Pulsed Electric Field Pretreatment of Switchgrass and Wood Chip Species for Biofuel Production

Abstract

In biomass-to-fuel conversion, the biomass needs to be pretreated so that the cellulose in the plant fibers is exposed for conversion of the lignocellulosic biomass to fuels and chemicals. In this study, we report on the design and fabrication of a pulsed electric field (PEF) system for pretreatment of wood chip and switchgrass samples. Wood chip samples were given 1000 and 2000 pulses of 1 kV/cm, and 1000, 2000, and 5000 pulses of 10 kV/cm with a pulse width of 100 μs and frequency of 3 Hz. Switchgrass samples were given 1000, 2000, and 5000 pulses of 2.5, 5, 8, and 10 kV/cm with a pulse width of 100 μs and frequency of 3 Hz. The uptake of a colored dye neutral red C15H17ClN4 (MW ∼ 289) in untreated and PEF treated samples was studied to quantify the effect of PEF treatment on diffusion in plant tissues. Wood chip samples treated at 1 kV/cm showed a dye uptake similar to that of untreated wood chip samples. The switchgrass samples were resistant to change in the structure at low field strengths up to 5 kV/cm. The samples treated at field strengths of ≥8 kV/cm showed faster and larger neutral red uptake, suggesting an increase in the porosity of switchgrass samples. Similar phenomena were observed for wood chip samples treated at 10 kV/cm. Permeabilization of switchgrass and wood chip species using PEF can be utilized to improve cellulose hydrolysis to sugar and hence efficient fuel conversion.