# Carbon Footprint of Biking

So, here’s an interesting experiment.  As I start writing this post, I have no idea what the conclusion is going to be.  See, the thing is, I recently started a new job, and like any citizen of the Netherlands I bike there.  The difference is it is roughly 40 km from my home, so on the way I have plenty of time to think.

A lot of people are very surprised I bike every day, even when I tell them that the second the weather gets annoying I’m on the train or something equally uncomfortable.  Normally, I rationally explain that going by train and bus will take approximately 75 minutes when I include having to wait and get from one means of transportation to the next.  Biking takes currently around 100-120 minutes, which means that for a 2 * (110 – 75) = 70 minutes investment get 220 minutes of biking, which is good exercise and nice in the sun.

Instead of trying to reason with people, I instead considered just giving some retard-explanation to satisfy the most feeble-minded socialists: it’s good for the environment.  Never mind that the train and bus ride every day regardless of whether I spend just under 4 hours commuting and getting a sore butt in the process, but a bike of course has no CO2 emissions, right?

That got the scientist in me thinking…  Of course that is not right.  My Sports Tracker fairly consistently lets me know that a ride in either direction burns roughly 1400-1500 kcal.  That has to come from somewhere, and that somewhere probably leads to CO2 emissions.  So, the question is: how much CO2 does biking one kilometer let out, and how does that compare to common means of transport: train, bus, car, plane, tank, helicopter, walking, …  I know it’s weird to talk about the environment without having a predefined conclusion tailored to fit with your political agenda, but let’s try this the scientific way instead.

I frankly have no idea what the answer will be, but let us take a look at the computations…  When I bike, I spend extra energy.  I know that in order to bike 2 * 40 km a day, I end up burning approximately 2900 kcal extra, just for the exercise.  For 3.5 hours, I also breathe heavier.  To stay on the good side of my new colleagues, I take a shower when I get to work, and I also need a shower when I get back home, which means at least one extra shower a day.  I also need to do more laundry, as I am not a damn dirty hippie and sit around in my bike-clothes at work.  We also need to factor in the production of the bike.  All in all, we are going to consider 5 contributions to extra CO2 emission: extra calories burned, extra breathing, extra showers, extra laundry, and bike production.  I’m sure there’s other contributions (I use extra deodorant, wear and tear of clothes, extra sewage from extra eating, …), but let’s keep things simple.

I need an extra 2900 kcal to bike every day.  I’m not a car, so I can’t just consume gas which would probably be much more efficient, but instead need food.  Food is not just food when it comes to CO2 emissions; according to some hippie web-site, the more hippie your diet, the less CO2 do you emit. Fuck that jazz. Hippies do not have jobs and hence do not bike to them, so let’s go with an average diet. With beef. Because yum. 2900 kcal/day is roughly doubling the daily energy consumption, so let’s just assume that the hippie-site-numbers for one day is the amount of CO2 we emit for biking 2 * 40 km. The hippies say we need roughly 2.5 ton CO2 ((Really CO2 equivalent, because a lot of it not actually CO2 but other gasses which may have more or less impact on the environment. To appease dumb idiots it is all condensed into a single number.)) for one person a year. This means biking 2 * 40 km leads out 2500 / 365 = 6.85 kg CO2 for production of food. We could add extra CO2 to that for transporting and cooking my food, but I like my steaks rare, so fuck that jazz. That’s approximately 6850 / 80 = 85.6 g CO2/km.

Next let’s take a look at the extra breathing I’ll inevitably do. This site is ugly as fuck, so it’s probably reliable. It says, that hard work yields emission of approximately 0.33 – 0.38 m3/hour/person whereas resting uncomfortably on the train while a hippie tries stealing my iPad causes me to emit 0.02 m3/hour/person, for a marginal emission of around 0.35 m3/hour/person. It’s late and I’m too lazy to brush up on my chemistry and do math, so here I found that 1 ton of CO2 = 556.2 m3. Thus, biking 2 * 40 km emits a bonus of 3.5 hours * 0.35 m3/hour/person / 556.2 m3/ton * 1000 kg/ton = 2.2 kg/person or 2200 / 80 = 27.5 g CO2/km.

