(Updated 1/10/14)
Carbon-sequestration from the atmosphere must be a component of a Solar Transition
By David Schwartzman
Following Hansen et al.’s (2008) analysis, a prevention program to have any chance of avoiding catastrophic climate change (C3) must include carbon-sequestration from the atmosphere to achieve an atmospheric CO2 level at or below 350 ppm (it is now 400 ppm) ASAP. His group recommends a 6% cut/year in fossil fuel consumption starting now, with 100 Pg of carbon sequestered from the atmosphere by reforestation from 2031-2080 leaving 350 ppm CO2 in the atmosphere by 2100 (Hansen et al., 2013).
Lal (2010) estimates 2-4 Pg per year of carbon from the atmosphere could be sequestered globally as soil carbon from the atmosphere using agroecological approaches. Assuming a rate of 2 Pg/year, in 50 years 100 Pg of carbon could be sequestered from the atmosphere.
A likely complementary approach is solar-powered industrial carbon sequestration from the atmosphere. For an energy requirement of 110 to 442 KJ/mole CO2 (House et al., 2011; Zeman, 2007), 100 Pg of carbon could be industrially sequestered from the atmosphere requiring 0.91 to 3.7 ZJ, equivalent to 1.6 to 6.5 years of the present global energy delivery (18 TW). In a robust solar transition, with an EROEI value of wind/solar power equal to 25 (same as their lifetime in years) then a total of 18.5 ZJ is consumed over 25 years, with wind/solar generating 54%, and industrial carbon sequestration energy requiring 5 to 20% of the total (see methodology and assumptions in How much Petroleum is needed for this Solar Transition?). This requirement would of course be reduced by the use of agriculturally-driven carbon sequestration into the soil.
References
Hansen, J., Sato, M., Kharecha, P., Beerling, D., Berner, R., Masson-Delmotte, V., Pagani, M., Raymo, M., Royer, D.L., and J.C. Zachos, 2008: Target atmospheric CO2: where should humanity aim? Open Atmos. Sci. J., 2, 217-231.
Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature. PLOS ONE 8 (12) e81648.
House, K.Z., Baclig, A.C., Ranjan, M., van Nierop, E.A., Wilcox, J., and H.J. Herzog, 2011, Economic and energetic analysis of capturing CO2 from ambient air. PNAS 108, No. 51: 20428-20433.
Lal, R., 2010, Managing soils and ecosystems for mitigating anthropogenic carbon emissions and advancing global food security. BioScience 60: 708-721.
Zeman, F., 2007, Energy and material balance of CO2 capture from ambient air. Environ. Sci. Technol. 41: 7558-7563.