(604af) Recovery of Phenolic Compounds from Biomass during Ethanol Production

Biomass to ethanol conversion represents an alternative liquid fuel technology that does not need to compete with food crops. Maintaining agricultural production of commodity crops such as corn and soybeans for the food supply and using agricultural waste or low input energy crops grown on marginal land for biofuel production is necessary although economically challenging. The separation and recovery of valuable co-products from biomass would improve the current process economics of ethanol production. Available biomass is primarily lignocellulosic with minor components including waxes and other lipids that are potential co-products which could be separated and recovered from the biomass on-site prior to conversion. The lignin is separated from the cellulosic substrate and recovered for use in plastics and resins or fractionated into the component phenolic acid compounds, e. g., ferulic and coumaric acids. These phenolic acids have applications as antioxidant and antimicrobial agents in foods and animal feeds. 

Process simulation software (SuperPro Designer 7.5, Intelligen, Inc., Scotch Plains, New Jersey, USA) was used to evaluate the initial design for a 70 T/day facility using Panicum virgatum  (switchgrass) as the biomass feedstock. Switchgrass is a perennial North Amercian prairie grass with harvests of 5-11 tonnes/hectare. It was chosen for this investigation due to the interest in it as an energy crop rather than for the amount or unique co-products it contains. The amount of recoverable surface lipids was estimated at 0.1% dry weight and the lignin content was estimated at 5.5% in the leaf with 7.5% in the stem. The recovery of a lignin as co-product was addressed by considering existing fermentation process designs where a de-lignified cellulosic substrate is used for saccharification and the lignin fraction is combusted as a heating fuel. This becomes an economic comparison of the market value for the lignin as co-product versus the heating value of some alternative fuel (ethanol). It is possible to change the operation of the facility in response to fluctuations in the market price. At a high value for lignin it could be recovered as co-product otherwise used as fuel with minimal interruption to bioethanol production. The results of this study suggest two paths to improve the process economics of bioethanol production.