ES&T
FEATURE
Alcohol fuels from biomass An overview of air, water, solid waste, and occupational safety and health problems that might arise at biomass-based ethanol and methanol production facilities
Ayub U. Hira Joseph A. Mulloney, Jr. Mueller Associates, Inc. Baltimore, Md. 21227 Gregory J. D'Alessio U.S. Department of Energy Washington, D.C. 20545
Many processes, ranging from lab oratory to commercial scale, convert biomass materials to energy or chem icals. Indeed, direct combustion of biomass (wood, wood wastes, and the like) has been carried out in commer cial facilities for many years; more over, anaerobic digestion processes for feedlot wastes and manures have been operational since the mid-1970s. Fer mentation ethanol is currently pro duced commercially both on the small scale [2 X 10 6 L / y (5 Χ 10 5 g a l / y ) - 4 X 10 6 L / y (10 6 gal/y) capacity], as well as in larger plants [ > 4 Χ 107 L / y (10 7 gal/y) capacity]. Facilities for methanol production from biomass are technically feasible; however, their commercial readiness remains in Feature articles in ES&T have by-lines, rep resent the views of the authors, and are edited by the Washington staff. If you are interested in contributing an article, contact the managing editor. 202A
Environ. Sci. Technol., Vol. 17, No. 5, 1983
doubt, primarily because of financial reasons. But while much progress has been achieved and reported in pro duction technology, relatively little work concerning environmental effects of biomass-based processes has been described. This article outlines the current status of the environmental informa tion associated with alcohol fuels pro duction from biomass feedstocks by identifying those areas that have been adequately studied and those that lack detailed information. The areas of air emissions, water effluents, solid wastes, and environment, health, and safety implications ( E H & S ) are re viewed as compiled from recent pub lications. Secondary data sources are used to provide an overview of E H & S concerns of both ethanol and methanol production facilities. No attempt is made to synthesize any new data or to address secondary issues such as en ergy efficiency or the food vs. fuel issue. The physical and chemical compo sition of a particular biomass feedstock will dictate the probable conversion process and, therefore, the emission and effluent characteristics of the pro cessing path. Each processing path has a different conversion efficiency, re quires a different level of capital in vestment, and poses its own set of po tential environmental problems. Thus,
a wide variety of impact levels are possible, depending on process feed stock and system configuration. Carbon dioxide (CO2), though not normally considered a pollutant, is produced in relatively large quantities in the alcohol plants. However, based on recent data from production of al cohols from biomass, such plants are expected to be very small contributors to the global C 0 2 inventory (/ ,2,3). Because of their comprehensive treatment in other literature, envi ronmental issues related to biomass production, harvesting and collection, and alcohol distribution and end-use need not be addressed ( / , 4). Ethanol production impacts The generic environmental concerns for ethanol plants are air emission control, wastewater treatment, and solid waste disposal. The type and quantity of air pollutants are deter mined largely by the type of energy source used to drive the conversion process, since the amounts of air emissions associated with the actual saccharification, fermentation, and distillation operations are relatively small. Again, depending on the type of fuel used as the process energy source, the water effluents and solid wastes of the conversion process itself will tend to be less significant than effluents and wastes from the process heat source.
