Thursday, August 27, 2009

So-called "synthetic trees" employ discredited mickey mouse chemistry!


 Both the BBC and the Times use this picture.  
The synthetic/artificial trees are the fly-swat shaped objects, not to be confused with wind turbines.  The BBC's caption reads "Artificial trees could be used in areas where carbon emissions are high".  The BBC's caption writer seems a little confused, inasmuch as CO2 "pollution" is a global, not a local problem.  He or she seems to be confusing it with vehicle pollutants like SO2, NOx, unburned hydrocarbons etc which are an immediate health hazard (asthma-inducing etc) as distinct from global-warming greenhouse gases.

There are reports right now on the BBC, in The Times, and no doubt elsewhere of so-called "synthetic trees" (aka artificial trees) that will help save the planet.

Your ever alert and  responsive critic of pop science has just  dashed off  the following and sent off to the Times:


"Sorry, but the technology for these synthetic trees, reported in 2003, has been totally discredited:

http://news.bbc.co.uk/2/hi/science/nature/2784227.stm

It uses plain old limewater* to sequester CO2. Where does the lime come from? It comes from roasting chalk or limestone at high temperature, which not only requires a lot of energy, but puts CO2 into the atmosphere.

1. calcium carbonate (+ heat) -> calcium oxide  + CO2 (gas)

2. Calcium oxide + water  ->  calcium hydroxide  (+ heat)

3. Calcium hydroxide + carbon dioxide  ->  calcium carbonate (regenerated!) + water

In other words the whole process, at least as originally described, is entirely self-defeating from the point of view of carbon sequestration. It's simply an expensive way of moving chalk or limestone from a hillside to a so-called synthetic tree by the roadside.

*an aqueous solution of calcium hydroxide"



The Telegraph is now running the same story, again with the same piccy, but unfortunately provides no Comment facility.

From the archives: here is a link to a BBC item on "synthetic trees" as long ago as 2003 which explained why the chemistry was a non-starter.
More later.

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