If I skip my morning shower, I can cut down the excess showering to 1 a day (one after I get to work, one when I get home). I can reasonably cut down on at least one of them to just cool me down and wash off the sweat. According to this miserable piece of propaganda, showering uses approximately 700-1700 kg of CO2 a year. No, they don’t have units or anything else to back that up, but they have Massachusetts in the name, just like MIT, and I also checked other sources that actually have information but are harder to read, and they seem to largely agree. It’s the Netherlands, so the showers probably use gas, and it’s corporate so there’s no chance in hell it’s the low-energy alternative. Let’s say 800 kg CO2/year for a 10 minutes shower. If we assume I can clean my delicate body in 5 minutes, that’s a total of 800 / 365 / (10 / 5) = 1.1 kg of CO2 for 2 * 40 km or 1100 / 80 = 13.8 g/km.

Using an intricate system, I only soil an extra pair of boxers and a t-shirt extra per day. I presume that adds up to around a load of laundry a week. One load of laundry emits 51 / 187 kg of CO2 according to this page. That’s 51 / 187 / 5 = 0.055 kg of CO2 for 2 * 40 km or 55 / 80 < 1 g/km. Finally, there's the production of the bike. I think I'm being generous if I assume a bike lasts approximately 10000 km. I tend to wear them down in around half that and after that they need repairs which undoubtedly also costs CO2. StackExchange is as reliable as Wikipedia, and says 113 kg for a bike, or 113000 / 10000 = 11.3 g/km.

Adding these together – I was hoping it wouldn’t come to this – we get that the carbon footprint of riding 1 km on a bike is approximately 85.6 + 27.5 + 13.8 + 1 + 11.3 = 139.2 g/km. We note that the shower and laundry isn’t that significant a part, so this is probably a fairly good number regardless of the distance.

How does this compare to other means of transportation…? The Guardian put up a shitload of numbers, but ignored the effects we have computed above for biking (though the article mentions some of them). Some highlights are: a small motor cycle (40-160 g/km)! Using a bus uses 20-80 g/km and a train 20-100 g/km (we’re avoiding electric vehicles as they ignore that the electricity has to come from somewhere – typically coal). Short-haul flying is just 230 g/km, and driving in a real car is around 150 g/km (less if car-pooling).

All in all, biking doesn’t really look that good. It emits significantly more CO2 than public transport, and even the worst cars come out better as long as you stick two persons in them. Given the quality of the numbers from the Guardian, they probably don’t add in production of vehicles, and definitely not all factors (production of electricity), so the numbers are likely too low. Yet, I think it is interesting that biking is almost uniformly worse for the environment than other means of transportation. Heck, I even emit 27.5 g/km of the CO2 in the traffic, which is approximately the same as a small scooter. The rest is emitted on the wrong side of the rivers or in Africa or some other place nobody cares about, but I pollute as much as a scooter when biking. And then some.

This result is genuinely surprising to me. I was expecting biking to come out on top, but still yield a fraction of the CO2-emissions of other means of transport. I expected the shower and laundry to have a huge impact and the impact of the food to be smaller (but still significant). Of course, biking doesn’t yield (as much) particle pollution, and none in the local environment, but that’s not what we were testing here.

So, henceforth, when people ask why I bike to work, I’ll tell them it is because the beach is too far away from home, so I support global warming to get it closer – nobody is going to miss Zeeland anyway.

## 25 thoughts on “Carbon Footprint of Biking”

1. Tobias Baunbæk Christensen on Facebook says:

Sjovt eksperiment. Men glemte du ikke at tilfoeje hvor meget det koster at lave en bil/bus/tog, samt reparationerne af disse. Og at tilfoeje det som det koster bare at sidde stille.

2. Michael Westergaard on Facebook says:

Jeg skriver at tallene sikkert ikke indeholder konstruktion (men da de ikke er mine ved jeg det ikke). Jeg nævner produktionen af cyklen ikke er videre stor og man ser de enkelte komponenter og kan ignorere dem af dem, man ikke mener er vigtige.

Alle beregningerne er marginaltal, så effekten af at trække vejret er renset for at sidde stille, men det er kun 0.02 m3/time vs 0.33-0.38 m3/time, så det kan i praksis ignoreres da altig alligevel er bygget på skøn.

