Biomass Conversion Processes for Energy and Fuels

Countless pages have been written on alternative energy sources since the fall of 1973 when our dependence on fossil petroleum resources became a grim reality. One such alternative is the use of biomass for producing energy and liquid and gaseous fuels. The term "biomass" generally refers to renewable organic matter generated by plants through photosynthesis. Thus trees, agri­ cultural crops, and aquatic plants are prime sources of biomass. Furthermore, as these sources of biomass are harvested and processed into commercial prod­ ucts, residues and wastes are generated. These, together with municipal solid wastes, not only add to the total organic raw material base that can be utilized for energy purposes but they also need to be removed for environmental reasons. Biomass has been used since antiquity for energy and material needs. In is still one of the most sought-after energy sources in most of the fact, firewood world. Furthermore, wood was still a dominant energy source in the U. S. only a hundred years ago (equal with coal). Currently, biomass contributes about 15 2 quadrillion Btu (l quad = 10 Btu) of energy to our total energy consump­ tion of about 78 quad. Two quad may not seem large when compared to the contribution made by petroleum (38 quad) or natural gas (20 quad), but bio­ mass is nearly comparable to nuclear energy (2. 7 quad).

I. Biomass Sources.- 1. Residues and Wastes.- 1. Introduction.- 2. Municipal Solid Wastes.- 2.1. Quantity.- 2.2. Characteristics.- 2.3. Fuel Value.- 2.4. Upgrading the Fuel Value.- 3. Municipal Sewage Sludges.- 3.1. Types.- 3.2. Quantities.- 3.3. Characteristics.- 3.4. Utilization of Sludges.- 4. Animal Wastes.- 4.1. Quantity and Quality.- 4.2. Utilization.- 5. Crop Residues.- 5.1. Types.- 5.2. Quantity.- 5.3. Quality.- 5.4. Seasonality of Generation.- 5.5. Location of Residues.- 5.6. Other Factors.- 6. Industrial Wastes.- 7. Forest Products.- 7.1. Logging Residues.- 7.2. Residues from Wood Product Manufacturing.- 7.3. Residues from Pulp and Paper Manufacture.- References.- 2. Agricultural and Forestry Residues.- 1. Introduction.- 2. Methods of Data Analysis.- 2.1. Species Selected for Study and Analytical Rationale.- 2.2. Sources of Information.- 3. Chemical Quality of Agricultural and Forestry Residues.- 4. Estimates of Agricultural and Forestry Residues.- 4.1. Regional Distribution.- 4.2. Seasonal Availability.- References.- 3. Aquatic Biomass.- 1. Introduction.- 2. Algal Biomass.- 2.1. Yield.- 2.2. Feasibility of Culture Systems.- 3. Aquatic Macrophyte Biomass.- 3.1. Yield of Selected Species.- 3.2. Yield of Marsh Communities.- 3.3. Energy Equivalents and Nutrient Contents.- 4. Discussion.- References.- 4. Marine Biomass.- 1. Introduction.- 2. Biological Characteristics of Marine Plants.- 3. Geographical Distribution of Marine Plants.- 4. Primary Production.- 4.1. Fundamental Considerations.- 4.2. Geographical Distribution of Primary Production.- 4.3. Some Highly Productive Plants.- 5. Chemical Properties of Marine Plants.- 5.1. Inorganic Chemistry.- 5.2. Organic Chemistry.- 5.3. Energy Content.- 6. Commercial Culture and Cultivation.- 7. Utilization of Marine Plants.- 8. Relationship of Primary Production and Chemical Composition to Marine Energy Crops.