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> They are the most energy efficient form of transportation. If the cyclist is vegan or even an average diet, yes. If the cyclist is paleo, a Prius with 2-pers

• prmoustache 4y ago
  At equal diet, the bicycle always win. You don't eat significantly more meat because you are using a bicycle to move vs a total couch potato that would use a Prius and eat the same.
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  • dheera 4y ago
    I disagree with this. On days I cycle 100km+ in a day I do eat vastly more than if I drive 100km and don't exercise. The energy does have to come from somewhere. If you're only cycling 5km in a day the reason you don't notice the difference in food quantity is because the amount of energy used for that small amount of cycling does not really exceed the amount of energy your body uses in a day for everything else. When you're cycling 100km, it's a different story. It's an interesting question, and in fact the conversion of food to mechanical energy isn't actually very carbon-efficient compared to electricity generation or even gasoline. Cars are actually very efficient at what they do, it's just that what they do (hauling around a 1000kg metal box) is an inefficient way to transport a human, and that's where the inefficiency comes from. If you fill up a large car with full occupancy and go on a long road trip, I'd venture to say it's carbon-wise likely to be more efficient than all of the occupants cycling, regardless of diet.
    • PaulDavisThe1st 4y ago
      This is completely false. See the numbers in the post that for me, right now, is directly below yours: https://news.ycombinator.com/item?id=35345400 https://news.ycombinator.com/item?id=35345400
      • hanoz 4y ago
        The numbers you link to completely fail to take into account the carbon footprint of producing energy in the form of food vs in the form of petrol.
        • deleted 4y ago
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        • PaulDavisThe1st 4y ago
          Part of the problem is that the former number is wildly variable depending on the type of food, the type of production and the amount of transportation to get it to where it is eaten. Whereas oil-derived fuels are ... well, they vary but not as much. Certainly some food production models (e.g. alfalfa-raised cattle eating for meet thousands of miles from where they are raised) are truly horrible, and may indeed be worse than using fossil fuels. That said, plant-centric, reasonably local food systems that don't use much in the way of synthetic fertilizer generate massively less carbon than any sort of oil production in terms of distance-travelled-per-unit-of-carbon.
          • prmoustache 4y ago
            Part of the problem is that people consider that the driver are some aliens that do not eat anything, or stay fit by just following a strict diet and without doing any exercise. But the true reality is most people eat more, make reserves and a huge fraction of the population is either overweight or do physical activities in the purpose of burning those reserves and feel better. Mixing transportation with the later is quite efficient.
    • scott_w 4y ago
      You can disagree all you want. You’re still wrong. 100km on a bike is 2000kcal. Back of the envelope maths on a 65mpg car puts it at 35,000kcal.
      • dheera 4y ago
        The original intent of my parent comment is: - 2000kcal from food = how much CO2 including all the energy needed to farm it? If it's 2000kcal from beef, you're looking at about 72.88 kg [1] If it's 2000kcal from fish, you're looking at about 15.21 kg [1] If it's 2000kcal from brassicas, you're looking at about 6 kg [1] - 35000kcal from gasoline emits how much CO2? 35000 kcal is 140440 kJ, which would consume about 4.36 liters of gasoline, which would be about 10 kg of CO2 emissions [2]. So the CO2 efficiency of a car isn't that much different, and falls somewhere in-between a biker on a fully meat and biker on a fully vegetable diet. Biking isn't vastly more efficient than a car, CO2-wise. That said, a motorized bike is hellishly efficient, CO2-wise, and trumps almost everything else. [1] https://ourworldindata.org/grapher/ghg-kcal-poore https://ourworldindata.org/grapher/ghg-kcal-poore [2] https://natural-resources.canada.ca/sites/www.nrcan.gc.ca/files/oee/pdf/transportation/fuel-efficient-technologies/autosmart_factsheet_6_e.pdf https://natural-resources.canada.ca/sites/www.nrcan.gc.ca/fi...
