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news
Commuter cyclistCycling is better than walking (or car sharing) when it comes to saving the planet finds study
Active modes of travel are not “zero emitters” when it comes to greenhouse gases, according to a new study. Researchers conclude that while cycling is better than walking, active travel may result in people eating more. This could mean that switching from driving to car-sharing could reduce emissions more than switching from driving to walking. (But it probably doesn’t.)
The study, published in the Scientific Reports journal, aimed to demonstrate that assessments of emissions associated with different forms of travel should take into account emissions associated with that person possibly eating more in response to their increased physical activity.
While conceding that, “studies of active transport do not currently provide us with definitive information on the extent or nature of compensatory food intake in response to increased walking and cycling,” researchers assume that a person who shifts from a passive mode of transport (e.g. driving) will eat a little more.
They base their calculations about the emissions cost of this on Mike Berners-Lee’s 2010 book, The Carbon Footprint of Everything. This estimated that a mile cycled in the United Kingdom generates emissions of between 65 gCO2e and 2,800 gCO2e, depending on what the journey was powered by (bananas or air-freighted asparagus).
Clarifying this detail, they write: “The notion that energy expended from a cycle ride may be substituted directly by air-freighted asparagus is far-fetched, but underlines the point that there is a high carbon cost of modern food systems.”
The study estimates that in the UK, emissions resulting from walking could range from 0.05 to 0.25 kgCO2e/km and from 0.03 to 0.13 kgCO2e/km for cycling.
(It’s worth pointing out that they found wide variability between countries for this, representing nearly a five-fold difference between the most and least economically developed countries.)
The Intergovernmental Panel on Climate Change estimates that emissions from cars range from 0.15 kg/km to 0.26 kg/km based on a ‘well-to-wheel’ life cycle assessment.
Based on the extreme ends of these estimations, the researchers at one point write that, “Taking account of walking and cycling emissions may suggest that car share schemes could have a bigger positive emissions impact than increasing walking.”
This – we are astonished to report – is the detail the Daily Mail has picked up on, resulting in its headline, “Walking to work is WORSE for environment than car sharing because it makes you eat more leading to higher greenhouse emissions, new study finds.”
In reality, the study only really concludes that emissions from food required for walking and cycling are “not negligible” in economically developed countries and that they should therefore be considered when estimating net-emissions impacts from transport interventions.
Alex has written for more cricket publications than the rest of the road.cc team combined. Despite the apparent evidence of this picture, he doesn't especially like cake.
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37 comments
really not sure why we're even debating this one...
Because the msm will use it to try to undermine cycling's green credentials; when they get around to noticing cycling at all that is. Has there been any coverage of Bike Week? I've seen none.
the funny part i found, last night i cycled 40 miles from bournemouth to portland, including quite a few hills, average speed 16.9 mph, two hours 22 minutes. The same route on my motorbike, 1 hour 20 minutes. So the engine powered vehicle is just one hour faster over 40 miles. Thats insane in my head. A car would actually be the same as the motorbike, if not slower in day time due to traffic, traffic lights etc, but would be costing far more than my 300 quid carrera. The bicycle is by far the most effecient and the one we should be looking to get more people onto safely. If you wanted to walk that same distance, it would take you at least ten hours, if not more. Bicycles are amazing designs.
Given obesity is such a problem in our society, I think it's fair to say a good proportion of the population eat significantly more calories than strictly required to fuel the mode of transport they use.
For me, when I cycle, using active transport, I become a lot more conscious of my choice of food, as I want to reinforce the health benefits of this exercise. In contrast, when not cycling, I pay less attention, and at times, over eat - more so than when I cycle.
While I understand more energy is required to fuel active transport, if we accept many people over fuel regardless (obesity), I don't think it should be assumed that there needs to be any actual increase in calory consumption, at all, from active transport.
Comparing obesity levels in active versus passive travellers could suggest whether passive travellers really do eat less calories. I think it's far too simplistic, given psychological and other factors, to assume higher daily calory usage leads to higher calory consumption, unless we assume that everyone only eats exactly what they burn in any given day, which would be a simplistic yet typically academic way to consider the issue.
