A Greenhouse Calculation

Here’s a lazyweb word problem:

John rides his bicycle to work, thus saving a half gallon (1.9 liters) of gasoline, consuming 700 calories in the process. If John replaces those calories by eating beef, what is the net reduction (increase?) in greenhouse gas emissions? If he gets the calories from soy protein? Etc? (Ideally, the answers should be expressed in gasoline gallon equivalents, because that’s the metric regular folks can grok.)


  1. How about John, being a bike rider loads up on carbohydrates….

    or, John, riding the bike because his cardiologist warned him about hardening of the arteries gives up meat and switches to a healthy diet as well as riding a bike to work…


  2. OK, Eli, I’m happy to adjust the question. What’s the greenhouse/gallon-of-gas equivalent emitted in the production of 700 calories of whole grain?

  3. Who thinks that 700cal is equivalent to half a gallon? The former is 20-30 miles, which is roughly a gallon for the typical US car.

    Nevertheless, a ballpark average for the US diet is 10 fuel calories per food calorie, making 7000 for the food vs 15000 for the car with your figures (a 50% reduction for the cyclist). But as I said, your numbers probably exaggerate the ratio by a factor of about 2, making a more typical answer 25%. Healthy and environmentally-conscious eating (local veg and grain rather than beef and flown-in Kenyan peas etc) could be a lot better.

  4. What really bothers me about these things is that they purposefully set up false expectations. It is easy enough to find studies that show bikes are MUCH more energy efficient than autos on any basis. The guy who asked this question was doing the equivalent of forcing the card and deserves to get his hands slapped for it.

    35 calories/mile to 1860 calories/mile

    Here is another
    another with pictures

    So that leaves us with the cost of energy to make the steak. That too can be found within 3.7 ns.

    “They defined the non-renewable energy inputs to animal production as the energy equivalent of fuels for operating machinery and ventilation, drying crops, production of inorganic fertilizers, and production of machinery and buildings.

    Energy outputs were defined as the energy equivalent of human edible products of animal production and animal wastes used as fertilizer….Beef energy output/input was 1.15″

  5. Actually, John likely knows his cal/min expenditure when riding, Eli. I do.

    It’s easy to see that riding is far more cal efficient than autoing, and the caloric expenditure for the beef is the point of the exercise, as the cal spend shipping it is great if not locally-grown, and most shipped ag products require much more energy to produce than they return [e.g. for iceberg lettuce grown in Imperial Valley and shipped to, say, New York, we usu. find 1 cal in food:35-50 cal in production].



  6. I was far too obscure and clever for my own good here, obviously. Dano got it. It’s a 700 calorie ride or a half-gallon drive, give or take a reasonably small margin of error, but that’s not the real point. I’m really after something fundamental, which would in general allow me to calculate the amount of greenhouse gas equivalent produced in the manufacture of various food items.

    We all get “gallons of gas”, and know how to save them. I’d like to know how many “gallons of gas equivalent” are used in the production of various foods I eat. The bike thing is just my little overly clever bit of business. This doesn’t apply to me at all, because I ride my N miles a week regardless. The commute just substitutes for equivalent recreation riding, so it’s free in terms of this particular scenario.

    I have this suspicion that the production of beef is so ungodly inefficient in terms of the required energy inputs that it makes a potentially useful case study. That’s why I chose it for my little anecdote.

    Eshel and Martin showed that there’s a vast difference in calories in/calories out between meat and vegetable calories. One of the implications of their work is that vegan eating is really low-hanging fruit for an individual who wants to act personally to reduce their greenhouse gas emissions.

    I just want some easy-peasy way to convert that to gasoline gallon-equivalents. And I still wanna know if the total greenhouse emissions from producing the extra burger I have to eat to fuel the bike ride are greater than the gasoline I save. Hypothetically.

  7. I did a paper in undergrad on this very thing, comparing organic vs industrial food production methods, calculating total caloric input vs output.

    I doubt I still have the paper, but the ‘gallons of gas’ equivalent are known if you set up a spreadsheet and use a column as a factor; that is: NH4/acre = x gal. At the time I wrote my paper there were perhaps ~15 papers that had done some sort of work on inputs, so the data are out there. Not sure I can help search in the next few days, as I’m in my new home and we’re inundated with the snow John wants so desperately.



  8. You are still going to have to convince me that the guy driving the car won’t eat the burger (and then get fatter, or drive to the health club)…..Sorry. This sort of stuff just gets in my ears and drives me batty. It is a major part of the don’t do anything, because it changes nothing attack.

  9. people

    im not trying to undermine anyone’s response, or dispute the purpose of the exercise, but there’s a fundamental flaw in the argument of considering the process chain of CO2 and/or greenhouse gas emissions associated with, for example, beef production for the purpose of comparing it to riding in an automobile. that is, when one considers the harvesting, processing, transport, etc. inherent in any given agricultural product, one must also look, from the point of view of the auto, at the mining of the ore, smelting of the iron, refining of the steel, fabrication of the individual components, assembly of the vehicle, and delivery to a given dealership. of couse a few things have been left out, but the idea is that the total consumption for owning and driving a car is orders of magnitude higher than eating a steak and riding a bicycle.

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