Fuel ethanol is typically made from corn, but chemical engineering faculty member Y.Y. Lee and his team have been working to make ethanol from non-crop raw materials, such as agricultural residues, energy crops such as switch grass and hardwood and waste material that includes pulp mill sludges.

While investigating a number of different feedstocks, Lee’s team found that one of the most promising is paper mill sludge. With 14 pulp and paper mills in the state of Alabama, these plants collectively generate nearly 2,000 tons of this waste material each day. If this was converted to ethanol, 150 thousand gallons of ethanol could be produced per day. This sludge is an attractive raw material for ethanol production because it is a free waste material created by the pulp and paper making process. It is also produced in fine particulate form and has a well-dispersed structure and large surface area, making it relatively easy to convert to ethanol when compared to other cellulosic materials.

The lab team has developed an efficient process to convert the sludge to ethanol with funding from Masada LLC, the Alabama Center for Paper and Bioresource Engineering and Auburn’s Center for Biofuels and Biomaterials. The process simultaneously uses a cellulase enzyme biocatalyst and a microorganism. The conversion is done by one-step processing. The Auburn team has also devised a process to extract non-cellulose sugars from pulp wood. The ethanol-plant-in-pulp-mill proposed by the Auburn team would use both the sludge and the pre-extracted sugar stream as the raw material for ethanol. With this design, the ethanol production capacity in a single mill could be about 20,000 gallons per day, a level that could be economically feasible.