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Bagasse. The moisture content of this residue from the milling of sugar cane determines the feasibility of its use as a fuel. Air emissions. Air emissions from an ethanol plant arise principally from three sources: • combustion of conventional and unconventional fuels; • feedstock preparation and byproduct processing operations; and • overall process schemes employed, such as the distillation/dehydration systems, flash coolers, evaporators, and cooling towers. The majority of the plant air emissions are associated with the combustion process used to supply steam and electricity to the plant. The type of fuel used and the degree of combustion will dictate the nature of these emissions. For example, uncontrolled emissions from coal- or biomass-fired boilers will be greater than those from facilities using natural gas or residual oil. As illustrated in Table 1, the degree of local impact of emissions from facilities using solar energy or process waste, such as bagasse, would be considerably different from that of a conventional fuel source. These air emissions, therefore, are not inherently coupled to the biomass-to-ethanol process. Particulate emissions, sulfur oxide (SO*) emissions, and, to a lesser extent, nitrogen oxide (NO*) emissions associated with coal combustion are likely to constitute the primary airrelated environmental problems for
most facilities. Polycyclic organic matter (POM) emissions from some of these sources are also significant. In a test performed by T R W Environmental Engineering Division (Redondo Beach, Calif.) the POM emission factors for coal and especially for wood were found to be extremely high, approximately 13.8 mg/kg and 484 mg/kg, respectively (6). In the study, dibenz[iz,/î]anthracene, a carcinogen, was identified, and the presence of other carcinogens, such as benzo[a]pyrene and benzo[g,/î,i]perylene, was also indicated. For this reason, particulate emissions, especially respirable particulates, and associated POMs from wood and wood residue combustion are of concern (7). Stack emissions from burning corn stalks or bagasse are primarily in the form of particulates and N O * since there is very little sulfur present. Little analysis of the chemical composition of these emissions has been done. On the basis of experience with burning bagasse in the sugar industry, one would expect the particulates to be lightweight and high in unburned carbon content (8). The moisture content of these residues will determine the feasibility of their use as fuel sources. At 1 μg/L·). These toxic organics are shown in Table 4. The presence of bisphthalate, ethylbenzene, and methylene chloride was attributed to laboratory tubing or sol vent contamination. Benzene was found at only one source. The concentrations of priority metals, cyanide, and asbestos are also shown in Table 4. Except for copper, nickel, lead, and zinc, the metals are present in untreated effluents at low concentrations. Mercury was the only metal limited to a single facility in untreated effluents. Antimony, lead, mercury, and selenium each were de tected at only one facility in treated effluents. The effluent was treated in a secondary biological wastewater system. Radian Corporation (9). Results of this study indicate that the cooling tower blowdown is the largest-volume influent to the treatment plant. Al though this stream carries 63% of the total solids loading, only 8% of the total BOD5 content is introduced by this waste stream. The composition of this stream varies widely, depending on the makeup water source, the materials of
Most of the solid wastes are either recycled and reused in the process or are processed and sold as animal food.
construction used in the cooling water system, and the process condensates that are added to the system. Approximately 23% of the total BOD5 load is contributed by plant and equipment washes. This stream is characteristic of washes used in many food- and grain-processing plants and can be reused after the settling and removal of solids. Bottom waters from the rectifying column and evaporator condensate, though high in BOD 5 concentration, are small-volume streams. These streams, as well as the boiler blowdown and sanitary sewage, contribute only minor loadings to the treatment plant. Also, benzene does not appear to be a major wastewater problem for this facility, which uses a benzene dehydration system, since it was detected at less than 6.0 X 10~ 2 m g / L in the wastewater. Overall, the existing literature indicates that the wastewater streams generated by ethanol plants will be acidic and will be high in BOD 5 , C O D , and suspended solids. However, there is a wide variation in data on BOD5, C O D , and total solids. This variation will depend strongly on process type, effluent recycling, and treatment options, which, in turn, depend on the location (regulations vary according to state), size of the plant, and economics of treatment systems. Larger scale plants appear to enjoy superior treatment efficiencies associated with economies of scale. Toxic materials (organic pollutants and metals) are not expected to be a problem in effluents from ethanol plants. Because ethanol plants involve a point source discharge, they will require permits from the National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act. The EPA has been engaged in preliminary efforts to develop guidelines for alcohol fuel plants, focusing on BOD5 and suspended solids. A final decision to proceed with formal effluent guidelines had not been made at press time. However, effluents from ethanol plants should not pose any hazard, since current wastewater treatment technology is adequate for their needs.
