How to make high and low adsorption biochars for small research studies
Hugh McLaughlin, PhD, PE, Alterna Biocarbon Inc.
As the world of biochar expands, the need for definitive research to answer core questions grows. One such question is “What is the role of adsorption and when does it make a pivotal difference in growing situations?” Answering those questions has been hampered by the historical absence of adsorption as a monitored property in soils and soil components (as compared to CEC) and the lack of a reliable method to create low and high adsorption biochars. While there is little that can be done about the former situation, the later may have a fairly facile solution, which will be presented here.
During studies of various TLUD stoves and investigating the pros and cons of Natural Draft (ND) versus Fan Assisted/Forced Air (FA), it was noticed that certain FA operating conditions yielded biochars with significantly higher adsorption capacity. Studies are continuing to pin down this phenomenon, but an early conclusion is that a simple modification of the existing 1G Toucan ( http://bioenergylists.org/en/mclauglintoucan ) will allow high adsorption biochars to be generated in half-gallon quantities. Since the traditional natural draft 1G Toucan, as originally detailed on the bioenergylists website in January 2010, generates biochars with low but significant adsorption capacity, a similar biochar with high adsorption appears to be easily achieved.
The key modification for high adsorption biochar is the addition of a fan assisted “Air Base”. The construction of the Air Base is detailed here. The starting point is the recycling center for some discarded tin cans – and one computer power supply fan, as shown in Figure 1.
Caution! In Natural Draft Mode, the 1G Toucan typically has a flame that is up to one foot tall. In Forced Air mode, the flame is more like four feet tall.
We recommend that you make biochar outside, or in an open area with flame-retardant surfaces and a fire extinguisher or method of quenching the flame close to hand.