# The Naked Scientists Forum

### Author Topic: In terms of CO2 produced per mile, how does a human compare with a car?  (Read 46590 times)

#### chris

• Neilep Level Member
• Posts: 5293
• Thanked: 61 times
• The Naked Scientist
##### In terms of CO2 produced per mile, how does a human compare with a car?
« on: 17/10/2008 09:30:49 »
When purchasing a new car these days we are informed that it pumps out 150g of carbon dioxide per mile travelled.

How does this compare with shank's pony?

Chris

#### RD

• Neilep Level Member
• Posts: 8084
• Thanked: 51 times
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #1 on: 17/10/2008 14:34:31 »

Say 40 breaths per every minute while jogging give total "exhaust" 184 litres per minute.
I doubt vital capacity could be maintained for a mile so lets call this 150 litres per minute.

5% of this 150 litres per minute exhalation is CO2, i.e. 7.5 liters of CO2 per minute while jogging.

Jogging speed is approximately 6 miles per hour, (a mile in 10 minutes), => 75 litres of CO2 per mile.

That's about  3.3 moles of CO2 which is 147 grams.

So the CO2 emission of an adult male jogger is approximately 150 grams per mile.
« Last Edit: 17/10/2008 14:37:27 by RD »

#### Pumblechook

• Hero Member
• Posts: 569
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #2 on: 17/10/2008 14:41:47 »
Carbon Dioxide Emission per Person (m3/h)  cu metres/hour

Sleep  0.013

Resting or low activity work  0.02

Normal work   0.08 - 0.13

Hard work   0.33 - 0.38

#### RD

• Neilep Level Member
• Posts: 8084
• Thanked: 51 times
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #3 on: 17/10/2008 14:57:00 »
Carbon Dioxide Emission per Person (m3/h)  cu metres/hour
Hard work   0.33 - 0.38

Using your figure of 0.38 m3/hour gives 63 litres per mile for a jogger,
assuming a 10 minute mile, (My estimate was 75 litres per mile).

Your figure would put a jogger's CO2 emission at about 126 grams per mile.
« Last Edit: 17/10/2008 15:00:47 by RD »

#### Pumblechook

• Hero Member
• Posts: 569
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #4 on: 17/10/2008 15:39:24 »
Very few people will be exercising like that and those who do will only do it for short periods so the average output from humans will be much smaller.

#### RD

• Neilep Level Member
• Posts: 8084
• Thanked: 51 times
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #5 on: 17/10/2008 15:49:16 »
Very few people will be exercising like that and those who do will only do it for short periods so the average output from humans will be much smaller.

Quote
According to a study by the United States Department of Agriculture,
an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day.
http://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiology

Presumably this 900g/day figure is for the average American.
« Last Edit: 17/10/2008 15:56:53 by RD »

#### Pumblechook

• Hero Member
• Posts: 569
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #6 on: 17/10/2008 16:26:34 »
And cars do 27 miles a day.

so 4100gm as against 900... Commercial vehicles may do far more miles and pump out far more CO2.

#### techmind

• Hero Member
• Posts: 934
• Un-obfuscated
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #7 on: 18/10/2008 13:24:45 »
Some of the figures for human CO2 emission seem surprisingly high to me, but I don't really know what they should be.

Of course also it's only fair to consider the excess CO2 the running/walking human produces compared to if they were sitting still not exerting themselves (eg driving the car).

The pedal bicycle is supposed to be the most energy-efficient way for people to move themselves around. A figure for the (excess) CO2 per mile on a bicycle would be an interesting number. After all, cycling 5-6 miles for most of us is a far more realistic proposition than running that distance.
« Last Edit: 18/10/2008 13:30:49 by techmind »

#### techmind

• Hero Member
• Posts: 934
• Un-obfuscated
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #8 on: 18/10/2008 13:38:37 »
Ok, it's only more discussion and not too many (verifiable) figures, but relevant, I thought:

Quote
It doesn't matter how much carbon dioxide you exhale when you ride
your bike, because none of it contributes to the buildup of carbon
dioxide in the atmosphere.  This buildup is caused by burning fossil
fuels, which releases carbon that has been bound up in the slow carbon
cycle for millions of years.  All the carbon you exhale came from
plants that you ate.  Or from animals or fungi you ate, but the
animals and fungi got it from plants.  The plants got it from the
atmosphere.  So the carbon you exhale was in the atmosphere no more
than a year or two previously, and even if you hadn't eaten it and
exhaled it, it would soon end up back in the atmosphere.  Bacteria
will eat it if nothing else (it will 'rot'). The movement of carbon
through the fast carbon cycle does not change the composition of the
atmosphere. So by riding your bike you are not contributing to the
greenhouse effect at all.