- 8.1. Preprocessing.- 8.2. Processing Byproducts.- 8.3. Potential Energy Yield.- References.- 5. Silvicultural Energy Farms.- 1. Introduction.- 2. The Silvicultural Energy Farm Concept.- 3. Conceptual Design and Operation of the Silvicultural Energy Farm.- 3.1. Energy Farm Design Parameters and Layout.- 3.2. Energy Farm Operational and Cost Data.- 3.2.1. Energy Farm Installation.- 3.2.1a. Land Acquisition.- 3.2.1b. Land Preparation.- 3.2.1c. Work Roads.- 3.2.1d. Irrigation Systems.- 3.2.1e. Planting.- 3.2.2. Energy Farm Operation.- 3.2.2a. Irrigation.- 3.2.2b. Fertilization.- 3.2.2c. Weed Control.- 3.2.2d. Harvesting.- 3.2.2e. Transportation.- 3.2.2f. Maintenance.- 3.2.2g. Support Costs.- 4. Biomass Production Economics.- 4.1. Biomass Production Costs.- 4.2. Production Costs Components.- 5. Energy Balance for Biomass Production.- 6. The Potential of Silvicultural Energy Farming.- 7. Conclusions.- References.- II. Conversion Processes.- Section A. Direct Combustion Processes.- 6. Basic Principles of Direct Combustion.- 1. Introduction.- 2. Composition.- 2.1. Moisture Content.- 2.2. Ash Content.- 2.3. Organic Content.- 3. Pyrolysis and Heat of Combustion of Biomass and Its Components.- 4. Combustion Process.- References.- 7. The Andco-Torrax System.- 1. Introduction.- 2. Description of Process.- 2.1. Gasifier.- 2.2. Fuel Gas System.- 2.3. Integrated Complete Combustion System.- 2.3.1. Gasifier.- 2.3.2. Secondary Combustion Chamber.- 2.3.3. Regenerative Towers.- 2.3.4. Waste Heat Boiler.- 2.3.5. Gas Cleaning System.- 3. Review of Plant Operations.- 3.1. Demonstration Plant.- 3.2. Commercial Plants.- 4. Heat and Mass Balances.- 5. Some Applications of the Process.- 5.1. Tires, Waste Rubber, and MSW.- 5.2. Sewage Sludge and MSW.- References.- Section B. Thermochemical Processes.- 8. Basic Principles of Thermochemical Conversion.- 1. Introduction.- 2. Kinetics and Thermodynamics Framework.- 2.1. Heating Values.- 2.2. Standard States.- 2.3. Enthalpy Tables.- 3. Gasification of Biomass.- 3.1. Types of Gasification Technologies.- 3.2. Governing Equations.- 3.3. Downstream Processing.- 3.3.1. Gas Purification.- 3.3.2. Shift Conversion.- 3.3.3. Additional Processing.- 3.3.3a. Substitute Natural Gas (SNG).- 3.3.3b. Methanol.- 3.3.3c. Ammonia.- 4. Liquefaction of Biomass.- 4.1. Types of Liquefaction Technologies.- 4.2. Governing Equations.- 4.3. Parallel or Downstream Processing.- 4.3.1. Gasification and Recycle.- 4.3.2. Solids Removal.- 4.3.3. Liquid Recovery/Drying.- References.- 9. The Occidental Flash Pyrolysis Process.- 1. Introduction.- 2. Process Description.- 2.1. Front End System.- 2.2. Pyrolysis System.- 3. Material and Energy Balances.- 4. Product Characterization.- 4.1. Pyrolytic Oil.- 4.2. Glass.- 4.3. Ferrous Metal.- 4.4. Aluminum.- 5. Further Applications.- 5.1. Solid Refuse Derived Fuel.- 5.2. Flash Pyrolysis of Industrial Wastes.- 5.3. Gasification.- References.- 10. Carboxylolysis of Biomass.- 1. Basic Process Description.- 1.1. Feedstock Applicability.- 1.2. Potential Products.- 2. Background.- 2.1. Albany PDU Design and Construction.- 2.2. PDU Operational Results.- 2.3. Supporting Research.- 3. Conceptual Process Description.- 3.1. Reactor.- 3.2. Product Separation.- 3.3. Gasification.- 3.4. Design Basis.