Surely it's a blatantly obvious statement to say that to eat more is to increase one's carbon footprint? Isn't the conclusion, as stated elsewhere, that to reduce carbon footprint, we all, active and passive travellers together, should eat food sourced eat less carbon intensive methods? Not that we should sit in a car versus exercising?
Nobody is a zero emitter, but active travel, esp cycling is the most efficient from a calorie per mile measure. Petrol/diesel is far more inefficient. And whilst engaged in active travel those calories aren't ending up clogging arteries that then have to be processed by the NHS at huge expense to us all.
Exactly. If the journey is going to be made, then the most efficient form of transport should be used, which is inevitably the bicycle for short trips. A point which seems to have completely escaped the notice of the authors of this study.
It's the dragging around of a fairly pointless one and a half tonnes of stuff that gets me. I have a relatively heavy bicycle, but it still weighs less than an "executive" car seat.
The study found exactly that Burt.
The bicycle was the most efficient.
Did you even read it?
No one should be powering their cycle ride with air freighted asparagus, British asparagus is a fine and indeed gourmet product, it is in season at the moment, though is about to come to an end. Wonderful fat spears.
I believe that there is about a week to go in the recognised season, at least according to the internet.
I occasionally visit the Hardwick Veg Shed, I ride there, it is shockingly muddy in parts during the winter but at the moment the route is dry and busy, or it was last time I went. Just up the Thames. Unfortunately quite expensive, but grown well and very tasty. We might be coming out of the spring gap, I could only get their strawberries last visit but they were fantastic. As the summer gets going, becoming the autumn and then winter the growing gets good. Their sprouts are fantastic, their squashes are strange. It is thier pumkins I carve at Halloween. Their Lady Balfour potatoes just make the best roast spuds, though I haven't managed to get them for Christmas for the past couple of years. My slaw is not the same without grated black radish. I only buy the stuff they have grown on the estate and ride it home. The food miles could only be lower if I could grow it myself.
Good work.
For me, that is the 'take home message' from the study.
Eat locally grown seasonal food as much as possible.
Up until a few years ago I was pretty oblivious to the environmental impact of the food I was eating. Studies like this definitely help to educate people as to the impact of their choices.
If that's the take-home message, doesn't it suggest that the results of the actual study, which was meant to be about the impact of different modes of travel rather than different diet choices, were indeed rather meaningless?
The study estimated the carbon footprint of cycling for different diets.
So the take home message for a cyclist is that the carbon footprint of your cycling is directly related to your diet.
Broadly speaking locally grown seasonal food has a lower carbon footprint. Bananas apparently being an exception!
I think bananas are generally transported by container, and many other fruit and veg that doesn't completely rely on freshness, and the reduction of picking to plate.
Container freight is shockingly efficient and cheap. The size of todays massive container shops allows such efficiency of scale. I heard on some TV programme, perhaps apocryphal, that it was cheaper to ship a pair of jeans, port to port, from China than it was to distribute them from the port by road, in the UK.
A lot of that cheapness will be savings in fuel, shockingly dirty that fuel oil is that they burn on those huge container ships.
Flying anything is incredibly fuel inefficient, most of that, as I understand it, coming from getting it up there. I remember, when I was temping in the mid 90s, when working nights for Geest at Heathrow, Kenyan sugar snap peas and fine beans would come in, already prepacked in small cellophaned polystyrene trays. Never really appealed to me as a consumer, I want cheapish, substantial veg when I'm cooking and eating it. Only job I ever worked with electric pallet trucks, fun, though a little scary when working that tired.
Life usually being way more complex than it appears, sometimes means that simplistic and usually context free food miles can be a terrible way of judging something's green credentials. Surprisingly, it can be greener to grown fine beans in season in Kenya or wherever than to do so out of season in UK.
Burning calories for a journey does not necessarily mean that the person consumes fewer. Just look at the queues for drive ins recently and the obesity problem in this country. People that participate in active travel are probably more likely to be concerned about what they consume.
Especially as they are generally barred from using drive-throughs ...
I certainly eat more when I cycle commute to work. I make a point of eating any cake/pastries that I like the look of.
Whereas I eat the cakes and pasties in case I have to commute one day. Preperation and all that.
I just eat the cakes and pastries (and pasties) because cakes and pastries (and pasties). My cycling is entirely coincidental.
