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Anderson, J. W., Hughes, H. K., Anal. Chem., 23, 1358 (1951). Connor, J. E., Jr., Rothrock, J. J.. Birkhimer, E.R., Leum, L. N.,I d . Eng. Chem., 49, 276 (1957). De Barry, Barnet, E.,Wilson, C. L., "Inorganic Chemistry", Longmans Green and Co., London, 2nd ed, Chapter 14, p 178, Chapter 15, p 193, 1957. Hawkes, H. E., Webb, T. S.,''Geochemkb'y in MineratExplotation", p 415, Harper and Row. New York. N.Y.. 1966. Hodgson, G. W.. AAPG. 38(12), 2537 (1954). Levorsen, A. I., "Petroleum Geology", W. H. Freeman, Chapter 5,p 190, 2nd U S . ed, 1st Indian reprint, 1972.
Mitchell, R. L.,"Trace Elements in Chemistry of Soil", p 373, Reinhold, New York, N.Y., 1955. Milner, 0. I., Glass, J. R., Kirchner, J. P., Yurick, A. N., Anal. Chem., 24, 1728 (1952). Shiray, W. 6.. Ind. Eng. Chem., 23, 1151 (1931). Wrightson, F. M., Anal. Chem., 21, 1543 (1949).
Received for review October 9, 1978 Accepted March 6, 1979
SIGNALS OF SCIENCE Methane Production from Biomass and Agricultural Residues Donald L. Wise," Ralph L. Wentworth, and Edward Ashare Dynatech RID Company, 99 Erie Street, Cambridge, Massachusetts 02 739
The status is presented of the Fuels from Biomass program of the U S . Department of Energy, especially wfth respect to fuel gas production from biomass and residues. The entire scope of this Fuels from Biomass program is given, followed by a perspective on fuel gas production. Anaerobic fermentation has been the primary processing system under investigation for methane production. Cattle manure, both beef and dairy, has been the primary substrate evaluated in this bioconversion process although agricultural residues, such as straw, and selected crops grown specifically for energy utilization are also being evaluated. Projects range from laboratory programs through large-scale experiments to full-scale facilities. Description is provided of current programs. I n every respect, the Fuels from Biomass program is oriented towards obtaining meaningful supplies of fuel gas.
Introduction Plants transform solar energy into chemical energy or biomass, which can then be harvested and converted into usable energy products. The biomass resources of residues and terrestrial and aquatic plants are renewable; they can potentially supply significant amounts of the future U S . energy requirements. These resources can be converted by a number of technologies into liquid transportation fuels, gaseous energy products, and other forms of energy. Research and development efforts of the Fuels from Biomass program (FFB) of the U S . Department of Energy are focused on: (a) growing terrestrial and aquatic crops on energy farms, (b) harvesting, collecting, transporting, and storing biomass, and (c) converting biomass to fuels and petrochemical substitutes. These are described as follows ( U S . Department of Energy, 1978). Terrestrial Biomass Production. The most important issue facing the production of terrestrial energy crops is the availability of land and water resources to be allocated to such an enterprise. If water could be made available at reasonable cost, marginal lands including some desert areas could be used for energy farms. Unfortunately, water is a relatively scarce resource in many parts of the U S . , and this may seriously restrict the use of marginal lands. A multitude of factors must be considered in the allocation of land resources to energy production. High product costs, small farm units, higher value crop alternatives, climatic limitations, and other economic considerations influence the decision to dedicate land to biomass production. The consolidation of currently 00 19-7890/79/1218-0150$01.OO/O
fragmented acreage in some U.S. areas into profitable units depends upon the size of tracts, types of owners, and proximity to existing farmlands. A considerable amount of the land will require special conservation projects and practices to minimize soil and water erosion. In addition, energy farm investors will have to be assured of a long term profit in order to offset the capital costs associated with bringing marginal lands into production. If biomass farming is to represent a viable alternative energy source, it must not only be economically competitive with other energy sources, but must also provide a favorable return in comparison with food and fiber crops. Residues. The present availability of biomass residues (field crop residues, animal manures, and forest and mill residues) is estimated to be 100 million dry tons, with a theoretical maximum of 427 million dry tons. Biomass residues are currently being used in animal feeds, fiberboard products, fertilizer, soil tilth, and as soil conditioners. The cost of biomass residues varies greatly according to type, application, region of the US., and location with respect to potential users. Field crop residues vary from $4.00 per ton for wheat and other small grain straws to $15 per ton for corn stover. Manure residues range from $0.50 per ton for cattle manure to $17 per ton for poultry manure. The cost associated with collecting, reducing, and transporting forest residues is estimated to range from $25 to $60 per ton, depending on location. Silviculture Energy Farms. The overall research objective in the growth of woody plants is to provide maximum energy content a t minimum cost. In this context, costs include all outlays associated with growing 0 1979 American Chemical Society
