Torrefied Wood Pellets Production Using Natural Biomass Compounds

The U.S. coal industry is highly interested in the potential for combusting torrefied wood as a co-feed with coal. Unlike biomass torrefied wood can be cofed with coal at a high percentage. Biomass combustion facilities cannot use the existing infrastructure and new biomass fed plants cost from $140 to $200 million to construct.

Torrefaction of biomass has attracted considerable attention as a means to reduce biomass weight by 70% through removal of water and the hemicellulosic fractions while retaining most of the original high-energy cellulose and lignin content.  A further advantage of torrefied wood is that it has anti-microbial properties as well as limited water resistance such that microbial degradation is eliminated.

             Unlike biomass torrefied wood can be co-fed with coal at a high percentage and requires no major infrastructure investment. One issue is the current inability to ship torrefied wood as coal is currently shipped. A waterproof pelletized product is required to allow bulk shipping via open railcar or by barge. Production of a waterproof torrefied wood pellets or briquettes has not been achieved to date.      

            A combination of low-cost non-traditional adhesive components that produce a high-density pellet with high water resistance was tested. Crushing strength and water repellence tests indicate that the added components produce a torrefied wood pellet with coal-like properties. The adhesive was tested with various feed stocks for producing waterproof pellets.