Biomass-based fuel and chemical production has shown significant promise. However, costs and utilization rates of biomass have still been a challenge for large scale commercialization. Through appropriate decomposition and treatment, biomass can be transformed into many of the same chemicals and fuels as petroleum-based products. Most research has focused on biomass with heavy sugar and starch content such as corn. Recent work has focused on lignocellulosic biomass such as agricultural residues. Lignocellulose biomass is considered the most abundant raw material available for production of biomass-based fuels and chemicals. Examples include include wood, sugarcane bagasse and switch grass.
Lignocellulose can be broken down into three main components: cellulose, hemicellulose, and lignin. Cellulose and hemicellulose can be processed into sugars to create bio-chemicals and bio-fuels such as cellulosic ethanol through well-known fermentative processes.
Lignin is a complex polymer of aromatic alcohols that is difficult to break down. Consequently, lignin has been underutilized as a waste product that is burned in boilers as a low quality fuel. Lignin accounts for up to 30% of biomass by dry weight. In the race to find economic value in non-food biomass feedstocks, utilization rates ignoring 30% of the mass are not efficient or economical. If lignin could be efficiently developed into value-added chemicals, there may be potential to make lignocellulosic biofuel production a more profitable venure.
Biomass derived fuels and chemicals are expected to grow significantly over the next 10 years. It is estimated that by 2020, 9% of all chemical production will be derived from biomass feedstock. Only 2% of lignin is currently used for low-value products (mostly binding agents). The other 98% is used for low-value boiler fuel in pulp and paper mills. With efficient decomposition, lignin and lignocellulose could have a wide-reaching impact on the chemicals and fuel market.
NREL scientists have developed solid based catalysts, specifically layered double hydroxides (LDHs), for depolymerization of lignin to aromatics. Aromatics can be fractioned and integrated into refining intermediate streams for selective upgrading to value-add chemicals.
Base-catalyzed deconstruction (BCD) of lignin is a well-known process. However, current state of the art processes rely on the use of homogenous, non-recyclable aqueous phase basic catalysts. This requires an excessive amount of basic material. Once BCD is complete, the excess base must be neutralized. The process is time consuming and expensive. The use of LDHs would allow for the reuse of basic material and eliminate the necessity for neutralization because the LDH would be a heterogeneous catalyst that could be separated from the resulting product stream by physical methods. Physical methods could include filtration in a batch process or use in a flow-through reactor system. This would ultimately save time and money in lignin decomposition.
Applications and Industries
- Alternative Fuel
- Material Science
- Efficient lignin decomposition
The technology is still in development. NREL would welcome industry partners in furthering development and/or adoption of the LDHs and lignin decomposition.
For more information, please contact Eric Payne at Eric.Payne@nrel.gov.