        • twobitshifter 4y ago
          On the beef numbers, Australia and NZ now have net zero farms, so it may depend on where you live.
        • scott_w 4y ago
          > - 35000kcal from gasoline emits how much CO2? If you're going to do that, what about the CO2 (gasoline) emitted to collect the gasoline? Given you need oil to extract oil, it's still far, far, far less efficient.
          • dheera 4y ago
            It's miniscule compared to burning the gas, or the oil industry wouldn't exist, considering a lot of the oil extraction and refinement industry is powered by oil itself. You could have also Googled that number instead of trying to make a comeback for the sake of it.
    • prmoustache 4y ago
      Eating more != eating significantly more meat. I used to be an elite racing cyclist, I know what it is to need fuel in a 200km bike race Besides, riding at conversational slower pace only need a fraction of that energy. When I was commuting 75km a day myy food intake may be at worst marginally higher than a day off.
• rmvt 4y ago
  if anything this is an argument against the paleo diet and nothing else...
  • dheera 4y ago
    Correct, I wasn't trying to make a statement about specific diets, just that diet does make a huge difference in evaluating the carbon efficiency of cycling.
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• loeg 4y ago
  This is definitely the kind of generic tangent / screed I believe to be discouraged here.
• ntonozzi 4y ago
  Perhaps more carbon efficient, but 15x less energy efficient: > Biking takes around 25 kcal/km [iii] above basal metabolism, which is equivalent to .11 MJ/km. A typical car in the US gets 25 mpg, or 9.5L/100 km, which is equivalent to 3.3 MJ/km. The Toyota Prius takes only 5 L/100km, or 1.7 MJ/km. So a typical car takes 30x more energy per kilometer than biking, and a Prius takes 15x more. This is what we expect given how much heavier cars are than bikes.
• scott_w 4y ago
  Not even close to true. I can ride 60-70 miles on reasonably hilly terrain on about 2000kcal. There’s no car that can come close to that. And that’s assuming drivers don’t eat (the McDonald’s wrappers I see by the side of the road proves that they do).
  • dheera 4y ago
    See my comment above with the numbers. 2000 kcal worth of food takes somewhere in the range of 6 kg (for vegetables) to 72 kg (for beef) of CO2 emissions to farm. If you assume a gas car needs 35000 kcal to make the same journey it's about 10 kg of CO2 emissions. You're making a kcal-to-kcal comparison, which is apples-to-oranges in terms of climate change. Climate change doesn't care about kcal, it's greenhouse gases like CO2 that do matter. I know internet forum people are going to come back with a retort about how drivers also eat, but the fact is that cyclists do need to eat more than drivers to make the same journey, and the math puts the answer somewhere in the middle, you need to do the interpolation.
    • scott_w 4y ago
      Your numbers are absolute nonsense. You excluded the CO2 to extract the oil and refine it into petrol/diesel. Nobody eats 2000kcal of beef: that's 6 whole burgers! On top of that, your numbers assume that drivers don't eat, which is self-evidently not true!
      • dheera 4y ago
        > You excluded the CO2 to extract the oil This is miniscule compared to the amount emitted by burning it. It sort of has to be, or the industry wouldn't exist. Congratulations, you're now deliberately fishing at the opposite and and nitpicking at the opposite end just to argue, at this point, when you could be looking at the entire pond. Of course nobody eats 2000kcal of beef, I never said that. I was providing an extremum of all-brassica and all-beef so that you can interpolate somewhere between them, but evidently you're more interested in taking the endpoints and call it nonsense instead of doing the interpolation. So go ahead and assume drivers eat. Bikers eat more. Again, do the interpolation. You get some data, you do the math, then argue. You will still find that it's within the same order of magnitude. CO2 from food production is a thing, and it's hugely variable depending on diet, that's the point.
• olabyne 4y ago
  But the cyclist is doing his required weekly activity. The prius occupants will have to do sport on the side to stay healthy ...