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the resource and delivering it to the conversion point, including harvest, collection, transportation to the conversion point, and storage until the conversion process begins , Within the framework of this objective, program goals include selecting and improving the most promising species, minimizing risks and costs of establishing growing stock, determining the most cost-efficient cultural treatments and management systems, and obtaining optimum yields. Yields and costs must be considered both in terms of dollars and net energy obtained. The major factor which will control the contribution of the energy farm concept to the nation’s energy supply is biomass productivity, or the yield that can be produced annually per acre. Productivity levels vary with the species planted, the cultural practices used, and the site conditions, including climate, weather, and soil characteristics. All of these factors may be controlled or modified to some extent by man. Promising species can be selected through experimentation and improved by genetic breeding programs. Cultural practices for each species and region of the U S . may also be selected and optimized through experimentation t o provide cost-effective approaches to energy crop management. Site-specific factors can be modified by cultural practices (e.g., irrigation, fertilization, and weed and disease control) and accommodated by appropriate species selection. Hence, biomass productivity is a technological factor that can be, within certain biological limits, molded and fashioned by man to best fit the needs of the concept. Success in optimizing biomass yield will largely depend on the time and research dollars spent on the problem. A comprehensive systems study providing information about promising tree species, management practices, availability of land for silviculture energy farming, sources of residues, and conversion processes has recently been completed. The major conclusions of the system study are the following. (1) A t least 30 million of the nation’s 1.3 billion acres of grassland and forest could be made available for wood energy farms. (2) Biomass productivity under close-spaced, short-rotation conditions is estimated to range from 5 to 13 dry-ton-equivalents per acre each year with current production technology, depending upon species and site selection. (3) The quality of energy produced in the form of wood biomass by the process of energy farming is estimated to be 10 to 15 times the amount of energy consumed, depending upon the level of productivity achieved. The energy farm, as envisioned in the systems study, would consist of selected, rapidly growing tree species planted a t close spacings. The crop would be harvested a t appropriate intervals or rotations, with succeeding crops growing by coppicing (sprouting from stumps), precluding the need to replant after each harvest. Since most conifers do not coppice, planting would be restricted in most cases to selected hardwood species. Intensive crop management would be practiced, including fertilization, irrigation, and weed and disease control. In this regard, energy crop production would be more similar to field crop production than to conventional forestry. The FFB program was substantially expanded in FY 1978 to include research programs to improve the yield and decrease costs of growing and harvesting woody plants, and the development of a harvesting system for small-diameter, closely spaced trees. A 1000-acre silviculture test plantation was established to investigate the short-rotation forestry concept on DOE-owned land near Aiken, S.C. Elements of the project include site preparation, seedling
