History

Arkansas’ rice crop in 2006 was approximately 4.795 million tons; of which, 20% by weight or 959,000 tons were rice hulls. With such large quantities of hulls the rice industry has devoted a lot of time and resources over the years to finding uses for this byproduct. There has been much written about what to do with these rice hulls but very little has been done commercially.

Trends for the last 25 years in the rice industry worldwide have been to burn the hulls for energy. The U.S. has played a major part in this technology as 5 of the 6 largest mills have been burning at least a portion of their hulls by adapting combustion technology from other industries or developing their own systems. Burning the hulls not only has the benefit of cheap energy but also the weight and volume of the hulls burned has been reduced by 60-80%.

Even though part of the disposal problem has been significantly reduced it is still a challenge to dispose of the ash. Much of the ash has been channeled into the steel industry to be used as an insulator and placed on top of ladles of molten steel to hold in heat until the steel can be cast. Another developing use is as a component in refractory formulation. Both of these applications are successful but they do not use all of the available rice hull ash; the remainder of which is being placed in landfills.

Producers Rice Mill in Stuttgart, AR is a 60 year old farmer-owned cooperative which has handled over 50 million bushels of rice for each of the last four years. They have been burning rice hulls for 23 years in a combustion system which they developed and patented. This technology produces a unique ash composition of about 20-30% activated carbon and 70-80% amorphous silica.

In their search for rice hull ash uses over the years, Producers Rice has developed a relationship with the University of Arkansas that can be traced back to the late 1980’s. In 1995 the University worked on a project for Producers which involved the same technology as they are now trying to commercialize. At that time it was not known that this technology was in the process of being patented by AgriTec, Inc.; however, the project later proved important as Producers became aware that the silica and carbon in the ash could be separated.

After exploring many possible ash uses through the years, in 2003 Producers Rice committed to the technology that had been patented by AgriTec, Inc. of Houston, TX and formed a partnership and company called AgriTecSorbents, LLC. This technology consists of alkaline extraction of the amorphous silica by the formation of sodium silicate, thus separating the carbon and silica. In this process two industrial products are formed; powdered activated carbon and liquid sodium silicate. Full-time commercial production is expected to start in January 2008.