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You often hear "Walk, it's better for the environment", but is that actually true?

If I walk 5 miles instead of taking say a public bus, given that I now will need to replace the energy I spent walking with food which has a cost on the environment to grow, which would really be more environmentally friendly? Given that the bus would be running anyway, so the only cost is hauling my extra weight on it. How do electric cars compare?

Cycling would cost me less energy, but then there's the wear and tear on my bicycle which again has a cost on the environment that is presumably greater than the food cost. Roller blades seem to last a long time (or is that because I rarely used mine?) so could they be more efficient? Would sailing be a more environmentally friendly mode of transport than walking? Again there's wear and tear on boat parts, but over a long distance humans would need a considerable amount of food and fresh water.

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    Nice question. To extend it a bit: Bikes need lubricants (partly containg persistent environmentally-converning substances) for their chain, which are emitted into the environment. Cars/buses also need lubricants for other parts. Walking/running causes abrasion of your shoe sole. Depending on your sole the abrased particles might be environmentally concerning (e.g. micro plastic particles). At the same time, tire wear also causes particulate air pollution in cities. Hulls of boats are commonly coated with anti-fouling agents, which are emitted during usage and cleaning acitivities.
    – daniel.heydebreck
    Commented Nov 2, 2016 at 12:59
  • "environmental friendly" is a very broad term. Do we look into the emission of substances and objects into the environment that have a negative primary impact on human health? Do we have a regional focus ("Who cares about pollution if it takes place 1000 km distant?") or a global focus? Do we look into emissions of green houses gases? It should be also questioned how the vehicles and are food are produced and transported. The mode of transport that leads to the death of most humans per year might be the most environmental friendly one because humans are the root of all bad ;-) .
    – daniel.heydebreck
    Commented Nov 2, 2016 at 13:03
  • btw, ONE mile walked, run, skipped, crawled is 100 calories spent. (gees this is an average within narrow parameters). Primarily from fat stores as this gets one into that TRUE fat burning mode. But each pound of fat is 4000 less maintenance fees or 3500 calories. So, to enter into your equation calories/energy spent per mile, use 100 calories.
    – stormy
    Commented Nov 3, 2016 at 23:49
  • We have several related questions on this site (e.g. Impact of various travelling options and Sustainablity of Telecommuting) but I AFAIK none that take the food consumed by people into account.
    – THelper
    Commented Nov 4, 2016 at 8:19

4 Answers 4

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This question is addressed in a paper by Shibahara et al, 2013 (doi:10.2208/jscejipm.68.I_285). They don't discuss walking, but they do discuss bicycling, which I suppose is a more realistic method for commuting (for example, I bike the 8 miles to work but I've never walked it).

The authors analyzed taxi, gas cars (GV), electric cars (EV), bus rapid transit (BRT), light rail (LRT), city-center shuttle buses, and bicycle (and battery-assisted bicycle, which I am going to ignore, because I think it is silly). They accounted for total system life-cycle carbon (SyLC-CO2) usage, including the cost of making bike paths and rails and roads and the farmland CO2 costs emissions needed to power the human on a bike.

enter image description here

The result is that taxis are unspeakably bad, gas cars go from 145-155 as traffic increases, electric cars are a little better in the 125 range. BRT and LRT have rapid exponential decreases from ~100 with low traffic to 25 for BRT and 15 for LRT at high traffic. City center have a slight decay from 30 to 25 as traffic increases, and bicycles a near constant 20.

So the conclusion is, bicycling is much better than cars or even electric cars, better than buses even in high traffic areas, but not as good as a light rail in the most densely populated areas. I would suspect that walking is similar to biking, maybe even better. The calorie demands would be similar, more paved sidewalk would be needed due to slower speed, but not manufacturing bikes would save you some carbon. But the time it takes to walk more than a couple miles is pretty prohibitive, so it isn't a reasonable transportation alternative in many cases.

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    Very interesting answer thanks! I'm surprised by how good the city center bus is!
    – James
    Commented Nov 2, 2016 at 15:12
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    Very interesting indeed. However, according to the figure the one that is constant near 20 SyLC-CO2 is the city center bus not bicycle. Bicycle is less than 10 and has the smallest SyLC-CO2 even for the largest traffic demands.
    – ZZZ
    Commented Nov 2, 2016 at 22:01
  • @ZZZ There are actually two bicycle lines. Somewhat confusingly, the authors calculate bicycles with human calories and without. The solid black line at 20 is with human calories, the dotted line at 10 is not. Since the OP specifically mentions food energy spent walking, the line at 20 is more relevant to this question.
    – kingledion
    Commented Nov 2, 2016 at 22:22
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    How did they account for time, I wonder? Most people prefer to spend less than an hour each way commuting, so there are huge city-design issues with method choice. Viz, the graphs should look very different for commutes of 1km, 5km, 20km and 100km.
    – Móż
    Commented Nov 7, 2016 at 2:44
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    Also, sadly, the study assumes that the cost of building and maintaining roads is zero, but both bike lanes and rail tracks have an environmental cost. That actually makes cars worse (much worse), but seems to be a gaping flaw in the study.
    – Móż
    Commented Nov 7, 2016 at 2:45
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Canoe! Seriously; depends where you're going. On moving water, when you're not paddling, it's gravity powered transportation. When you do paddle, there's often very little air resistance while you push & pull your weight around without much friction. Works well for me. Even with a heavy load.

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Walk. And probably naked [*].

Because any time one includes any means of transportation one should also include the industry behind it. Trains, buses and bikes don't grow on trees. Neither do clothes... :)

[*] A grape leaf may be deemed advisable for decency.

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  • Discussing environmental issues could be somewhat depressing to many people because any time they are discussed they come with some level of criticism and suggestions for regulations. And some people don't like neither of those two. Just trying to lighten up a discussion on an environmental issue with my approach here, though I stand 100% behind the idea. Please don't shoot me down just for trying. :)
    – ZZZ
    Commented Nov 2, 2016 at 21:44
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    But in cold weather, you would need more energy to keep warm. Also damage to your feet could cause injuries. So maybe more sustainable to wear some sort of clothes and shoes.
    – vclaw
    Commented Jan 27, 2017 at 2:50
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Low-speed electric scooter.

One of the answer found bicycles to be pretty sustainable. However, bicycles are powered by food. Food is an extremely polluting way of producing energy. One kilocalorie of food produces more carbon dioxide emissions than one kilocalorie of electricity. And due to 25% efficiency of humans, you need 4 kcal to have the same impact as 1 kcal of electricity.

What you want is something similar to a bicycle: a lightweight two-wheeled vehicle traveling at low speed. However, you want the polluting food engine to be replaced by a non-polluting electric motor.

By taking one of the most environmentally friendly transport modes (bicycle) and replacing the propulsion method by one that is 10x more sustainable, you will definitely have a winner.

If you're feeling very adventurous, you can also travel on an electric unicycle that has only one wheel instead of two.

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