It’s funny because it’s true!

[DismalScientist]

@TwoWheelsDC 31677 wrote:

Whoa, very informative. I do have one question though. How does 1 gallon of gasoline, weighing in at about six pounds, produce 19.6 pounds of CO2? Does that include the entire production cycle and petroleum byproducts that get consumed as well?

It’s the chemistry. Gasoline is basically carbon and hydrogen atoms. When burned, the light hydrogen is replace by heavy oxygen atoms. The basic formula is that CH2 + (3/2)O2 becomes CO2 + H2O. CH2 weighs 14 atomic units and CO2 weighs 44 atomic units.

Why are these arguments always based on CO2 equivalents? This is like assuming that CO2 production is the only relevant cost of energy use, a proposition with which I disagree vehemently.

Secondly, these arguments often say that bicycling (without electric assistance) gives infinite MPGs. Under this methodology, this cannot possibly be true as, at least some, bicyclists tend to pant while cycling.

[jnva]

@culimerc 31679 wrote:

The increase in weight is due to Oxygen molecules being added to the weight of the waste product.

The internal combustion engine is terribly inefficient. I am guessing that also has something to do with it? Even taking into account the transfer of energy from a power plant, into a battery and out to a bldc motor, it’s still more efficient than an ICE motor. I have read some “wells to wheels” research papers, but nothing directed at small electric vehicles, which are way more efficient because of the low weight of the vehicle.

[Tim Kelley]

@jnva 31685 wrote:

The internal combustion engine is terribly inefficient.

What do you mean? I hear that they are terribly efficient at burning gasoline!

[rcannon100]

Assume exercise is a fix cost. Assume that the human desires to be healthy, and will exercise – either by commuting, or by driving home from work – and then driving to the Spinning Club (or whatever). Whatever the cost in fuel consumed or the CO2 produced by the healthy human, its a fixed cost which is going to occur whether I bike or whether I drive.

When comparing cost of commute / fuel consumed / CO2 produced, the assumption is an either / or choice. Either I am going to commute by car or by bus or by bike (and if I choose by car, I will not bike). But this isnt so. Part of my agenda is how do I get home. Part of my agenda is how do I stay healthy. So the equation is

COMMUTE + EXERCISE = X

where

CAR + GYM WORKOUT = Y

and

BIKE COMMUTE (commute / exercise combined) = Z

and

Z < Y where the calculation is for (a) fuel consumed (b) cost (c) CO2 produced or (d) time expended.

[DismalScientist]

@jnva 31685 wrote:

The internal combustion engine is terribly inefficient. I am guessing that also has something to do with it? Even taking into account the transfer of energy from a power plant, into a battery and out to a bldc motor, it’s still more efficient than an ICE motor. I have read some “wells to wheels” research papers, but nothing directed at small electric vehicles, which are way more efficient because of the low weight of the vehicle.

The problem may be that all devices to convert chemical energy into electrical energy via mechanical energy may be inefficient. I hear power plants aren’t necessarily all that efficient either.

[DismalScientist]

@rcannon100 31690 wrote:

Assume exercise is a fix cost. Assume that the human desires to be healthy, and will exercise – either by commuting, or by driving home from work – and then driving to the Spinning Club (or whatever). Whatever the cost in fuel consumed or the CO2 produced by the healthy human, its a fixed cost which is going to occur whether I bike or whether I drive.

When comparing cost of commute / fuel consumed / CO2 produced, the assumption is an either / or choice. Either I am going to commute by car or by bus or by bike (and if I choose by car, I will not bike). But this isnt so. Part of my agenda is how do I get home. Part of my agenda is how do I stay healthy. So the equation is

COMMUTE + EXERCISE = X

where

CAR + GYM WORKOUT = Y

and

BIKE COMMUTE (commute / exercise combined) = Z

and

Z < Y where the calculation is for (a) fuel consumed (b) cost (c) CO2 produced or (d) time expended.

Once you assume that exercise is a fixed cost, you have assumed your answer. I’m sure that there are some folks out there who wouldn’t be exercising as much if they did not ride bicycles regularly.

[Bilsko]

@DismalScientist 31682 wrote:

Why are these arguments always based on CO2 equivalents? This is like assuming that CO2 production is the only relevant cost of energy use, a proposition with which I disagree vehemently.

