The first artificial tree that I remember was a shiny, aluminum-branched contrivance that had a floodlight with a motorized color filter, sequentially bathing the tree in red, blue, and green. If you recall in A Charlie Brown Christmas, the cast of the Christmas play requested the bald-headed, insecure and introspective, Charlie Brown to procure a 'modern' Christmas tree instead of something natural. But I digress...
Could mechanical trees save the world? proposes that 'modern' trees could have leaves of algae and collect carbon dioxide more efficiently than natural trees. The BBC article suggests an artificial tree could remove 10 metric tons of carbon a day. Included in the proposal is equipping buildings with skins of algae tubes that could also collect CO2.
Wiki reminds us that Carbon dioxide (CO2) is an incredibly stable molecule. It takes a lot of energy to separate the oxygen and carbon atoms once the molecule has formed. The CO2 molecule has two double bonds where two carbon electrons are shared with an oxygen atom. It is the formation of these covalent bonds that releases the heat energy that enabled early mankind to industrialize the world by burning fossil fuels. It is also the bane of modern civilization, although Wiki reminds us that during the Jurassic era, CO2 in the atmosphere was 4 to 5 times greater than today. A factoid you might not have known, CO2 never occurs in liquid state, regardless of temperature at pressures less than 5.1 atmospheres. Unless pressurized, it transitions directly from solid state (dry ice) to its gaseous state.
The Colorado Trees website provides some interesting statistics about natural trees. An average tree absorbs about 48 pounds of CO2 a year. It takes about one acre of tree coverage to compensate for driving an automobile about 8000 miles. If every American family to were to plant a new tree, the aggregate CO2 sequestration would equal about 5% of the global CO2 production. An average tree produces enough oxygen for two humans.
An interesting Department of Energy study tells that algae reactors could produce 20 grams of biomass per square meter per day, for the purpose of harvesting artificial petroleum. But that requires far greater CO2 concentration levels than present in the atmosphere. A CO2 pond with only atmospheric CO2 concentrations sequesters about 0.2 g carbon per square meter per day. If I did the math correctly, a 20 foot diameter algae pond will thus sequester 17 pounds of CO2 a year. (It is consistent with the CO2 sequestration of a tree.) Compare this to the 3.3 pounds of CO2 that a 60 watt light bulb produces for only 24 hours.
Mmm. CO2 sequestration does not seem to scale, does it? In other words, 7 billion people on the planet burning fossil fuels produces so much CO2 it seems unlikely that we can capture the CO2. Methinks we need something other than artificial trees.
Comments