There's more and more information being available about biochar from pyrolysis and hydrothermal carbonization (HTC).
In 2011 the USDA commissioned a really comprehensive report on the current state of pyrolysis and HTC research.
http://ddr.nal.usda.gov/bitstream/10113/47781/1/IND44489931.pdf
Youtube has some good videos I threw together into a biochar playlist,
http://www.youtube.com/playlist?list=PL854DE82D788D5E2E