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supply, stand establishment, cultural practices, irrigation, harvesting, and conversion of the harvested material. The economics and energy balance of the operations will be determined. Beginning in FY 1980, the program will include other silviculture research demonstrations, using farms of 1000 to 3000 acres. A g r i c u l t u r a l a n d Nonwoody Plants. The research objectives for agricultural and nonwoody plants are similar to those for woody plants. These objectives include selecting the most promising species, preparing sites, establishing growing stock, and using appropriate management techniques to obtain optimum yields in terms of economics and energy production. Studies include the impact of row spacing, nitrogen fertilization, irrigation, and frequency of harvest yields of sugar cane and sweet sorghum crops. Sugar cane and tropical grass production is being investigated in Puerto Rico, including evaluation of harvest frequencies, yields, and regrowth after cutting. A series of species screening projects will be initiated beginning in FY 1978. These projects will be designed to identify plant species that have a high Btu content, growth rate, disease resistance, and dry weight production per unit area. Aquatic Biomass Production. The FFB program is currently supporting research in three aquatic resource areas: freshwater systems, open ocean systems, and shoreline brackish systems. The program includes screening various species for yield, potential growth, nutrient assimilation, fermentability, and economic feasibility. The effort also entails determining possible sites, energy balances, and operating concepts within the three resource areas and selecting systems for detailed engineering design and cost analysis. Various marine and freshwater biomass sources being investigated include red, brown, green, and blue-green algae, water hyacinth, duckweed, and kelp. I n t r o d u c t i o n t o Biomass Conversion Systems Many processing options can be applied to the conversion of biomass to energy or chemicals. These processes range in their stage of development from laboratory scale to commercially proven processes. Commerical combustion facilities have been used for many years, and anaerobic digestion facilities for feedlot manures are scheduled to be operating soon. Fermentation to produce ethanol and petrochemical substitutes, gasification to produce ammonia, SNG, hydrogen, and methyl fuel, and liquefaction to produce fuel oil are technically feasible but not yet economically competitive. Photochemical processes are being pursued on a long-term, low-emphasis basis. Some biomass materials may require pretreatment, which usually consists of drying or further volume reduction. After suitable preparation, biomass can theoretically be processed using any of a number of proven technologies. However, the chemical composition of any biomass feedstock will dictate the probable conversion process and path for utilization. For example, direct combustion or gasification is the most likely alternative for low-moisture content biomass, while anaerobic digestion and fermentation are more adaptable to highmoisture biomass materials. The processing paths shown in Figure 1 produce a wide range of products. These products are suitable for direct use or can be upgraded further to serve markets with more critical needs or to produce transportable products more economically. The production of steam through the direct combustion of biomass can be used to produce electric power via standard, acceptable technology. In addition,
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. Chem. Prod. Res. Dev., Vol. 18, No. 2, 1979 RESOURCES BASES
TECHNOLOG I ES
PRODUCTS
MARKETS Transportation
Biochemical Industrial/ Commercial Sector Thermochemical Substitutes (Ketones, Higher Photochemical
Y
1 Water
E lect riciIy
Chemical Sector
Utility Sector
Figure 1. Fuels from Biomass program overview.
ethanol from the fermentation of biomass can be used directly as a motor fuel or converted to ethylene, a major petrochemical feedstock for polymers. The product priorities for this program are liquid transportation fuels, SNG, and other energy-intensive fuels and chemicals. Each processing path that produces a primary product has a different conversion efficiency, requires a different level of capital investment, and has a distinct economy of scale. Because of these unique features, it is necessary to conduct a detailed analysis of market needs and process economics based on each possible biomass feedstock which will then be ranked on a comparable basis. Each of the conversion paths will be discussed/presented separately, with emphasis on unique requirements and product outputs. Specific Contribution of Fuels from Biomass The Fuels from Biomass program encompasses the production and harvest of all forms of plant biomass and their conversion to clean fuels, petrochemical substitutes, and other energy-intensive products. Biomass is all plant life, whether grown on land (terrestrial) or in water (aquatic) and includes forest, agricultural crop, and animal residues. Biomass is not municipal solid waste, sewage sludge, or industrial process waste of any kind. Fuels from Biomass systems offer a potential for converting biomass to a variety of liquid and gaseous fuels, petrochemical substitutes, other energy-intensive products, and steam and/or electricity. Fuels from Biomass is a solar technology