Assessing the Global Technical Potential for C Sequestration by Biomass Carbonization.

Converting harvestable biomass to a recalcitrant form of C that can be incorporated into soil for long-term storage offers a new approach to terrestrial C sequestration with side-benefits of energy production and enhanced soil fertility.  In the absence of economic constraints, the potential contribution of biomass carbonization to C sequestration is large.  Four variables need to be considered: sustainable biomass production level, carbonization efficiency, land storage capacity, and characteristic storage time (i.e., the rate of C oxidation by soil processes).  In scenarios we have run that assume a 30-year start-up period for the adoption of maximum sustainable biomass carbonization (13% of global net primary production), even a characteristic storage time of 80 years yields a net sequestration of 240 Pg C in the next century.  Fossil-C offsets from the energy produced could increase the net impact to as much as 600 Pg C, enough to stabilize atmospheric C levels at the 550 ppmv level.  Net sequestration and impact increase to 320 and 680 Pg C, respectively, when a characteristic storage time of 500 years is assumed.