Cost of carbon capture as timber

Cost of carbon capture as timber

     People are pushing the idea of saving the world from overheating by capturing atmospheric CO2. But need that be an industrial process? It happens naturally; in photosynthesis. The world has been through many cycles of high and low levels of atmospheric CO2. I want to know if we can encourage carbon capture by fostering the growth of plants: trees and algae. 

    I have long looked for a comparison between costs of 'Carbon Capture and Storage' (CCS) as an industrial activity compared with simply growing trees. 

     Timothy Taylor's blog essay on Carbon Capture and Storage gives us a start. Carbon capture is cheapest when done at the sources of CO2 for the concentration can be far higher than ambient; let us say $80 (ranging from $15 to $120) per metric tonne captured. Capture at ambient concentration of 0.04% is about $200 (ranging from $120 - $350) per tonne.

     I have seen a figure of 48 pounds weigh of CO2 fixed per tree-year. Likewise a figure of 2014 trees/km^2. Based on those figures, I find the capture of carbon dioxide (per Km^2-year) to be: 

    48 x 2014 = 96,672 lb, 

    or 43,850 kg, 

    or 43.85 metric tonnes per Km^2-year. 

So to fix a metric tonne each year you need land of:

    1/43.85 km^2, = 0.0228 Km^2 = 5.634 acres. 

     The fixing is free; the cost is the cost of the land. In the United States the average cost of land is $14,326 per acre. If annual rent was at 1% of the capital cost (which is admittedly low),  to fix a metric tonne as wood, in the USA, would cost:  

    $14,326 x 5.634/100 = $807 per tonne-year.

     Hmm! A pity, for I hoped forestry would turn out to be cheaper than fooling around with chemical engineering. Unless, of course, the land is loaned free of charge, when the cost comes down to zero.