Solid waste. Solid waste streams from an ethanol plant are generally limited to: • grain dust from feedstock preparation and by-product processing; • grain rejects such as stones, twigs, and mold clumps from grain handling; • sludge from wastewater treatment systems; and • bottom ash and particulate matter from the combustion process. In addition, although not unique to alcohol plants, the scrubbing of the stack gas from the plant boilers will contribute scrubber sludges and collected fly ash to the solid waste. The tonnage will vary widely, depending on the type of coal burned and the nature of the SO* removal system. Consider two large-scale ethanol plants. Both plants burn Illinois No. 6 coal and use corn as their feedstock. However, they employ slightly different mitigation technologies for their solid waste. In the case of the smaller (5.7 X 107 L / y ) ethanol plant, the wastewater treatment sludge is recycled to the dryer where it becomes part of the D D G by-product. Detailed analysis of the sludge by Radian revealed no traces of benzene or pesticides (9); from the study it is inferred that the pesticides are apparently decomposed during feedstock preparation or mash cooking operations. On a per-liter basis, the quantity of sludge generated by the smaller plant is lower than that of the larger ( 1.89 X 10 8 L / y ) ethanol facility. But the ash generation rate is higher for the smaller plant. Most likely, this ash would go to a landfill. For the larger plant, the sludge from the wastewater treatment system is dried, flaked, and finally burned in the boiler plant. Sulfur dioxide scrubbing is accomplished in an ammonia-scrubbing system that produces ammonium sulfate, a useful by-product marketable as a fertilizer. Consequently, no waste disposal is required. Alternatively, S O x emissions can be mitigated by the use of conventional lime/limestone scrubbing systems. The product of this control technique produces a solid waste that requires disposal in a landfill. A summary of
solid waste production estimated by several studies is shown in Table 5. Ethanol plants will sometimes use a separate wastewater treatment system to treat sanitary wastes. In such instances the wet sludge produced, although small in amount, will require proper disposal. For the South Point (Ohio) gasohol plant, the proposed secondary treatment of sanitary wastes is expected to produce 6.8 X 10 3 kg/y of solid waste compared to the 3.27 X 10 5 k g / y sludge produced by process wastewater treatment systems (79). Since the process wastewater from the facility is treated separately, its solid waste can be combined with DDG and marketed as an animal feed. The plant also generates 1.72 X 107 k g / y of ash from the burning of coal. Present plans propose that the ash will be disposed of in a 25-acre (10.1 hectares) ash pond that will be constructed on the site with proper lining so as to prevent surface water discharge. By and large, the solid wastes generated from ethanol production include wastes from by-product processing (stillage), grain dust, sludge from the wastewater treatment system, ash from solid fuel combustion, and solid waste from sulfur abatement techniques. Typically, a large portion of the solid wastes except the sludge, ash, and sulfur-containing matter are either recycled and reused in the process or are processed and sold as animal feed. Sometimes the sludge can be recycled to the by-product processing section, after treatments such as dewatering and stabilization. This option is viable only for facilities that do not combine the sanitary wastes with their process wastewater. Consequently, the solid wastes generated by ethanol plants will consist primarily of ash- and sulfur-containing waste material. The EPA has decided not to propose solid waste regulations specific to alcohol fuel plants. On this basis, solid wastes can be viewed as not too serious a concern. Occupational safety and health. Accidents, fires and explosions. Ethanol-producing facilities can pose certain hazards to employees. For exEnviron. Sci. Technol., Vol. 17, No. 5, 1983
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ample, the unloading, conveying, cleaning, grinding, and storing opera tions for grains create dust that can be explosive. Small particles of dust settle on beams, ledges, machinery, walls, and other surfaces. At rest, these dust particles are harmless and diffi cult to ignite. However, when they are agitated and ignited in the air, the flame propagation may be so rapid that an explosion results. The handling of coal and DDG in an ethanol plant also produces a hazardous dust cloud. The potential of hazard from dust depends on the particle size, dust con centration, turbulence, presence of impurities, oxygen concentration, uniformity of dispersion, and strength of the ignition source. The smaller the particle size, the easier the ignition. Settled dust will not explode since it is not dispersed in air. However, there is still a potential for explosion since the dust can be quickly dispersed by vari ous means such as air hoses. Conse quently, dust accumulation should be kept to a minimum via thorough cleaning (21). Since the ethanol-for-fuel industry is relatively new, no information about injury and fatality rates is available for that industry. Based on experience in the brewing and distilling industries and on the statistics reported for the industrial organic chemicals sector, one study reports that the projected annual death and injury incidence rates for a 1.89 Χ 108 L/y plant will be 8.61 Χ ΙΟ" 3 (4.55 Χ Ι Ο " " per L/y) and 6.84 (3.61 Χ 1 0 - 8 per L / y ) , re spectively (12). Cellulosic feedstocks for use in al cohol production generally do not have
tions. The chemicals commonly used include benzene and, to some extent, ethyl ether and cyclohexane (14). Benzene has been identified as a leukemogen, and both of the other two dehydrating agents can be harmful. Ethyl ether has predominantly narcotic properties and is mildly irritating to the eyes, nose, and throat. Contact with both ethyl ether and cyclohexane may produce a dry, scaly, fissured dermatitis. Mild conjunctivitis may result from acute exposure to cyclohexane (23). Contact with low-pressure steam will cause scalding burns. During denaturation, ethanol is mixed with certain approved chemicals (usually gasoline for fuel purposes) to render it unfit for human consumption. Both the dehydrating agents and the dénaturant are toxic, and safety problems may arise from improper handling. The handling of these and other chemicals, including ethanol, will require that certain precautions be exercised with these materials during the process. Some of these chemicals are also flammable. Although strong acids, bases, and solvents are used for hydrolysis and pH adjustment, and should be handled with the same precautions as other industrial solvents, fermentation or digestion operations are not particularly hazardous. The most serious safety hazards are those of explosion from grain dust or ethanol fume ignition, and boiler/steam line overpressurization (24). The principal chemicals used in alcohol fermentation plants are ethanol, benzene, ethyl ether, and the like. Some of these chemicals are very flammable. The others vary in toxicity.
