(516b) Alkaline Preconversion of Corn Stover: Effects on Feedstock Quality and Liberation of Organic Acids, Lignocelluloses and Other Chemicals

Authors: 
Aston, J. E., Idaho National Laboratory
Thompson, V. S., Idaho National Laboratory
Lacey, J. A., Idaho National Laboratory
Thompson, D. N., Idaho National Laboratory

The goal of feedstock preconversions by mechanical or chemical separation is to improve the quality attributes and reduce the cost targets. The work outlined by this abstract describes the effects of alkaline preconversion on various quality attributes of multi-pass corn stover.

 Multi-pass corn stover was placed in a well-mixed reactor for 24 hours at 8 wt% solids loading at 80°C to achieve alkaline preconversion. The subsequent effects on ash content, ash composition, acetate content and organic solubilization were measured. The chemistry and composition of the extraction liquid and the precipitated residues were also determined. In addition, experiments to determine the required energies for grinding and pelleting for the processed/preconverted corn stover are currently underway using material dried to 10 wt% moisture as well as  20 wt%, 30 wt%, 50 wt% and ‘as is’ moisture contents.

The alkaline preconversion resulted in the removal of over 50 wt% of the total ash from the feedstock, including 70 wt% of the silica. Other significant elements removed include sulfur, phosphate, iron, calcium and potassium. Acetate concentrations in the liquid media were 1.70 ± 0.13 g L-1, and sugar concentrations ranged between 20 and 50 mg L-1for glucose, xylose, galactose, arabinose and fructose. Molecular weight tests of recovered and solubilized material suggest that significant amount of the material solubilized was hemicellulose and lignin.

Alkaline preconversion was successful at removing a majority of the ash and significant amounts of lignin and hemicellulose from the feedstock.  This compilation of data provides reference points for determining the cost/benefit trade-offs of performing alkaline preconversions on corn stover to improve the feedstock quality attributes and/or the production of biochemicals.