In order to achieve high surface areas the key engineering parameter of oxygen starved biomass gasification is temperature formation, where the optimal range is approximately 500 to 700 degrees C (~900 to 1,300 F).
While quite a bit of research is on-going to create biochar with small scale gasifiers (e.g., laboratory, stove, etc.), our research and demonstration effort is focused on large-scale, commercial up-draft gasifiers where the biochar is a waste product in creating biogas (for end-use applications such as product drying/heating, electricity, steam).
In our approach, we extract biochar (just above the incandescent zone) on a semi-continuous basis using nitrogen to “quench and cool” the biochar removed/recovered from the bed cooled to room-temperature for storage and eventual soils application. The recovery of biochar from the gasifier will not significantly impact the gasifier continuous operation of biogas generation for power/heat/steam. It is also important to note that our approach to "quench and cool" in a nitrogen environment is also attempting to address the extremely high carbon/nitrogen ratio of biochar.
On a final blog note, recent published studies suggest that biochar has the potential of sequestering ~12 percent of global CO2 emissions.