A SYSTEMS ANALYSIS FOR THE PRODUCTION OF SELECTED FUELS AND CHEMICALS FROM BIOMASS
An extensive analysis is presented involving alternative processes and costs for producing liquid fuels and chemicals from sources other than petroleum. A number of critical conclusions are drawn and recommendations for future development are made.^ Earlier studies conclude that the highest priority is the development of synthetic fuels; because of capital cost (1 to 5 billion $) other alternatives must be sought. Liquid fuels from biomass is an attractive alternative because biomass is renewable.^ Acid or enzyme hydrolysis converts the cellulosic fraction of biomass into fermentable sugars. Acid hydrolysis recovers about 50 to 60% of the available sugars; moreover, glucose decomposition products are unavoidable and costly to separate. Enzyme hydrolysis also converts cellulose to reducing sugars but the cellulose should be separated from about 50% of the lignin for effective enzyme action. In contrast to acid hydrolysis, no commercial enzyme hydrolysis plants are operating yet.^ Acid hydrolysis costs are estimated to range between $1.90 to $2.00 per gallon (25 million gal/yr plant); the capital investment is about $100 million. For the same size plant using enzyme hydrolysis from Thermomonospora the capital expenditure is $104 million with a selling price of $1.90 per gallon for a 24% return; 60% of the investment is borrowed. A sensitivity analysis shows that by-product recovery is important; an income increase of $0.37 per gallon results if at least 60% is recovered. The wood feedstock cost can vary up to $37 per ton and still return 18% after taxes. Sensitivity to several other factors arises: enzyme activity and enzyme production schedule; level of by-products recovered; model assumed for cellulose hydrolysis; batch or continuous method of glucose fermentation.^ Computations show that extractive distillation of 5% ethanol to 99.6% ethanol using calcium chloride reduces the steam consumption by more than a factor of 2 compared to conventional distillation.^ Stopping the process at the glucose step is not economic; the cellulose pulp is then more valuable as a paper feedstock than as a substrate for hydrolysis to glucose.^ Finally, a detailed material and heat balance is given in addition to new ethanol-water enthalpy tables at atmospheric and reduced pressure. ^
EDWARD JOSEPH NOLAN,
"A SYSTEMS ANALYSIS FOR THE PRODUCTION OF SELECTED FUELS AND CHEMICALS FROM BIOMASS"
(January 1, 1981).
Dissertations available from ProQuest.