I suspect there's probably exceptions; food still uses some fossil fuels (these days) to produce (fertilize), store, and transport. But it's an interesting argument, I thought.

Another quote from the same discussion
Quote
Forget about CO2 and consider energy. Energy usage should correlate
well with polution. Passenger trains get about 250 passenger miles per
gallon (100 to 500 depending on occupancy). This equates to about 126
kilocalories per passenger mile. Riding a bicycle at 15 miles per hour
uses about 35 kilocalories per mile of which 27 is due to cycling and
8 are from basal metabolism. This includes lots of assumptions about
weight, wind, hills, and other things, but is probably typical. So a
bicycle is almost 5 times as efficient as the train.
« Last Edit: 18/10/2008 13:46:13 by techmind »

#### techmind

• Hero Member
• Posts: 934
• Un-obfuscated
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #9 on: 18/10/2008 13:44:13 »
http://www.sightline.org/maps/charts/climate-CO2byMode

Another site which has a plot purporting to show the CO2 per person-mile for different transport modes. There is a second page with more explanation of the sources and caveats for the figures, but details are sketchy (to say the least) for walking/cycling.

#### techmind

• Hero Member
• Posts: 934
• Un-obfuscated
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #10 on: 19/10/2008 22:15:58 »
Here's another search result on this topic especially for Neilep

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=370859

Quote
Role of metabolic CO2 production in ventilatory response to steady-state exercise.

We examined the role of metabolic CO2 production in the hyperpnea of muscular exercise by comparing the response of alveolar ventilation to moderate levels of exercise with the response to venous infusion of CO2 at rest. Studies were performed in four awake sheep that were trained to run on a treadmill. The sheep had been cannulated for veno-venous extracorporeal perfusion so that CO2 could be infused into the peripheral venous blood through membrane lungs in the perfusion circuit. The sheep breathed room air through an endo-tracheal tube inserted through a tracheostomy, and samples of expired gas were collected for measurement of the rates of CO2 production and O2 consumption. All measurements were made in the steady state. In each of the four sheep, the relationship between alveolar ventilation and the rate of CO2 production could be described by a single linear function (r greater than 0.99; P less than 0.001), regardless of whether CO2 production was increased by exercise, venous CO2 infusion, or combinations of both procedures. ...

#### RD

• Neilep Level Member
• Posts: 8084
• Thanked: 51 times
##### In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #11 on: 20/10/2008 08:28:13 »
Neilep sequesters some of his CO2 in one of these...

« Last Edit: 20/10/2008 09:18:35 by RD »

#### TabbB

• First timers
• Posts: 1
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #12 on: 30/01/2012 02:17:35 »
Very few people will be exercising like that and those who do will only do it for short periods so the average output from humans will be much smaller.

Actually when I was in my 30s I would run 3 - 5 miles/day five days a week and 15K on Saturday, average pace of 8 minutes/mile, fastest pace, about 6 1/2 minutes/mile. Weekdays had a lot of hills to run up...But then when I was in the Navy I had a Chief tell me I was a scholar (graduated 8th out of 33 in Advanced Electronics Theory class, only non-nuke ET in the top 10, and ran a 6 1/2 minute 1.5 mile for PRT). Generally up until the year before I retired I only did a 10 minute mile to cool down.

But to generalize a problem like this you have to take the average male, or average female. But the most critical factor to take into consideration is VO2 max which is the peak O2 uptake. Respiratory Ratio is the CO2 exhaled to O2 inhaled ratio, which for the average person ranges between 0.8 to 0.9

But also you have to take into consideration methane emissions (passing gas, breaking wind, etc) which is also considered a greenhouse gas. I do believe the average human being would flunk the smog check. (Maybe we should ban the consumption of legumes based on the amount of methane produced.)

