Wet oxidation treatment of organic household waste enriched with wheat straw for simultaneous saccharification and fermentation into ethanol.
Organic municipal solid waste enriched with wheat straw was subjected to wet-oxidation as a pre-treatment for subsequent enzymatic conversion and fermentation into bio-ethanol. The effect of temperature (185-195 degrees C), oxygen pressure (3-12 bar) and sodium carbonate (0-2 g l(-1) ) addition on enzymatic cellulose and hemicellulose convertibility was studied at a constant wet oxidation retention time of 10 minutes. An enzyme convertibility assay at high enzyme loading (25 filter paper unit (FPU) g(-1) dry solids (DS) added) showed that up to 78% of the cellulose and up to 68% of the hemicellulose in the treated waste could be converted into respectively hexose and pentose sugars compared to 46% for cellulose and 36% for hemicellulose in the raw waste. For all wet oxidation conditions tested, total carbohydrate recoveries were high (> 89%) and 44-66% of the original lignin could be converted into non-toxic carboxylic acids mainly (2.2-4.5 % on DS basis). Simultaneous saccharification and fermentation (SSF) of the treated waste at 10% DS by Saccharomyces cerevisae yielded average ethanol concentrations of 16.5 to 22 g 1(-1) for enzyme loadings of 5 and 25 FPU g(-1) DS, respectively. The cellulose to ethanol conversion efficiency during SSF was 50, 62, 65 and 70% for a total enzyme loading of 5, 10, 15 and 25 FPU g(-1) DS, respectively. Hence, this study shows that wet oxidation is a suitable pre-treatment for the conversion of organic waste carbohydrates into ethanol and that compatible conversion yields (60-65%) can be achieved at moderate enzyme loadings.
Lissens
G
G
Risø National Laboratory, Plant Research Department, P.O. Box 49, DK-4000 Roskilde, Denmark.
Klinke
H
H
Verstraete
W
W
Ahring
B
B
Thomsen
A B
AB
D019149:Bioreactors; D002241:Carbohydrates / Q000032:analysis; D000431:Ethanol / Q000737:chemistry; D005285:Fermentation; D010084:Oxidation-Reduction; D010100:Oxygen; D012037:Refuse Disposal / Q000379:methods*; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D014908:Triticum
D002241:Carbohydrates; D012997:Solvents; D000431:Ethanol; D010100:Oxygen