Broad improvements produce underwhelming results, while replacing the really bad polluters is mandatory if we are serious about improving air quality.
By Ted Mitchell
Published March 24, 2008
The next several essays in this column will be on the subject of air quality and health impacts. I will take an approach that is politically incorrect, that is, not soaring with the eagles of the environmental skies, but rather concentrating on the easy targets of environmental turkeys.
If you prefer other metaphors, this is where the low-hanging fruit lies, mathematically speaking.
When the known balance of risk/benefit tilts such that it becomes desirable to change behaviour, there are three strategies we can take. Before moving to air quality, I will give a simpler example to illustrate the most effective target. Let's say you wish to improve the fuel economy of a fleet of vehicles for whatever reason. This can be done in three ways:
Targeting the leading edge: promoting super efficient cars in the hope that it will inspire people to buy them
Broadly improve everything: making improvements to all cars
Replacing the undesirables: removing the worst offenders from the road.
If you are really serious about achieving this goal, you would combine all three approaches. Here in Canada, several taxes and rebates exist to support point 1 and to a mixed extent point 3. The most effective strategy of these three depends on the nature of the problem.
Fuel economy for personal automobiles in Canada has a fairly narrow range, a factor of about 5 - say, 19.6 L/100 km to 3.9 L/100 km (12 to 60 mpg) - with most vehicles squarely in the middle. Therefore, small incentives aimed at small targets on each side of the great mass of average vehicles are going to have relatively little effect compared with going after improvements for all cars.
The most effective point is 2, in this case, because the entire fleet is targeted. The obvious way to implement this is a large hike in the gas tax.
This strategy would lead to consumer behaviour such as less travel all around, more carpooling, and better maintenance. It would also create long term demand for practical and technological design shifts in the efficiency of all vehicles.
But a gas tax, however rational, is currently politically infeasible. The next most effective target is point #3, distantly followed by #1.
Unfortunately, point #1 is the main focus of media and government. Since math is not the strong point of politicians, they prefer highly visible efforts like rebates for hybrids and penalties for gas guzzlers.
The penalties, however, are riddled with loopholes. The federal EcoAuto program rewards an efficient vehicle and penalizes a gas guzzler if it is a car or SUV but not a truck, which are totally exempt for reasons known only to politicians.
A similar situation exists in Ontario with the Tax for Fuel Conservation, where the discriminatory tax is applied against passenger cars while SUVs with identical efficiency pay less, and again trucks and large vans are exempt entirely.
Both levels of government are sending mixed messages, effectively granting subsidies that could have the opposite of the intended effect by encouraging sales of trucks.
Let's look mathematically at the consequences of changing the mix of our fleet. To explore this with real examples, we will use Toyota vehicles.
All three drive 20,000 km per year (the Canadian average). So, Luke burns 820 L (or roughly, dollars) per year, Jim 1,580 L, and Bob gulps 2,880 L.
A rough estimate in Canada of the actual vehicle mix shows 5 percent of us are like Luke, 55 percent like Jim and 40 percent like Bob.
Probably three quarters of Bobs can't honestly justify their big vehicles based on need, so let's convert them to Jims. This saves (2,880 - 1,580L = 1,300 L/year) per ex-Bob.
So if you can convince 30 Bobs to become Jims out of every 100 Canadians, that's (30 x 1,300L = 39,000 L/year) per 100 Canadians.
Now let's green up every single Jim and make them into Lukes. Since there are 55 Jims out of every 100 Canadians, (55 x (1,580 - 820L) = 41,800 L/year) per 100 Canadians.
The fuel savings of each strategy are almost identical, although the first option affects only about half as many people.
In other words, on one hand is the fuel saved from taking off the road three quarters of the large trucks, vans and SUVs that are not really used for what they are designed for, and replacing them with more appropriate and cheaper conventional mid-sized cars and minivans.
On the other hand is the fuel saved from converting every single midsized car and minivan to an expensive, high-tech compact hybrid. These options have about the same effect.
Which strategy is more sensible? The first actually saves money, and has other beneficial side effects such as a lower body count at the end of the year. The second is expensive, requires the participation of almost double the number of people, and raises many new environmental questions about recycling and disposal of batteries.
What has been presented is a version of the law of diminishing returns. I hope you can see mathematically from this example that pursuing efficiency favours bagging turkeys over soaring with eagles.
This is an unfortunate conclusion for those who insist that environmentalists mind their own business. In many cases, if our environmentalist moves to an unheated cave, reducing their carbon footprint to zero, they have less impact than someone with a lavish lifestyle who simply reduces their consumption to an average level.
My example above holds for just about any fossil fuel consumption problem. Air quality is a different problem, because of the extremely wide range of cleanliness of pollution sources. A big truck may be five times thirstier than a Prius, but a wood burning stove produces some 5,000 times the pollution of a natural gas furnace.
Because the problem is so different, so is the relative effectiveness of strategies 1, 2 and 3 introduced above. As you might guess, promoting the leading edge is almost inconsequential. Broad improvements produce underwhelming results, while replacing the really bad polluters is mandatory if we are serious about improving air quality.
In the next essay I will tackle one of the biggest proverbial turkeys.
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