gerv 

Odd you should say that. That guy walked wherever he needed to go, didn't buy over-packaging consumer items, rarely let food rot in his refrigerator, didn't leave the lights on all night, bought only local produce...

Mobile 155

Wasn't one method of hunting by Neolithic or Palio man to drive whole heards of Wolly Mamouths or Bison off of a cliff? Didn't they use copious amounts of wood to cook on?

Roody

Yes. It's certainly possible that primitive people caused the extinction of large animals--especially in Australia and Siberia, but also possibly in North America and other locations as well. Europe was once sea-to-sea forests, but humans largely deforested it before historic times.

These dire lessons from the distant past lend great urgency to the modern environmental movement. With greater technology, we obviously have even greater abilities to alter the environment than our prehistoric ancestors did.

Walter S

What was "negative" about the human impact 100k years ago?

metro2005

So car drivers dont eat and breathe? I kinda miss that in the opening post. What is the EXTRA CO2 from someone riding a bike against someone who is driving a car.

Something similar was told to me a while ago:

I have had someone tell me that if i rode my bike to work and ate beef to get the calories i was indeed adding more CO2 in the atmosphere then driving a car.
He failed to mention:
- That i dont eat any extra food when i ride my bike , i burn my fat. We are over consuming food in the west anyway, why not burn it off when riding a bike.
- That i rarely eat beef
- That the average car driver also feeds himself and eats beef and is fat (because he doesnt ride a bike. )

Its just a weak excuse to drive a car.

rhm

Sure, pre-industrial people did a great deal of damage in the form of deforestation, spreading invasive species around, hunting some species to global extinction while driving many more to local extinction, and so on. They were cruel to animals, cruel to each other, and hard on the environment. Cooking over a wood fire was nothing compared to the fuel used for smelting copper and casting bronze. I'm not exaggerating, they really made a mess of things. I don't think anyone's denying this.

More recently (broadly speaking, let's just say it's since the industrial revolution), we've accelerated that damage exponentially. And the main thing that has facilitated this acceleration is fossil fuel.

McBTC

CO2e/km is a made-up, nonsense number derived from the amount of energy in a gallon of gasoline --e.g., in kW and then calculating how many miles a car might do on that amount of electricity. It disregards the energy that is needed to manufacture and transmit that many kW of electricity. It is similar to equating the amount of energy needed to create a human being to the calories burned during the act of sex.

cooker

You expend calories to ride a bike, and every mile you ride, your body is burning calories and generating CO2 above the rate you you would be generating it if you were sitting in a car. Those excess calories and that carbon can only come from your diet, whether you eat them that day, or are consuming fat from eating in the past. And they come with an even larger extra caloric and carbon cost related to to the agricultural, transportation and refrigeration energy/carbon costs of providing you with that diet. That excess carbon turnover both by your body and by the food industry, is a per mile cost of cycling. You can't pretend it doesn't exist. Cycling has a carbon footprint.

You can lower the carbon footprint of cycling in several ways - eat less meat, eat organic and so on. Also, don't go to the gym too much, but get the bulk of your exercise in cycling and walking somewhere you need to go, or other chores like yardwork. At least then you are putting that all that consumed energy and released carbon to productive use.

Roody

Calories expended are actually measured as oxygen breathed in, or more commonly, as CO2 breathed out. This is related to heart rate, which can be used as a fairly accurate indirect measurement of CO2 produced by a person during a given activity. The higher the heart rate, the more CO2 that is being given out by the person.

Exercise, as we all know know, increases a person's heart rate, indicating that more CO2 is being produced.

But, less well known, a person's heart rate can go up dramatically as a result of stress and anxiety. Driving is said to produce more stress and anxiety than riding a bike. People who are stressed out by driving may actually have heart rates that are higher than another person who is peaceably riding a bike alongside them. This indicates that the driver is actually emitting more CO2 than the bicyclist. Are you taking this into account, or do you feel it's not an important factor?

Also, as people exercise habitually, their muscles and cardiovascular systems --metabolism--become more efficient. This is one reason that athletes have extremely slow pulses, both when exercising and when resting. Somebody who regularly rides a bike will therefore emit less CO2 than a sedentary cager--indicated by lower heart rates both while riding a bike and while resting, 24 hours a day. The cyclist might breathe out a skosh more CO2 right while they are exercising for a couple hours, but emit much less during the remaining 22 or 23 hours of the day when they are not riding. Are you taking this into account? Or do you feel it doesn't matter?

cooker

I'm pretty confidant that a relaxed person riding a bike is still expending more calories per mile - from their body - than a nervous driver from their body. So there is an energy cost of riding a bike, and when you factor in the multiplier effect of the energy cost of food, it is conceivable that propelling a bike uses more fuel per mile than propelling a small, efficient motor vehicle.

However this is not a comparison of the energy costs of the whole lifestyle of living car free vs car dependent. For example, it doesn't take into account the energy costs of building and disposing of cars or building and maintaining the much greater highway infrastructure required for car driving, or the much greater mileage drivers typically cover compared to utility cyclists. And as you say it doesn't cover the energy cost of other activities the driver might engage in.

