We had only planned to run this series to #10. But once we got started we kept finding data so cheerful that we had to postpone the end. Including this week, when we cheerily swap the C in CO2 for an S, and show you SO2 or Sulfur dioxide levels in the US since 1980. This actual pollutant used to be a much bigger problem in urban air in North America and Europe, but improved technology allowed it to be scrubbed from smokestacks and automobile exhaust, getting it out of the air before it even got in. To show just how far SO2 levels have fallen, despite the growth of the economy, the following chart from the US Environmental Protection Agency shows, not the annual average exposure in American urban air, but the 99th percentile (i.e. the worst people encountered) of each year’s daily maximum readings from 29 locations around the country. In 1980 these spikes ranged from about 55 to 340 parts per billion (ppb) and averaged 173 ppb. Kaff! Ugh! But in 2023 they had dropped to a range between about 3 to 14 ppb and an average 9 ppb. Yes, that’s right, a 95% reduction. Despite the enormous growth over that interval in economic activity and energy consumption.
This chart cheerfully illustrates what it looks like when people solve a real environmental problem using methods that actually work. And here you might be wondering why, if the US was so successful at reducing SO2, the same ingenuity, “Yankee know-how” even, can’t cut CO2 in the same way and to a similar extent? The answer is that it’s a different challenge altogether. You can scrub sulfur from smoke and have it emerge as sulfur, basically a solid that can be disposed of or reused, and the reason behind the reason is that it was always an undesirable byproduct of using the fuel.
People who bought coal for a power plant, or their furnace, or oil and other petroleum products would have been happier to get it without sulfur, and paid a premium to do so. Such oil, for instance, is referred to in the trade as “sweet”; as one investor’s guide put it:
“Sweet crude refers to crude oil that is extracted that is found to contain very low amounts of sulfur. It is considered a valuable and efficient source of crude oil due to the fact that sulfur lowers the yield of various refined petroleum products such as gasoline, diesel fuel, and even plastics.”
By contrast when CO2 is scrubbed from smoke it emerges as a gas, the necessary product of burning carbon-based fuels, burning being, you recall from chemistry class, a rapid exothermic process of oxidization. Coal or oil without carbon wouldn’t burn, and nobody would pay for it. (The same is true of natural gas, or CH4, despite politicians’ dreams of pure hydrogen as a fuel). And this resulting gas, carbon dioxide, cannot be deoxidized back into solid soot without putting back in at least as much energy as was released when it burned. So it either has to be released, making the whole exercise pointless, or pumped underground, which is very costly and generally infeasible in most locations even if you’re very sure it won’t leak out.
As a result, as long as we use fossil fuels we’ll be emitting CO2, until someone invents a machine that can suck CO2 out of the air and turn it into a useful product like wood. Wait. We already talked about that one. Looks like someone already had that idea and it was Mother Nature. So if you care about the environment, plant a tree.
Some years ago an engineering professor at Purdue University decided to solve the coal fired power plant emissions problem by dehumidifying the air prior to pumping it into coal fired boilers. He recalled from his days as a B-17 pilot that on cool dry days his aircraft had a significant power boost making takeoffs with a full bomb and fuel load very easy. He determined that a large percentage of the energy created by burning fuel is consumed to dehumidify the air, he invented a series of baffles designed to compress then decompress the intake air thus reducing coal consumption by 25% which would allow all coal fired plants to meet all emissions standards. It was never used because cleaning up the emissions was NOT the goal!
Oh yes I would like a Tee Shirt displaying the happy chart/graph of SO2 Air Quality 1980 - 2023. I would wear it and wear it proudly of such a significant achievement towards a less polluted atmosphere for my children born in the 80's and all children born since then.