Which mode of transportation produces the least amount of CO2?

Question

I'm trying to determine which mode of transportation produces the lowest CO2 emissions for my commute to work.

I know a Prius emits 104 g/km. Driving to work would be about 15 miles, or 2496 g CO2.

My scooter uses 0.75 kWh of energy to get to work, which corresponds to about 300 g CO2 based on the California power grid mix.

http://www.epa.gov/cleanenergy/energy-and-you/how-clean.html

The tricky one to calculate is bicycling. An hour of bicycling (which is how long it takes me to get to work) burns about 600 calories. According to the paper linked below, the average American consumes 3,774 kilocalories per day, which corresponds to ~1 kg of CO2 per day.

http://achangeinthewind.typepad.com/achangeinthewind/files/diet_energy_and_global_warming.pdf

So if 3774 calories = 1 g CO2, 600 calories = 0.16 g CO2.

That number doesn't include non-CO2 emissions associated with food, but it still seems really low to me.

Could bicycling really produce such low CO2 emissions?

Answer 1

My horse produces the least CO2.  However we're talking about YOUR modes of transport.

Can you carpool with anyone else in your Prius?  If you carpool in your Prius, that probably makes it the least CO2.

Riding your bike 26 miles total a day may cause you to eat more, which causes more CO2 to be emited, to grow your food, HOWEVER, in the long run, because of the SIGNIFIGANT health benifits biking is probably the very best choice.  Biking that much is going to put you in really great physical condition.  So as almost every knows, far too much oil is used to produce our U.S.A. grown groceries.  However, exactly how much oil is used to produce medication?  80% of the U.S. medication, both over the counter, and perscription comes from China.  What kind of CO2 /oil/ect did it take to ship the medication over the ocean from China?

So if you are in great physical shape, and hardly ever needing to access the medical community for perscriptions how much CO2 is that saving?  

If you can couple biking to work, with buying from a farmers market, cooking from scratch as much as possible....well that's a pretty signifigant CO2 savings.

~Garnet

Homesteading/Farming over 20 years

P.S.  Those CO2 savings from biking to work go out the window, the first time some idiot in a Hummer runs you over and your in the hospital for 3 weeks.

Answer 2

Cycling

Answer 3

you are also forgetting that the more muscle you have the more energy you require each day but that sounds roughly correct.

glucose provides about 17 kj/g (4 .06309751 cal) assuming that you are using 600 calories you would need 600/4 or 150 g of glucose for your trip.

the molar mass of glucose 180

so you would need 150 /180=0.833333 mols of glucose

each mole of glucose when burnt liberates 6 CO2 molecules.

so you will have released 0.833333* 6= 5 moles of CO2 for your trip

molar mass of CO2 is 44 so 5*44 = 220g so you would have released 20g of co2 from your trip assuming you are only using glucose. also this is not taking into account any processing emissions and this is only counting glucose that is already in the body.

d/dx+d/d... thanks for pointing out that error.

Answer 4

Walking. You are forgetting the manufacture of the bike, plus its transport to the shop, etc.

  Walking naked would be the best, so you do not have to buy, clean and replace clothes and trainers etc..... ;=)

Actually, I ride my bike because untill now I had not considered walking around town naked..... the ride in the police car would probably create more pollution than I do in a week....

Answer 5

Except for a math error at the end, Gengi is essentially correct.  Bomb calorimeter measurements in my laboratory give the energy content of wheat (84% carbohydrate, 14% protein, 2% lipid) as 16.6 +- 0.1 MJ/kg.  Although a mole is an ill-defined concept when dealing with macromolecules, a reasonable approximation is to represent the mass as moles of glucose monomers, which represent 84% of the total mass.  Your 600 kcal bicycle ride uses about 0.843 "moles" of glucose monomer, which at a 6:1 stoichiometric ratio gives 223 g of CO2.  Note that this number makes sense because it is of the same order of magnitude as the mass of the food that you would consume to fuel the trip.  Bicycling is your lowest CO2 option, provided the energy cost of transporting your food is not factored in.  To make a fair comparison, you should add your basal metabolic energy consumption to the Prius and scooter options because this energy is included in the bicycle option.

Answer 6

Yes, it can.  Another way of doing the calorie conversion is to note that the metabolization of one gram of sugar releases 4.2 dietary calories (i.e., kilocalories) of energy.  But the generic formula for sugars is CH2O, so 12 grams of sugar produces 44 grams of CO2.  You can take the math from here.  Personally, I never worked at a place where biking was practical -- the distances were too great.

Answer 7

Operating from your house with an office at home is the obvious answer.

At least to me .

i live below my office ,in a garden.

your scooter seems a good idea

what are the figures for a horse and buggy by the way is that very high???

An electric car would be the most practical would it not in rainy cold places.

somewhere along the line most practical must also be a factor.

Answer 8

Yes since you would be releasing almost the same amount not biking as biking so that is the cleanest form.  If you really want to reduce your CO2 foot print, sell your car and use either public transportation or your bike.

Answer 9

You switched from 3774 calories = 1 kg to 3774 calories = 1 g, so instead of 0.16 g CO2 it should be 160 g CO2?

From the standpoint of the choices available to you instead of cycling, the two hours you're not inside somewhere with lights and heat turned on probably save some CO2.  You'll also save health costs (unless you ride on smog alert days) so there's more economic benefit on top of the mileage/gas savings.

Answer 10

It could.  But technically speaking your estimate is still too high.  You need to take into account that if you weren't biking to work, you would still be producing CO2 emissions as you breathed.  To accurately measure you need to calculate the amount of the CO2 output that you have from increasing to your higher exercise level when you are biking.  An estimate of 200 calories for that hour if you are walking around or 100 calories if you are just sitting should be used.  So calculate based on 400-500 calories, which equals .132-.106 g CO2.

Yep, that's a dang low number.  Good job.

By the way, I don't think making calculations based on your production of CO2 while breathing will be relevant in global warming arguments if you choose to do so later.  CO2 that is breathed out is generally already accounted for in calculations regarding human emissions.  I would pick the bicycling for so many other reasons than to reduce the carbon impact on the environment.

Also consider when you use the scooter you are reducing your emission compared to the Prius by about 88%.  You only get approximately another 11.5% by bicycling.

EDIT:

I ws looking at your formula and was wondering if you dropped to g when you meant kg.  If so, then you would use somewhere between 106-132 g of CO2 (or 160 by your estimate)