There are several char related pursuits in progress. There's been popular buzz lately about pyrolysis efforts that produce materials for soil amendment and carbon sequestration, but in many ways other char technologies seem more advanced though they see biomass and residual char solely as an energy hack.

Biomass gasifiers seek to produce gasses that can be burned as fuel in various systems that produce heat and electricity. Torrefaction systems seek to produce char which can later be burned as a coal substitute.

One effort, utilizing a technology developed at North Carolina State University in Raleigh, that I found to be especially interesting is the development of a mobile torrefaction system. It travels to a source of materials - such as a forest where there is slash available - and converts the material to char. The weight and volume are reduced, which cuts the costs of transport to a facility that uses the char as a coal substitute. Those savings offset the cost of char production.

Although torrefaction may be new to some, it is really an old process that researchers are breathing new life into . . . “Torrefaction research is old—30 to 40 years,. . . Similar to other research, such as biodiesel, it was sort of shelved when the not-so-renewable alternative fuels were entering the marketplace. . .

In Agri-Tech’s torrefaction process, wood is heated to 300 to 400 degrees Celsius (572 to 752 degrees Fahrenheit), in a low-oxygen environment. The volatile organic compounds and hemicellulose, which are separated from the cellulose and lignin along with water, are combusted to generate 80 percent of the torrefaction process heat. The remaining warm lignin acts as a binder once the torrefied wood is pelletized.

Water removal is a key factor in the economical use of wood as a biomass source. The moisture content of fresh biomass is about 50 percent, according to NCSU and Agri-Tech. Transporting water requires 20 percent to 50 percent of the delivered cost; 10 percent to 25 percent of the total delivered cost. Water may also reduce the heating value of biomass by roughly 50 percent.

Torrefied wood is dense when it’s pelletized, reducing transportation costs of the otherwise bulky material. NCSU and Agri-Tech have found that it costs 23 cents per ton per mile to transport chips and torrefied wood.

The torrified wood is also dry and water resistant because at the high temperatures used in the process, the lignin becomes plastic and is transformed into a binder for individual wood particles. In addition, torrefied wood, which has a low sulfur and mercury content and is carbon neutral, can be easily crushed and doesn’t rot.

Furthermore, torrefied wood has a heating value of 11,000 British thermal units (Btus) per pound, compared with coal at 12,000 Btus per pound, according to NCSU and Agri-Tech. Similar to coal, torrefied wood generates electricity at 35 percent fuel to electricity, compared with untreated wood which has a conversion rate of 23 percent fuel to electricity.

I can imagine having a small fleet of such units that travel to material sources and convert problem materials into useful soil amendments. Everything from pistachio shells and orchard prunings to forest slash could be converted and used on the spot, returning the material to its source as char which would enhance the soils.