 |
 |
 |
 |
 |
 |
|
|||
 |
 |
 |
|||||||
|
||||||||||||||||
|
||||||||||||||||
|
||||||||||||||||
| ||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
| Copyright © 2012. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 46
Nonfood Industrial Wastes
INTRODUCTION
The intent of this chapter is to examine the type, quantity, and quality of
nonfood industrial wastes that are available in North America and to
describe the status of available processing technology suitable for con-
verting such industrial wastes to nutritive animal feeds. Typically, nonfood
industrial wastes are not used as feedstuffs and as such fall into the category
of underutilized resources. While a few nonfood industrial wastes are
suitable for direct animal feeding, most are not and require some pro-
cessing. This processing is needed to (1) achieve nutritional enrichment
through synthesis of protein; (2J increase the availability of nutrients through
hydrolysis of large-molecular-weight components; (3) change the physical
form by concentration, dilution, or entrapment; (4) convert nonutilizable
organics to nutritionally useful materials, such as carbohydrates, fats, and
fatty acids; or (5) remove or destroy toxic components.
The nonfood industrial wastes to be covered are those derived primarily
from the organic chemical and fermentation industries, with some con-
sideration of municipal solid waste. Note will be made of cases in which
wastes are currently being used for animal feed, but the focus will be on
underutilized materials.
In order for an underutilized waste to be utilizable, it must (1) be
nontoxic or capable of being detoxified completely; (2) be available in
sufficient quantity at each source to allow for economic recovery; (3) have
some nutritive value either before or after processing.
46
OCR for page 47
Nonfood Industrial Wastes 47
ORGANIC CHEMICAL INDUSTRY
Quantity
The chemical industry in the United States is large and highly diversified.
In 1979 the top 50 chemicals produced totalled about 2.56 billion tons
and displayed a typical growth rate of about 7.6 percent per year. Of this
total, 86 million tons were synthetic organic chemicals, and the remainder
were inorganics (Anonymous, 19801. There is relatively little waste uti-
lizable as a feedstuff, either directly or with processing. Most organic
waste is burned to provide process heat. When the waste is too dilute to
be burned, it is usually too dilute for useful recovery.
The organic chemical industry traditionally has utilized coal, natural
gas, and petroleum as primary feedstocks, with heavy reliance on the latter
two. However, as a consequence of the rapidly increasing prices of these
commodities and the trend to use indigenous energy resources, changes
are occurring in the organic chemical industry (Dasher, 1976~. These
changes are important to consider because they have direct impact on the
types and quantities of wastes generated. Increased use of coal and shale
oil, which are likely to be processed via gasification or liquefaction, will
lead to increased availability of aromatic and fatty acid compounds. Jahnig
and Bertrand (1977) described the environmental problems produced by
a coal gasification plant with a capacity of 16,000 tons/day that would
generate 6,000 tons water/day containing 2.0 to 4.0 g phenolics/liter, 0.5
to 1.5 g fatty acids/liter, and 8.0 to 11.0 g ammonia/liter. This translates
to about 18 tons phenolics, 6 tons fatty acids-, and 57 tons ammonia/day.
If all of the organic carbon could be converted to microbial single-cell
protein having a protein content of 60 percent (Cooney et al., 1980), then
about 5,000 tons single-cell protein/year could be produced from a coal
gasification plant. Similarly, if coal liquefaction were used, then waste-
water generation would be 13,000 tons/day with a composition similar to
that from a gasification plant (Magee et al., 19771. While such plants do
not exist in the United States today, they are anticipated, and it is clear
that major changes in primary energy feedstock will change the availability
of a potentially important nonfood industrial waste. Current technology
for processing and refining natural gas and petroleum produces little waste.
Another possible change in primary feedstocks in the chemical industry
is a shift to using cellulosic biomass, such as crop residue, forest by-
products, or animal waste, as a source of chemicals and fuels. A change
from using traditional liquid or gaseous hydrocarbon feedstocks to using
solid lignocellulosic feedstocks will cause a major change in waste prod-
ucts. Lignocellulosic biomass is primarily a mixture of cellulose, hemi
OCR for page 48
48 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
cellulose, and lignin, with some ash, protein, fats, and other minor
components. In fermentation processes for converting the biomass to
chemicals and fuels, only the cellulose and hemicellulose are consumed,
while lignin, along with the other materials, remains as a residue. As the
use of biomass develops, there will be increased availability of these
residual materials. In addition, there will be large amounts of microbial
cell mass associated with the residues. While the cell mass is likely to be
used as much as possible as an animal feed, its use will not be without
major difficulty because most of the microorganisms that will be produced
are not approved for use as feed materials. Analyses of the wastes gen-
erated through these changes in technology are, to a large extent, presented
in the sections of this report that focus on forest by-products, food pro-
cessing by-products, and animal waste.
The availability and use of wastes from coal, shale oil, and cellulosic
biomass processing will not be dealt with further, since these are not
currently underutilized materials, though they may be in the future.
Physical Characteristics
The major organic chemicals derived from primary feedstocks are meth
ane, ethylene, propylene, and aromatics. In 1973 the chemical industry
was analyzed by the U.S. Environmental Protection Agency (1973) for
the purpose of developing effluent limitations for the industry. The EPA
report separates the various chemical products into four processing cate-
gories, which are useful for understanding the nature of the wastes from
nonfood industries. These categories are (l) continuous nonaqueous pro-
cesses, (2) continuous vapor-base processes, (3) continuous liquid-phase
reaction systems, and (4) batch processes. The processes of interest are
primarily those of continuous liquid-phase reaction systems, because these
are most likely to involve organic chemical wastes that can be processed
to achieve nutritional enrichment. The continuous liquid-phase processes
are summarized in Table 3. Batch processes are mostly run on a smaller
scale and produce fewer wastes. Nonaqueous as well as vapor-phase wastes
are more commonly recovered as an energy source by direct burning.
Aqueous wastes are frequently too dilute for burning.
