[graemep]

Shoes have a lower environmental impact and cost than than steel, plastic, rubber tyres (which AFAIK use at least some synthetic rubber made from oil), etc. Walking does not use fuel so efficiency is not really relevant. It requires less physical extortion so is more efficient that way, but another way to phrase that is that it is less exercise.

[tpm]

> another way to phrase that is that it is less exercise

Biking is less demanding on some parts of the body that only can take so much stress. So you can push other parts more if that makes sense: top cyclists can do 400-600 W sustained or 1-2 kW in short sprints. That's not less exercise, that's several times more than a walker or runner can do. So in the same time as walking you can either be faster at your destination and save time and/or energy, or go further while spending the same or less energy, or output more energy. The choice is yours.

Anyway, from the CO2 perspective, biking vs walking is splitting hairs really.

[graemep]

> So you can push other parts more if that makes sense: top cyclists can do 400-600 W sustained or 1-2 kW in short sprints.

Very few people are top cyclists, or top anything else. Top cyclists are doing it as a sport, not as a means of transport.

> Anyway, from the CO2 perspective, biking vs walking is splitting hairs really

I agree. I am responding to people who are claiming it is better than walking to a significant extent.

[tpm]

> Top cyclists are doing it as a sport, not as a means of transport.

Well you were mentioning exercise, so I reacted to that. The point is everyone biking as exercise can push more watts than when walking, if they want to.

[cogman10]

Bikes require very little steel and the rubber tires end up lasting longer (typically) than the shoes you do.

> Walking does not use fuel so efficiency is not really relevant.

Ah, it is. You eat food, that's fuel. It's the major source of CO2 for both activities. Now, it can be insignificant. If the only food you eat is like oatmeal and beans that you grow yourself, then yeah it's going to have a non-existent impact.

However, if you have any sort of meat or imported foods, that CO2 budget can go up pretty quickly.

The actual energy for making the steel for a bike, which will outlast your children, isn't significant.

[graemep]

> Ah, it is. You eat food, that's fuel. It's the major source of CO2 for both activities.

That implies all exercise is a bad thing. i think you will find very few people are sufficiently keen to reduce CO2 that they will deliberately get less exercise and damage their health. I am certainly not doing that. At the moment I am trying to get more exercise.

> Bikes require very little steel

Compared to a car, certainly. Compared to shoes, an awful lot.

> a bike, which will outlast your children

The typical life span of a bike seems to be about five and ten year years. I really hope my kids last a reasonable multiple of the top end! The level of sales of cycles in the UK (well over 1 million a year) vs the number of people who cycle at least once a week (less seven million) implies a life of about five years. About half of that is leisure cyclists so not really comparable to people using transport to get somewhere.

Leisure cyclists want to get more exercise so by your argument about that being a bad thing they (and therefore half of all UK cyclists) are actively harmful.

https://road.cc/content/news/uk-cycle-sales-plummet-early-19...

https://assets.publishing.service.gov.uk/media/64e71a4f20ae8...