because the solar energy is processed by living plants and stored as plant biomass. The Fuels from Biomass program is unique among all of the solar technology options because the fuels and energy-intensive materials produced from plant biomass directly replace natural gas and petroleum. No other solar technology product serves energy consumers in the transportation and other sectors of our economy so directly. In the near term, the Fuels from Biomass program emphasizes the deployment of systems that use regionally available forestry and agricultural residues as substitute feedstocks for fuel products. The contribution of nearterm systems to our domestic energy supply by 1985 could be 0.5 to 1.0 quad (quadrillion Btu), a displacement of 230 000 to 460 000 barrels of oil per day. This amount is in addition to the over 1 quad already produced by the forest products industry utilizing residues. For the longer term, the program emphasizes producing an assured supply
of biomass feedstocks from energy farms and developing conversion processes to provide cost-competitive clean fuels (primarily to the transportation sector), petrochemical substitutes, and other energy-intensive products. The long-term impact could be significant, contributing up to 7.2 quads per year by 2000. This amounts to approximately 12% of the 1978 national energy demand. The resource base for this contribution is illustrated in Figure 2. The biomass resources available for energy use are collected forest and crop residues, animal manures, and silvicultural, herbaceous, or aquatic crops grown on energy farms expressly for their conversion to fuels. Conversion technologies include a variety of biochemical and thermochemical processes. The former describes the conversion of biomass by microorganisms to clean fuels, and other petrochemical substitutes, whereas thermochemical conversion to clean fuels, petrochemical substitutes, and other energy-intensive products is accomplished by elevated temperatures and/or pressures, catalysts, or chemical reactants. Figure 3 shows the four major sources of biomass and several of the processes that can be used to convert them into biomass fuel products. The program does not include the technology for converting municipal solid wastes or industrial wastes. This program is the responsibility of U.S. Environmental Protection Agency and the Assistant Secretary for Conservation and Solar Applications of the U.S. Department of Energy. Potential for Near-Term Systems Near-term systems are identified as those that are ready by or before 1980 for transfer from the Fuels from Biomass branch to other Department of Energy organizations and/or to appropriate market sectors for commercialization. The biomass sources for all near-term systems are forest, crop, and animal residues or standing forest biomass. Since these resources are regionally dispersed, systems will be relatively small compared with fossil or nuclear power plants. Near-term systems are expected to contribute from 0.5 to 1.0 quad to our domestic energy supply by 1985, depending on market forces and federal incentive programs. Although near-term systems do not produce oil or gas substitutes directly, they will replace conventional oil- or gas-fired systems of up to 60 MWe. Thus, near-term systems can displace as much as 460 000 barrels of oil per day by 1985.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 18, No. 2, 1979
'1 0 3gt
153
400n l l
AVAILABLE
CAPTURE POTENTIAL
3* T
5t
FORESTRY RESIDUES
CROP RESIDUES
ANIMAL RESIDUES
SILVICULTURE ENERGY FARMS
HERBACEOUS ENERGY FARMS
AQUATIC ENERGY FARMS
Figure 2. Estimated potential for supplementing US.energy supply.
L I I I I
RESOURCE BASES TERRESTRIAL RESIDUES SILVICULTURE HERBACEOUS AQUATIC
I
VERSION TECH1NOLOG IES
PRODUCTS
I
1
MARKET SECTORS
I
BIOCHEMICAL
-
ANAEROBIC DIGESTION
11 1 FERMENTATION
THERMOCHEMICAL
GASIFICATION
-t
GASEOUS FUELS PETROCHEMICAL SUBSTITUTES ENERGY-INTENSIVE PRODUCTS
LIQUEFACTION
DIRECT COMBUSTION
PHOTOCHEMICAL
Figure 3. Fuels from Biomass program overview.
Technical and economic issues include identifying the regional resource base and designing the residue collection and transportation system to supply conversion facilities. At issue is the economic competition between conventional fossil fuels and biomass-based fuels. Fuels from Biomass activities for systems utilizing direct combustion of forest residues and anaerobic digestion of manure are currently in the demonstration phase. Future commercialization activities for manure systems on small farms are scheduled for transfer to USDA. The cost of these Fuels from Biomass systems is near economic viability and can be deployed regionally through aggressive technology transfer activities and implementation of economic incentive packages in the early 1990's. All other near-term systems are ready for commercialization activities a t this time.
