Can your car's engine be used to dispose of organic chemicals?

Dear Car Talk

Dear Car Talk | Aug 01, 2009

Dear Tom and Ray:

When I was in college during the late 1980s, I remember one of my chemistry professors telling me that he disposed of organic chemical waste by just pouring it in his gas tank and burning it along with the gasoline. I imagine the waste would have contained things like benzene, xylene, toluene, cyclohexane, cyclohexene and cyclohexanol, just to name a few. I'm a high-school chemistry teacher and have a supply of organic waste collecting. I was wondering if disposing of organic waste this way would do any damage to my '94 Dodge Dakota or my wife's '01 Ford Windstar. It seems like this would work, since gasoline already is a mixture of organic compounds. But if I ruined one of my vehicles, I'd never hear the end of it at home or at work.

-- Tom

TOM: Well, perhaps in the old days, before we cared about things like the environment, dying at a young age or growing extra fingers, you could have tossed that stuff into the gas tank and driven off. But we strongly recommend against it.

RAY: For two reasons. One is environmental. Some of this stuff -- like benzene -- are known carcinogens. And even though there's a small amount of benzene in gasoline, its quantity is severely limited because we now know how nasty it is.

TOM: And I don't think any of your neighbors would appreciate waking up to the wafting aroma of benzene coming out of your tailpipe over their morning Grape Nuts.

RAY: The second reason is that there are dangers to your car. Like we said, in the old days, fuel systems were exceedingly simple, and you could burn almost anything. My brother would burn his hair tonic when he was low on fuel.

TOM: But now there are a lot of expensive plastic parts in a fuel system, like the gas tank, the fuel line and the O-ring seals on the fuel injectors. And benzene is a powerful solvent. So if you have too much benzene in your fuel, it can melt stuff.

RAY: And it's not just the benzene. Some of the compounds you mention can form peroxides when heated and mixed with air. And peroxides can cause fuels to gum up. Plus, if any of the solvents have trace metals in them, those are not good things to burn in your fuel system, either.

TOM: So I'd move on to plan B, Tom. I know it's expensive to have a licensed waste-disposal company dispose of these chemicals properly, but that's the right thing to do.

RAY: Perhaps you can get some other local chemistry teachers together and the schools can split the cost of one legal disposal a year. And while you're together, you guys can discuss the latest in pocket-protector technology.

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