Brilliant or Bogus: Warren's CO2 Idea

Dear Car Talk:

Why can't I use carbon dioxide gas to fill my tires instead of air (78 percent nitrogen) or instead of 100 percent nitrogen? If EVERYONE in the world filled their tires with carbon dioxide, wouldn't that take a LOT of carbon dioxide out of the atmosphere and slow global warming? Think of the amounts involved! Thank you!

-- Warren

Warren, it's thinking like that that's kept you out of the country's best institutions of higher learning!

It's actually a great theory. So let's do the math on it.

The average car tire holds about 1,700 cubic inches of air. So if we take five tires per car (including the spare), the average car could hold about 8,500 cubic inches of carbon dioxide. If we convert that to pounds, it's about 0.6 pounds.

But, as you say, think of the amounts involved. Let's say there are roughly a billion cars on the road worldwide. So now you've sequestered 600 million pounds of carbon dioxide! Wow!

But here's the problem: Every time you burn a gallon of gasoline, you create 20 pounds of carbon dioxide. So filling up your tires with carbon dioxide would negate the carbon dioxide produced by using 0.03 gallons of gasoline -- or enough to let you back out of your driveway and run over your kid's Big Wheel.

So, unfortunately, it's only a drop in the proverbial carbon bucket.

And if you look at it globally, and include the carbon dioxide created by fossil fuels, power plants and cement production, we humanoids create about 60 trillion pounds of carbon dioxide a year -- give or take 20 trillion pounds. And if you compare that to the meager 600 million pounds you could hide in all of the world's tires, you'll see that you're not making a lot of headway.

And we haven't even figured in the cost of capturing the carbon dioxide and delivering it to 5 billion tires.

So it's a great concept, Warren. And we encourage you to keep thinking. But if the goal is to reduce carbon dioxide, the money and effort would be better spent replacing older fossil-fuel plants with solar or wind generation. Or figuring out how to make every factory on the planet run on cow farts