Agreed that the CO2 equivalencies metrics don’t do the best job of capturing the discrete effects of other emissions associated with fuel combustion ((N20 and a bit of CH4, in the case of gasoline combustion)

Note that my above calcs *do not* include any CO2 equivalencies – that’s just the CO2 emissions values. I could have done a little more legwork and retrieved the CO2 equiv. from the EPA calculator for the other grid emissions, but for the sake of simplicity in a forum thread titled “Its funny b/c its true!” I went with the easiest calc. Same goes for the N2O and CH4 emissions on the gasoline side.

[culimerc]

@DismalScientist 31696 wrote:

Once you assume that exercise is a fixed cost, you have assumed your answer. I’m sure that there are some folks out there who wouldn’t be exercising as much if they did not ride bicycles regularly.

Problem is that exercise is not a fixed cost. As you become more fit you become more efficient, both in movement (actual pedaling/ bike handling) and in converting food to calories to miles, and decrease your waste (CO2) by not working as hard for the same output.

[jnva]

@DismalScientist 31692 wrote:

The problem may be that all devices to convert chemical energy into electrical energy via mechanical energy may be inefficient. I hear power plants aren’t necessarily all that efficient either.

True, but I have read that power plants are required by law to maintain and improve efficiency and reduce emmisions as they age. Compare that to a typical car engine that does not have that requirement – you can actually get a waiver for older cars that don’t meet new car emmisions standards.

[rcannon100]

Once you assume that exercise is a fixed cost, you have assumed your answer. I’m sure that there are some folks out there who wouldn’t be exercising as much if they did not ride bicycles regularly.

Yah. Being pretty explicit with that – I would say, once you assume that exercise is a fixed cost, the answer is easy math – the answer is not assumed. For me I do assume exercise is a fixed cost. If exercise were not so important, the math would be different. It might be quite hard to justify cycle commuting.

For example, does bike commuting take more time or less time? If I dont assume the need for exercise, bike commuting takes more time than driving – and in a time squeezed life style – would be very hard to justify. 15 minutes by car compared to 35 minutes by bike + need for a shower? If I am taking that time away from, say, sitting down with my kid to do homework – the math does not add up.

But because I do place a priority on exercise, and would have it in the schedule one way or another – than assuming exercise, bike commuting takes less time.

I am not assuming my answer – I am assuming the need for exercise. I would not be getting less exercise if I didnt bike commuted – but I would have less time.

[lordofthemark]

@DismalScientist 31696 wrote:

Once you assume that exercise is a fixed cost, you have assumed your answer. I’m sure that there are some folks out there who wouldn’t be exercising as much if they did not ride bicycles regularly.

IF those other folks are overweight, they may eat the same amount when cycling as when being sedentary – the extra exercise will lower their weight till they reach equilibrium with same calorie consumption and lower weight (their non exercise calorie burn will be lower at lower weights, which is why weight tends towards an equilibrium for a given diet/exercise regimen)

OTOH IF they are normal weight and sedentary, the extra calories burned MUST be offset by higher calorie intake (or they will lose weight regaining equilibrium only at a (unhealthy?) point below normal weight. So for that group they need to eat more calories (with accompanying GHG resulting from food production and delivery)

So,(to simplify) three cases – A. Exercising already and transportation cycling subs for other exercise – no net food cost (no improvement in health though) B. Sedentary, Overweight, and cycling results in lower weight for same diet regimen – no net food cost (and significant improvement in health) C. Sedentary and normal weight – Significant net food cost (some improvement in health, probably)

In case C the GHGs associated with food production, delivery, preparation, etc COULD offset the GHG’s saved by not using a motorized form of transport. I defer to the experts on wattage and MPGs for that discussion.

(note also – differences in GHGs associated with production of bikes vs motor vehicles, and production of infrastructure — Im not sure of those, but they also impact net GHG’s – this came up with cash for clunkers – subsidizing new more efficient vehicles isnt necessarily optimal from a GHG POV)

[lordofthemark]

On the other hand increasingly we are substituting Natural Gas for coal in electricity generation, and while NG is superior to coal in CO2 emissions per BTU, that is IIUC somewhat offset by leakage in NG transmission, methane itself being a significant green house gas. Thats also an issue for CNG fueled vehicles (where there is even more leakage, IIUC)

[Author]

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