3. Mich Bruus Pedersen on Facebook says:

Med mindre du er begyndt at drikke råolie og spise kul, tæller din personlige forbrænding ikke – kun som dét der skal til at producere/transportere din mad…

4. Michael Westergaard on Facebook says:

Ja, og det er de værdier jeg estimerer. Det koster enormt meget CO2 at producere mad, specielt kød, med oksekød som værste synder. Køer prutter metan, som er over 20 gange værre end CO2. Hvis jeg ikke havde brug for at forbrænde 2900 kcal ekstra, ville køerne ikke være der, så det er kun fair at tage det med (antager at “alle” cykler, så det ikke bare er en smule, der ville være kasseret i stedet). Faktisk ser det ud til, køer forurener mere end biler på globalt plan efter nogle målestokke.

5. Tobias Baunbæk Christensen on Facebook says:

Saa hvis du ikke spiste koed saa ville det vaere bedre end at tage toget?

6. Michael Westergaard on Facebook says:

Næsten. Ifølge et af mine links, ville det reducere CO2-udslip for forbrænding med op til 40% og reducere de små 90 g/km ud af 140 G/km til godt 50 G/km og med 100 g/km stadig være ca 4 gange værre end tog. Bare den ekstra respiration er ca på niveau med togets udledning.

7. Marco Carbone on Facebook says:

I’m impressed…why don’t you write a short paper on this and send it somewhere…if it goes on the news, the US government will make rich, while you won’t be able to come back to Denmark anymore 🙂

8. Peter Sebastian Nordholt on Facebook says:

Hvis du vejede mindre ville du skulle bruge mindre energi på at transportere dig selv. Ville du evt. kunne tabe dig nok til at gøre cykelturen grøn i forhold til tog og bus?

9. Michael Westergaard on Facebook says:

Marco: while both are interesting prospects, my time as a paper writer are over. Now I just give serious thought to stupid ideas 😉 – besides, while I mostly believe my numbers, everything is based on quick google searches (I did double check all the numbers from multiple sources though). In fact the entire post, including research and math was done in 2.5 hours after a long day (including 90 km of biking just to spite Greenpeace). This is also written in the alarmist tone preferred by many environmental organizations. Real science couldn’t ignore particle pollution and other things I left out in favor of focusing on CO2 like mainstream media likes to.

10. Michael Westergaard on Facebook says:

Peter: TL;DR: Nej. Som nævnt er alene den øgede respiration nok til at gøre knallert eller et fyldt tog bedre. Ifølge Sports Tracker forbrænder jeg ca 36-37 kcal/km. Hvis min vægt var 70 kg, ville det falde til ca 30 kcal/km. Hvis vi puttede mig på et urealistisk og stærkt undervægtigt 50 kg kunne det måske falde til 20 kcal/km. Hvis vi er generøse og siger det er halvt så meget som nu og antager en vegansk diæt (passer godt med sygeligt undervægtig), kunne jeg måske reducere udledningen til 25 g/km, eller på højde med et fyldt tog og knallert indtil man medregner respiration, som er i samme størrelsesorden.

11. Peter Sebastian Nordholt on Facebook says:

Det tænkte jeg nok. Dog forestiller jeg mig at respirationen også må gå ned med vægten. Den CO2 du udånder må jo komme fra din krops forbrænding og derfor blive mindre når du forbruger mindre energi.

12. Peter Sebastian Nordholt on Facebook says:

Har du forøvrigt medtaget din krops øgede udledning af … andre drivhusgasser … som resultat af øget fødeindtag?

13. Michael Westergaard on Facebook says:

De tal, jeg så, nævnte ikke vægt, men det er måske det, intervallerne dækker over? Det går i hvert fald ned, omend jeg mener at huske noget med, det afhænger af overflade eller volumen og ikke masse direkte.

Som nævnt i indlægget regner jeg ikke øget forbrug af kloakering og lignende med. Det er altid en balance hvad man skal regne med, så jeg tog bare de 5, jeg var kommet frem til mens jeg cyklede.