as great a hazard of dust explosion, but present a fire hazard just the same. The hazards associated with the tech nology for cellulose conversion to eth anol also differ from conventional sugar- or starch-to-ethanol conversion processes. Specifically, acid hydrolysis of cellulose to simple sugars requires the handling of dangerous acids, such as sulfuric acid, that vaporize readily and can irritate the skin, eyes, and throat. An alternative conversion scheme is the use of enzymatic hy drolysis, which presently uses the microorganism Trichoderma reesei. In powdered form, the commercial ver sion of this enzyme-producing organ ism is a minimal hazard. Nevertheless, it should be handled, as recommended, with safety glasses and gloves, since it is a mild irritant to skin and eyes (22). A potentially serious hazard asso ciated with the widespread use of eth anol fuel is that of misuse as a bever age. Invariably some people will un intentionally or willfully ignore the warnings against ingestion of fuelgrade ethanol. In other cases, an at tempt to extract pure ethanol for con sumption will be attempted. In any case, danger of poisoning by the dénaturant (gasoline, methanol, and the like) exists. Contact dermatitis is another major problem. Chemical exposures. A potential threat to worker health and safety arises from exposure to hazardous and corrosive chemicals used in the alcohol fermentation plant. Current technology for the final distillation step to produce anhydrous ethanol uses chemicals that could present an occupational hazard under certain condi-
TABLE 5
Summary of solid wastes from ethanol production TABLE 5 Study
Solid wastes (kg/y) Plant Size (L/y)
Raw material
Scrubber waste
S&W ( 10)
7.57 X 10 7
Corn
NA
4.90 X 10 6
ANL ( 17)
8.33 X 10 7
Corn
NA
1.64 X 10 7
M\L· (11)
Mueller ( 12) South Point ( 19)
7.57 X 10
7
5
Corn
7.30 X 10
9.46 X 10 7
Corn residue
8.07 X 10 5
9.46 X 10 7
Wheat straw
1.25 X 10 8
Wood
1.89 X 10 8 2.27 X 10
8
" Includes scrubber waste b Includes unhydrolyzable wheat solids NA—no data available
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Wastewater sludge
Environ. Sci. Technol., Vol. 17, No. 5, 1983
3.86 X 1 0
7s
NA 2.18 X 10
NA 6
NA
4.54 X 10 7
— 6.09 X 10 7
NA
NA
8.07 X 10 5
NA
NA
5.22 X 10βί>
1.08 X 10 6
NA
NA
3.65 X 10 7
Corn
4.49 X 10 6
7.03 X 10 6
Corn
5
7
3.26 X 10
1.72 X 10
2.86 X 10 6
—
NA
NA
The principal chemicals used in alcohol fermentation plants are ethanol, benzene, ethyl ether, and the like. Some are very flammable. The others vary in toxicity.
