How fuel efficient is cycling and walking

clonmahon

Interesting article
http://physics.ucsd.edu/do-the-math/2011/11/mpg-of-a-human/

monument

A little information is a dangerous thing.

He calculates the external costs of food for energy, but not even the external costs of fuel for cars. Never mind the other energy external costs, once he starts getting into external costs and he is selective, I have to ask why and to what point. And presumably the car drivers and passengers don't exert any energy what so ever?

He says "So far, our bodies have not figured out regenerative braking" but misses the wider point that cycling commuting isn't only energy being used on transport but also energy positively being used for exercise.

He talks about what happens to cyclists when in cities and the nature is stop and start, but he does not talk about the energy costs of cars in traffic. Or, to an extreme, cars in stuck in traffic in the winter with the heater on. He also seems to be using the same wind calculations for cyclists in open air as among urban cover, but I could be wrong.

He also mentions "A Prius loaded with four people" but fails to mention anything about the average loading and that most motorists don't drive a Prius.

And then you've got the affects of planning for cars rather than cyclists and the affect that has on travel distances. And so on...

tomasrojo

I haven't time to read it, but this comes up quite often, and usually it's based on ignoring the hidden energy uses involved in car use.

This was said about a previous calculation:

The hidden carbon costs of automobile travel are gigantic, more than double the final emissions for the car. They include the cost of mining and smelting the steel, pumping the oil, shipping the oil, refining the gasoline, shipping the gasoline, creation and maintenance of roads, construction of the car, etc etc. To leave out these costs while counting every drop of fertilizer sprinkled on a cow's pasture is extremely foolish and, frankly, disappointing.

http://www.ecogeek.org/ask-the-ecogeek/867

This is relevant too:

Walkers don't travel thirty miles to go to the grocery store, but drivers do. Walkers opt for the corner grocer over the Wal-Mart. Driving doesn't encourage waste because just because it's inefficient. It also exponentially increases the amount of ground we can cover, creating sprawling cities and destroying local economies. Even if walking produced four times more CO2 emissions per mile than driving, walking reduces the number of miles traveled for most errands by ten to forty times.

Pretty much what monument said.

tomasrojo

And indeed (just skimming the article), that seems to be the case here again (reading the comments):

First, you’ve considered the efficiency of converting solar energy to chemical energy of an Iowa cornfield, but gasoline is taken as the raw MPG of a car. This ignores the EROEI of extracting oil, refining it, and delivering it to a gas station. Perhaps you can update your figures to give an equivalent comparison to gasoline?

I think it would also be useful to compare gallons of a standard fuel, in order to directly compare the energy required of travel. The true metric should be distance per unit of energy. Either keep the numbers in terms of energy required or convert them both to a standard fuel of known energy density.

Last, as a cyclist, I disagree with the assumption that on a long distance trip you should consider all of your energy intake as necessary to continue pedaling. 100mi at 15mph is near enough to seven hours of cycling. This still leaves 17 hours (70% of the day) as non-active. So why do the energy calculations for long-distance cycling include base nutritional requirements? Significant food intake is still necessary for you to continue living, which I think we can all agree is a base requirement for any form of travel. It makes no sense to ignore our biological requirement for food during short trips, but include it for longer ones.

HivemindXX

To be fair the article writer has disclaimers indicating that his figures as just ballpark numbers and not be be analysed within an inch of their lives. Also, unlike another study I've been pointed to, his conclusion is that cycling and/or walking is far more efficient than driving.

It's probably more effective as an opinion piece that he pre-emptively brings up the main arguments against this sort of analysis that the car fans immediately jump on. He addresses these issues and still concludes that for a lot of purposes cycling/walking is more efficient.

What Tomasrojo quoted about usage patterns is something that I never really thought about before but it really rings true. The vast majority of my groceries get bought in a Tesco that's on my way home from work. I literally go 0 extra metres to do my grocery shopping. My car driving friend who lives in Crumlin tends to get his shopping in Blanch or Dundrum or Newry!

chakattack

Semi-regularly do a 160k round trip to my parents place. Last time I spent about 3 euro each way on a midway can of coke and a few cereal bars.

The same round trip is probably 15 euro in petrol + 10 euro in tolls. Saves time and the planet win/win

Not counting the sh*t load of food I eat at either end :cool:

tomasrojo

This just up on the Guardian's bike blog:

Europe could cut its total greenhouse gas emissions by more than 25% if every population cycled as regularly as the Danes, according to a pioneering study which tracks the environmental impact of cycling down to the extra calories consumed by riders.

This figure is likely to be a significant underestimate as it deliberately excludes the environmental impact of building road infrastructure and parking, or maintaining and disposing of cars.

http://www.guardian.co.uk/environment/2011/dec/12/cycle-like-danes-cut-emissions

Don't know how true this is either, but will read it properly later.

Lumen

tomasrojo wrote: »

This just up on the Guardian's bike blog:


http://www.guardian.co.uk/environment/2011/dec/12/cycle-like-danes-cut-emissions

Don't know how true this is either, but will read it properly later.

It uses an estimate of 175 calories an hour for cycling. That seems on the low side, perhaps about 50W of output. I wonder where they got the figure from? I would expect even a fairly leisurely effort would see about double that.

tomasrojo

I think it's 175 in excess of what someone driving would use.

