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:
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.