To place the chemical industry and its potential waste in perspective,
the list of chemicals and processes in Table 3 is compared with the top
50 organic chemicals (Anonymous, 1980), which represent, in total, about
80 million tons or 93 percent of organic chemicals manufactured. Only
those chemicals that are in both category 3, liquid-phase reaction systems,
and the top 50 (as noted in Table 3) are considered further. This list
provides an indication of those processes that use technology likely to
OCR for page 49
Nonfood Industrial Wastes 49
TABLE 3 Major Chem
icals Produced in Liquid-Phase Reaction Systems
Product
Manufacturing Process
Ethanola
Isopropanola
Acetonea
Phenola
Oxo-chemicals
Includes: N-butyl alcohol
Isobutyl alcohol
2-ethylhexanol
Isooctyl alcohols
Decyl alcohols
Acetaldehyde
Acetic acida
Methyl ethyl ketonea
Methyl methacrylate
Ethylene oxidea
Acrylonitrilea
Ethylene glycola
Acrylic acid
Ethyl acrylate
Styrene monomera
Adipic acid
Terephthalic acida
Dimethyl terephthalatea
Para-cresol
Cresylic acida
Anilinea
Sulfuric acid hydrolysis of ethylene
Sulfuric acid hydrolysis of propylene
Cumene oxidation with cleavage of
hydroperoxide in sulfuric acid
Raschig process, chlorobenzene process
Sulfonation process
Cumene oxidation with cleavage of
hydroperoxide in sulfuric acid
Oxo-process (carbonylation and condensation)
-
Ethylene oxidation via Wacker process
Oxidation of LPG (butane)
Oxidation of acetaldehyde
Carbonylation of methanol
Sulfuric acid hydrolysis of butene-2,
dehydrogenation of sec-butanol
Oxidation of LPG (butane) by-product of
acetic acid manufacture
Acetone cyanohydrin process
Chlorohydrin process
Acetylene-HCN process
Sulfuric acid catalyzed hydration of ethylene
oxide
CO synthesis with acetylene
Acetylene and ethanol in presence of nickel
carbonyl catalyst
Oxidation of propylene to acrylic acid followed
by esterification
Reaction of ketone with formaldehyde followed
by esterification
Alkylation of benzene with ethylene,
dehydrogenation of ethylbenzene with steam
Oxidation of cyclohexane/cyclohexanol/
cyclohexanone
Direct oxidation of cyclohexane with air
Oxidation of para-xylene with nitric acid
Catalytic oxidation of para-xylene
Esterification of TPA with methanol and
sulfuric acid
Vapor phase methylation of phenol
Oxidation of para-cymene with cleavage in
sulfuric acid
Caustic extraction from cracked naphtha
Nitration of benzene with nitric acid (L.P.),
hydrogenation of nitrobenzene
OCR for page 50
50 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
TABLE 3 (continued
Product
Chloroprene
Bis-phenol-aU
Propylene oxidea
Propylene glycola
Vinyl acetatea
Anthraquinone
Beta naphthol
Caprolactam`'
Toluene di-isocyanate
Silicones
Naphthemic acids
Ethyl cellulosea
Cellulose acetatea
Chlorobenzene
Chlorophenol
Chlorotoluene
Hydroquinone
Naphthosulfonic acids
Nitrobenzene
Amyl acetate
Amyl alcohol
Ethyl ether
Ethyl butyrate
Ethyl formate
Tetraethyl lead
Formic acid
Methyl isobutyl ketone
Naphthol
Manufacturing Process
.
Dimerization of acetylene to vinyl acetylene
followed by hydrochlorination
Vapor phase chlorination of butadiene followed
by isomerization and reaction
Condensation of phenol and acetone in
presence of HC1
Addition of propylene and CO2 to aqueous
calcium hypochlorite
Liquid phase oxidation of isobutane followed
by liquid phase epoxidation
Hydration of propylene oxide catalyzed by
dilute H2SO4
Liquid phase ethylene and acetic acid process
Catalytic air oxidation of anthracene
Naphthalene sulfonation and caustic fusion
Hydroxyl amine production, cyclohexanone
production, cyclohexanone oximation,
oxamine rearrangement, purification, and
ammonium sulfate recovery
Toluene nitrification, toluene diamine
production, HC1 electrolysis, phosgene
production, TD1 production, purification
Reaction of silicon metal with methyl chloride
From gas-oil fraction of petroleum by
extraction with caustic soda solution and
acidification
From alkali cellulose and ethyl chloride or
sulfate
Acetylation of cellulose with acetic acid
(followed by saponification with sulfuric acid
for diacetate)
Raschig process
Direct chlorination of phenol
From chloroaniline through diazonium salt
Catalytic chlorination of toluene
Oxidation of aniline to quinone followed by
hydrogenation
Sulfonation of ,B-naphthol
Caustic fusion of naphthalene sulfonic acid
Benzene and HNO3 in presence of sulfuric acid
Esterification of amyl alcohol with acetic acid
Pentane chlorination and alkalin hydrolysis
Dehydration of ethyl alcohol by sulfuric acid
Esterification of ethyl alcohol with butyric acid
Esterification of ethyl alcohol with formic acid
Reduction of ethyl chloride with amalgam of
Na and Pb
Sodium hydroxide and carbon monoxide
Dehydration of acetone alcohol to mesityl oxide
followed by hydrogenation of double bond
High-temperature sulfonation of naphthalene
followed by hydrolysis to p-naphthol
OCR for page 51
Nonfood Industrial Wastes 51
TABLE 3 (continued
Product
Pentachlorophenol
Sodium pentachlorophenate
Toluidines
Hydrazine
Oxalic acid
Oxalates
Sebacic acid
Glycerol
Diethylene glycol diethyl ether
Dichloro-diphenyl-trichloroethane
(DDT)
Pentachloroethylene
Methylene chloride"
Pentaerythritolt'
Chloral (trichloroacetic aldehyde)
Triphenyl phosphate
Tridecyl alcohol
Tricresyl phosphate
Amyl alcohol
Acrylamide
Higher alcohols
Synthetic amino acids
Organic esters
Trialkylacetic acids
Fatty acids
Lauric acid esters
Oleic acid esters
Acetophenone
Acrolein
Ethyl acetate a
Propyl acetate
Acetin (glyceryl monoacetate)
Propionic acid
Fatty alcohol