(Maybe that's your understanding too.)

Cookie_Monster

tomasrojo wrote: »

I think it's 175 in excess of what someone driving would use.

(Maybe that's your understanding too.)

Still low imo, I'll burn 800 odd an hour on an 18km spin around south Dublin, I really doubt I'd use even half of that on the same 18 km in the car.

carthoris

Putting fuel in me is an awful lot more enjoyable than putting fuel in a car.

Seweryn

clonmahon wrote: »

Interesting article
http://physics.ucsd.edu/do-the-math/2011/11/mpg-of-a-human/

One important thing, as I did not get a chance to read the above:
Did yer man added the energy consumed by the driver of the car, i.e. food and drink? Because as far as I can see the car needs a driver, same as the bike needs a rider. Both of them need energy, not just the rider.

Secondly, the bike is unbeatable in terms of efficiecy by a long shot...

From Wikipedia:

A bicycle's performance, in both biological and mechanical terms, is extraordinarily efficient. In terms of the amount of energy a person must expend to travel a given distance, investigators have calculated it to be the most efficient self-powered means of transportation...

smacl

Seweryn wrote: »

Secondly, the bike is unbeatable in terms of efficiecy by a long shot...

From Wikipedia:

A bicycle's performance, in both biological and mechanical terms, is extraordinarily efficient. In terms of the amount of energy a person must expend to travel a given distance, investigators have calculated it to be the most efficient self-powered means of transportation...

Depends on the terrain, length of journey, and how many journeys are made over the same route. To get between two points not connected by road or track, walking is going to win. If you repeat the journey often, and amortise the cost of constructing a track and building your bike over the number of journeys, you'll reach a point where a MTB will win. Add many more journeys and amortise out the cost of laying a paved road and the road bike will win. Add enough of a load / luggage / people travelling, and a train on tracks wins, albeit we've moved away from 'self powered' at this stage. There's more variables to consider than is obvious at a glance, and these are just a few of them.

tomasrojo

Cookie_Monster wrote: »

Still low imo, I'll burn 800 odd an hour on an 18km spin around south Dublin, I really doubt I'd use even half of that on the same 18 km in the car.

I remember as an undergraduate learning how much exercise it would take to expend the amount of energy contained in one pot of yoghurt, assuming none of the energy went into basic metabolism. It was an awful lot. Most of the energy you take in goes on basic cell replication and system maintenance.

But I don't know any exact figures for any of the above.

EDIT:
http://www.caloriesperhour.com/index_burn.php
This works out calories required per day for various lifestyles. I tried entering 25 years, male, 6' and 165lb.

For a man like this with a very sedentary lifestyle you require about 2125, and for a very active lifestyle about 3365. So about 1200 extra. I don't know how this ties in with the journeys the ECF had in mind making their calculations, but moderately active lifestyle gives you 2745, which is about 600 extra per day. Depending on how much of that day is cycling, does that tie in with the 175 per hour for cycling? Sounds reasonable on the face of it.

EDIT: If you increase the man's weight to 220lb, a sedentary lifestyle requires about 2425, which is only about 300 fewer than the moderately active, lighter man needs.

Beasty

Not sure how that 800 calories was measured Cookie_Monster, but bear in mind the older Garmins significantly overestimate calorie burning.

I managed just over 1,000 in the hour racing yesterday, but that was pretty much flat out at 37 kph and 250w or so (and carrying about 90kg + bike)

christeb

Beasty wrote: »

Not sure how that 800 calories was measured Cookie_Monster, but bear in mind the older Garmins significantly overestimate calorie burning.

I managed just over 1,000 in the hour racing yesterday, but that was pretty much flat out at 37 kph and 250w or so (and carrying about 90kg + bike)

that makes sense, the 800 quoted by Cookie_Monster seems a bit much though, even for a big(gish) guy

NeedMoreGears

Cookie_Monster wrote: »

Still low imo, I'll burn 800 odd an hour on an 18km spin around south Dublin, I really doubt I'd use even half of that on the same 18 km in the car.

18km in a car would burn a litre of diesel (maybe a bit more) - that's around 32,000 KJ of energy or just under 8,000 kilocalories. Cycling it would take around 350 - 400 for me depending on speed. Of course neither figure includes the indirect energy consumption.

To be fair to the author his main point seems to be "This should in no way be taken to suggest setting aside the bike or boots for a car that gets better performance. Rather, we should consider ways to make our agriculture or eating habits less energy-intense " -Having said that, I struggle to see how making healthy exercise look less attractive is a good idea when trying to encourage less energy intensive food production.

Cookie_Monster

Beasty wrote: »

Not sure how that 800 calories was measured Cookie_Monster, but bear in mind the older Garmins significantly overestimate calorie burning.

I managed just over 1,000 in the hour racing yesterday, but that was pretty much flat out at 37 kph and 250w or so (and carrying about 90kg + bike)

yeah I realise that, it used to show 950-1000 before the heart monitor was added, that brought it down to 750-800ish. More accurate but still not bible by any means

having said that I'm sure now that I'm fitter and a bit lighter and used to it it'd take less again now...

hardCopy

Someone posted this recently: