Emissions 101 / The Basics of Vehicle Emissions

by Carl Duivenvoorden (www.changeyourcorner.com). Carl is one of 22 Atlantic Canadians trained by Al Gore to deliver presentations of 'An Inconvenient Truth.' His column runs every other Monday in the Telegraph Journal.

Not long ago I read an SUV ad that claimed the vehicle produced 80% less emissions than the same model of a few years earlier. Was it a miracle new technology? Or was there more to the claim than met the eye?

It turned out to be a bit of both.

Vehicles produce 2 major types of pollutants: smog forming emissions and greenhouse gas emissions. Unfortunately, the same word - ‘emissions’ - is used to describe one, or the other, or both. But they are very different from each other, both in terms of their effects on the environment and the amount produced by a vehicle.

Smog forming emissions

Smog forming emissions are chemicals with names like carbon monoxide, nitrous oxides, hydrocarbons, ozone and particulate matter. They’re the puff you might see when a warm engine is restarted or when the driver ahead of you tramps on the gas pedal. They’re also the stuff you can see coming out of the tailpipe of a poorly tuned car.

The bad news is that they are the most poisonous part of vehicle exhaust. They are responsible for much of the bronze coloured haze that hangs over large cities on hot summer days, causing air quality problems and health issues.

The good news is that smog forming emissions are a very small part of what comes out of a tailpipe, and they are relatively easy to control with modern technology. Catalytic converters (devices in the exhaust system), better engines and purer fuels mean a 2008 model vehicle produces only a tiny fraction of what the same type of vehicle would have produced in the 1970s. Regular tune-ups and maintenance can keep your car’s smog forming emissions low.

Greenhouse gas emissions

The vast majority of a vehicle’s exhaust pipe emissions are the natural by-products of burning gas or diesel: water and carbon dioxide. Except when engines are cold, both are usually invisible. Neither is poisonous. In fact, carbon dioxide is required by plants as they grow.

But – and it’s a really big BUT – that same carbon dioxide is the main greenhouse gas causing climate change. Worldwide, vehicles are a huge source of carbon dioxide, and the problem’s getting worse as more and more vehicles are added to streets and highways in Canada and abroad. Simply put, the plants of the world aren’t able to absorb back all our emissions, the level of carbon dioxide in the atmosphere is climbing, and the planet is warming.

And here’s another sobering fact: carbon dioxide emissions are absolutely unavoidable when we burn gasoline or diesel fuel. There is no technology today to remove them from tailpipe emissions, and there isn’t anything on the horizon.

Every single litre of gas burned, no matter the vehicle it’s burned in, produces 2.4 kilograms of carbon dioxide. That means a 40 litre fill-up will result in 100 kilograms carbon dioxide being produced, and ten such fill-ups will produce a tonne of greenhouse gas emissions.

The ratio is worse for diesel fuel: every litre burned produces 2.7 kilograms carbon dioxide.

The only way to reduce your vehicle’s greenhouse gas emissions is to burn less fuel, period. That means driving less, and walking, biking, carpooling and taking the bus more. And it means using the most fuel efficient vehicle possible when you do have to drive.

Back to that ad

Remember that SUV ad with the claim of an 80% reduction in emissions? It was clearly a reference to smog forming emissions only. That’s good, of course. But since the new model’s fuel economy was no better than the one from a few years earlier, its greenhouse gas emissions were unfortunately not reduced at all. So perhaps it’s a bit of a stretch to claim an 80% emissions reduction without giving the full story.

And defenders of drive-throughs sometimes use a similar definition of ‘emissions’. It is true that an idling engine and one that is turned off and then restarted produce about the same amount of smog forming emissions. But greenhouse gases are produced every second an engine is idling. So if you are concerned about climate change, the 10 second rule still applies and it’s best to avoid drive-throughs.

Clarity in the air is always a good thing. Clarity about emissions is a nice start.