Short-term exposure to high concentrations of ethanol (5000 m g / L ) results in coughing, eye irritation, and headaches. The hazards of long-term, low-level exposure to ethanol are presently uncertain (22). In addition, some of these chemicals, after entry into the body, result in metabolites that are more toxic than the parent chemical (25). Procedures to minimize these hazards are well established in terms of prudent "housekeeping" practices and federally mandated standards. Standards for worker protection are set forth in the Occupational Safety and Health Act, which applies to all aspects of an ethanol facility. Methanol production effects In contrast to known environmental characteristics of ethanol-producing facilities, relatively little work has been done on the characterization and measurement of environmental impact associated with the production of methanol from biomass. Currently, no facilities for converting biomass to methanol exist in the U.S., although several are planned (26). The environmental characteristics of biomass-to-methanol facilities may be compared to similar size coal liquefaction plants for producing methanol, but with one difference: The relative magnitude of their emissions will be different. The effects associated with biomass facilities will likely be less than those of coal units, since the concentration of toxic substances is less in biomass. Also, the lack of extreme temperature and pressure conditions in biomass units implies that certain in-plant hazards may be less than those associated with coal liquefaction processes. Air emissions. In a biomass-tomethanol facility, the gasification process, which can vary with the type of gasifier, is the major source of concern. The quality and quantity of pollutants generated by biomass gasification sections will depend largely on the gasification conditions, as well as on the environmental control and type of feedstock employed. For example, the concentration of oxygen and hydrogen in the gasification re-
actor will determine the amount of ammonia, hydrogen sulfide (H2S), carbonyl sulfide (COS), and other oxygen-containing compounds, such as phenols and polynuclear aromatic compounds. In addition, the process conditions will dictate whether organic acids, tars, oils, aldehydes, or ketones will be present. Ordinarily, at low gasification temperatures, these compounds remain intact; at higher temperatures, however, these volatile organic compounds decompose into C O , CO2, and H2 and become part of the synthesis gas leaving the reactor. Compared to coal gasification, these emissions will have lower nitrogen- and sulfur-containing pollutant levels, since biomass contains less of these elements. N O j emissions also will be lower because of the low flame temperatures in the gasification reactor. In addition, the majority of the original sulfur and nitrogen would remain in the char, a by-product of the gasification reaction. Generally, the char can be used as a fuel source for the plant, thereby eliminating a potential source of solid waste. Its combustion, however, will be another source of air pollution. It will produce N O x , SO*, and fly ash as well as trace elements such as potassium, magnesium, sodium, iron, barium, boron, cadmium, chromium, copper, lead, strontium, zinc, beryllium, arsenic compounds, and fluorides (26). Compared to coal units, the concentration of these pollutants would be small. Any pesticide present in the original substrate would be decomposed. A major issue regarding biomass liquefaction plants is the potential hazard posed by the products of the gasification reaction. Particulates from wood combustion are suspected of being hazardous, since small particles can act as sites for condensation of organic substances and trace elements such as arsenic, mercury, and cadmium (14). Increased particulate emissions could lead to increased exposure to toxic elements and polycyclic organic compounds. Some of these polycyclic compounds are suspected carcinogens. Because their presence in
gasification emissions is not yet confirmed, more research is needed to identify potential hazards. Since the product gases from the gasification reaction are scrubbed and purified to remove particulates, acid gases, and other volatile organic compounds, the air emissions from the methanol synthesis section should be low. Commercial-size units exist today for producing methanol from purified synthesis gas. Their major sources of pollutants are controlled sufficiently and should not pose any serious hazards. The estimated process residuals associated with the production of methanol from wood at two facilities are summarized in Table 6. Unfortunately, the residuals quantified by these studies are not complete. They provide only a brief overview of the environmental residuals. For example, the A N L study estimates a particulate emission rate of 1.32 X 105 kg/y from the wood preparation section, which includes milling and drying. N o attempt was made to identify the other emissions associated with this operation, such as C O , H 2 S , C O S , and methane (CH4). This topic, however, was alluded to in a study by S R I International, which quantified only the air emissions and ash generated by the methanol process. The process CO2 stream from the S R I process contains approximately 6 m g / L of sulfur or sulfur-containing compounds. Data indicate that the major contaminant from the methanol processes is process C 0 2 . Approximately 9.07 X 10 5 kg/d of CO2 will be released to the atmosphere from a 2.12 X 10 8 L / y methanol plant. Water effluents. The majority of water effluents will be contributed by process wastes. In addition to cooling tower and boiler blowdowns, they will consist of scrubber blowdowns containing the various air pollutants, such as ammonia (as ammonium hydroxide), phenols, and other trace elements (28). Leaching and runoff from biomass and char storage piles will contribute to this waste stream. Although the effluents from biomass liquefaction have not been characterized, they are expected to have a moderate BOD 5 Environ. Sci. Technol., Vol. 17, No. 5, 1983
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TABLE 6
Residuals from production of methanol from wood Residual
Quantity genei•ated (kg/y) 9.46 X 10 7 L/y ( 11) 2.12 Χ 10 8 L/y
(27)
Air emissions: Feedstock preparation 1.31 X 10 5
ΝΑ
H2S
NA
2.51 Χ 10 5
COS
NA
7.17 Χ 10*
CH 4
NA
6.47 Χ 10 6
Methanol
4.19 X 10 5
ΝΑ
C02
3.00 X 10 8
3.00 Χ 10 6
BOD 5
1.91 X 10 5
ΝΑ
Flow rate
4.93 X 10 e
ΝΑ
Ash and unburned carbon
7.54 X 10 e
7.58 Χ 10 6
Biological waste
1.80 X 10 6
ΝΑ
Particulates
Liquid effluents: After wastewater treatment
Solid wastes:
NA—no data available
loading ( 100-1000 mg/L) resulting in large measure from the organic com pounds generated during the process In addition, substances contained in the aqueous effluents may be toxic or carcinogenic. Although there is no further information confirming the carcinogenicity of the liquid waste stream, it appears that the contami nants will present potential health and environmental problems. Conse quently, proper disposal techniques will have to be developed. Solid wastes. The solid wastes from the biomass-to-methanol process in clude ash, unconverted carbon, and the biological sludge associated with the wastewater treatment plant. Depend ing on the mineral content of the raw material, the ash will contain 40-90% potassium and calcium salts, along with small amounts of magnesium, iron, silicon, phosphorus, and sulfurcontaining compounds. The ash, un converted carbon, and sludge should not have any adverse effects and could, therefore, be placed in a landfill. Occupational safety and health. The production of methanol from biomass poses a substantial health and safety risk. Its effects, however, are not completely known, since there is not nearly as much familiarity with the process as with that of ethanol. Generally, the production of meth anol via gasification creates a number of potentially dangerous substances. The gasification step produces C O , hydrogen, and other gases from bio 212A
Environ. Sci. Technol., Vol. 17, No. 5. 1983
mass combustion. Worker exposure to CO can lead to a variety of adverse health effects, including decreased ability to concentrate and aggravation of heart disease (14). The synthesis gas may also provide a fire hazard should it escape the process stream. However, data are presently not available on methanol-from-biomass risks, since there are no commercial-scale plants in operation. Still, it is expected that some of the health and safety effects should be similar to those of conven tional methanol synthesis plants. Methanol itself is fairly toxic. Consumption of as little as 0.03-0.06 L can result in death. The ingestion of smaller quantities can cause blindness (29). Methanol can also be absorbed through the skin in a sufficient quan tity to result in adverse health effects or even death. Moreover, unlike gaso line, methanol is colorless and rela tively odorless, and is easy to confuse with ethanol or even water. In addi tion, methanol burns with a low flame luminosity similar to that of ethanol, increasing the risk of accidental burns. The threshold limit values for ethanol and methanol are 1000 and 200 m g / L (time-weighted average), respec tively. No evidence of mutagenicity and carcinogenicity has been reported from several different screening test systems (30). Testing is still in the preliminary stage. Insufficient data are presently available to make any evaluation on embryotoxicity/teratogenicity/ reproductive effects of methanol.