Manufacturing Process
Chlorination by phenol
Reaction of caustic soda with
pentachlorophenol
Reduction of nitrotoluenes with Fe and H2SO4
Indirect oxidation of ammonia with sodium
hypochlorite
Sodium formate process
Sodium formate process
Caustic hydrolysis of ricinoleic acid (castor oil)
Acrolein epoxidation/reduction followed by
hydration
Propylene oxide to allyl alcohol followed by
chlorination
Ethylene glycol and ethyl alcohol condensation
dehydration
Monochlorobenzene and chloral in presence of
sulfuric acid
Chlorination of acetylene
Methane chlorination
Methanol esterification followed by chlorination
Acetaldehyde and formalydehyde in presence of
basic catalyst
Chlorination of acetaldehyde
Phenol and phosphorous oxychloride
From propylene tetramer
Cresylic acid and phosphorus oxychloride
Chlorination of pentanes and hydrolysis of
amyl chlorides
Acrylonitrile hydrolysis with H2SO4
Sodium reduction process
Acrolein and mercaptan followed by treatment
with Na2CO~; and NaCN
Alcohol and organic acid, H2SO4 catalyst
Olefins and CO followed by hydrolysis
Batch or continuous hydrolysis
Esterification of lauric acid
Esterification of oleic acid
By-product of phenol by cumene peroxidation
Condensation of acetaldehyde with
formaldehyde
Acetic acid and ethyl alcohol in presence of
sulfuric acid
Acetic acid and propyl alcohol in presence of
sulfuric acid
Glycerol and acetic acid
Carbonylation of ethyl alcohol with CO at high
pressure
Oxidation of propionaldehyde
Reduction of fatty acid with sodium metal
High pressure catalytic hydrogenation of fatty
acids
OCR for page 52
52 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
TABLE 3 (continued
Product
Manufacturing Process
Butyl acetate
sec-butyl alcohol
N-butyl alcohol
N-butyl propionate
Chloroacetic acid
Sodium chloracetate
Chloropicr~n (nitrotr~chloromethane
CC13NO2)
Thioglycolic acid
Adiponitr~le
Sodium benzoate
Sodium sulfoxalate formaldehyde
Sodium acetate
Tartary acid
Ester~fication of acetic acid and butyl alcohol in
presence of sulfuric acid
Hydrolysis of butylene (in H2SO4) with steam
Condensation of acetaldehyde to
crotonaldehyde followed by hydrogenation
Esterification of propionic acid with butyl
alcohol (H2SO4)
Chlorination of acetic acid
Esterification of chloroacetic acid
Picr~c acid and calcium hypochlor~te
Nitr~fication of chlorinated hydrocarbons
Monochloroacetic acid and H2S followed by
. .
neutra 1zatlon
Adipic acid and ammonia
Benzoic acid neutralized with sodium
bicarbonate
Zinc hydrosulfite, formaldehyde and caustic
soda
Neutralization of acetic acid with caustic soda
Maleic anhydride and hydrogen peroxide
aDenotes those chemicals listed in the top 50 organic chemicals (Anonymous, 1980).
SOURCE: U.S. Environmental Protection Agency (1973).
generate substantial wastes. It is possible to further reduce this list to
meaningful terms by examining (1) the raw materials used in manufacture
of the major product, (2) the processes, and (3) the products themselves
in order to identify waste streams that contain organics suitable for nu-
tritional enrichment by fermentation. A basic premise in this analysis is
that none of the wastes from the organic chemical industry will be suitable
for direct animal feeding and that fermentation will be required to nutri-
tionally enrich the waste via protein synthesis. At the same time, easily
metabolizable compounds will convert the chemicals to a more metabol-
ically usable form and allow conversion of dilute waste streams to solid
material (biological cell mass) that is readily recovered.
Nutritive Value
From the brief description of manufacturing processes identified as pro-
viding potential underutilized waste (see Table 3), an analysis of process
effluents (U.S. Environmental Protection Agency, 1973) and of process
flow sheets (Lowenheim and Moran, 1975) was made and is summarized
in Table 4.
OCR for page 53
Nonfood Industrial Wastes 53
TABLE 4 Processes Identified as Possibly Having Underutilized NFI
Waste
Product Process
Possible Usable Components in
Effluent
Ethanol Ester~fication and hydrolysis of
ethylene
Ethanol
Catalytic hydration
Isopropanol Esterification and hydrolysis of Isopropanol, other alcohols
propylene
Acetone Dehydrogenation of isopropanol Acetone, isopropanol
Phenol Cumene peroxidation Phenol, acetone, cumene
Acetic acid Acetaldehyde oxidation Acetic acid, formic acid
Methanol carboxylation Acetic acid, methanol, propionic
acid
Butane oxidation
Terephthalic acid
Propylene oxide
Propylene glycol
Oxidation of p-xylene
via propylene chlorohydrin
Oxidation of isobutane
Hydration of propylene oxide
Vinyl acetate Ethylene and acetic acid
Cellulose acetate Acetylation
Methylene chloride Methanol esterification
Pentaerythritol Catalytic
Ethylacetate Catalytic
Acetic acid, acetone, methanol,
formic acid, methylethyl ketone
Acetic acid, xylene
Propionaldehyde, propylene
glycol
t-butylalcohol, isopentanols
Propylene glycol
Dipropylene glycol
Acetic acid, acetaldehyde
Acetic acid, cellulose
Methanol
Acetaldehyde, formaldehyde,
formic acid, erythritols
Ethanol, acetic acid, esters
From the list of organic chemicals, relatively few materials can be called
potentially underutilized wastes. These wastes, which generally are in
dilute solution (total organic carbon less than 2 percent), are not suitable
for direct animal feeding. Furthermore, they require concentration prior
to fermentation processing. Some wastes will contain toxic metals and
organics that will preclude their use for feeding or make their detoxification
difficult.
