Bio-energy in the Black

Tom Miles

Bio-energy in the Black
Johannes Lehmann, Frontiers in Ecology and the Environment, 2007

Common renewable energy strategies can at best off-set fossil fuel emissions of carbon
dioxide, but are not able to reverse climate change. One promising approach of lowering
carbon dioxide in the atmosphere while producing energy is bio-char bio-energy based on
low-temperature pyrolysis. This bio-energy technology relies on capturing the off-gases
from thermal decomposition of wood or grasses to produce heat, electricity or bio-fuels.
Bio-char is a significant by-product of this pyrolysis with remarkable environmental
properties. Bio-char in soil was shown to persist longer and to retain cations better than
other forms of soil organic matter. The precise half-life of bio-char is still disputed,
however, and will have important implications for the value of the technology including
carbon trading. In addition, the cation retention of fresh bio-char is relatively low
compared to aged bio-char in soil and it is not clear after what period of time and under
which condition bio-char attains its adsorbing properties. In order to maximize the
favorable attributes of bio-char and fully evaluate environmental risks, research is needed
at this critical juncture in the development of a bio-char bio-energy technology that has
the potential to provide a significant carbon sink and to reduce environmental pollution
by fertilizers.

In a nutshell: