All things environmental

Musings about the environment and all it touches, from education to city planning

Vancouver’s rubber sidewalks

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The city is experimenting with a new type of material for its sidewalks: rubber.

This is rubber that is recycled, mainly from tires.  It costs a bit more than the standard concrete sidewalk, but it should last longer – specially where roots from mature trees put pressure on the paving surface.  So, long run, costs should even out.

A rubber sidewalk on East 17th

The city is trying it out in a recent installation tried out on east 17th.

I think this is great.  I’m all for recycling.  But I think there is another important feature to this sidewalk that hasn’t been given enough emphasis: its role in climate change.

Recycling puts something (rubber, in this case) back into use, and that avoids having to manufacture something new, with all of the carbon emissions that it implies.

In the case of concrete, this is very significant.  Concrete is made by heating limestone to a temperature above 1400C, which requires a large amount of energy, usually from coal or other fossil fuels.  The heat can be re-absorbed in efficient processes, to a degree, but the energy requirement remains high.

Further, any Portland cement – the key ingredient in concrete – is made by heating limestone, which turns it into quicklime, by evaporating carbon dioxide.  This means that the emission of greenhouse gases is unavoidable, no matter how efficient the process can be made.  (For the science nerds out there: limestone is calcium carbonate, and quicklime is calcium oxide – so we get the reaction CaCO3 -> CaO + CO2)

I have nothing against concrete, and in many applications it is the best material.  But this is an example of where choosing an alternative material can have a huge effect on net greenhouse gas emissions.  And it’s easier on jogger’s ankles.  It lasts longer.  And it helps recycling, to boot.  What’s not to like?

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Written by enviropaul

October 8, 2011 at 10:04 am

Posted in Uncategorized

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