Here is something from The Marshall Institute.
"Now, back to the biker and the SUV. And let?s start with the very worst of the SUV. With a single occupant, the SUV is moving 30 times its weight in useful payload. And it?s all dead weight; wasted weight; 3,000 pounds or more, moved for no "good" reason at all. So that?s a factor of 30 worse than the bike right there -- we?ll assume you have a weightless bike, so you?re just moving the payload of your own weight. The SUV also needs, say, ten times the width of roadway, right? All that useless junk needs a lot more space to barrel down the ribbon of highway. So now we?re at a factor of 300-times worse for the SUV. From the get-go, a 300-fold penalty. And that?s where ordinary intuition always leaves it.
But let?s finish the calculation. A car engine (including the refining and distribution systems behind it) is about twice as efficient in converting crude oil to locomotion as the grain-bread-muscle systems are in converting the energy in food to locomotion. So the SUV regains a factor of two or so there. It can pick up more than that if the biker eats a lot of meat, because he?s wasting a lot of land for all those cows. So maybe the SUV can get back a factor of ten so on the fuel cycle. Still, that doesn?t begin to close a 300-fold gap.
But what completely eclipses everything else is simply this -- at the source, crude oil is at least 1,000 times more frugal than growing grain, in terms of land consumed to extract and deliver energy. For obvious reasons: you make a very little hole in the earth; you extract a lot of energy. The biker, by contrast, is fueled too -- by granola, one presumes. It takes a lot of field to grow the granola to move a useful pound of biker payload down the road. Bottom-line: per mile, and per useful pound moved, drilling for oil and building an SUV-grade highway system uses ten times less land than growing food to fuel the bicyclist.
To repeat: I?m not endorsing SUVs -- for the most part they?re profligate and wasteful and certainly not to my green taste. But I do think that unless you do the numbers and follow their implications through to their logical limits, you aren?t thinking rationally about such issues at all.
A sanity check: as late as 1910, almost a third of all U.S. farmland was still devoted to feeding horses. Horses were the "organic" transportation system of that day. Feeding that organic transportation system required twice the land used today by all our roads and highways, oil pipelines, refineries, and wells.
Impossible though these numbers may sound to many right-thinking Greens, they are easy to verify. They are, in fact, obvious once one gets used to seeing plants, cows and bikers for what they are: land-hungry, territory-expanding, surface-dwelling automatons, which are optimized for survival and reproduction, not for locomotion. To be sure, a bike or a horse looks incomparably greener than an SUV or eighteen-wheel truck, but only because we so easily overlook such things as corn field and pasture and the rest of the energy cycle."
