Bicycle MPG

In A convenient lie, I asserted that a hypothetical 60-MPG car requires enough energy every hour to take a bicyclist 1250 miles. I gave some indication of my reasoning there. I also mentioned that ”precision is not required when the comparisons span orders of magnitude.”

I’m having second thoughts about that last assertion, or at least with its premise that the differences are enormous. Yes, bikes are far more energy efficient than cars, but depending on how you conduct the analysis, the difference may not be as gross as I’ve assumed in positing that mass scale, heavy, high-energy personal transit is inherently non-sustainable without greater-than-real-time solar energy inputs (i.e., without fossil fuels).

Over the years I’ve heard MPG-equivalent figures for bicycles ranging from >2,000 to just barely over 100 MPG. The degree of variability comes mainly from how you account for the fuel requirements to produce and distribute food. Food, that old Malthusian bugbear under the rug of cheap oil, might be waking up as we run out.

It’s beyond my analytical competence (or enthusiasm) to sort out the conflicting estimates to pronounce a winner. But among the more interesting documents I’ve perused recently is a life-cycle analysis that puts the energy efficiency of electrically assisted bicycles 2-4 times ahead of purely human-powered ones, unless the cyclist eats only home-grown food — then it’s closer to a draw.

Off you go, math-heads! I have some bicycle motor kits to assemble:

14 thoughts on “Bicycle MPG”

  • odograph

    Hi, I noticed your trackback coming in to my page. For what it’s worth I had a later entry on the costs per mile of electrics (Electric Bicycle Efficiency).

    I probably didn’t want to think about the upstream ecological impacts of food vs. electricity :-/ … I’ll definitely give that PDF a look.

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  • Jess Austin

    Just to be clear: The question of how much fuel is used to bring us our food seems to speak to the question of what food we purchase and from whom we purchase it. It doesn’t really speak to the question of whether we should bike or not, which seems entirely unrelated to me. Sure, elite spandex studs might consume two or three times as many calories as they would need if they didn’t bike, but they don’t count. I have to think that the multiplier for commuters is more like 1.5 at the most. This isn’t enough to offset the virtues of not burning gas, which after all must also be transported to the places we need it.

    Somewhat in contradiction to the above, a recent reading of The Bottomless Well has me thinking that mimimizing energy ”use” in any particular activity is the wrong way to go about this anyway. We need to look instead at actual harms that result from human activities and find a way to reduce harmful activities regardless of the energy ”used” in doing so. When we find a way to provide convenient intra-urban transport that seems to be a better deal to the average American than driving SUVs, the average American will quit driving SUVs. As a result, more energy than ever went into fueling cars will go into the new transport mode.

    I only read TBF a couple of weeks ago, so I’m probably not done digesting it yet. I will say that the chapter on global warming, Chapter 10, was certainly the weakest. The authors spend most of the book arguing that the initial form of energy (coal, oil, wind, whatever) is becoming less and less important in an economic sense. Then they use some sort of sophistical accounting to ”prove” that solar and wind energy could never meet our energy needs in an environmentally sound way, when their primary thesis seems to beg the opposite conclusion.

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  • Bill Manewal

    “This isnââ?¬â?¢t enough to offset the virtues of not burning gas, which after all must also be transported to the places we need it.”

    I asked a gasoline truck operator the other day what kind of mileage he gets. The answer was 8 mpg and the particular station where he was stopped has its tanks filled three times a day! Of course this doesn’t count the mpg that an oil tanker gets. I have no idea what that figure is but the Queen Mary went 13 feet on a gallon of bunker oil. She displaced 81,000 tons and the largest tanker, the Jahre Viking – weighs in at a hefty 260,000 tons.

    I’m SURE I get better mileage on my Stokemonkey, even considering my organic whole grain cereal in the mornings.

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  • Ken Heronheart

    Bicycles are definitely only part of the overall sustainability equation. (but a vital part). Another part is my 2.5 mile bike ride to our local horse and goat farmer to buy cheese, eggs and vegies.

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  • Erik Sandblom

    I don’t understand the issue. If you eat more due to biking, then that’s healthy. Since my body is a natural part of the environment and ecology, it’s ecological and environmentally friendly too.

    If any of that is not to be taken for granted, I think it’s a religious or philosophical issue. In school, I was taught that my body is a temple of worship. Later close encounters re-inforced that view.

    So for me, eating right and exercising is a fundamentally and inherently ecological and green thing to do.

