have you factored in the number of breaths taken per post ?
What happened to global warming then?
- Thread starter Brandane
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have you factored in the number of breaths taken per post ?
jonesy
Guru
However, that isn't a marginal emission rate.
What is a "marginal emission rate"?
jonesy
Guru
The same meaning as in "marginal cost", the additional emissions resulting from an additional search. i.e. the energy costs of the server are largely fixed, so if the average emissions per search is 6g that doesn't mean that 6g of CO2 are produced for each additional search, or that you can save 6g by not doing a search. The confusion between average and marginal emission rates comes up frequently and can lead to misleading conclusions, for example when comparing carbon emissions for travel by car or public transport at the level of an individual journey the marginal emissions for going by public transport are essentially zero. Unfortunately this isn't recognised by a lot of online multi-modal journey planners, which give you a carbon cost for individual journeys that is entirely meanginless. The carbon emissions of public transport vehicles matter, but have to be managed at the system level, i.e. how you plan for the transportation of millions of trips, not at the level of individual trips.
Edit, the most absurd example of this confusion, (previously argued about at great length in P&L...) is to compare per km emissions from motor vehicles with the 'average' CO2 per km for cyclists.
Edit, the most absurd example of this confusion, (previously argued about at great length in P&L...) is to compare per km emissions from motor vehicles with the 'average' CO2 per km for cyclists.
I remember someone arguing that cycling wasn't particularly green, as we breathed more, and had to eat more food!!
Yellow Fang
Legendary Member
- Location
- Reading
I read a book called Electric Bicycles by David Henshaw and Richard Peace (which I think Arch reviewed for Velo Vision). It says an electric bike consumes 1kWh per 100 passenger km, which is a tenth of what a passenger on a half full train or electric scooter would use, a fortieth of a car driver with a passenger, and a fiftieth of a jumbo jet passenger. It says that an electric cycle can produce even less carbon emissions than an ordinary cycling because:
"When riding a non-electric bicycle you are still, of course, expending energy, but in this case the energy has to come from food (and after using energy cycling, you will eat a quantifiable amount of extra food). Growing, transporting, processing and cooking that food has a surprisingly high energy cost. So, the amount of carbon that can be attributed to a conventional cycle ride depends on your diet. Similarly, with electric-assist cycling much will depend on the source of electricity."
It then gives a few examples:
"When riding a non-electric bicycle you are still, of course, expending energy, but in this case the energy has to come from food (and after using energy cycling, you will eat a quantifiable amount of extra food). Growing, transporting, processing and cooking that food has a surprisingly high energy cost. So, the amount of carbon that can be attributed to a conventional cycle ride depends on your diet. Similarly, with electric-assist cycling much will depend on the source of electricity."
It then gives a few examples:
- conventional bike plus imported food = 18.5 g CO
- electric bike charged by gas power station and imported food = 13.65 g CO
- conventional bike plus UK grown food = 10.5 g CO
- electric bike charged by renewable energy and imported food = 9.81 g CO
- electric bike charged by gas power station and UK grown food = 9.65 g CO
- electric bike charged by renewable energy and UK grown food = 5.81 g CO
jonesy
Guru
The key weakness is this "you will eat a quantifiable amount of extra food".
But they haven't quantified the "extra" food, they have merely worked out how much food energy is expended when cycling. Unless they can provide evidence that this food energy would not have been consumed anyway then they can't assert it to be extra. And that's the point. The other aspect of course is that there is far more variability arising from the source of the food and how it is transported and prepared than in the amount of travel undertaken, so it is entirely meaningless as an average and useless as a comparison with vehicular transport.
But they haven't quantified the "extra" food, they have merely worked out how much food energy is expended when cycling. Unless they can provide evidence that this food energy would not have been consumed anyway then they can't assert it to be extra. And that's the point. The other aspect of course is that there is far more variability arising from the source of the food and how it is transported and prepared than in the amount of travel undertaken, so it is entirely meaningless as an average and useless as a comparison with vehicular transport.
Archie_tect
De Skieven Architek... aka Penfold + Horace
- Location
- Northumberland
Whivh serves to demonstrate that obese people eating unnecessary food are exponentially increasing CO2 emissions. More reason for me to lose 1.5 stones.
And screw everyone else.
U
User482
Guest
If CO2 has the tiny effect you claim, then there must be some other reason why the Earth has such a pleasant climate. Could you explain what it is?
