Should I Cash In On My Clunker?

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Photo by austrini via flicker Creative Commons.
Dear Pablo: My old car still has a few years left on it, but I'm wondering, would it would be better to get a new, greener vehicle?

I have gotten many questions like this and recent political developments have made this topic very relevant. The short answer is that a newer, more efficient car can reduce overall greenhouse gas emissions, even when you take into account the emissions from manufacturing the new car. Of course there are exceptions and additional considerations. Let's have a look at some numbers and the current political efforts that make this article so timely.

Is "Cash for Clunkers" lowering emissions or just boosting car sales?

"Cash for Clunkers" is the unofficial name of HR 1550, the "Consumer Assistance to Recycle and Save Act of 2009," introduced into the House by Representative Betty Sutton (D-Ohio). If passed into law, this bill would provide up to a $5,000 credit toward a "passenger automobile assembled in the United States with a minimum highway label fuel economy value of 30 miles per gallon." This credit only applies if the old car is an "inefficient or high polluting automobile" and if that vehicle is scrapped. Clearly the language of the bill is designed to improve the average fuel efficiency of the US vehicle fleet, but it is also designed to boost domestic car sales. The credit does not apply to the purchase of foreign-made cars, except for those made within North America, which are eligible for a lesser credit of $3,000 or $4,000 (depending on type and fuel economy).

What are the greenhouse gas implications of scrapping my clunker?

The Argonne National Lab has done a great job in analyzing the material intensity and energy consumption in manufacturing vehicles and vehicle fuels. Their work is packaged in the GREET 1.7 and 2.7 models. According to the assumptions in their model for the average conventional internal combustion engine vehicle (ICEV), it takes 100 million BTU to make the vehicle, batteries, and fluids in an average 3,201 pound vehicle. This comes out to 31,362 BTU/lb. The obvious lesson in this is that heavier vehicles require more energy to make than lighter ones, in general. There has been a study circulating that states that hybrids are more environmentally damaging than Hummers because of the battery production but this has been widely disputed. According to the GREET model, a Hybrid Electric Vehicle (HEV) that weighs 2,632 pounds requires 102 million BTU to make, or 38,650 BTU/lb. This small difference in production energy becomes negligible when you factor in the increased fuel efficiency.

Gasoline contains 113,500 BTU per gallon so the manufacture of the average car is roughly equivalent to 880 gallons of gasoline. If a new car will save at least this much gas it definitely makes sense to get rid of the old car. If we assume that your clunker has around 100,000 miles left on it, with good maintenance, your new car would need to be at least 6 miles per gallon better to make up for the emissions from manufacturing. This means that, if your old car gets less than 24 miles per gallon, it makes environmental sense to get a new, 30 mpg vehicle. Not only can you feel better about your environmental impact but you also get a $5,000 discount on the new car! You also need to keep in mind that the clunker must be scrapped--that is taken off the road--in order for the environmental benefit to be realized. If you just sell the car, someone else will continue to drive it and put out the same emissions.

What are some other considerations I should know about scrapping clunkers?

Of course, greenhouse gas emissions and the resulting contribution to climate change are not the only considerations. You may have an older vehicle that gets great gas mileage but, if it was built prior to requirements for emission control systems such as catalytic converters, you car may be contributing to air quality and health issues. Older cars tend to emit more SOx, NOx, particulate matter, and volatile organic compounds. These can cause damage such as the smog that famously obscures L.A.'s "Hollywood" sign on all but the clearest days, but also increase heart disease rates. So if you have an older car, consider taking advantage of the cash for clunkers program if it becomes law.

Ask Pablo is a weekly column that aims to answer your pressing eco-quandries. Want to ask Pablo a question? Simply email Pablo(at)treehugger(dot)com. Wondering why Pablo's qualified to answer? As the Vice President of Greenhouse Gas Management at ClimateCHECK, he helps major corporations measure and manage their greenhouse gas emissions.
Additional Resources on Clunkers
Obama Favors Clunkers For Cash
Is Buying Up the Country's Clunkers Smart, Eco-Friendly Policy?
Additional Resources on Scrapping Clunkers
Time to Get a New Car?
Keep the Beater?
Cash-for-Clunkers Could Drive New Sales

Should I Cash In On My Clunker?
I have gotten many questions like this and recent political

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