Anaerobic Digestion Anaerobic digestion is the controlled microbial decomposition of organic matter in the absence of air to produce methane and carbon dioxide. While most biomass can be digested anaerobically, the current state-of-the-art of the technology provides digestion of biomass feedstock with high moisture content. Two favorable temperature ranges exist for anaerobic fermentation-the mesophilic 30-45 "C and the thermophilic 50-65 "C. The use of thermophilic bacteria may allow faster rates of reaction and a smaller plant size.
The gaseous product of digestion medium-Btu gas or MBG, a mixture of carbon dioxide, methane, hydrogen sulfide, and water vapor, can be burned without substantial treatment. Alternatively, MBG can be converted to SNG by drying the MBG, stripping it of its carbon dioxide and hydrogen sulfide, and compressing it. Because of associated economics of storage and transportation, and lack of suitability for fuel substitution, MBG users will probably be limited to on-site users or commercial and industrial customers who are near the site of gas production. The advantage of SNG production is that it can be substituted for natural gas and fed into the existing distribution networks. A key technical issue is the use of biomass feedstocks other than manure for anaerobic digestion. Most biomass has a relatively high moisture content but is resistant to attack by microorganisms. Pretreatment could improve the digestibility of cheaper or more plentiful feedstocks. Pretreatment, as well as other process modifications, could improve overall efficiency and reduce costs. An anaerobic digestion involves three concurrent phases of development. In one phase, the applied research program continues to improve digestion kinetics and the pretreatment of various feedstocks. At the same time, technical feasibility and cost estimates are provided in larger test facilities, and operational experience, a refined technology, and process economics are developed by operating large experimental facilities.
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Table I. Fuels from Biomass Projects in Anaerobic Digestion organization Agricultural Research Service
title
projected contribution
Anaerobic Fermentation of Livestock Manures and Crop Residues
Recover high protein biomass methane, and plant nutrients from livestock manures and crop residues through anaerobic processes. Harvest microalgae by a nonfouling membrane process. Control algal and wood digesters with permselective membrane.
Columbia University
Algal Concentration by Ultrafiltration
Columbia University
Permselective Membrane Control of Algal and Wood Digesters for Increased Production and Chemicals Recovery Anaerobic Fermentation of Agricultural Residues Potential for Improvement and Implementation Engineering Evaluation of Program t o Recover Fuel from Gas Waste
Cornel1 University Dynatech RID Company Ecotope Group Hamilton Standard Hamilton Standard
University of Illinois Stanford University
Monitor, Test and Evaluate an Operational Digester for 350 Cattle Units Feedlot Energy Reclamation Demonstration Pipeline Fuel Gas from an Environmental Cattle Feedlot Biological Conversion of Biomass to Methane Heat Treatment of Organics for Increasing Anaerobic Biodegradability
Anaerobic Digestion of Animal Manures on Small Farms and Environmental Feedlots This near-term technology involves the conversion of animal manure (a biomass resource) through anaerobic digestion to produce medium-Btu gas, MBG, or SNG. The manure, which is aggregated on small farms or in environmental feedlots, is converted by a process that is similar to that used for treating sewage sludge. The product of conversion is an MBG, a mixture of methane, carbon dioxide, and water vapor, which can be further upgraded to SNG by removing the carbon dioxide, water vapor, and other impurities. An economic analysis has been carried out on fuel gas production from animal manure (Ashare et al., 1977; Wentworth et al., accepted for publication; Ashare et al., accepted for publication). The resource base, animal manure, is smaller (about 0.3 quad) and more dispersed than forest residues, resulting in small-scale systems. For most of the systems, the MBG produced is likely to be used on site or close to the conversion plant. However, for the larger systems, gas compression and clean-up to pipeline-quality SNG may be required for distribution in existing natural gas pipelines. The key to commercializing the anaerobic digestion of animal manures is identifying users, their resources, and requirements through commercialization activities that include market and incentive studies. Since the emphasis of many feedlot owners is on cattle refeed potential rather than energy per se (energy being a byproduct), recommendations will be made to transfer this activity to U S . Department of Agriculture by 1980. Status of Current Projects In Table I is presented a summary of Fuels from Biomass projects dealing with the area of anaerobic fermentation to fuel gas. In the following is also given a brief summary description of these current projects. Title: Heat Treatment of Organics for Increasing Anaerobic Biodegradability
Optimize fermentor designs for use in large-scale pilot plants. Evaluate various methods of methane production, and monitor technical anaerobic digestion projects. Apply the knowledge of digester applications to full-scale dairy farm operations. Produce fuel gas to achieve feedlot energy self-sufficiency. Produce fuel gas and other products from animal residues, and t o promote commercialization of the process Convert organic refuse t o methane in an efficient, cost-effective manner. Increase biodegradability and methane production from waste organic materials by heat treatment under pressure.
