[OFB Cafe] Bio Fuels

[Chris Olson]

From: Timothy Butler

> For the record, I drive a relatively efficient petroleum VW New  
> Beetle (33 or so MPG on the highway)

OK, it's time for a mechanical engineering lesson:

Do you realize that your VW New Beetle is not really all that efficient?  Convert efficiency to ton-miles.  How much does your Beetle weigh - about 2,200 lbs?  How big of a load can it carry?  Maybe pull a 3,000 lb trailer and it'd be maxxed out?  How much fuel mileage would you get pulling that 3,000 lb trailer with it?  Maybe 16 or 17 mpg on a good day?  That's 44.2 ton-miles to the gallon of fuel.  Running at minimum weight, and assuming 33 mpg, the math (using my theoretical mileage figure of 17 mpg loaded) shows it to be less fuel efficient yet at about 36.3 ton-miles per gallon.

Now, lets look at my Freightliner FLD120 with a big fuel-sucking Cummins N14/565 hp engine and grossing 80,000 lbs.  It'll get 7.6 miles per gallon, average, on 55 mph roads.  That's 304.0 ton-miles per gallon of fuel - almost 7x more fuel efficient than your VW Beetle.

This is the problem with the whole transportation industry.  You think your Beetle is so fuel efficient, simply because you're using it for a one person people mover, and it's really not.  One person people movers are merely convenient - they're not efficient.  In order to compete with the trucking industry on fuel efficiency you need a one person people mover that can attain 300 miles per gallon, assuming a 2,200 lb automobile.

This has some to do with economy of scale.  It also has to do with design.  The trucking industry exceeded rail transportation on ton-mile efficiency 7 years ago, mainly due to new diesel designs with articulated pistons that can handle maximum torque loads at 1,150 rpm (diesels run more efficient at slower rotational speeds), and emphasis on building lighter, more aerodynamic trucks that can haul more payload.  As the current fleet of older trucks continues to be replaced, ton-mile fuel efficiency will continue to improve.

The people-moving (automotive) industry has made some advancements in the last 4 decades, but not anywhere close to what would be considered adequate to compete with much more efficient ground-based mass people-moving methods such as busses or rail.
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Chris