Wood waste, sugar from

The production of sugar from wood waste has claimed the attention of chemists for the last fifty years. It is of interest, both as a process of producing a supplement to agricultural products and also as a means of converting the vast amount of wood waste resulting from lumber manufacture into useful products. 

In the acid hydrolysis process (79—81), wood is treated with concentrated or dilute acid solution to produce a lignin-rich residue and a Hquor containing sugars, organic acids, furfural, and other chemicals. The process is adaptable to all species and all forms of wood waste. The Hquor can be concentrated to a molasses for animal feed (82), used as a substrate for fermentation to ethanol or yeast (82), or dehydrated to furfural and levulinic acid (83—86). Attempts have been made to obtain marketable products from the lignin residue (87) rather than using it as a fuel, but currently only carbohydrate-derived products appear practical. 

Although the hydrolysis of wood to produce simple sugars has not proved to be economically feasible, by-product sugars from sulfite pulping are used to produce ethanol and to feed yeast (107). Furthermore, a hemiceUulose molasses, obtained as a by-product in hardboard manufacture, can be used in catde feeds instead of blackstrap molasses (108). Furfural can be produced from a variety of wood processing byproducts, such as spent sulfite Hquor, bquors from the prehydrolysis of wood for kraft pulping, hardboard plants, and hardwood wastes (109). 

Wood and wood waste includes residues from the forest and the mill. Bark, sawdust and other mill wastes are all suitable fuels. Agricultural residues include corncobs, sugar cane bagasse (the stalks after processing), leaves, and rice hulls. MSW materials include paper products, cloth, yard wastes, construction debris, and packaging materials. 

Wood wastes from the lumber and woodworking industries form a great potential source of sugars and alcohol by acid hydrolysis of its polysaccharides followed by fermentation. Wood hydrolysis processes, however, are not yet economically competitive with other sources of sugars and alcohol in this country and many other areas of the world. 

Xylose Modified Phenol-Formaldehyde Resins. Xylose (I) and byproducts streams containing xylose (e.g., wood prehydrolysates from the production of chemical pulps and waste liquors from the wet process for hardboard production) are readily available. Our previous experiments (2) showed that free reducing sugars are not acceptable modifiers for phenol-formaldehyde resins cured under basic conditions. 

Table XIV. Sugar Extracted from Washed Feces Fiber of Wood Waste-fed Cattle...

In some preliminary experiments concerning the manufacture of ethyl alcohol from wood waste, F. W. Kressman described a process as follows The process of producing ethyl alcohol from wood consists, in (general, of digesting sawdust or hogged and shredded wood with a dilute mineral acid at from 60 pounds and more, of steam pressure. This converts part of the wood into a mixture of pentose and hexose sugars. The latter are then fermented, producing alcohol. 

In Germany during World War II, yeasts were produced on wood sugars obtained by hydrolysis of wood wastes. However, these uneconomic processes will not be viable in a free economy. In the Soviet Union today, over 900,000 tons of fodder yeast are produced from wood sugars. Several major processors have been trying to develop a direct fermentation of cellulose. However, slow reaction times and low cell yields have caused most processes to be uneconomical. 

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