Roody

I think you might be minimizing the increased metabolic efficiency of a regular bicyclist. Many of the members here have mentioned that they don't eat more even though they ride every day. If they're right about this (and there's really no reason to think they're not) it's undoubtedly because their bodies have become more efficient users of food calories because of regular exercise. A person who rides every day may have a resting pulse of 50 or 60, compared to a sedentary person's typical rate of 75 or 80. That's quite a difference. Oh well, it's just guess work at this point, until some research results are found.

And I'm still not clear that you're taking into account the fact that only a fraction of the additional food calories involved in cycling are from sequestered fossil fuel. (That is, the fossil fuel actually used to produce, process, and transport the food.)

Many of the excess calories are part of the biological carbon cycle This fraction of the calories results in no net increase in atmospheric carbon levels, and has no effect on climate change. (That is, the actual food calories that are metabolised while bicycling.) This is not guess work, but well established science.

McBTC

An acre of land produces about 30,000 lbs of potatoes, enough to fuel 35 people a year on a 2500 calorie diet --e.g., 2 people can live on 2/35's of an acre. If one of'm tends the potatoes and the other pedals 70 miles per day, that's an average of ~35 miles/day per person on 2/35s of an acre. So, how many miles a day can two people drive a Prius on 2/35s of an acre?

spare_wheel

The LCA i cited above did take into account the costs of building cars but your point about infrastructure is valid. (Nevertheless, I think much of this infrastructure is a sunk cost.)

spare_wheel

I did not disregard this and cited LCAs that estimated the CO2e cost of generation and transmission. Obviously none of these measures are "perfect" but we need to start somewhere.

McBTC

Let's start with something other than government-sponsored propaganda. Any realistic measure of fuel efficiency puts the actual "mpg" of a Tesla at far less than – e.g., a Mercedes E250 BlueTEC.

cooker

The person riding 70 miles a day (!!) will need an extra 3000 kcal/day to fuel that cycling, on top of the basic 2500 kcal diet. The energy in that extra food is about the same energy as 1/10 gallon of gas. If the other person harvests the potatoes by hand without using gasoline or diesel powered equipment, and no petrochemical fertilizer or pesticide, and they store them in a root cellar, eat them on site and use solar power or sustainable fuel to cook them, then yes, you can travel more miles per potato on a bike than in a car.

However most modern agriculture uses a lot of energy to produce the food - several times more input than the energy yield from the food. Plus people need to eat a diet that is more varied than potatoes,and can’t all be grown locally, so your food usually requires energy for fertilizing, pest control, harvesting, transportation, packaging, refrigeration etc. That’s why it ends up taking more energy to provide you with the extra food you need to bike 70 (or even 35) miles a day, than if you used that energy to drive an efficient car 35 miles a day.

spare_wheel

Your completely unsupported claim that scientists studying this issue are stupid enough to confound net respiration with CO2e is nonsense.

Some resources:

FAO -*News Article:*Agriculture's greenhouse gas emissions on the rise

https://www.fao.org/docrep/019/i3671e/i3671e.pdf

https://ccafs.cgiar.org/about-low-em...e#.Va6u_5Ntxph

Some examples of the source literature:

Forecasting Agriculturally Driven Global Environmental Change

https://www.nature.com/nature/journal...ture13959.html

Food and life cycle energy inputs: consequences of diet and ways to increase efficiency

McBTC

Not so, according to this: Is there a way to compare a human being to an engine in terms of efficiency? - HowStuffWorks

spare_wheel

I think most people agree that in areas where the bulk of electricity being generated comes from coal e-vehicles can be worse then efficient ICE vehicles. I'm charging via renewable offsets so that's not really relevant to my op.

McBTC

Only if you ignore what it takes to manufacture things like solar cells --e.g., there's a toxic lake the Chinese have created in Mongolia you can buy real cheap. As it turns out, rare earth minerals aren't really rare at all but separating them from the Earth comes at a huge environmental cost that only China is willing to incur.

MZilliox

what a crappy spin on this topic. I could ride 26 bikes for the rest of my life before i emitted the amount of crap that producing one electric car makes. this is just silly. bike more, drive less.

cooker

Personally I'm not arguing on behalf of cars, I'm arguing on behalf of good math

cooker

That link says the energy cost of cycling is 34 kcal/ mile - I used 40, but let's say it's 34. Then the energy cost of two people biking 35 miles is 34X35X2 = 2380 kcal, above their baseline caloric intake. However, many sources claim that it takes 10 kcal of fossil fuel energy to produce 1 kcal of food energy in a typical American diet. Thus the fossil fuel cost of two people cycling 35 miles is actually 23,800 kcal, equivalent to 0.77 gallons of gas, which works out to 45 mpg. If there is a fuel efficient small car that can get better than 45 mpg while transporting 2 people, then it is more fuel efficient on the road than two cyclists.

McBTC

The article is pretty simple: assuming a cyclist burns 34 calories to the mile, given that there's 31,000 calories in a gallon of gas, the comparison is 911.8 mpg.

cooker

Only if people ran on gasoline, but a gallon of our fuel is made using ten gallons of gasoline, so we get 91.18 mpg, and if you compare biking to two people riding in the car as you suggested, then the benchmark for the car to beat is 45 mpg as I said.