Thank you both for the insightful comments. Interesting points raised, thanks Nick for those figures.
As for the plywood cargo-bike? I’m just jealous that I don’t have one!
Keep us posted on it’s progress.

… though in any case, a cargo bike like the one you’ve built should be strong enough to hold several people to piss on that fire at once.

I take your point and it’s fascinating to see the figures laid out like that. I guess I have become jaded with claims of ‘sustainability’. My point is that humanity has become one vast and unstoppable resource and energy drain on the planet and although I am passionate about bicycles and their potential to empower people and heal our communities I sometimes feel like we are trying to put out a forest fire by pissing on it.

I don’t believe a solid argument can be made in favor of any bicycle as far as sustainability. Sure, we burn no gas while riding it, and that has localized benefit but there is a vast industrial/consumer infrastructure involved to bring it to that stage.

This is true of virtually all forms of transportation though, so doesn’t that argument reason itself into a corner? If bicycles aren’t sustainable, what is the (non-hypothetical) benchmark form of transport that is? Running, naked and barefoot? (or maayyyybe mass transit?) It seems like an argument over the semantics of sustainability at that point.

I wanted to do some REALLY loose math to see if we could put any (equally loose) numbers to this…

-Let’s say my commuter bicycle is 10kg, and for simplicity’s sake, is 80% virgin aluminum and 20% plastic/rubber by weight. (virgin aluminum because it is probably the most energy intensive building material available)

-Cast/Extruded Virgin aluminum has about 220MJ/Kg of embodied energy (Recycled has about 10% this energy… though I don’t know what percent aluminum for bike tubing is recycled… probably not a lot)

-Plastics and Rubbers average about half of that, let’s say 100MJ/Kg.

…That means 8Kg * 220MJ/Kg + 2Kg*100MJ/Kg = 1960MJ

For the sake of argument, since a bicycle is made of not a block of extruded/molded material but many complicated components, let’s double that number (probably wouldn’t really be that high), and round up, to an even 4000MJ of embodied energy. I feel like it would be a reasonable claim to say that this is the higher-end of what the embodied energy of a bicycle might be.

What does 4000MJ translate to in terms of driving a car? Gas has 34.8MJ/L when combusted (couldn’t find stats for the embodied energy of gas)… so our 4000MJ Bicycle is equal to (at minimum) about 115 liters, or 30 gallons, of gasoline.

Assuming I’m driving an efficient car (40MPG)… my hypothetical 4000MJ Bicycle is (probably) energy neutral after offsetting 1200 miles I would have otherwise traveled by car.

At this point, even if you don’t consider the industrial infrastructure (factories, mines, ships) a sunk cost, continued use of the bicycle will begin to soak up those energy uses as well.

Anyways, I’m sure no one needed convincing that bikes are the way to go. I just got curious and wanted to see how the numbers might possibly go down.

I suspect that means that a steel bike is going to have the edge in terms of sustainability because CNC’ing profiles is a very energy intensive and materially inefficient way of making what you want, versus making relatively simple cuts from lengths of tubing.

Which is not to say that wood must be at a disadvantage – steel bikes have been made for hundreds of years now – the certainly have time on their side. With a refined design, local sourcing, and low-energy shaping and joining methods, a strong case could probably be made for sustainable wooden bikes.

Seems like sort of a moot point, though… as a replacement for a car, it could probably be made out of whale bones and still end up being more environmentally responsible. (Only joking… but… maybe? I’d like to see the life-cycle-analysis on that one.)

I also really love the cargo bike they linked to in their blog – the forkless cargo bike made by Elian Cycles. ( http://www.eliancycles.com/gallery/ ) I had no idea such tech existed, and am a little skeptical about its practicality, but it sure makes a very elegant front end. I wonder how much a hub like that costs.