- 3.5. Conceptual Plant and Equipment Description.- 3.5.1. Wood Preparation.- 3.5.2. Syngas Production.- 3.5.3. Reaction Process.- 3.5.4. Product Separation.- 3.5.5. Plant Balance.- 4. Process Efficiency.- 5. Conceptual Economics.- References.- 11. The Tech-Air Pyrolysis Process.- 1. Introduction.- 2. Bench-Scale Reactor.- 3. Prototype Plant.- 4. Pilot Plant.- 5. Demonstration Plant.- 6. Process Description.- 7. Product Yields.- 8. Product Characteristics.- 9. Product Uses.- 10. Process Efficiency.- References.- 12. The Purox Process.- 1. Introduction.- 2. Description of Process.- 2.1. Preprocessing Plant.- 2.2. The Basic Process.- 2.3. Purox Gasification Scheme.- 2.4. Gas Cleaning.- 2.5. Wastewater Treatment.- 2.6. Oxygen Plant.- 2.7. Gas Compression and Drying.- 2.8. Process Equipment.- 3. Performance.- 4. Case History.- 5. Economics.- 5.1. Construction and Operating Costs.- 5.2. Product Cost Analysis.- 6. Applications of Purox Fuel Gas.- References.- Suggested Reading.- 13. Gasification.- 1. Introduction.- 2. Types of Gasifiers.- 2.1. Fixed Bed.- 2.2. Fluidized Bed.- 2.3. Entrained Bed.- 3. Fuels for Gasifiers.- 4. Thermochemistry.- 5. Design Considerations.- 6. Performance Characteristics.- 7. Combustion Characteristics.- 8. Ancillary Equipment.- 9. Utilization of Biomass Fuel.- References.- Suggested Reading.- 14. The Syngas Recycle Process.- 1. The Concept.- 2. Experimental Basis for the Process.- 3. Reactor Design Considerations.- 4. Material Balance.- 5. Integrated Process Flowsheet.- 6. Process Energy and Material Balances.- References.- Section C. Biochemical Conversion Processes.- 15. Basic Principles of Bioconversions in Anaerobic Digestion and Methanogenesis.- 1. Introduction.- 2. Stages of the Fermentation.- 2.1. Two-Stage Scheme.- 2.2. Three-Stage Scheme.- 2.3. Metabolic Groups Involved in Partial Methane Fermentation.- 3. The Methanogens.- 3.1. Physiology.- 3.2. Phylogeny and Taxonomy.- 3.3. Substrates.- 4. The Fermentative Bacteria.- 4.1. Fermentation of Polysaccharides.- 4.2. First Site of H2 Regulation.- 4.3. Fermentation of Other Complex Substrates.- 5. The H2-Producing Acetogenic Bacteria.- 5.1. Ethanol and Lactate Fermentations.- 5.2. Fatty Acid-Oxidizing, H2-Producing Bacteria.- 5.3. Second Site of H2 Regulation.- 6. Stoichiometry, Kinetics, Environmental and Nutrient Parameters of Fermentation.- 6.1. Stoichiometry.- 6.2. Kinetic Factors Influencing Efficiency.- 6.2.1. Effect of Retention Time (RT).- 6.2.2. Rate-Limiting Step.- 6.2.3. Effect of Volumetric Organic Loading Rate.- 6.3. Nutrient and Environmental Requirements.- 7. Summary.- References.- 16. Design of Small-Scale Biogas Plants.- 1. Introduction.- 2. Biomass Conversion to Methane.- 2.1. The Biogasification Process.- 2.2. Large-Scale Commercial Endeavors.- 2.3. Potential for Small-Scale Facilities.- 3. Small-Scale Biogas-Processing Facilities.- 3.1. Biogas Plants for Dairies and Farms.- 3.2. Pollution-Control Advantages.- 3.3. Development of Small-Scale Biogas Plants.- 4. Biogas Plant Design and Construction.- 4.1. Process Flow Description.- 4.2. Methane Storage System.- 4.3. Fertilizer Production.- 5. Economic Feasibility and Marketability.- References.- 17. Anaerobic Digestion of Kelp.- 1. Introduction.- 2. Characteristics of Kelp Feeds.- 3. Biomethanogenesis of Kelp.