POSTER SESSION

Biomass carbonization:  The dark side of terrestrial carbon sequestration.

JE Amonette1, J Lehmann2, and S Joseph3

1Pacific Northwest National Laboratory
2Cornell University
3University of New South Wales

Biomass carbonization involves the capture of CO2 from the atmosphere by photosynthesis and its ultimate conversion to charcoal (black carbon or biochar) by pyrolysis.  Energy is obtained during the pyrolysis process and the biochar, which is considerably more stable than biomass, may then be incorporated into agricultural lands where it may serve to increase the nutrient- and water-holding capacity of soil.  With an estimated half-life in soil on the order of centuries to millenia, biochar offers a way of safely storing C for long periods of time while enhancing the productivity of terrestrial ecosystems.  Moreover, biomass carbonization, like other biomass conversion approaches that include C-sequestration options, offers a way to decrease the levels of CO2 in the atmosphere.  That is, biomass carbonization is one of the few inherently “carbon-negative” sources of energy. 

Depending on the feedstock and type of pyrolysis, 15% to more than 95% of the C originally in the biomass may be converted to biochar.  Energy in the form of process heat, electricity, bio-gas, or bio-oil may be produced representing between 25% and 60% of the original energy stored in the biomass.  The properties of the biochar, such as pH and surface area also vary with the nature of the pyrolysis process.  A preliminary global estimate suggests that carbonization of 10% of the 60 Gt of C fixed each year by photosynthesis could decrease atmospheric C by 4.6 to 8 Gt/yr through a combination of biochar formation and displacement of C emitted by fossil-fuel combustion.

VIEW POSTER