#### smartdave

• First timers
• Posts: 1
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #13 on: 12/05/2012 21:25:44 »
On Monday, I drove the 5 miles to the shops and back.  I arrived home as fresh and clean as when I left.

On Tuesday, I ran to the shops with my rucksack on my back and jogged home with a heavy rucksack full of shopping.  I then had a shower, used more aerosol deodorant, and put the clothes in the washing machine and spin dryer.

I think CO2 figures should include all aspects of the comparison.  How much co2 is used to provide the clean water for the shower/washing machines?  How much Co2 for the electricity?

How much co2 for the trainers which need replacing every few months?

However, my exhaust is used to judge co2 emissions, yet I am confident that those bubbles coming off the car's battery are carbon dioxide.  How much is that?

#### peppercorn

• Neilep Level Member
• Posts: 1466
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #14 on: 12/05/2012 21:37:21 »
On Tuesday, I ran to the shops with my rucksack on my back and jogged home with a heavy rucksack full of shopping.  I then had a shower, used more aerosol deodorant, and put the clothes in the washing machine and spin dryer.

Try getting a push-bike!
....
In answer to your question, the overheads don;t come close to those for dragging a ton of metal around at <15% fuel efficiency (average car; esp for short journeys); actually worse with city driving (rem. braking is all loss).

[edit: you get through trainers every few (3) months?!]
« Last Edit: 12/05/2012 21:41:24 by peppercorn »

#### CliffordK

• Neilep Level Member
• Posts: 6321
• Thanked: 3 times
• Site Moderator
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #15 on: 13/05/2012 00:42:51 »
yet I am confident that those bubbles coming off the car's battery are carbon dioxide.  How much is that?
The bubbles from a fully (over) charged lead acid battery are hydrogen.
Which is why there can be an explosion risk.

#### Geezer

• Neilep Level Member
• Posts: 8328
• "Vive la résistance!"
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #16 on: 13/05/2012 01:02:42 »
yet I am confident that those bubbles coming off the car's battery are carbon dioxide.  How much is that?
The bubbles from a fully (over) charged lead acid battery are hydrogen.
Which is why there can be an explosion risk.

It's worse than that. They are hydrogen and oxygen bubbles in exactly the right proportions to form a highly explosive mixture.

#### damocles

• Hero Member
• Posts: 756
• Thanked: 1 times
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #17 on: 21/05/2012 23:13:11 »
yet I am confident that those bubbles coming off the car's battery are carbon dioxide.  How much is that?
The bubbles from a fully (over) charged lead acid battery are hydrogen.
Which is why there can be an explosion risk.

It's worse than that. They are hydrogen and oxygen bubbles in exactly the right proportions to form a highly explosive mixture.

It is better than that: while hydrogen is indeed produced at the cathode, the anode reaction will simply continue to produce lead sulfate from metallic lead, or lead dioxide from lead sulfate; oxygen generation does not readily happen.

#### Geezer

• Neilep Level Member
• Posts: 8328
• "Vive la résistance!"
##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #18 on: 22/05/2012 18:09:40 »
yet I am confident that those bubbles coming off the car's battery are carbon dioxide.  How much is that?
The bubbles from a fully (over) charged lead acid battery are hydrogen.
Which is why there can be an explosion risk.

It's worse than that. They are hydrogen and oxygen bubbles in exactly the right proportions to form a highly explosive mixture.

It is better than that: while hydrogen is indeed produced at the cathode, the anode reaction will simply continue to produce lead sulfate from metallic lead, or lead dioxide from lead sulfate; oxygen generation does not readily happen.

Only if all the current goes into the production of lead sulphate. If the battery is fully charged, or the battery is getting old, plenty of oxygen will be produced.

#### The Naked Scientists Forum

##### Re: In terms of CO2 produced per mile, how does a human compare with a car?
« Reply #18 on: 22/05/2012 18:09:40 »