Overall, very little quantitative in formation is available regarding the environmental concerns associated with producing methanol from bio mass. These concerns, however, would be similar to those of ethanol-producing facilities employing biomass as fuel with one major exception: Their magnitude will be greater, since bio mass-to-methanol facilities will have to be very large to be economical. Control techniques employed by these plants would be similar to those used by many industrial thermal processes. These facilities, therefore, should not pose any hazards. Problems are avoidable The major environmental concerns of biomass-to-ethanol plants are the effects of potential air emissions and wastewater effluents, particularly for large numbers of small-scale ethanol plants. Attention to proper solid waste disposal methods and corrosive chemicals used in the plants should adequately mitigate associated haz ards. To date, studies of emissions, ef fluents, and wastes of fuel-ethanol production facilities do not give evi dence that such facilities generate en vironmentally significant concentra tions of toxic substances. Generally, the characteristics of the pollutants present are well known, but the levels of emissions and effluents and the magnitude of their effects will depend on the process, the associated control techniques, and a variety of federal and state regulations. In most cases, environmental prob lems will be avoided by the use of conventional control techniques in large-scale ethanol plants. Small plants, on the other hand, will require the application of innovative tech niques such as alternative by-product recovery and concentration techniques to reduce potential water and air pol lution. In general, the biomass-toethanol production technology does not present an insurmountable envi ronmental constraint and can be ex pected to operate with a high degree of reliability whenever conventional sources of biomass feedstock are used. Additional data should be available in the near future from plant designs that have been analyzed under the De partment of Energy Alcohol Fuels Loan Guarantee Program. Further characterizations will be necessary, however, for plants employing cellulosic feedstocks either as fuel or as ethanol feedstock. In contrast to ethanol-producing facilities, relatively little information
is available about the environmental characteristics of methanol plants, because of the early stage of techno logical development. Initial surveys indicate that both methanol emission and effluent streams can contain sub stances of greater environmental con cern than do corresponding streams from ethanol facilities. Λ similar sit uation exists in the area of occupa tional safety and health. Detailed as sessments and quantitative evaluation of the air emissions, water effluents, and solid wastes, as well as potential occupational safety and health haz ards, are needed to predict the effects of future biomass methanol production facility operations accurately. Acknowledgment This project was supported by the De partment of Energy, Office of Environ mental Analysis, under contract number DE-AC01-81EV10450. David O. Moses was technical project officer. Before publication, this article was read and commented on for suitability as an ES&T feature by R. Rhodes Trussell, James M. Montgomery Engineering, Pas adena, Calif. 91101. References (1) U.S. Council on Environmental Quality. "Environmental Quality The Eleventh Annual Report of the Council on Environ mental Quality"; U.S. Government Printing Office. 1980:325-801/7090. (2) U.S. Department of Energy. "Workshop on Environmental and Societal Consequences of a Possible CO^-lnduced Climate Change." Report No. CONF-7904143; Carbon Dioxide Effects Research and Assessment Program, Washington. D C . October 1980. (3) U.S. Department of Energy. " A Compre hensive Plan for Carbon Dioxide Effects Re search and Assessment, Part I—The Global Carbon Cycle and Climatic Effects of In creasing Carbon Dioxide," Report No. D O E / E V - 0 0 9 4 ; Carbon Dioxide Effects Research and Assessment Program, Wash ington, D.C.. August 1980. (4) Office of Technology Assessment. "Energy from Biological Processes"; Congress of the U.S., Washington, D C , July 1980; Vol. I, G P O Stock No. 052-003-00762-2. (5) The Aerospace Corporation. "Environ mental Control Perspective for Ethanol Pro duction from Biomass," Aerospace Report No. A T R - 8 0 (7848-01)-! for U.S. Depart ment of Energy, Washington, D.C., August 1980. (6) Shih, C. C ; Takata, Λ. Μ. "Emissions As sessment of Conventional Stationary Com bustion Systems—Summary Report"; T R W Environmental Engineering Division for En vironmental Protection Agency, Research Triangle Park, N.C., July 1981; N T I S No. P882-I09414. (7) Mueller Associates, Inc. "Wood Combus tion: Statc-of-Knowlcdge Survey of Envi ronmental Health and Safety Aspects"; for U.S. Department of Energy, Washington, D C , October 1981. (8) Argonne National Laboratory. "Draft Report on Environmental Concerns of Etha nol from Corn"; Energy and Environmental Systems Division for U.S. Department of Energy, Washington, D C . January 1980. (9) Scarbcrry, R. M.; Papai, M. P.; Braun. M. A. "Source Test and Evaluation Report:
Alcohol Facility for Gasohol Production"; Radian Corporation for U.S. Environmental Protection Agency, Cincinnati, Ohio, No vember 1979; N T I S No. PB82-23704I. (10) Mills, A. J. ct al. "Environmental Re quirements for Fuel-Ethanol Facilities," Chem. Eng. Prog. 1 9 8 1 , 6 , 4 2 - 4 8 . (11) Argonne National Laboratory. "Alcohol Production from Agricultural and Forestry Residues," Report No. D O E / E V - 0 1 0 8 ; Washington, D.C., September 1980. (12) Mueller Associates, Inc. "Alcohol Fer mentation Plant—Environmental C h a r a c terization Information Report"; for U.S. Department of Energy, Washington, D C , September 1981. (13) Roop, R. D„ Sharpies; F. S. "Fuel Ethanol from Agriculturally-Derived Feedstock: En vironmental, Health and Safety Issues" (draft); Oak Ridge National Laboratory for U.S. Department of Energy, Washington, D C , January 1981. (14) Oak Ridge National Laboratory. "Envi ronmental Assessment—Biomass Energy Systems Program"; for U.S. Department of Energy, Division of Biomass Energy Systems, Washington, D.C., April 1980. ( 15) Sweeten, J. M. et al. "Nutrient Recovery and Pollution Control from "Ethanol Stal lage," "Proceedings of the Energy from Bio mass and Wastes VI Symposium"; Institute of Gas Technology, Lake Buena Vista, Fla., Jan. 2 5 - 2 9 . 1982. (16) Dock, J. S. et al. "Environmental Control Perspective for Ethanol Production from Biomass," "Proceedings of the Energy from Biomass and Wastes V Symposium"; Insti tute of Gas Technology, Lake Buena Vista, Fla.. Jan. 26 30, 1981. (17) Argonne National Laboratory, "Envi ronmental Implications of Accelerated Gas ohol Production Preliminary Assessment," Report No. A N L / E S - 9 1 ; Energy and Envi ronmental Systems Division for U.S. De partment of Energy, Washington, D.C., January 1980. (18) Dahab, M. F.; Young, J. C. "Energy Re covery from Alcohol Stillage Using Anaerobic Filters"; "Proceedings of the Third Sympo sium on Biotechnology in Energy Production and Conservation"; Gatlinburg, Tenn., May 12-15. 1981. (19) Groves. C. J. et al. "South Point Gasohol Project -A Water Assessment Study"; Ohio Department of Natural Resources for the U.S. Water Resources Council. May 1981: Contract No. W R 2 0 4 2 4 4 9 1 . (20) Smith, W. Effluent Guidelines Division, U.S. Environmental Protection Agency, Washington, D.C. 20460, personal commu nication. (21) Distilled Spirits Council of the U.S.. Inc. "Safe Practice Guide for the Distilled Spirits Industry"; Washington, D . C , November 1973. (22) U.S. Department of Energy. "Environ mental Readiness Document Alcohol Fuels from Biomass" (prepublication draft); As sistant Secretary for Environmental Protec tion, Safety and Emergency Preparedness. Washington, D . C , May 1981. (23) U.S. Department of Health, Education, and Welfare. "Occupational Diseases—A Guide to Their Recognition." rev. éd.; Washington. D . C , June 1977; U.S. GPO Stock No. 017-033-00266-5. (24) Watson. A. P.; Smith, J. G.; Elmore, J. L. "Survey of Potential Health and Safety Hazards of Commercial-Scale Ethanol Production Facilities," Report No. O R N L / T M - 7 8 l 7 , O a k Ridge National Laboratory. Oak Ridge. Tenn., April 1982. (25) Keller. J. L. "Methanol and Ethanol for Modern Cars"; presented at the 44th Refinery Mid-year Meeting Section on Fossil Fuels in the Eighties; American Petroleum Institute. 1979. (26) U.S. Department of Energy. "Environmental Development Plan Alcohol Fuels
from Biomass" (draft); Assistant Secretary for Environment, Washington, D . C , January 1981. (27) Kohan, S. M. "Production of Methanol from Wood": presented at the Third International Symposium on Alcohol Fuels Technology. Asilomar. Calif., May 2 9 - 3 1 , 1979. (28) Office of Technology Assessment. "Energy from Biological Processes -Volume II: Technical and Environmental Analysis"; Congress of the U.S., Washington, D . C , September 1980; G P O Stock No. 052-003-00782-7. (29) M e d i u m , P. W. ct al. "Alcohol Fuels for Highway Vehicles," Chem. Eng. Prog. 1982, 7^(8). 5 2 - 5 9 . (30) Muendcl, C. H. Presentation at the Mellon Institute Workshop on Methanol Fuel Use, Detroit, September 1981.
Ayub U. Hira (I. ) earned his BS and MS degrees in chemical engineering at the University of Rhode Island. At present, he is a senior engineer in the Transportation/Fuels Systems Department at Mueller Associates, Inc., Consulting Engineers, Baltimore, Md., specializing in energy conversion processes, systems modeling, and fuel cell technologies. Joseph A. Mulloney, Jr., is a senior project manager with Mueller Associates, Inc., Consulting Engineers, Baltimore, Md. He received his BS in food technology from the Massachusetts Institute of Technology and his MS in engineering administration from Washington University in St. Louis and is a registered professional engineer in the state of Maryland. He has had 20 years' experience in industry. His current research interests are biotechnology and the conversion of biomass to food, feed, fuels, and chemicals.
Gregory J. D'Alessio is a senior program scientist with the U.S. Department ofEnergy in Washington, D.C. He directed the Solar and Biomass Energy Technology Assessment Program for the Department's Office of Environmental Analysis. Before that, he managed the energy-related measurements and atmospheric research programs at the U.S. Environmental Protection Agency's Office of Research and Development. D'Alessio received a PhD in physics from the University of Florida.
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