Sulfur and the summer of discontent: the Polluter is Paying, and complaining

It’s a bit of a joke. We elect governments. Most of us who vote in elections don’t get the government we want, but the government we get does what we do want. When we see, touch, and feel the results of the government we get doing what we want, we freak out and complain like spoiled children. Anger at the gas pump, called Pump Rage by some, is a perfect example. We want “clean” gasoline. So our government has, over the years, forced the gasoline industry to make it “clean.” So now that our gasoline is “clean,” we gripe about how much it costs. Why does it cost so much, especially when petroleum prices are currently so low? Because we screamed at the government to make gasoline, a refined petroleum product, clean.

We all scream, for clean gasoline. Otherwise our urban air would look like it does in this photo, of a Chinese city on a bad air day. Funny then that we complain when we see the bill for our clean air, in the form of high gasoline prices. The prices are high because it costs money to remove sulfur, a superpollutant, from gasoline.

If you want clean gasoline, then take the sulfur out of it. Sulfur is not only a bona fide air pollutant in and of itself, it is the cause (enabler might be a better word) of the other major air pollutants that belch out of the exhaust stream of a car engine. These include:

1. Carbon monoxide (CO), the most prolific toxic killer on the planet.
2. Oxides of nitrogen (NO_x, a family of nitrogen compounds that like sulfur are pollutants by themselves but also important precursors to acid rain and ground level ozone (O₃).
3. Volatile organic compounds (VOCs), an even more diverse category; they include a wide range of complex hydrocarbons.

To deal with these dangerous substances, automakers install catalytic converters between the engine and the tailpipe. In theory, a catalytic converter catalyzes the CO, NO_x, and VOCs in the exhaust stream and turns them into relatively innocuous substances like carbon dioxide, water, and free nitrogen.

The operative phrase in that last sentence is, In theory. In practice, if there is sulfur in the fuel, it will, depending on how much of it there is, impede or altogether prevent those catalytic reactions from taking place. Sulfur in the presence of catalysts is like a weed: it aggressively occupies catalyst sites and leaves no opportunity for reactions involving the target pollutants. Its presence in fuel turns your car’s catalytic converter into basically useless weight—your engine exhaust stream, with its CO, NO_x, VOCs, and of course sulfur enters the atmosphere substantially not much different from when it first left the combustion cylinder.

Canada’s government, in virtual lockstep with the US EPA, has over the years forced gasoline and diesel refiners to reduce sulfur content in fuel. This has necessitated expensive sulfur-removal additions to refinery equipment, as well as equally expensive ethanol manufacturing and blending with gasoline. The current Canadian limit for sulfur content is 30 milligrams per kilogram of gasoline , which is equalivalent to the 30 parts per million limit in the US. This puts refiners under more pressure. It is supposed to, in the next couple of years, go down to 10 milligrams in Canada (10 ppm in the US). Under the principle of Polluter Pay, we—gasoline and diesel consumers, i.e., the polluters—are paying for these expensive measures.

So get used to expensive gasoline, even with a glut of petroleum on the world market that is keeping crude prices low and smothering Canada’s oil sands with bad economics.

I filled up yesterday at the Shell on Merivale in Ottawa. Each litre cost me $1.13. Given that each litre contains 9.4 kilowatt-hours of energy, and that my car’s engine efficiency is such that more than 80 percent of the energy from the gasoline is dumped as heat, noise, carbon dioxide, and small amounts of sulfur into the environment, I figure that though each kilowatt-hour cost me 12.02 cents, I effectively paid 60.1 cents for each of the kWh that will actually move my car.

Moreover, because I burn five litres of gasoline in order to receive the motive-power benefit of one litre, my driving CIPK is much greater than the nominal 245 grams that are obtained by dividing the total CO₂ produced by burning one litre of gasoline (2,300 grams) by the number of kilowatt-hours per litre (9.4).

No, the real (efficiency-adjusted) CIPK of driving a gasoline car is obtained by dividing the nominal CIPK of 245 grams by the efficiency, which is at most 20 percent. So 245 divided by 0.2 = 1,225 grams.

Good thing, for our personal financial health, that we are allowed to dump that CO₂ into the air for free. If we had to pay to remove it, like we pay to remove sulfur, we would be paying a hellishly high price: so high we could not afford to fill up our cars.

Why? Because under the new federal rules the sulfur content of a kWh of gasoline energy in a car cannot be more than about 4 milligrams (30 milligrams per kg = 39 mg per liter; divide 39 mg by 9.4 kWh/litre = 4 mg). While it is very difficult to tell exactly how many of the 113 cents per litre I paid for the gasoline went towards the removal of however many mg of the sulfur that was in that litre prior to refining and blending, I believe it explains a big part of why I paid 113 cents for a litre of gasoline yesterday when I was paying 90 cents a few months ago—when the world price of oil was the same as it is now.

It costs money to take sulfur out of gasoline. Next time you complain about that, take a deep breath. Is it worth it?

The generators that feed the electric power grid in Ontario produced 17,443 megawatt hours last hour (see Table A1 on the upper right). The most polluting of these generators run on natural gas; as you can see, they produced more than 1,200 tons of CO₂. But how much sulfur did they dump into our air? According to Table 1.4-2 in this US EPA document, 0.6 pounds of sulfur per million standard cubic feet. That works out to 0.0009 grams per kilowatt-hour in natural gas. Factor in say 30 percent power-conversion efficiency (I know that gas advocates will claim 50 percent for combined cycle, but who are they kidding) and you get a sulfur content of 0.0029 grams (2.9 milligrams) per kilowatt-hour.

By that, we can estimate that gas-fired generators in Ontario put around 8 kilograms of sulfur into the air last hour. That works out to a sulfur intensity per kWh of 0.4 milligrams—one-tenth of that from a kWh of gasoline energy.

You can easily see why the sulfur content of a kWh of Ontario electricity is ten times lower than that of a kWh of gasoline energy. Most of Ontario’s electricity is made with non-emitting sources. And the biggest of those, by far, is nuclear.

Nuclear kills carbon. It kills sulfur too.