Bioconversion of mixed solids waste to ethanol

A mixed solids waste (MSW) feedstock, comprising construction lumber waste (35% oven-dry basis), almond tree prunings (20%), wheat straw (20%), office waste paper (12.5%), and newsprint (12.5%), was converted to ethanol via d ilute-acid pretreatment followed by enzymatic hydrolysis and yeast fermenta tion. The MSW was pretreated with dilute sulfuric acid (0.4% w/w) at 210 de grees C for 3 min in a 4-L steam explosion reactor, then washed with water to recover the solubilized hemicellulose. The digestibility of water-washed , pretreated MSW was 90% in batch enzymatic hydrolysis at 66 FPU/g cellulos e. Using an enzyme-recycle bioreactor system, greater than 90% cellulose hy drolysis was achieved at a net enzyme loading of about 10 FPU/g cellulose. Enzyme recycling using membrane filtration and a fed-batch fermentation tec hnique is a promising option for significantly reducing the cost of enzyme in cellulose hydrolysis. The hexose sugars were readily fermentable using a Saccharomyces cerevisiae yeast strain that was adapted to the hydrolysate. Solid residue after enzyme digestion was subjected to various furnace expe riments designed to assess the fouling and slagging characteristics. Result s of these analyses suggest the residue to be of a low to moderate slagging and fouling type if burned by itself.