Disrupting Cellulose for Conversion to Glucose in Loblolly Pine Using Ionic Liquid-Glycerol Mixtures

Forestry products such as Loblolly pine, containing highly crystalline cellulose and high lignin content, can be difficult to convert into the liquid biofuels our world needs to replace fossil fuels.  One way to remove lignin and disrupt cellulose in lignocellulosic biomass is to use ionic liquids such as 1-ethyl-3-methylimidazolium acetate or 1-ethyl-3-methylimidazolium formate. These ionic liquids are effective in producing high cellulose residues of a less crystalline nature, which can be hydrolyzed to produce glucose that can be fermented to ethanol or other biofuels. However, ionic liquids are quite expensive. Since they are salts molten at room temperature, ionic liquids can be recycled in pine-to-glucose processing, but there are inevitable losses.  Diluting ionic liquids with other “green” solvents while maintaining their efficacy is necessary for this process to be economically viable.  One such environmentally-friendly solvent is glycerol, also known as glycerine.  It is a low-cost (~20 cents per kg) by-product of biodiesel production, which is a growing industry.  The ionic liquid 1-ethyl-3-methylimidazolium formate can be diluted half and half with glycerol to pretreat Loblolly pine for 3 hours at 140 °C and atmospheric pressure. The residue obtained gives better glucose yield from Loblolly pine after enzymatic hydrolysis than if pure ionic liquid or pure glycerol were used. More than 40% of the cellulose in the original pine was able to be converted to glucose after the 50:50 ionic liquid: glycerol pretreatment.