Trust the Daily Mail, or rather don't....
Couple of observations if I may be so bold; a 25 stone sedentary driver, is likely to eat more than a 10 stone cyclist as the driver has a huge metabolism to support which consumes calories despite them being inactive.
Secondly the Daily Mail completely ignores the point that extra walking, which may involve extra calorie 'use', will greatly lower the possibility of disease (diabetes, obesity, cancer, stroke, heart attack etc etc etc) and therefore 'Protect the NHS'. How quickly recent lessons are forgotten.
The mamils who drive their SUV miles before starting a ride to the cafe for a gourmet civet espresso & half a cake might be feeling a little less virtuous. Though hopefully they might have forgotten about the cake stop by now, and be benefitting from a lowered BMI?
My recollection from reading the Berners Lee book some months ago is that he found the most planet-friendly means of transport was the e-bike.
Have they realised that a full car of sharers also emits a little more than one with just the driver?
If we are going to attribute walking/cycling with the carbon footprint of increased food intake - we make the assumption that a gym session (which one might drive too) isn't being replaced with an Active commute.
We also make no allowances for the carbon impact of a sedantary lifestyle - I very much doubt it is negligible.
These are 2 factors that certainly undermine their assumption. A few thoughts:
Is the driver assumed to be using zero calories from their diet for their journey? And not stopping at McD or wherever for a throwaway cup of brown water on their way to work? (with engine idling in the queue at the drive-thru)
Those who drive daily are likely to replace their vehicle much sooner than the regular cyclist whose car may be used less often. Households with 1 or more cyclists may have lower car ownership rates.
Is the active commuter's diet that much larger than the driver? How do you establish the energy use of a cycle commute? And does some of their diet not come from staples such as bread, potatoes, oats, rice and pasta? All cheap sources of energy and likely low in CO2 per kg.
Beyond their own health, what about the driver's negative impact on the rest of society including noise, pollution (15 million in the UK exposed to "the invisible killer" says the BHF) and casualty statistics?
This graphic from a few years ago suggests that walking and cycling have a net benefit to society while buses and cars cost society quite a lot:
https://averagejoecyclist.com/wp-content/uploads/2016/03/infographic_2_s...
I have printed the report PDF to read over the weekend and would be interested in further observations.
The driver is not assumed to be using zero calories. They are assumed to be using no more than if they were equally sedentary elsewhere.
Whereas a cyclist will be burning more calories than if they were sedentary.
If you own a car then unfortunately you are responsible for some of the carbon footprint of that car even if you never drive it.
All other things being equal, a car owning cyclist has a far greater carbon footprint than a non car owner.
The paper examines the impact of a range of diets, that's pretty much the point.
If you dine exclusively on Peruvian asparagus then your carbon footprint is going to be enormous regardless of what transport you take.
".....researchers assume that a person who shifts from a passive mode of transport (e.g. driving) will eat a little more."
Basing a whole research paper on an unproven assumption is, to be frank, absurd, unscientific and completely lacking in any credibility. In my experience, people who cycle probably eat less than those who just sit around all day, constantly snacking.
To call this unscientific rubbish would be a compliment.
You just don't get science do you Burt?
I haven't read this particular paper but the original Berners Lee book tried to assess all forms of transport on the basis of how much energy from the sun (whether converted via solar panels into electricity, via fast-growing wood - willow? - into renewable fuel, or via wheat bread into pedal power) each took. So I don't think he was making specific assumptions about how much more a cyclist might eat, more measuring the energy input required to move a bike over a given distance.
I've had a quick read of the paper and a couple of the references they cite and I cannot see any figures for increased calory intake in any of the studies, either from self reported figures or lab studies, any conclusions are therefore based on an untested assumption. There have however been studies, the study comparing calorie requirements of the Hamsa[I think that was the tribe) and New York office workers springs to mind, that suggest that with increasing fitness comes increasing physiological efficency, ie that non competitive but physically active individuals have calorific requirement similar to largely sedentary individuals.
While it is obvious that cycling a mile requires fewer calories than walking or running a mile, until there are some controlled studies to determine how much a comuting walking or cycling persons calorie intake increases studies such as this are, largely, meaningless.
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