Organization: Stanford University, Stanford, CA 94305 Principal Investigator: Professor Perry L. McCarty Project Summary. Experiments are continuing under this two-year study to increase biodegradability and methane production from organic waste materials by heat treatment under pressure. The materials under study include farm residues, forest product wastes, and municipal waste-water sludges. The objective of the project is to develop a general model for heat treatment which is applicable to all organic materials. Once optimum conditions for heat treatment are found, project tasks will include evaluating bench scale anaerobic digestion and heat treatment systems with the various wastes in order to determine the overall resulting benefits. Among the benefits anticipated are increased methane yield per unit of waste treated, reduced costs for methane production, and a lower quantity of more readily dewatered residue for ultimate disposal. The major variables are temperature (25 to 25OoC), time of treatment (0 to 3 h), and pH (1 to 13). Past research has shown that many of the single ring aromatic compounds expected to be formed from heat treatment of lignin are fermentable to methane. Direct measurements on methane production are in progress. The effect of heat treatment on waste activated sludge is being evaluated. Preliminary data shows increased biodegradability can be achieved by heat treatment. Further project tasks will include studying possible sources of toxic substances and the fate of specific nitrogen compounds. Studies on aromatic biodegradability have produced a reliable method of long-term culture maintenance. Cultures were acclimated to higher substrate concentrations; volatile fatty acids and acetic acid have been detected. In future research, substrate concentration will be increased and the cultures monitored. Title: Biological Conversion of Biomass to Methane Organization: University of Illinois, Department of Civil Engineering, Urbana, IL 61801
Ind. Eng. Chem. Prod. Res. Dev., Vol. 18, No. 2, 1979
Principal Inuestigator: John T . Pfeffer Project Summary. Research has shown that the biological conversion of organic refuse to methane is a technically feasible process. The objective of this project is to obtain experimental data on conversion efficiency to predict the cost of gas production. An experimental system consisting of four completely mixed heated fermentation tanks was constructed and began operation in 1976. To provide additional information to other ongoing projects, cattle manure was chosen as the substrate. The tanks produce from 50 to 100 L of gas per hour. Current project tasks include evaluating the methane yield as a function o f (a) plant species and fiber composition, (b) thermochemical pretreatment or posttreatment, (c) mesophilic and thermophilic temperature, (d) liquid recycle, and (e) residence time. Residues from the fermentor will also be evaluated to determine fiber composition, plant nutrient content, and slurry dewatering characteristics. A simple simulation model of the fermentation, residue processing, and disposal systems will be constructed to help determine optimum operating and design parameters of the substrate being tested. Title: Pipeline Fuel Gas from an Environmental Cattle Feed Lot Organization: Hamilton Standard Company, Windsor, CT 06096 Principal Inuestigator: Daniel J. Lizdas Project Summary. The objective of this program is to determine the technical and economic viability of producing fuel gas and other useful products from animal residues through the anaerobic fermentation process, and to promote early commercialization of the process. In addition, the feasibility of utilizing the protein rich fermentor discharge as an animal feed ingredient will be evaluated. T o accomplish this objective, the system and its operational program will demonstrate the utilization of the products produced and monitor their quantity and quality. This information will support an evaluation of its commercial potential relative to existing alternate energy sources. Title: Feedlot Energy Reclamation Demonstration Organization: Hamilton Standard Company, Windsor, C T 06096 Principal Inuestigator: Robert E. Breeding Project Summary. The objective of this program is to demonstrate to the feedlot industry a process of producing fuel gas to achieve feedlot energy self-sufficiency. Using cattle manure as feedstock, the process will generate methane for fuel and carbon dioxide as a refrigerant. The process will also produce a high protein “residual” which is suitable for an animal food supplement or fertilizer. The original project contract has been extended to allow work on an alternate start-up method and evaluation of temperature on productivity. This work continues a t the Hamilton Standard Mobile Cattle Waste Processing trailer a t a Monfort, Colorado, feedlot. Gas yields have been less than anticipated. Operating characteristics and feedstock biodegradability are being reevaluated. System studies on the most useful size demonstration unit, cost analysis, and utility usage have been discontinued. Title: Monitor, Test, and Evaluate an Operational Digester for 350 Cattle Units Organization: Ecotope Group, 747 16th East, Seattle, WA 98112