14. Peter Sebastian Nordholt on Facebook says:

Det er fair nok, og det egentlig ikke for at sige at det ikke er en interessant beregning. Men den bærer lidt præg af at du har koncentreret dig meget om cykling og udledningerne i den sammenhæng og så skøjtet lidt let over de andre. Det ville klæde udregningen hvis du havde tænkt lidt mere over de udledningen i forbindelse med tog-bus-bil. F.eks. må men næsten regne med at der er trafik på de tidspunkter hvor du rejser. Det vil gøre tog og bil en del mindre effektivt. Og hvad med dit øgede forbrug af iPhone/Pad i forbindelse med tog kørsel? osv. osv.

15. Michael Westergaard on Facebook says:

Jeg er helt enig, og naevner ogsaa, jeg ikke er 100% tilfreds med de beregninger for traditionelle transportmidler (jeg naevner eksplicit at elektriske koeretoejer takseres som 0). For at holde boevlet nede, tog jeg bare tal the the Guardian uden at lave nogen dybere analyse afderes korrekthed.

16. Peter Sebastian Nordholt on Facebook says:

Det er jeg godt med på, men derfor er det jo ikke helt fair at sige at du en mindre effektiv end en bil, nå du bedømmer det ud fra tal, som du allerede har dømt at være for positive (ellers havde du jo bare taget Guardians tal for cykling :-)). Desuden, din udåndede CO2 må vel være CO2 neutral eftersom den kommer fra de ekstra køer der produceres for at tilfredstille din sult. Produktionen af køerne giver selvfølgelig et CO2 overhead, men den faktiske CO2 du udånder kommer jo fra en ko’s krop.

17. Peter Sebastian Nordholt on Facebook says:

… ok den sidste del er jeg ikke helt sikker på holder vand, men det virker værd at overveje.

18. Michael Westergaard on Facebook says:

Den udåndede CO2 kommer primært fra affaldsstoffer produceret under fordøjelse. Vi indånder meget lidt CO2 (under 1% SVJH).

19. Peter Sebastian Nordholt on Facebook says:

Det er vel hovedsageligt fra den forbrænding der skal til for at bevæge dine ben og cykle? Alt andet lige kommer kulstoffet fra den udåndede CO2 vel fra din føde … Dvs fra en ko, der har fået det fra nogle planter der har fået det fra noget CO2 du har udåndet. The circle of life, og alt det der.

20. Michael Westergaard on Facebook says:

Ah, på den måde. Det er meget muligt.

21. Dirk Fahland on Facebook says:

Do the food CO2 emission numbers factor in that your cows had to eat lots of stuff made of CO2? On the other hand, cow methane emissions are heavy climate gases so that might ditch the numbers even worse. I assume by going vegan, your equation comes in more favorable for biking (every home grown carrot has negative co2 emissions, the more you bike, the less you emit, ha!)

22. Michael Westergaard on Facebook says:

The numbers are just from some hippie site, so I’m not entirely sure what they include. I’m assuming “everything.” The numbers do not seem to change too much around the internet (it’s at least within an order of magnitude).

Going vegan eliminates approximately 40% of the emissions from food, but it’s still worse than almost any of the alternatives – even the inevitable weight loss due to the unhealthy lifestyle most vegans adhere to, you still end up emitting more CO2 via your food. With a vegan diet you need to be very careful to not die of malnourishment, so just because one component has negative energy impact doesn’t mean the diet as a whole has. And I think if you had to consume 2900 kcal worth of carrots you’d end up with a very bad case of carotenemia 😉

The The Guardian article I used for the transport numbers even mention that some environmental organization admitted walking was worse than the train – I just showed biking is too.

23. Peter Sebastian Nordholt on Facebook says:

Well, if you did die that would probably save a lot of CO2 emissions, so maybe going vegan is not so bad … Just kidding of course ;-).

24. Michael Westergaard on Facebook says:

Vegan is not too bad (except for the food, of course); biological or – even worse – raw food biological on the other hand is bad for the environment and basically robbing people in China/India/Africa of food. But yeah, the only environmentally correct choice is to just man up and die – preferably in a manner so you don’t decompose and release more CO2 😉

25. Peter Sebastian Nordholt on Facebook says:

Anyway, I think my argument is sound that your exhaled CO2 is CO2-neutral. But I guess it really doesn’t matter. Even if you cut everything else but the production of your meaty diet you will never get more efficient than a decently full train (or bus perhaps, but I think once you correct for rush-hour traffic that gets pretty inefficient). That’s pretty interesting because it basically says I am right to be lazy and take the train, yay!

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