Arkansas Agricultural Experiment Station, University of Arkansas Division of Agriculture
Dale Bumpers College of Agricultural, Food and Life Sciences

A newsletter for faculty, staff and students

May-June 2005 • Vol. 31, No. 3

New Company Converts Rice Hulls to Carbon and Silicate

A new company in the heart of Arkansas' rice production region uses a process proven by Division of Agriculture research to turn a rice industry waste product into a profitable raw material for manufacturing.

Dr. Andy Proctor, Food Science, collaborated with Producers Rice Mill of Stuttgart to develop the technology used by Agritecsorbents, L.L.C., to turn rice hull ash into carbon and sodium silicate.

Carbon is used as an industrial absorbent in filtration systems, Proctor said. Sodium silicate is a starting material for silica-based products, such as the silica gel packs used to keep packages dry.

The Stuttgart plant is in production and the company received the first purchase orders for its products in May, said Jim McDaniel, vice president and general manager of Agritecsorbents. The company is a joint venture of Producers Rice Mill and the Texas technology company Agritech Systems of Houston.

Producers Rice Mill handles 50 million bushels of rice per year, McDaniel said. From this it produces 225,000 tons of rice hulls.

"Mills have been innovative in finding uses for rice hulls, especially burning it to produce energy to run the plants," McDaniel said. "That produces rice hull ash, and that's where this technology comes in."

Some of the raw ash is sold to the steel industry, where it is used as insulation for steel processing, but that has little value beyond removing the waste, Proctor said.

Rice hull ash is about 38 percent carbon and 62 percent silica. Proctor developed a technique that uses sodium hydroxide to extract the silica, in liquid sodium silicate form, and leave the carbon.

"Turning rice hull ash into these two products eliminates waste removal from rice hull combustion and becomes a 'green' source of valuable raw products," he said.

The most common source of industrial silica is sand. "When extracted from rice hull ash, silica is not mined from hillsides or other sources," Proctor said.

"It has an amorphous form with a random molecular structure," he said. "This makes it easier to extract and easier to process than silica from sand, which has a crystalline structure and requires more heat to process."

Processing silica from sand requires a temperature of 2,800 degrees Fahrenheit, McDaniel said. Sodium silicate from rice hull ash only requires 220 degrees Fahrenheit, and that means using less energy for production.

Typically, carbon comes from coal mined out of the ground or from burning wood. Carbon from rice hull ash is more environmentally friendly because it recycles a waste product, Proctor said.

"Such 'green industries' are becoming more popular, especially in Europe, where there's a lot of interest in them," he said.

Construction of the Agritecsorbents plant was completed in fall 2003 and equipment was installed and adjusted through 2004. Production began this year.

McDaniel said markets are already established for the products. "We're working with a new process, but not making a new product," he said.

At full capacity, Agritecsorbents will produce about 8 million pounds of carbon per year and about 28 million pounds of silica per year, McDaniel said. The U.S. markets use 135 million pounds of carbon and about 2 billion pounds of silica annually.

The world markets for these products are 2 billion pounds of carbon and 18 billion pounds of silica, he said.

Proctor and McDaniel have been talking about developing value-added uses for rice hull ash since the mid-1980s. Proctor approached McDaniel with the idea of producing sodium silicate from rice hull ash and began working on the project with funding from the U of A Institute of Food Science and Engineering, and eventually attracted support from the U.S. Department of Agriculture.

McDaniel said Proctor's data were important in determining whether to start the new company and build the plant. "It really has been a good relationship working with Andy," he said. "The work he did has been invaluable to us.

"To commercialize an idea takes a lot of money, perseverance and faith that you can make it work," McDaniel said. "Andy proved in a lab that this process is viable."