads over the region. “What the media has failed to address are particulates, the tiny particles resulting from the imperfect combustion of fuel,” says Mr Seymour. “The larger molecules generally appear as smoke. The particulates of concern are the ones you don’t see and that wouldn’t show up on a white handkerchief.”

Auckland Regional Council (ARC) research tells us that there is a particulate problem in Auckland, and that 47.2 per cent of these emissions come from motor vehicles. Petrol cars account for about two per cent, while diesel cars contribute 36 per cent but only make up 18 per cent of all cars on the road. The ARC says 91 per cent of air pollution costs in Auckland are from diesel vehicles.

DO EMISSION STANDARDS MAKE A DIFFERENCE?
Governments worldwide have been legislating for emissions since California began the process in the 1970s. The prime objective of the original legislation was to reduce smog created by HC and NOx. So if you buy a new car, do you have to worry? Yes and no. The legislated standards are set to reduce emissions and over time the standards tighten.

The current European regime is referred to as Euro 4 but it is different for petrol and diesel engines. The regulation levels for diesel currently allow up to 5.6 times the volume of HC and NOx per kilometre travelled than for petrol engines. Petrol engines are relatively stable, holding their emission level well, while diesel engines move away from their standard over time. The standard for petrol engines is tight for HC and NOx as it has been a focus for some time and is easier to control. The standard for diesel engines is significantly looser as the engine outputs are harder to contain and require complicated secondary systems to do so.

“If consumers of the major vehicle brands shift to diesel then the CO2 output may reduce slightly,” says Mr Seymour. “But our local environment and skies will continue to turn brown and our 100 per cent pure New Zealand image will be lost forever.”

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