Guest post by Rud Istvan,
This is the sixth and final guest post dissecting SoCalEd’s new roadmap to full California (well, at least their southern California service territory) decarbonization by 2045. This last part of the plan is ‘simple’: sink the remaining CO2 through either biological or physical (carbon capture and sequestration, CCS) means.
The figure estimates this to be 108 million metric tons of CO2 (not carbon) per year, with trees preferred. The 108mmt estimate assumes that the four other plan elements are fully implemented. As the previous posts in this series have explained, that is highly unlikely. To the extent they aren’t, the amount needing to be sunk is much larger. As we shall show below, California runs out of trees.
The Alabama Forestry Service has a ‘carbon in wood’ pamphlet providing a starting number. There is about 1 ton of actual carbon in two tons of dry wood. The molecular weight of CO2 is 44 (ignoring isotopes) of which 12 is carbon. So 108 million metric tons of CO2 is about (108*[12/44]) 29.5 million metric tons of actual carbon, requiring about (29.5*2) 59 million metric tons of wood growth per year. That is a LOT of trees, especially for semiarid/desert southern California.
Trees grow slower when older. That is why Alabama’s southern yellow pine (actually about 20 different species) is harvested at about 20 years for pulp, and at about 40-60 years for plywood peeler blocks and lumber.
There are many published studies of annual tree carbon sink rates, since tree biomass is about 90 percent of the global terrestrial total. A typical per tree temperate zone carbon sink rate is about 10-15Kg/year depending on species and age. So SoCalEd needs AT LEAST (29.5E6 metric tons of carbon sunk per year *1E3 kg per metric ton/10 to 15 kg per year) 2 to 3 billion trees.
California forestry surveys estimate about 7.1 billion trees total of all types, of which at least 129 million are standing dead from drought or bark beetles. Biological carbon sinks appear to be a viable part of the SoCalEd plan—provided California’s utilities stop causing large forest fires.
Except for one problem. The 2 to 3 billion trees needed are new trees for future emissions, not California’s existing trees already doing the job. No double counting. SoCalEd will have to find somebody, someplace, willing to be paid to plant a few billion trees and nurture them for centuries. Dunno who or where, and SoCalEd doesn’t either.
CCS is not viable. Many projects have been proposed, but only one large commercial project has been attempted, SaskPower’s Boundary Dam generating station in Canada. One of its four coal fired units (BD3) was converted to CCS in 2014, with the captured CO2 sold to the nearby Weyburn field for tertiary oil recovery.
BD3 CCS has been more than just problematic for SaskPower. After 5 years of tweaking, it is presently operating only about 65% of the time because of chronic maintenance issues. The CCS parasitic load was planned to be about 25%, but is actually about 35%, meaning BD3 only produces about 100Mw of saleable electricity from its 150Mw generator.
Little wonder that all other announced commercial scale CCS projects have been canceled. MIT’s now defunct CCS Technologies program still maintains a global list of 43 proposed CCS projects cancelled as of 2016, when the MIT program went defunct.