Researchers at Weyerhaeuser are finding ways to make valuable products from the lignin-rich material leftover after slash piles have been converted to biojet fuel. Finding commercial uses for this material is an essential part of producing economically competitive biojet fuel. One promising product generated from this lignin-rich material is activated carbon. Activated carbon is derived from any organic substance with high carbon content such as coal. Its structure contains numerous cavities and pores that help trap impurities and environmental contaminants in water and air.
Turns out that the activated carbon made from this lignin-rich material adsorbs mercury nearly as well as commercially available products. Weyerhaeuser researchers Ian Dallmeyer, Carter Fox and David Fish recently made activated carbon from the wood material produced by various conversion methods being explored by NARA. When the mercury adsorption of these activated carbon products was compared to commercially available products, they found similar properties. There are a number of ways to influence the porosity of activated carbon, and efforts are currently underway to enhance mercury adsorption of these new activated carbon materials.
Mercury pollution is a big deal. Mercury in the air enters water and soils, is converted into methylmercury, and moves up the food chain. Methylmercury exposure is toxic to wildlife and humans. In December, 2012, the U.S. Environmental Protection Agency (EPA) finalized changes to the Clean Air Act that require boilers and some incinerators to reduce the amount of air pollutants, including mercury, emitted into the atmosphere. To comply with these regulations, materials like activated carbon are in high demand. According to Transparency Market Research, “global market for activated carbon was valued at USD 1,913.2 million in 2012 and is expected to reach USD 4,180.5 million by 2019”.
Finding value in co-products
According to NARA’s most recent economic analysis, biojet fuel produced from forest residuals is more expensive to produce than petroleum-based jet fuel when a brand new facility is built from the ground up. The lignin-rich material leftover from the conversion process could be burned to produce electricity and heat, but higher value products may be the key to improving the price of biofuels. Because there is no preprocessing required to convert the lignin-rich residual into activated carbon, the cost of production maybe well under the current commercial selling price. “Given the economic assessment, market factors, and the maturity of technology for producing activated carbon, it is not unreasonable to suggest that co-production of activated carbon in conjunction with biofuel is a feasible and potentially lucrative strategy to implementing a commercial scale biorefinery”, says David Fish.
The NARA co-products team is working on many fronts to discover additional products from the lignin-rich material. In addition to activated carbon, other potential products being developed include a replacement for carbon black in rubber products, an anti-oxidant for asphalt and a viscosity modifier for cement.
Some researchers on the team target products made from a purified lignin source, which means that they must first separate the lignin from the other leftover materials such as unused carbohydrates, yeast bodies and ash. Work by NARA researchers Jinwen Zhang and Michael Wolcott at Washington State University are exploring ways to convert lignin into smaller molecules that can be used to make a variety of products (see earlier story). NARA researcher Simo Sarkanen, at the University of Minnesota, is finding ways to convert lignin into plastics and thermal insulation products.