An alternative to the production of single-cell protein is production of
carbohydrates or fat materials for use as a calorie source in animal feeding.
Such technology was used during World War II. The process technology
is similar for production of single cells for either a protein or calorie
source. However, attention here will focus on protein production. It should
be kept in mind that processing for calorie production also could be a
useful approach.
OCR for page 54
54 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
Processing
Single-cell protein is a generic term for crude or refined sources of protein
whose origin is bacteria, yeast, molds, and algae. There have been a
number of reviews published on this subject (Davis, 1974; Pirie, 1975),
but the most comprehensive treatments of organisms, processes, and nu-
tritional and food technological aspects of utilization are the books based
upon two conferences devoted to single-cell protein (Mateles and Tan-
nenbaum, 1968; Tannenbaum and Wang, 19751.
The need for and use of single-cell protein as a protein supplement is
well established, and research and development on microbial protein pro-
duction has been intense for over a decade. There are a number of large
plants in operation and several more under construction.
It is interesting that microbial protein produced from nonagricultural
raw materials, such as organic chemical wastes, is not dependent on
agricultural sources. It is a synthetic yet complete source of food whose
composition can be controlled (Cooney et al., 1980) and contains nu-
merous nutrients in addition to protein.
Some forms of single-cell protein have been used as human food for
millenia. All fermented foods contain significant quantities of cellular
mass as diverse as bacteria, yeast, and fungi. Thus, the use of such
organisms as a basic protein food is a logical extension of previous ex-
perience.
There is also good scientific evidence that various types of single-cell
protein can be useful as additional protein and vitamin sources in animal
diets. During the last few years, much data have accumulated about nu-
tritive value and safety of different kinds of yeasts and bacteria grown on
chemicals such as n-alkanes and methanol. Technological processes have
been developed for industrial production of these products and good es-
timates for their application are available. These processes consider eco-
nomic aspects and the safety of single-cell protein use for feeding swine,
broilers, and calves. Amino acid patterns, content of nucleic acid and
lipids, and data on possible toxic substances have been studied (Tannen-
baum and Wang, 1975~.
A complete description of individual processes is outside the scope of
this chapter. However, it is important to note that single-cell protein
production is carried out in intensive processes that permit high-volume
production of protein. A typical process flow may appear as shown in
Figure 1.
There are several problems in adapting this technology to organic chem-
ical wastes. The first is the need to concentrate the organic waste to levels
of 4 to 8 percent usable carbon. The capital investment for a single-cell
OCR for page 55
Nonfood industrial Wastes s5
Water
Minerals (K, P. Mg, S. etc.)
Nitrogen Source (NH3)
Carbon Source (Sugar or Hydrocarbon)
l ~
_
Medium
Mixer L Sterilizer
(Optional )
Coolant
con
| Spent Air
Cells
Spent
Medium
Separator
(Centrifuge
or Other
Harvesti ng
Devices)
Wash
1
it'
To Recycle
or Disposal
Air
h Air
Filter
Heat
Removal ~- Air
(O2)
U
.
_ Dryer
Washed Dried
Cells Product
(50% Protein Dry
Cells Weight Basis)
FIGURE ~ Simplified flowsheet of production of single-cell protein. SOURCE: Cooney et
al. (1980).
protein manufacturing facility is usually high and it is necessary to max-
imize both the process productivity and the conversion of organic carbon
to cell mass (Cooney, 19751. Second, unlike most single-cell protein
fermentations where the substrates are pure, these are variable mixtures
of organics. Limited research has been done on the use of mixed substrate
fermentation (Silver and Mateles, 1969; Wilcox et al., 1978~. Choosing
a process, including the organism and the substrate, is extremely complex,
and there are many potential processes. In fact, flexibility in process design
is an important attribute of single-cell protein. Some important factors,
however, will be considered here.
Raw Materials
One of the major advantages of single-cell protein production is the flex-
ibility in being able to choose a variety of organisms able to utilize many
OCR for page 56
56 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
different substrates. A brief summary of some substrates considered is
presented in Table 5, along with an indication of the typical conversion
efficiencies to cell mass. The choice of a carbon source in the design of
a process usually depends on factors such as availability, purity, cost,
acceptability, and lack of toxicity. In the case of nonfood industrial wastes,
the carbon sourceLs) is fixed by the particular chemical process (see Table
41. It is useful to consider some of the general characteristics of several
classes of organic chemicals that serve as substrates for single-cell protein
production.
Paraffin Hydrocarbons Paraffin hydrocarbons with 4 to 24 carbons have
been of particular interest for microbial protein production. In the pro-
duction of diesel fuel, it is important to remove the paraffinic fraction to
lower the pour point of the oil. Since gas-oil contains approximately 10-
40 percent paraffins (the only fraction readily used as a carbon source),
it is possible to use microorganisms to dewax the gas-oil. Typically, 1 g
of cell mass (dry basis) is produced per gram of paraffin consumed.
However, a large unutilized portion of gas-oil passes through the fer-
mentor, creating problems in cell recovery and in removal of residual
hydrocarbons from the cells. The removal of residual hydrocarbon is a
significant problem in the use of petroleum fractions as carbon sources
and requires that the final cell mass be washed extensively with detergent
TABLE 5 Cell Conversion Yields on Various Substrates
Cell Yield
Temperature (g Cell/g
Carbon Source Organism (°C) Substrate) Reference
N-paraffins Pseudomonas 30 1.07 Wodzinski and
spp. Johnson (1968)
Nocardia spp. 30 0.98 Wodzinski and
Johnson (1968)
Candida 30 0.83 Miller and Johnson
intermedia (1967)
Methane Mixed bacteria 40 0.62 Sheehan and
Johnson (1971)
Methanol C. boidinii 28 0.29 Sahm and Wagner
(1972)
Hansenula 37 0.37 Levine and Cooney
polymorpha ( 1973)
Mixed bacteria 56 0.42 Snedecor and
Cooney (1974)
Pseudomonas 32 0.54 Goldberg et al.