- 3.1. Performance Parameters.- 3.1.1. Gas Production.- 3.1.2. Conversion of Organic Matter.- 3.2. Maximum Theoretical Yields and Heat of Reaction.- 3.3. Bench-Scale Digestion Studies.- 3.3.1. Organic Composition of Feeds.- 3.3.2. Potential Nutrient Limitation.- 3.3.3. Inoculum.- 3.3.4. Temperature.- 3.3.5. Inhibitory Substances in Feed.- 3.3.6. Hydraulic Retention Time (HRT).- 3.3.7. Feed Concentration.- 3.3.8. Particle Size.- 3.3.9. Mixing.- 3.3.10. Feeding Frequency.- 3.3.11. Catabolite Repression.- 3.4. Component and Energy Balance for Biomethanation of Raw Kelp.- 4. Summary.- References.- 18. Basic Principles of Ethanol Fermentation.- 1. Introduction.- 2. Why Microbes Produce Ethanol?.- 3. Substrates for Ethanol Production.- 4. Substrate Preparation.- 5. Substrate Metabolism.- 6. Effect of Microorganisms on Ethanol Production.- 7. Effect of Fermentation Parameters.- 8. Fermentation Systems.- 9. Conclusions.- References.- 19. Ethanol Production by Fermentation.- 1. Introduction.- 2. Feedstock Selection.- 2.1. Pretreatment Design.- 2.2. Pretreatment Costs.- 2.3. Feedstock Price.- 2.4. By-Product Credit.- 2.5. Waste Treatment.- 3. Process Description.- 3.1. Feedstock Preparation.- 3.1.1. Physical Reduction.- 3.1.2. Substrate Hydrolysis.- 3.1.3. Feedstock Sterilization.- 3.1.4. Concentration Adjustment.- 3.2. Ethanol Fermentation.- 3.2.1. Batch Fermentation.- 3.2.2. Continuous Fermentation.- 3.2.3. Yeast Supply.- 3.3. Ethanol Recovery.- 3.3.1. Stillage Separation.- 3.3.2. Anhydrous Distillation.- 3.3.3. Product Specifications.- 3.4. By-Product Recovery.- 4. Conversion Efficiency.- 4.1. Independent Plant.- 4.2. Integrated Plant.- 5. Energy Efficiency.- 6. Conclusion.- References.- III.Technical and Economic Considerations.- 20. Technical Considerations of Biomass Conversion Processes.- 1. Material Balances.- 1.1. Basic Equations and Guidelines.- 1.1.1. System Boundaries; Choosing a Basis; Composition Data.- 1.1.2. Chemical Reactions and Yields.- 1.1.3. Units.- 1.2. Applications to Conversion Processes.- 1.2.1. Air-Blown Gasifier.- 1.2.2. Pyrolysis-Gasification Reactor.- 1.2.3. Pyrolysis of Wood.- 2. Energy Balances.- 2.1. Basic Equations and Guidelines.- 2.1.1. Calculation of Enthalpy Changes.- 2.1.2. Simplified Forms of the Energy Balance Equation.- 2.2. Applications to Conversion Processes.- 2.2.1. Pyrolysis of Wood.- 2.2.2. Pyrolysis-Gasification Reactor.- 3. Evaluation of Process Efficiency.- 3.1. Criteria.- 3.2. Thermal or Energy Efficiency.- 3.3. Thermodynamic Efficiency.- 3.4. Recommendations.- References.- 21. Economic Considerations of Biomass Conversion Processes.- 1. Introduction.- 1.1. Level of Estimating the Desired Precision.- 1.2. Assumed Study Purpose and Conditions.- 2. General Guidelines.- 2.1. Analysis Uniformity.- 2.2. Life Cycle Costing.- 2.3. Money Time Value.- 3. Capital Investment Economics.- 3.1. Plant General Facilities.- 3.2. Plant Utilities.- 3.3. Land Investment.- 3.4. Working Capital.- 3.5. Organization and Start-Up Costs.- 3.6. Depreciable Investment.- 3.7. Plant On-Stream Factor.- 3.8. Conversion Plant Capacities.- 4. Feedstock Prices.- 5. Operating and Maintenance Costs.- 6. Calculation of Revenue Requirements.- 6.1. Revenue Required—Non Regulated Industry.- 6.2. Revenue Required—Regulated Industry.- References.