Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Novel processing methods for various raw materials (for future demonstration)

Steam pretreatment of softwood in one- and two-step configurations with the addition of SO2 or H2SO4 was optimized. The highest yield of hemicellulose sugars (measured as mannose) was around 85%, which was slightly lower than the target 90%, but the yield of glucose, i.e cellulose, was slightly higher than 90%. The overall yield of ethanol after SSF of the pretreated material was 80% of the theoretical based on available fermentable sugars in the raw material, which corresponds very well with the target. The maximum overall yields obtained for corn stover glucan and xylan were 89 % and 78 %, respectively. Continuous steam pretreatment was used for the steam explosion of corn stover. Both the solubilized total matter and sugar concentrations after the steam pretreatment were higher than obtained by the batch treatment. Steam pretreatment of willow resulted in glucose yields exceeding 90 % and xylose yields higher than 80 % after enzymatic hydrolysis both with and without the addition of an acid catalyst.

Two step wet oxidation aimed at extraction of the majority of hemicellulose fraction at mild conditions during the first step and improving the digestibility of the cellulose by the subsequent, second stage performed at more severe conditions. A two-stage pre-treatment process was generally shown to improve significantly the sugar yields, especially the hemicellulose yield of woody materials (softwood and willow).
Improvement of sugar yield from willow by a two stage wet-oxidation pretreatment was generally demonstrated.

The highest hydrolysis yield (as glucose) of all wet oxidation experiments on soft wood was 61%, corresponding to a cellulose recovery of 83%. The highest total hemicellulose yield achieved for willow with additives was 87% in single step. The highest glucose yield was 58%. Acidic conditions of wet oxidation resulted in higher glucose yields. The highest total glucose yield was 80%, which was significantly higher than after alkaline pretreatment. For corn stover, the highest overall hemicellulose yield was 78% of the original hemicellulose content. The enzymatic conversion of cellulose after wet oxidation was between 40 and 77%, as compared to 18% conversion for the native, untreated corn stover.

Experiments on corn stover were carried out also in pilot scale. No effect of the scale on the yields of hemicellulose sugars was observed, but the effect was significant on glucose yield. The highest overall glucose yield, 84% was achieved in optimal conditions in the pilot reactor, compared to 63% obtained in laboratory-scale. The final ethanol yield was about 70% in lab scale, while an average yield of 76% in pilot-scale was obtained.

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Lund University
P.O.Box 124, S-221 00 Lund, Sweden
S-221 00 Lund
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