(1976)
Ethanol C. utilis 30 0.68 Johnson (1969)
Glucose C. utilis 30 0.51 Johnson (1969)
OCR for page 58
58 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
TABLE 6 Protein Content of Various Microorganisms
Protein Content
(gig Dry Cell
Microorganism Weight) Reference
Bacteria
Pseudomonas methylotropha 0. 83 Cow et al. (1975)
Nethylomonas methanolica 0.82 Dostalek and Molin (1975)
Yeast
Hansenula polymorpha 0.50 Levine and Cooney (1973)
Candida spp. 0.71 Laine and Chaffaut (1975)
Molds
Aspergillus niger 0.35 Imrie and Vlitos (1975)
A. oryzoe 0.41 Rolz (1974)
Fusarium graminearum 0.66 Anderson et al. (1975)
Algae
-
Spirulina 0.64-0.70 Clement (1975)
inexpensive waste carbohydrate sources. The molds might be of consid-
erable interest because of ease of harvesting from fermentation media and
their mycelial nature, which provides natural texture.
Utilization Systems
Experimental
A wide variety of experimental systems utilizing microorganisms to con-
vert a chemical to single-cell protein have been examined (Tannenbaum
and Wang, 19751. However, these studies have focused more on low-cost
methods of protein production than on utilization of chemical wastes.
Purified chemicals such as methanol, ethanol, acetic acid, n-alkanes, etc.
have been used for production of microorganisms to be used in animal
feeding studies. Shacklady (1974) reviewed the response of livestock and
poultry to yeast and bacterial single-cell protein. Animal feeding trials
with microfungi were described by Duthie (19751. Despite the success of
these efforts, microbial protein has remained too expensive in comparison
to soybean meal and has not been commercialized to a major extent.
Industrial
The industrial production of single-cell protein from chemicals is limited
to a few examples. Amoco Foods has a plant to produce 5,000 to 10,000
ton/year of the food yeast Candida utilis from ethanol. Imperial Chemical
Industries Ltd. has a 70,000 ton/year plant in England for the production
of bacteria on methanol. There are also several large plants producing
OCR for page 59
Nonfood industrial Wastes 59
yeast from paraffins in the USSR. In all cases, the product is utilized as
a nutritional supplement. As a consequence, the pricing must be such that
it can compete with alternative protein commodities.
Animal and Human Health
Pathogens
Unprocessed organic chemical waste is not likely to contain pathogenic
microorganisms. However, the processing by fermentation can introduce
pathogens. For this reason, guidelines for single-cell protein used in the
feeding of animals have been recommended by the International Union
of Pure and Applied Chemistry with regard to limits on enterobacteriaceae,
salmonella, Staphylococcus aureus, clostridia (total), Clostridium per-
fringens, and Lancefield Group D streptococci (Hoogerheide et al., 19791.
In addition, guidelines for preclinical and clinical trials for single-cell
protein for human consumption have been published by the United Nations
Protein Advisory Group (see appendix in Tannenbaum and Wang [1975]
for a summary of these guidelines).
Harmful Substances
A major problem in the utilization of organic chemical waste is the pres-
ence of toxic organic chemicals and heavy metals; both can concentrate
in microorganisms used for conversion of waste to animal feed. In the
production of single-cell protein from alkanes containing aromatic com-
pounds, the single-cell protein is solvent-extracted in order to remove any
accumulated or residual material prior to animal feeding.
FERMENTATION INDUSTRY
The fermentation industry can be divided into three broad categories: (1)
antibiotics and other therapeutic compounds, (2) chemical catalysts (en-
zymes), and (3) beverages such as wine, beer, and distilled spirits. Wine
industry waste is considered in Chapter 2.
Quantity
The antibiotics industry in the United States has annual sales of about $1
billion, and the total amount of antibiotics produced is 10,000 to 20,000
tons/year (U.S. Tariff Commission, 1970~. A summary of all the anti-
biotics produced was presented by Perlman (1978), showing that there are
a large number of different products and hence an expected diversity of
OCR for page 60
60 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
waste. However, the major fermentation antibiotics, penicillin, cephalo-
sporin, tetracycline, erythromycin, and the aminoglycosides, account for
most of the production and produce most of the pharmaceutical fermen-
tation waste.
In the United States there are approximately 25 fermentation plants
producing antibiotics and organic acids; most of these are located in the
Midwest, the Middle Atlantic region, and Puerto Rico. The primary waste
from this industry is the spent mycelia. Unlike chemical industry wastes,
pharmaceutical waste is collected in a highly concentrated form, with a
high protein content. Estimating a total antibiotics production of 15,000
ton/year and a ratio of 2.5 kg waste/kg antibiotic, it is possible to estimate
the yearly production of waste mycelium at 38,000 tons dry material/
year. Currently, these wastes are primarily burned, treated in waste treat-
ment systems, or used as fertilizer.
The alcoholic beverage industry (wine, beer, and distilled spirits) is
large and produces substantial waste. About 5.5 kg dry brewers grains
are recovered for each 117 liters (31 gallon barrel) of beer brewed (Anon-
ymous, 1977a). This means that about 1 million ton/year were available
from 5.5 billion liters (176 million barrels) in 1978 for use in animal feeds
(U.S. Department of Commerce, 19801. The distilling industry produces
about 1 billion liters of distilled spirits at 50 percent ethanol per year
(U.S. Department of Commerce, 1980) and in the process generates an
estimated 360,000 tons of waste per year. Essentially all of the brewers
and distillers wastes are currently utilized for animal feeding and do not
represent underutilized materials.
Physical Characteristics
Most of the waste from antibiotic manufacture is the fungal mycelia that
is removed from the fermentation broth by filtration. It will typically have
a solids content of about 15 percent. Even with 85 percent moisture, the
material is a nonflowing cake. Mycelia contains 20-50 percent protein,
about 10-30 percent ash (depending on how much fiber aid is used in
filtration), and has a C/N ratio of about 10 (on a dry basis).
