[alancalverd]

Most of the CO2 produced by 4 adults on bikes would also be produced by 4 adults in a car.
Did that get added to the "car" figure?

Yes but it's now divided by 50 mph. Not a lot of cyclists can manage that.

[Bored chemist]

You get the same uptick with cycling if you include basal metabolism as well as the energy burnt by the exercise,

You should also get it for driving a car. The driver is still breathing, even if the car is stationary. (and there's also "idling" fuel)

[alancalverd]

The graphs were of CO2 emission per mile for moving at various speeds. Unlike humans, my diesel car switches off when it's not moving.

The train figures become horrendous if you add in the carbon footprint of the infrastructure. HS2 so far has cost over £500,000 per meter without even building a train, let alone running it. Assuming that no money has been wasted on "consultancy fees" to "companies" that have never built a railway, or as "compensation" to "companies" that were not invited to tender, and that no contractor is actually related to a Tory MP, at least half of the money will have been spent on fossil fuel to make or move stuff. Or do I smell incompetence and corruption? 

[Petrochemicals]

60 Watts 15 miles

Er, the watt is a unit of power, not energy, let alone CO2

extrapolate

From the wiki article

"The required food can also be calculated by dividing the output power by the muscle efficiency. This is 18–26%. From the example above, if a 70 kg person is cycling at 15 km/h by expending 60 W and a muscular efficiency of 20% is assumed, roughly 1 kJ/(km∙kg) extra food is required"

Meaning 70kj of food per km, or 2 grams of fat, or 2 grams of diesil biofuel. Or about 5g of CO2. 

Or in your imperial terms 8gco2/mile

The bicycle is a very efficient machine compared to walking, as can be seen from the plot, but nothing much else in the system is.
The human body is only 18-25% efficient compared to ~90% of an electric motor.
Motors are reversible, muscle isn't.
.

What do you mean by reversible?

Motors are efficient, but on cars add in battery inefficiencies, charging inefficiencies, aerodynamic drag, rolling resistance, the fact that all of this 2000+kg has to be moved it cannot be anywhere as efficient.

This is before we add in manufacturing and maintenance costings. All of the people who built the car also expended Co2 making it. The extra generation capacity also entails some CO2 production.

[Bored chemist]

Unlike humans, my diesel car switches off when it's not moving.

True, but even if you are sat in traffic, you are still metabolising something like 2400 KCal per day.
That's the equivalent of burning roughly 270 grams of fat per day.
And that produces something like 800 grams of CO2 per day or about 35 grams per hour.


It doesn't make a lot f sense to include that in the "travel" figure- because you aren't traveling.
But it also doesn't include base rate metabolism in the cyclists case and, as far as I can tell, that uptick indicates that they have included it.

So it's not a level playing field.

In the limit, at zero MPH, the rate of production of CO2 is the same for a car or a bike; about 35 grams per person per hour.
So, it's worse for a tandem or for a car with passengers.

That's plainly silly, so it should be subtracted from (or not included in) the figures on the graph.

How much more food does a cyclist need than he would normally consume?

[vhfpmr]

Since you already have most of the data, perhaps you could add the figures for a train or two.

Not for trains I haven't (or buses). It would get quite complicated wouldn't it: rush hour or half-empty, or during lockdown, diesel or electric. Then there's the complication that the route and distance are rarely the same, and a train journey often includes a car to get to the station.

I suppose the reason I posted this was that it's interesting that there isn't as clear a winner as might be supposed, electric car and bike are surprisingly similar, and deciding what's best is quite complicated and dependent on all sorts of individual details. Alan C suggested including showers and laundry, but there's also motive for cycling to consider too. Anyone cycling anyway for health & fitness can choose whether to combine essential journeys with their health rides or keep them separate, which in turn will make a big difference. And as I mentioned previously, it makes a huge difference whether you've already bought the electric car or not, because it's easier for the bike to compete with a car that hasn't yet been made than one parked on the drive. The green thing to do is travel less.

[vhfpmr]

You get the same uptick with cycling if you include basal metabolism as well as the energy burnt by the exercise,

You should also get it for driving a car. The driver is still breathing, even if the car is stationary. (and there's also "idling" fuel)

Yes, but driver CO2 only contributes 4-6% of car total, so it's pretty negligible. I plotted the car at a nominal 30mph, because there's no speed info on that VW reference.

[Bored chemist]

Alan C suggested including showers and laundry

Guess again.

but there's also motive for cycling to consider too. Anyone cycling anyway for health & fitness can choose whether to combine essential journeys with their health rides or keep them separate, which in turn will make a big difference.