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  • t

    Vegan bicyclists win, hands down!

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  • Bastiaan

    Erik, you have to keep in mind that most food today has been made by using large quantities of oil products (like fertilizer, gasoline, pesticides, etc). Eating more is not nessesarily an ecological thing to do.

    Reply
  • [...] cleverchimp has an interesting discussion going. I learned about it when I saw the “trackback” link come in for one of my old bicycle fuel efficiency posts. [...]

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  • mike

    We haven’t even started adding in the cost of health care into this formula. A person who maintains an active lifetstyle (healthy eating, regular exercise, etc) will be a much less burden on the health care system than someone who leads a typical suburban life. Heart disease, diabetes, and cholesterol and all the assorted care as the population ages starts to play with take home pay, insurance premiums, cost of care, etc, and as Social Security disappears (or is mangled by politics), and universal healthcare remains a dream – more of these costs will become large portions of the younger populations burden.

    My bet is that the cyclist eats the same or more, but long term, being in far greater shape and taking better care of her body, will be less a burden on society than a car driving “typical” American. I’d wonder what the linkage to fuel efficiency would be if we could somehow add it all together.

    Sort of an expanded ecological footprint, as we need to take all sorts of things into consideration. MPG is one thing, but factor in what it takes to build the car, the infrastructure and technology needed to maintain it, and add all the problems with pollution, health, and etc… and the equations looks pretty grim.

    Perhaps it could be the EL (effective living) number. Some sort of formula that starts to reduce everything to life energy, or units of energy derived from the sun that we are burning… or something – to show all the hidden “costs” our typical lives take.

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  • BruceMcF

    On the question of how high up the foodchain the food comes from, the energy accounting I ran into when looking at corn-ethanol had corn at a kilcalorie yield of 3.84 kcal output for 1 kcal input (it is in the ethanol processing that corn-ethanol tips over to a net energy loss).

    And corn is a fairly energy intensive crop, because of the fertilizers …

    And if takes 14 pounds of grain to produce 1 pound of beef, that flips over to less than 0.27 kcal of energy from beef for 1 kcal input.

    So if the extra food intake is grain, it will be 70% solar energy or more. If the extra food intake is meat, it could cost 4 times its weight in fossil fuels.

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  • krylon

    This is surely an interesting discussion. But does our
    prototypical urban cyclist really eat much more than her
    much-maligned SUV-driving counterpart? Isn’t it true that
    North Americans in general tend to eat more than they really
    need to? I would bet that the average cyclist of typical
    build weighs somewhat less than the average motorist, not
    because he eats more or less, but because the calories he
    consumes are used in a different way (ie. to power muscles as
    opposed to being stored in tissue).

    Reply
  • Mauricio Babilonia

    krylon wrote:

    “[...] does our prototypical urban cyclist really eat much more than her much-maligned SUV-driving counterpart?”


    My question exactly. A more interesting comparison of MPG would

    a) subtract the number of calories needed to stay alive from the total caloric intake of the cyclist, and thus consider only the differential as what’s needed for transportation;

    b) subtract the number of calories needed to stay alive from the total caloric intake of the motorist, and thus consider how much of the differential is used for transportation (probably close to zero); and

    c) consider resources consumed for the entire life of the automobile and bicycle as part of the mileage calculation

    I suspect the bicycle would win handily.

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  • dr2chase

    I don’t think the additional calories are that large — most likely the auto driver is either gaining weight or burning calories at the gym — and you can get them from nuts and honey, and you can keep your own bees. We did when I was a kid, there’s a guy in town here who keeps a beehive, too.

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  • David Chase

    It's an old blog entry, but I checked the math based on figures from a reliable source, and if you assume 50 kCal/mile to ride a bike, then the full-cycle mpg ranges from 15 to 3000.

    If you eat 100% beef protein for your fuel calories (no fat, and nobody else is eating the fat either), then the mpg is 15. That's far-fetched. If you eat 85% lean hamburger, ALL OF IT, including the fat that drips out, the mpg is 30 (there's a pile of energy in fat).

    If, on the other hand, you eat oats (ignoring energy costs of preparation, which is not really accurate), the effective MPG of fossil fuel inputs is 3000. That's because oats generate a lot of food energy (5x) for the fossil fuel inputs to their production.

    Details here: http://dr2chase.wordpress.com/2011/01/12/overselling-a-vegetarian-diet-underselling-utility-cycling/

    Reply
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