Nutritive Value
There are very few published data on the nutritive value of antibiotic-
producing organisms, primarily because of the low incentive for industry
to develop a feed market for its waste mycelia. However, it is possible
to compare some of the data available with information on other fungi
and attempt to draw some general conclusions. In Appendix 1, Tables 1
through 3, information on several fungi and actinomycetes is presented.
OCR for page 61
Nonfood Industrial Wastes 61
The protein content of the antibiotic producer is generally low (Pfizer,
Inc., Groton, Conn., personal communication); it is diluted by a high ash
level resulting from use of insoluble inorganic materials for pH control
and as a filtration aid.
Doctor and Kerur ( 1968) conducted rat feeding studies with Penicillium
chrysogenum in which mycelia was used in combination with peanut meal
to provide the total protein in the diet. It was necessary to supplement
mycelia with peanut meal in order to make the feed palatable to the rats.
These results demonstrated the usefulness of the mycelia in supplementing
lysine and threonine, two amino acids which are low in concentration in
peanut meal. In addition, the authors refer to unpublished data on the use
of mycelia in chick feeding. Earlier studies by Pathak and Seshadri (1965)
and Yakinov et al. (1960) also examined P. chrysogenum as a protein
feed for animals.
There is a substantial amount of knowledge and experience in the use
of fermentation wastes from the brewing and distilling industry, and the
composition and nutritive value of these by-products is well defined. A
recent study of the feeding value of by-products from ethanol production
has also been published (National Research Council, 1981) and represents
a good source of relevant information.
Processing Technology
One of the limitations in the use of fungi and other mycelial organisms
for animal feed is the problem of digestibility. When waste mycelia is
processed to allow reuse as a complex nutrient in fermentation, the problem
of digestion may be overcome by acid or enzymatic hydrolysis to solubilize
the mycelia. This process has the further advantage of permitting the
organic material to be concentrated by evaporation to a molasses-like
product (Cooney, unpublished results).
The digestion of fungal cell walls has typically been performed using
fermentation broth containing extracellular enzymes. It has most often
been observed that treated cells are harder to decompose than cell wall
suspensions; viable cells are still harder to digest (Kawakami et al., 1972;
Matsuo et al., 1967; Okazaki, 1972; Tabata and Terui, 19631.
There are a number of enzymes involved in degrading cell walls since
the mycelial cell wall is composed of a mixture of polymers including
chitins, 3-glucans, lamarins, and peptides; in addition, many of these
polymers are cross-linked.
Microbial digestion of cell walls was reported by Sonoda and Ono
(1965~; they examined the mycelial cake obtained from kanamycin, strep-
tomycin, and penicillin fermentations. They also used the digest from
these mycelia to produce methane in an anaerobic digestor.
OCR for page 62
62 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
Utilization Systems
Experimental
Utilization of antibiotic waste has been examined by blending it with other
feed components and incorporating it directly into animal diets. However,
there are palatability problems (Doctor and Kerur, 1968~. The high in-
organic content often precludes its direct use in concentrated form. Deg-
radation of the mycelial cell wall to facilitate dehydration has been examined
by Ackerman (19751. It was shown that over 50 percent solubilization of
the mycelial solids could be accomplished with less than 20 percent loss
to carbon dioxide during aerobic treatment. This material was much easier
to dehydrate than the whole mycelia.
Industrial
While antibiotic fermentation waste is not used as animal feeds, the dried
by-products from the brewing and distilling industries are used widely for
animal feeds. Experience with these materials will facilitate the evaluation
and utilization of other fermentation residues if they become available.
Health Considerations
One major problem with the use of mycelia from antibiotics manufacturing
is the presence of residual antibiotics. In the case of antibiotics used in
animal feed (e.g., tetracycline, bacitracin) the whole broth frequently
contains cells plus antibiotics that are both dried and fed. In this situation,
there is no waste. However, with wastes from processes for antibiotics
destined for human use, it is important that residual antibiotics in the
mycelia are not permitted to be widely dispersed. Otherwise, there will
be selection processes favoring drug resistance (Smith, 19771. It is nec-
essary to remove traces of some antibiotics from the mycelia before it can
be fed to animals.
Regulatory Aspects
For the antibiotics industry, a major limitation in the utilization of mycelial
wastes is the problem of residual antibiotics. It may be necessary to develop
processing methods to eliminate antibiotics if mycelia is-to be used for
feed. In order to obtain approval from regulatory authorities for use of
any feed material, it is necessary to establish standards for the product.
This may be very difficult with antibiotic processes because variable raw
OCR for page 63
Nonfood Industrial Wastes 63
material quality and variable process operation may cause significant changes
in the waste product. Since the primary product of the fermentation has
such a high value, there is little economic incentive to alter process op-
eration to assure routine high-quality mycelia. Thus, establishment of such
standards may provide a negative incentive to develop the use of antibiotic
mycelia as animal feed.
MUNICIPAL SOLID WASTE
Quantity
Municipal Solid Waste (MSW) is often cited as an important and under-
utilized resource. The total municipal solid waste available through col-
lection in 1975 in the United States was estimated at 68 million dry tons
per year (U.S. Department of Energy, 19791. In Canada, it was estimated
by Pequegnat (1975) to be 12.7 million dry tons/year. The availability of
municipal solid waste is concentrated in large metropolitan areas, and it
is anticipated that large quantities will continue to be available. Compet-
itive uses include direct combustion or possible future conversion to al-
cohol.
Physical Characteristics
The physical characteristics of municipal solid waste are quite variable
and depend strongly on the source. There are usually substantial quantities
of cellulosic materials, metals, glass, plastics, and dirt. Furthermore, there
is no control over the source. The quality of the municipal solid waste
fraction used for animal feeding will be determined by the ability of the
processor to separate out undesired materials. Belyea et al. (1979) have
examined the composition of municipal solid waste that had been frac-
tionated by several methods. Ash content was quite variable and often
above the usual level present in farm animal diets.
The bulk density of municipal solid waste is low and, as a consequence,
its collection and storage are problems. Not surprisingly, collection costs
are a major fraction of the cost of municipal solid waste.
