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All's well that ends oil: On biodiesel vs. hybrids

By Umbra Fisk, Grist.org

Posted Mon Jan 12, 2009 1:32pm PST

Related topics: Shopping, Tips, Biofuels, Hybrids, Cars, Buying a fuel-efficient car

More from Grist.org - Ask Umbra blog

Dear Umbra,

I live in Massachusetts and am trying to decide whether to buy a hybrid or a biodiesel. Since it is cold here, I would need to use 20 percent biodiesel and 80 percent diesel in the winter. How does this compare with a hybrid's emissions? Which would be better for the environment?

Tom
Conway, Mass.

Dearest Tom,

Either choice is a good one as long as you continue to find alternatives to driving, and your car-n-fuel expenses do not prohibit other environmentally beneficial acts (e.g., insulating your house). These guidelines apply to everyone, not just you. I usually mention them at the end, but thought I'd try setting them up front.

A good passenger diesel car will get about 34 mpg, according to the EPA, and about 50 mpg or more according to the word on the street. A good gas-electric hybrid, the Prius, will get in the mid-40s mpg, according to both accounts. Gasoline emits about 24 pounds of CO2 per gallon, regular diesel about 28, biodiesel (B100) about 7.3, and your 20-80 mix (B20) around 23.

We can do a little math to compare the emissions from two cars: Using the EPA's handy charts, I chose the '06 diesel VW Bug to go up against the Prius. In 100 miles at 45 mpg, the Prius emits 53.3 pounds of CO2. Over the same 100 miles, the 34 mpg Bug will release 81 pounds on diesel, 21 pounds on B100, and 67 pounds on B20.

To go further with this little cul-de-sac of carbon math, you would then figure out how many months and miles of B100 vs. B20 per year for your climate. Compare those to the emissions from yearly gasoline miles of your chosen hybrid, and there you are. (I'm not going to bother with the further calculations, as we would be delving too far into the theoretical.)

Diesel fuels are also responsible for significant particulate matter emissions, which are almost all reduced with both B100 and B20. Nitrogen oxides are slightly increased -- here's a handy chart [PDF]. The Biodiesel Board also provides an interesting Emissions Reduction calculator for diesel fuels.

That's the emissions roundup, but as to which will be better for the environment ... Down here in the stacks it's always Clark Williams-Derry Appreciation Week, and Clark has interesting things to say about car comparisons. Here is a thought-provoking Clark piece about the role of spending money in car choices, which you may enjoy: Is it better to put money into a car (and its expensive fuel) or keep the money in your pocket for that insulation project?

As I said at the outset, I think both your choices are good, with the added benefit of pushing the car economy toward more efficient private vehicles. Just avoid plain old diesel, whatever you do.

Asthmatically,
Umbra

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Posted by E Sat Feb 7, 2009 7:21pm PST
Plan old diesel is just as good with modern technologies. Hybrids are not thought about in terms of environmental impact. The batteries that are used in them are not so eco-friendly. We need to start seeing some diesel hybrids. Diesel engines are more efficient period. I would take a diesel over a spark ignited motor any day of the week.
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Posted by taxgirl09 Thu Apr 30, 2009 7:58am PDT
To be fair, the diesel VW will get far more than 34 mpg. We have a VW diesel (a Jetta), and the minimum mpg is 40. That's with city driving and an automatic transmission. On the highway it gets between 50 and 60 mpg. You even admit that owners report higher mileage, yet you used 34 mpg. Since this figure is a huge factor in your calculation, you should revise accordingly and at least provide a range. Plus, the diesel has lots of torque and feels very powerful when you drive it. I can't say as much for the hybrid.
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Posted by Blue star of New York Wed May 27, 2009 7:20am PDT
Those figures are really low for the VW diesel bug a few friends i know get around 40-45 mpg about the same as the Prius, The co2 figures now are very close also factor the the diesel design will go 270,000 miles before a rebuild the prius about 175,000. and the prius has much more costly things to repair or replace like the electric motors and batteries down the road .. the VW is much better overall.
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Posted by Blue star of New York Thu May 28, 2009 6:54am PDT
Here is a test report from Edmunds. After extensive testing . Round 4: Lowest Fuel Costs To find a winner for this round, we averaged the fuel economy of all the legs of the journey and divided by the total cost of the fuel consumed. While some of the contenders burned less fuel, the type of fuel they ran on was more costly and hurt them more than a tombstone pile-driver. Diesel got slammed to the mat big time on fuel that cost up to $4.43 per gallon during our test. The Smart also got whacked because it required premium gas at prices up to $4.17 a gallon. The champ: Toyota Prius, $53.32 of regular gas with a trip average of 47.7 mpg Challengers: 2nd Place: Smart Fortwo, $66.37 of premium gas with a trip average of 40.0 mpg 3rd Place: VW Jetta TDI, $66.66 with a trip average of 43.81 mpg 4th Place: Ford Focus, $75.96 with a trip average of 33.3 mpg Round 5: Greenhouse Gas Smackdown This is a horrible contradiction in terms. Greenies don't usually smack each other, bash each other with folding chairs or drop each other on their heads. But in our test we pitted these tree-huggers against each other for one final dust-up. We calculated the amount of greenhouse gases that each emitted. Greenhouse gases are not the visible pollution (called particulate matter) that can be seen chugging out of the Jetta's tailpipe. It's the gases that are blamed for turning up the thermostat on the planet. Here's how the contestants stacked up over the 669.2 miles driven. The champ: Toyota Prius, emitting 0.18 ton of greenhouse gasses Challengers: 2nd Place: VW Jetta TDI, emitting 0.19 ton greenhouse gasses 3rd Place: Smart Fortwo, emitting 0.22 ton of greenhouse gasses 4th Place: Ford Focus, emitting 0.26 ton of greenhouse gasses "" NOTE DIESEL is about the smae price as UNlEADED As Of 5/2009" ""
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