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Principal Inuestigator: Kenneth D. Smith Project Summary. The objective of this project is to advance the knowledge of digester applications to full-scale dairy farm operations. Project tasks will include monitoring, testing, and performing laboratory analyses on a 100000-gal anaerobic digester a t the State Reformatory Honor Farm in Monroe, Wash. The system is a complete-mix mesophilic digester with a 15-day detention time. Based on test results, an operator’s manual will be prepared for farm personnel, a final report evaluating system viability will be written, and engineering drawings will be updated to show the actual operating system. T i t l e : Engineering Evaluation of Programs to Recover Fuel from Gas Waste Organization: Dynatech R / D Company, 99 Erie Street, Cambridge, MA 02139 Principal Investigators: D. L. Wise, R. L. Wentworth, E. Ashare Project Summary. The objective of this project is to coordinate the research and development efforts of those projects evaluating biomass feedstocks of methane production. T o facilitate the presentation of results in a consistent format, project tasks include assisting in information exchange, evaluating engineering design and systems analyses, and reducing economic analyses to a common set of assumptions. This will help identify areas in which additional or more accurate data are required to produce a complete, reliable assessment of methane production from biomass. A comprehensive mathematical model of anaerobic digestion of animal residues has been developed, taking into account material and energy balances, kinetics, and economics of the process. A computer program for this model includes a routine to minimize unit gas cost. The sensitivity of unit gas cost to changes in the major contributions to unit gas cost was analyzed, and results point out areas in the anaerobic digestion system design where reasonable improvements could be expected to make gas production economically feasible. The continuously stirred task reactor system is already considered to be commercially feasible. T i t l e : Anaerobic Fermentation of Agricultural Residues Potential for Improvement and Implementation Organization: Cornel1 University, Ithaca, NY 14853 Principal Inuestigator: Professor W. J. Jewel1 Project Summary. This contract covers the third year of a three-year project. The objectives of the project include: (a) identification of improved fermentor designs using small scale laboratory models, (b) definition of optimized fermentor designs, and (c) demonstration of new process feasibility in large-scale pilot plants. A pilot scale reactor, using no mixing, produces one volume of gas per volume of reactor per day. The reactor operates as a plug-flow reactor without recycle, with a feed concentration of 12% solids. Solid concentrations of 25% result in high methane production; 35% result in inhibition of methane production. The project has identified the design of a simplified fermentor as the most promising in terms of total energy generation potential. Title: Permselective Membrane Control Algal and Wood Digesters for Increased Production and Chemicals Recovery Organization: Columbia University, 353 Terrace Building, New York, NY 10027 Principal Inuestigator: Professor Harry P. Gregor
,
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Project Summary. The objective of this project is to investigate permselective membrane control of algal and wood digesters. In this study, various forest product pulps and algal species are digested using 2-4 L capacity vessels under conventional or high-rate organic loadings. The steady-state process is seeded by an anaerobic sludge and operated with a 2-4-week hydraulic detention time. Project tasks include monitoring gas production, solids, percent volatiles, and COD. The contents of the vessel are then circulated through the appropriate membranes to remove various end products, especially ammonia, methane, and short chain fatty acids such as acetic