How much carbon dioxide does a cyclist breathe out per km?

davidtirrell

This is a purely spontaneous thought / question.

I see the most fuel effcient cars pump around 100g of carbon dioxide into the atmosphere per km.

Anyone have any idea what a cyclist pumps out every km, let's say travelling at 24-30km/h?

Cressers

It doesn't matter.

How are cyclists supposed to reduce their perfectly natural CO2 emissions? Stop breathing?

spen666

davidtirrell wrote:

This is a purely spontaneous thought / question.

I see the most fuel effcient cars pump around 100g of carbon dioxide into the atmosphere per km.

Anyone have any idea what a cyclist pumps out every km, let's say travelling at 24-30km/h?

Doesn't the driver ( and any passengers ) in the car emit CO2 as well, so you are not comparing like with like.

You must compare CO2 from Car, driver and passengers with CO2 emitted by cyclist to be more accurate.

You will need to divide the CO2 for car driver and passenger by number of occupants of car to get CO2 per person per journey

simple_salmon

IIRC it depends on the intensity of the effort since that will affect how much O2 is converted into CO2 according to how aerobic/anaerobic the exercise.

Your VO2 max will also be relevant since this is a measure of how efficient you are at converting said oxygen.

musttriharder

I saw this discussed elsewhere recently, for running it is about the same as a small car. I'd imagine for cycling it would be about a quarter of this value, maybe 25g per mile. If nob one else comes up with the proper answer I might try and work out a better answer.

el_presidente

It's irrelevant because the cyclist is exhaling carbon that was extracted from the environment by her in the previous minute / hour / week.
So there is not net gain.


A car is outputting carbon that was extracted from the environment by sea creaures many millons of years ago. Thus increasing the net carbon in the environment.

bompington

Even without taking any exercise, you actually breathe out a bit less than 2kg of carbon dioxide per day.
A lot of environmentalists would be quite concerned if they knew this, there is of course a simple way to stop...

The stat is essentially calculated from the amount of carbs needed to produce 2000 calories, so you've got roughly 1kg per 1000 calories. It depends on whose figures you believe (whenever I try to look this up I see figures for cycling ranging from 400cals/hour to over 1000) , but if you take a nice round 1000 cals per hour to go at 20mph, that means 50g per mile.

You see a lot of carbon stats flying around these days (and I don't mean frame weight) but it can be very hard to contextualise them, baseline figures for normal everyday life might help to introduce some perspective. El_presidente's comment is probably the most important factor in comparing car and bike use - but even then you have to start factoring in the energy used to grow crops, etc. etc. etc...

beverick

musttriharder wrote:

I saw this discussed elsewhere recently, for running it is about the same as a small car. I'd imagine for cycling it would be about a quarter of this value, maybe 25g per mile. If nob one else comes up with the proper answer I might try and work out a better answer.

I saw it mentioned somewhere as well. I had a figure of 20g pm in my mind.

Bob

priory

Nobody yet mentioned the fossil fuel carbon emitted during the manufacture and maintainance of the vehicles.


tj

will3

priory wrote:

Nobody yet mentioned the fossil fuel carbon emitted during the manufacture and maintainance of the vehicles.


tj

True, to be perfectly accurate you'd have to sum up all the emissions of every operation/employee/worker etc etc needed to get the car and the fuel on the road
same for the bike.

sirmy

bompington wrote:

El_presidente's comment is probably the most important factor in comparing car and bike use - but even then you have to start factoring in the energy used to grow crops, etc. etc. etc...

But if you factor in carbon released in the production and transportation of food wouldn't that end up being counted twice - once when it's emitted by a vehicle and again as a result of respiration? Wouldn't t be much better to break it down into distinct groups - farm emissions, processing emissions, transport emissions and end use emissions?

el_presidente

sirmy wrote:

bompington wrote:

El_presidente's comment is probably the most important factor in comparing car and bike use - but even then you have to start factoring in the energy used to grow crops, etc. etc. etc...

But if you factor in carbon released in the production and transportation of food wouldn't that end up being counted twice - once when it's emitted by a vehicle and again as a result of respiration? Wouldn't t be much better to break it down into distinct groups - farm emissions, processing emissions, transport emissions and end use emissions?

yes but you're tranporting the food whether the eater is sat on his a*se behind a steering wheel, or riding a bike. So it's irrelevant.

iainment

See the link

http://www.irishtimes.com/newspaper/mot ... 20868.html

priory

that link has got me all confused


the journalists, editor, and more amazingly the university researchers have not noticed the difference between fossil fuels and food sourced co2
and there is no account taken of manufacturing, maintainance, transport and manufacture of fuels, road building etc etc.

is this how you get a phd?


is it me?
or is it that famous irish sense of humour.

BikingBernie

Surely, the amount of CO2 produced is directly related to the energy being used to move along? A cyclist going at a 30 km hr will be generating less than 0.2 Hp. A car at city speeds will be generating 100 times this or more, due to the huge rolling resistance a car has, the heat losses from the engine and so on. At higher speeds the car will be using proportionately more and more energy due to air resistance.

A car engine of say 1.5 litres will be typically running at 3000 rpm or more, and modern engines have a very good volumetric efficiency, so will pump around 375 litres a minute at 3000 Rpm. OK, so the RPM and energy consumption is speed related but cars don’t get driven at 30 km/ hr very much…

A cyclist at 30 km / hr would be breathing in perhaps 50 L/Min. However, the cyclist will only be converting a fraction of the Oxygen in that breathed air into CO2, which is why mouth to mouth resuscitation works. The car engine will be converting practically 100% of the oxygen to CO2.

Gorillaman

priory wrote:

that link has got me all confused


the journalists, editor, and more amazingly the university researchers have not noticed the difference between fossil fuels and food sourced co2
and there is no account taken of manufacturing, maintainance, transport and manufacture of fuels, road building etc etc.

is this how you get a phd?


is it me?
or is it that famous irish sense of humour.

It isn't clear what method they've used to calculate their numbers but they're talking about 5g/km for a cyclist whereas the numbers for the best small cars are nearer 100g/km; and their numbers for pulic transport show that they still produce double the CO2 emissions for cycling. So fear not, even if you thought you were only going for a ride, you are actually an environmental warrior...!

on the road

or the emission embodied in the manufacture of the bicycle

Compared with the emissions embodied in the manufacturer of a car?

mcdonji1

Can I offset my breathing by carbon capture? There is the frame and various bits of carbon bling to take into account.

Jim :twisted:

rake

musttriharder wrote:

I saw this discussed elsewhere recently, for running it is about the same as a small car. I'd imagine for cycling it would be about a quarter of this value, maybe 25g per mile. If nob one else comes up with the proper answer I might try and work out a better answer.

this is total B***S*** ! a car engine revs at on average lets say 2500 rpm which is 41.6 revs per second. if its a 1.4 litre thats a volume of 29.16 litres per second . id like to see your lungs breath that kind of volume.

Sirius631

mcdonji1 wrote:

Can I offset my breathing by carbon capture?

Yes, if you want to spend your life blowing up balloons. :P