There are two ways to look at that.
You can buy t shirts printed with "I don't run because I like running; I run because I like cake".
Running and cycling are often ways to extend your own life, in spite of hedonism, at the expense of the Earth's resources.

The green thing to do is travel less.

And running or cycling for health is doing the opposite.
Mind you, the most "green" thing we can do is die.

[Bored chemist]

You are right, it's horribly complicated.

Yes, but driver CO2 only contributes 4-6% of car total, so it's pretty negligible.

Not if the car is stationary.
And it's unfair to compare a car doing 30 MPH to a cyclist doing 15 (or a pedestrian doing 5)  without taking account of the fact that the person's "tickover" still burns about 100W regardless of how fast they are moving.

If the place I'm heading for is 10 miles away, the journey time is obviously influenced by the speed.
Is it "fair" to penalise the walker because he takes 2 hours, during which his brain uses more energy than it does during a 20 minute car journey?

[vhfpmr]

And that produces something like 800 grams of CO2 per day or about 35 grams per hour.

Which CO2 are you talking about? The CO2 you breathe is what was absorbed when the food grew, the CO2 in my data is what was produced by farm tractors, fertiliser factories, Tesco lorries etc etc. That amounts to about 6000g/day. A mile in a car  takes about 2 mins, so 6000/24/30 = 8g/mile. That compares with ~200g/mile for the car itself.

[vhfpmr]

Not if the car is stationary.

If the car is stationary the emissions per mile are infinite, and you don't arrive at your destination. If you're travelling 2 miles to work, it's the emissions per mile that are relevant, not the emissions per hour.

[vhfpmr]

And running or cycling for health is doing the opposite.

Not necessarily, what is the environmental cost of increased healthcare, and what is the health cost of a poor environment.

Not all motoring is essential, going on holiday or for a day out is just hedonism, and there's no health benefit to sitting in a  car.

[vhfpmr]

But it also doesn't include base rate metabolism

On reflection I realised that that USC data is total energy including basal met, so I spent this morning altering my spreadsheet to remove it. There's not a whole lot of difference, because it's not significant. In the case of the motorist, it's not significant because >90% of the CO2 is from the car not the driver, and in the case of the cyclist is not hugely significant because ~90% of the energy is from the cycling not BMR.

Excl bmr 80kg.png (21.69 kB . 593x438 - viewed 1731 times)

[Bored chemist]

Ticks.JPG (12.98 kB . 199x179 - viewed 1663 times)I'm puzzled by that data.
I'm looking to find data for the difference between how much energy you use because you are moving, and how much you would use if you were not moving.

If I'm not moving then there is obviously zero difference.
So, the limit at zero MPH should be zero. The problem is that the division by the distance leaves that result undefined.

But imagine I'm moving at a vanishingly small rate.
Then, clearly I must only be using a tiny bit of energy; much less than if I was running, for example.
So the graph should fall to very near zero for speeds very near zero (because I'm doing very nearly nothing)

But, with your new graphs, the data seems to be heading in the wrong direction; the uptick is still there.

The rate of use is going up for the case where you do nothing, when common sense says it should be going down.

Based on this scrappy extrapolation, the data seems to suggest that (very nearly) not moving takes produces 220 g of CO2 per mile.

It might be useful to know the rate per unit time, rather than per distance.

[Petrochemicals]

There is even a handy Web page to help with the cycling problem

https://www.exploratorium.edu/cycling/humanpower1.html#:~:text=It%20takes%20less%20energy%20to,times%20more%20efficient%20than%20walking.&text=A%20comparison%20of%20the%20energy,bicycle%20is%20most%20energy-efficient.

[Bored chemist]

There is even a handy Web page to help with the cycling problem

https://www.exploratorium.edu/cycling/humanpower1.html#:~:text=It%20takes%20less%20energy%20to,times%20more%20efficient%20than%20walking.&text=A%20comparison%20of%20the%20energy,bicycle%20is%20most%20energy-efficient.

That page also makes the important point that most cars run of non renewable fossil fuels but people run on renewable food.

[vhfpmr]

But, with your new graphs, the data seems to be heading in the wrong direction; the uptick is still there.

You're getting far too preoccupied with just two data points out of 23. The reason that I'm satisfied with the data from USC is that it matches very well with my own data.