Nutritive Value
Chemical Composition
The composition of shredded and air-classified shredded solid waste is
presented in Appendix 1, Tables 1 to 3 (Belyea et al., 1979~. The minerals
OCR for page 64
64 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
found in major (> l percent) amounts are Si, Al, Ca, Mg, and Fe; in
minor (0.01-1 percent) amounts are Na, Zn, Pb, Bo, Cr. Ti, and Cu.; and
in trace amounts are An, Ar, Mn, P. Vn, Mo, Ni, Co, and Bi. An
examination of potentially harmful elements suggested that six Ba, Sn,
Se, Pb, Cr. and Cd may be present in unacceptable levels. Mertens and
Van Soest (1971) analyzed a variety of different paper sources; results for
the Washington Post are shown in Appendix Tables 1 and 2 for compar-
ison. Newspaper is high in indigestible fiber and low in protein and ash.
Nutrient Utilization
A number of studies have been done on the inclusion of municipal solid
waste, more specifically newspaper, into animal diets. Kesler et al. ( 1967)
examined the use of waste paper as an absorbent or carrier for molasses
in cattle feeding. Compared with controls using corn silage or corn and
soybean meal, digestibility of crude fiber was reduced when paper was
the absorbent.
The addition of newspapers to diets of growing dairy steers was studied
by Daniels et al. (19701. Newspaper was evaluated at 8 and 12 percent
levels, replacing 8 percent cottonseed bulk in the control diet. They found
no significant differences in rates of gain and feed efficiency. Carcass
grade was not affected. It appears that newspaper can be added up to 12
percent of the diet with no detrimental effect. When paper was used at
the 20 percent level in lactating dairy cows, however, there was a decrease
in milk yield (Mertens et al., 19711.
Processing
An alternative to direct feeding of MSW would be to hydrolyze the cel-
lulase faster by acid or enzymes to produce a sugar syrup. This syrup
could be used as a carbohydrate feed or further processed by fermentation
to produce products such as single-cell protein. The process of hydrolysis,
followed by a solid-liquid separation would be useful in removing un-
desired materials from the MSW feedstock.
Animal and lIuman Health
Although municipal solid waste and newspaper have been shown exper-
imentally to be usable as fiber sources in animal diets, there are several
serious health concerns. Excess amounts of several minerals were mea-
sured in St. Louis municipal solid waste. In addition, Belyea et al. (1979)
reported dangerous levels of polychlorinated biphenyls and other toxic
OCR for page 65
Nonfood Industrial Wastes 65
compounds. There is no control over the source of waste, and variable
levels of harmful materials may occur. Their removal would be expensive.
As a consequence, the use of municipal solid waste for animal feed is not
considered viable at this time.
RESEARCH NEEDS
The major factors limiting the use of underutilized nonfood industrial waste
are the need for nutritional upgrading and the need to remove toxic ma-
ter~als. Therefore, the research needs relating to the problem of nonfood
industrial waste utilization should focus on:
1. Evaluation of nonconventional organisms that will utilize chemical
process stream wastes and produce microbial proteins. Such an evaluation
should include not only effectiveness of conversion to single-cell protein,
but also value of the product for use in animal diets.
2. Development of innovative ways to remove or destroy toxic materials
from chemical waste streams, municipal solid wastes, and fermentation
industry wastes.
SUMMARY
An examination of the nonfood industry to identify underutilized wastes
that could be used directly or after further processing for animal feeding
has identified a number of areas where better utilization might be achieved.
However, there are two major limitations to the use of waste from these
nonfood industries: the need and hence expense of processing to achieve
nutritional upgrading and the need to remove toxic or otherwise harmful
materials from the waste. Problems in nutritional upgrading are associated
with factors such as dilute chemical waste stream and variable quantity
and quality.
LITERATURE CITED
Ackerman, R. A. 1975. The Degradation of Solid Wastes M.S. thesis. Massachusetts
Institute of Technology.
Anderson, C., J. Longton, C. Maddix, G. W. Scammell, and G. L. Solomons. 1975. The
growth of microfungi on carbohydrates. P. 314 in Single-Cell Protein II, S. R. Tannen-
baum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press.
Anonymous. 1977. Animal feeds in the brewing industry. Pp. 5-6 in Proceedings of the
U.S. Brewers Association Feed Conference.
Anonymous. 1980. Facts and figures for the chemical industry. Chem. Eng. News. 58(23):33
90.
OCR for page 66
66 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
Belyea, R. L., F. A. Martz, W. McIlroy, and K. E. Keene. 1979. Nutrient composition
and contaminants of solid cellulosic waste. J. Animal Sci. 49: 1281 - 1291.
Clement, G. 1975. Producing Spirulina with CO2. P. 467 in Single-Cell Protein, II. S. R.
Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press.
Cooney, C. L. 1975. In Microbial Utilization of C '-Compounds. Japan: Society for Fer-
mentation Technology. 183 pp.
Cooney, C. L., and D. W. Levine. 1972. Microbial utilization of methanol. Adv. Appl.
Microbiol. 15 :337-365.
Cooney, C. L., C. K. Rha, and S. R. Tannenbaum. 1980. Single-cell protein: Engineering,
economics and utilization in foods. Adv. Food Res. 26: 1-52.
Daniels, L. B., J. R. Campbell, F. A. Martz, and H. B. Hedrick. 1970. An evaluation of
newspaper as feed for ruminants. J. Anim. Sci. 30:593-596.
Dasher, J. R. 1976. Changing petrochemical feedstocks Causes and effects. Chem. Eng.
Prog. 72:15-26.
Davis, P. 1974. Single Cell Protein. New York: Academic Press.
Doctor, V. M., and L. Kerur. 1968. Penicillium mycelium waste as protein supplement in
animals. Appl. Microbiol. 16: 1723- 1726.
Dostalek, M., and N. Molin. 1975. Studies of biomass production of methanol-utilizing
bacteria. P. 385 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds.
Cambridge, Mass.: MIT Press.
Duthie, I. F. 1975. Animal feeding trials with a microfungal protein. P. 505 in Single-
Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT
Press.