acid, propionic acid, butyric acid, valeric acid, and isovaleric acid. The project will also monitor separation processes such as ultrafiltration using nonfouling membranes, electrodialysis, reverse osmosis, water-splitting membranes, solvent extraction, and enzyme-coupled membranes. These permselective membranes not only allow practical separation, but control the operations of digesters. T i t l e : Algal Concentration by Ultrafiltration (ULTRA) Organization: Columbia University, 353 Terrace Building, New York, NY 10027 Principal Inuestigators: Professor Harry P. Gregor, Professor R. Cardenas Project Summary. The objective of this project is to develop a nonfouling membane process for harvesting microalgae. Project tasks include growing 24 different algal cultures, representing freshwater species grown under different conditions. Ultrafiltration studies are carried out at varying flux rates and constant pressure. The experiments run in the laboratory have shown that concentration cells are yielding up to 500-fold concentrations, exceeding initial estimates. A preliminary design of a larger device with increased membrane surface area has been completed. The device will use double membranes employed in spiral-wound configurations. Title: Anaerobic Fermentation of Livestock Manures and Crop Residues Organization: Agricultural Research Service, U S . Meat Animal Research Center, P.O. Box 166, Clay Center, NE 68933 Principal Investigator: Dr. Andy Hashimoto Project Summary. The objective of this project is to evaluate the technical and economic feasibility of the anaerobic process for recovering high protein biomass, methane, and plant nutrients from livestock manures and/or crop residues.
Specific project tasks include: (a) developing design criteria (optimum temperature, mixing requirement, solids loading rate, solids retention time, etc.) for optimum production of biomass and/or methane from anaerobic fermentation of livestock manures and crop residues, (b) developing efficient methods to recover high protein biomass from fermented residues, (c) evaluating the nutritional value of the biomass for feed and the liquid fraction for plant nutrients, and (d) determining the capital and operational costs and energy, manpower, and safety requirements for anaerobic fermentation systems associated with livestock operations. Conclusions It is seen that the Fuels from Biomass program of the US. Department of Energy includes a broad array of biomass sources and residues for conversion to meaningful amounts of energy. Of several near-term conversion systems, anaerobic digestion appears to offer immediate potential for conversion of selected biomass to fuel gas. Initially, animal manure bioconversion appears to be foremost among the several possibilities. A broad but well defined research program is underway in the Fuels from Biomass program. Brief summaries of these programs show the present projects range from laboratory research through larger scale experiments to full-scale operation. Acknowledgment The information for this presentation was obtained from Dr. Roscoe Ward and Dr. Robert Spicher, U S . Department of Energy, Washington, D.C. Their assistance is acknowledged with appreciation. L i t e r a t u r e Cited Ashare, E., Wentworth, R. L., Wise, D. L., "Fuel Gas Production From Animal Residue. Part 11: An Economic Assessment", accepted for publication in Resource Recovery and Conservation. Ashare, E., Wise, D. L., Wentworth. R. L.. "Fuel Gas Production From Animal Residue", Dynatech Report No. 1551 on ERDA Contract COO-2991-10, Jan 14, 1977. U S . DeDartment of Energy -. document DOE/ET-0022/1 "Fuels From Biomass Program", Jan 1978. Wentworth, R . L., Ashare, E., Wise, D. L., "Fuel Gas Production From Animal Residue. Part I: Technical Persepctive", accepted for publication in Resource Recovery and Conservation
Received for review October 4, 1978 Accepted January 22, 1979 Presented at the Symposium on Economics of Fermentation Processes, Division of Microbial and Biochemical Technology, 176th National Meeting of the American Chemical Society, Miami, Fla., Sept 12, 1978.
CORRECTION
In the article, "Functionally Modified Poly(styrenedivinylbenzene). Preparation, Characterization, and Bactericidal Action", by D. W. Emerson, D. T. Shea, and E. M. Sorensen [ I n d . Eng. Chem. Prod. Res. Deu., 17, 269-274 (1978)], the following corrections should be noted. On page 273, eq 3 should read
Pol-S02NC1Na
+ H20
-
PolS02NH2+ OC1- + Naf
On page 274, the last word in the Acknowledgment should read: Amberlyst-15. Also, the eighth literature citation should read: Daykin, H. D., Biochem. J., 11, 79 (1917).