Firstly, here's a plot of my own daily energy consumption against exercise hours. The data were collected at a mean bodyweight of 71kg, and an average speed of 10.8mph. My average calorie consumption is 477kcal/hr inc. bmr, and 372 excl. bmr, compared with 420 and 357 from the USC data at the same speed & weight. That's an error of 12% and 4%, not a bad correlation for a bit of home science.


Met 08-11.png (11.14 kB . 589x358 - viewed 1703 times)

Secondly, I can use the results from a couple of Bruce tests to measure the relationship between workload and heart rate, and then use my training data to convert average heart rate into average speed. The result plotted against the USC data again matches very well at 10-12mph, the speeds I typically cycled at, and the diversion at higher speeds errs on the side of higher energy consumption, not lower.


USC Bruce.png (15.72 kB . 558x432 - viewed 1707 times)

Finally, here's the a repeat of the same plot with my data added.


Plot own.png (22.78 kB . 593x438 - viewed 1701 times)

Nothing much there to suggest the USC data are 'utter rubbish'.

[Bored chemist]

Firstly, here's a plot of my own daily energy consumption against exercise hours.

Neat!
How was that measured?

[vhfpmr]

"The required food can also be calculated by dividing the output power by the muscle efficiency. This is 18–26%. From the example above, if a 70 kg person is cycling at 15 km/h by expending 60 W and a muscular efficiency of 20% is assumed, roughly 1 kJ/(km∙kg) extra food is required"

So we have 15kph = 9.3mph, and
60W output power = 300W input power at your assumed 20% efficiency.

300W = 1080,000J/hr = 257kcal/hr

257/70 = 3.67 METs

And what does the USC reference that I'm using say:

"bicycling, <10 mph, leisure, to work or for pleasure: 4METs"

You might have the sense to check whether the data you're using is actually different before you try to use it to contradict.

Meaning 70kj of food per km, or 2 grams of fat, or 2 grams of diesil biofuel. Or about 5g of CO2. 

Or in your imperial terms 8gco2/mile

And where are you accounting for the CO2 emitted by farm machinery, agri-chemical factories, transport, livestock farts etc.?

What do you mean by reversible?

A reversible machine is one that will work with the input and output swapped around. You can't put mechanical energy back into a human and refill the stomach.

Motors are efficient, but on cars add in battery inefficiencies, charging inefficiencies, aerodynamic drag, rolling resistance, the fact that all of this 2000+kg has to be moved it cannot be anywhere as efficient.

This is before we add in manufacturing and maintenance costings. All of the people who built the car also expended Co2 making it. The extra generation capacity also entails some CO2 production.

This is all included in the data I'm quoting from the VW reference: manufacturing emissions (43% of which is the battery), emissions during use, and also emissions from recycling at the end of life (tiny). I've already referred to these in my posts.

[Petrochemicals]

"The required food can also be calculated by dividing the output power by the muscle efficiency. This is 18–26%. From the example above, if a 70 kg person is cycling at 15 km/h by expending 60 W and a muscular efficiency of 20% is assumed, roughly 1 kJ/(km∙kg) extra food is required"

So we have 15kph = 9.3mph, and
60W output power = 300W input power at your assumed 20% efficiency.

300W = 1080,000J/hr = 257kcal/hr

257/70 = 3.67 METs

And what does the USC reference that I'm using say:

"bicycling, <10 mph, leisure, to work or for pleasure: 4METs"

You might have the sense to check whether the data you're using is actually different before you try to use it to contradict.

Meaning 70kj of food per km, or 2 grams of fat, or 2 grams of diesil biofuel. Or about 5g of CO2. 

Or in your imperial terms 8gco2/mile

And where are you accounting for the CO2 emitted by farm machinery, agri-chemical factories, transport, livestock farts etc.?

the figure is from Wikipedia. The article on cycling efficiency. 1 kj per kg per mile extra food.

What do you mean by reversible?

A reversible machine is one that will work with the input and output swapped around. You can't put mechanical energy back into a human and refill the stomach.

Motors are efficient, but on cars add in battery inefficiencies, charging inefficiencies, aerodynamic drag, rolling resistance, the fact that all of this 2000+kg has to be moved it cannot be anywhere as efficient.

This is before we add in manufacturing and maintenance costings. All of the people who built the car also expended Co2 making it. The extra generation capacity also entails some CO2 production.

This is all included in the data I'm quoting from the VW reference: manufacturing emissions (43% of which is the battery), emissions during use, and also emissions from recycling at the end of life (tiny). I've already referred to these in my posts.

So you have accounted for the farts of the windfarm workers?