Pulp mill wastes, ethanol production

Aqueous solutions of these alcohols occur when sugar solutions are fermented and may be separated by distilling the mixtures. It is a common, economically valuable process for manufacturing potable liquors and for producing industrial alcohol from fermented molasses solutions or pulp mill wastes. One of the authors (A.Y.M.) reports that design and operation of these columns is hampered by lack of vapor-liquid equilibrium data, especially for making potable liquors, where small amounts of the alcohols other than ethanol greatly affect the flavor and, therefore, the products marketability. 

Figure 3. Merriam ethanol production from pulp mill wastes...

Figure 6 shows the projected selling price for a 15% return on investment after taxes for the 50,000.000 gal/yr Gulf cellulose alcohol plant and for fermentation corn and synthetic ethylene-alcohol plants of the same capacity (Table VI). The ethylene costs are escalated at 9%, per industry projections, cellulosics at 7%. and according to USDA projections, corn at 5%. Feedstock costs used as a basis for these graphs are (starting 1983 as in Tables V and VI) MSW 14.00/oven-dried ton (ODT), SMW 21.00/ODT, Pulp mill wastes 14.00/ODT, Ethylene 0.18/pound and corn 3.00/bushel. Thus, the total feedstock cost per gallon of ethanol produced is 0,104 in the case of cellulose. 0.75 for ethylene, and 1.20 for corn. By-product credits used escalated from prices listed in 1983 at a 7% rate. 

The situation with regard to ethanol is much clearer there is long industrial experience in the manufacture of ethanol from wood, by fermentation of the sugars in the waste effluents of pulp mills, or of the sugars made by wood hydrolysis ( ). In the years following World War II, wood hydrolysis plants have been unable to compete economically with petroleum-based ethanol synthesis, mainly by hydration of ethylene, and they have been shut down in most countries. However, in the Soviet Union, we understand, there are still about 30 wood hydrolysis plants in operation (10). Many of these are used for fodder yeast production (11) but the wood sugars are also available for ethanol production. 

Another potential feedstock for ethanol production is the lignocellulosic biomass . Lignocellulosic biomass is the most plentiful of all naturally occurring organic compounds. It includes such materials as wood, herbaceous crops, agricultural and forestry residues, waste paper and paper products, pulp and paper mill waste, and municipal sohd waste. Unlike starchy materials, lignocellulosic biomass is structurally complex. The conversion of this material into ethanol has been the subject of intense study over the last 20 years. 

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