Goldberg, I., J. S. Rock, A. Ben-Basset, and R. I. Mateles. 1976. Bacterial yields on
methanol, methylamine, formaldehyde, and fermate. Biotechnol. Bioeng. 18:1657-1668.
Gow, J. S., J. D. Litchailes, S. R. L. Smith, and R. B. Walter. 1975. SCP production
from methanol: Bacteria. P. 370 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C.
Wang, eds. Cambridge, Mass.: MIT Press.
Gutcho, S. 1973. Proteins From Hydrocarbons. Park Ridge, N.J.: Noyes Data Corp.
Hoogerheide, J. C., K. Yamada, J. D. Littlehailes, and K. Ohno. 1979. Guidelines for
testing of single-cell protein destined as protein source for animal feed II. Proc. Appl.
Chem. 51:2537-2560.
Imrie, F. K. E., and A. J. Vlitos. 1975. Production of fungal protein from carob. P. 223
in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.:
MIT Press.
Jahnig, C. E., and R. R. Bertrand. 1977. Environmental aspects of coal gasification. Pp.
127-132 in Coal Processing Technology. New York: American Institute of Chemical
Engineers.
Johnson, M. J. 1969. Microbial cell yields from various hydrocarbons. Pp. 833-842 in
Fermentation Advances, D. Perlman, ed. New York: Academic Press.
Kawakami, N., H. Kawakami, and T. Sato. 1972. Cell wall disintegration with Physarium
enzyme in Sahizosaccharomyces pombe. J. Ferm. Technol. 50:567-711.
Kesler, E. M., P. T. Chandler, and A. E. Branding. 1967. Dry molasses product using
waste paper as a base for a possible feed for cattle. J. Dairy Sci. 50:1994-1996.
Kihlberg, R. 1972. The microbe as a source of food. Ann. Rev. Microbiol. 26:427.
Laine, B. M., and J. Chaffaut. 1975. Gas-oil as a substrate for single-cell protein pro-
duction. P. 424 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds.
Cambridge, Mass.: MIT Press.
Levine, D. W., and C. L. Cooney. 1973. Isolation and characterization of a thermotolerant
methanol utilizing yeast. Appl. Microbiol. 26:982-990.
OCR for page 67
Nonfood Industrial Wastes 67
Lowenheim, F. A., and N. K. Moran. 1975. Industrial Chemicals. New York: John Wiley
& Sons.
Magee, E. M., C. E. Jahnig, and C. D. Kalfaldas. 1977. The environmental influence of
coal liquefaction. Pp. 16-22 in Coal Processing Technology. New York: American
Institute of Chemical Engineers.
Mateles, R. I., and S. R. Tannenbaum, eds. 1968. Single-Cell Protein. Cambridge, Mass.:
MIT Press.
Matsuo, M., T. Yasui, and T. Kobayashi. 1967. Cytolytic enzymes from thermophilic
microorganisms: I. Cytase production from Thermoinactinomyces vulgaris. J. Ferm.
Technol. 49:860-868.
Mertens, D. R., J. R. Campbell, F. A. Martz, and E. S. Hildebrand. 1971. Lactational
and ruminal response of dairy cows to ten and twenty percent dietary newspaper. J.
Dairy Sci. 54:667-672.
Mertens, D. R., and P. J. Van Soest. 1971. Paper composition and-estimated nutritive
value. Paper presented at National ASAS Meeting.
Miller, T. L., and M. J. Johnson. 1967. Utilization of normal alkanes bv yeast. Biotechnol.
Bioeng. 8:549-565.
At, ~_~. ~ am._ .... .
National Research Council. 1981. Feeding Value of Ethanol Production By-Products. Wash-
ington, D.C.: National Academy Press.
Okazaki, H. 1972. On cell wall lytic activity produced by thermophilic actinomyces. III.
Some properties of the components of the lytic enzyme produced by Micropolyspora sp.
J. Ferm. Technol. 50:580-591.
Okazaki, H., and H. Iizuka. 1972. On cell wall lytic activity produced by thermophilic
actinomyces. I. Lysis of intact cells of various yeasts (including hydrocarbon assimilating
yeasts), thermophilic fungi, and green algae. J. Ferm. Technol. 50:405-413.
Pathak, S. G., and R. Seshadri. 1965. Use of Penicillium chyrogenum mycelium as animal
food. Appl. Microbiol. 18:262-266.
Pequegnat, C. 1975. Economic feasibility of waste as animal feed. P. 26 in Waste Recycling
and Canadian Agriculture. Ottawa: Agricultural Economics Council of Canada.
Perlman, D. 1978. The fermentation industries. ASM News. 43(2):82-89.
Pirie, N. W. 1975. Food Protein Sources. Cambridge, Eng.: Cambridge University Press.
Reed, G., and H. J. Peppler. 1973. Yeast Technology. Westport, Conn.: AVI.
Rockwell, P. J. 1976. Single Cell Protein From Cellulose and Hydrocarbons. Park Ridge,
N.J.: Noyes Data Corp.
Rolz, C. 1974. Utilization of cane and coffee processing by-products as microbial protein
substrates. P. 273 in Single-Cell Protein II. S. R. Tannenbaum and D. I. C. Wang, eds.
Cambridge, Mass.: MIT Press.
Sahm, H., and F. Wagner. 1972. Mikrobielle verwettung von methanol. Arch. Mikrobiol.
84:29-42.
Shacklady, C. A. 1974. Response of livestock and poultry to SCP. Pp. 115-128 in Single-
Cell Protein, P. Davis, ed. New York: Academic Press.
Sheehan, B. T., and M. J. Johnson. 1971. Production of bacterial cells from methane.
Appl. Microbiol. 21:511.
Silver, R. S., and R. I. Mateles. 1969. Control of mixed-substrate utilization in continuous
cultures of Escherichia coli. J. Bacteriol. 97:535-543.
Smith, H. W. 1977. Antibiotic resistance in bacteria and associated problems in farm
animals before and after the 1969 Swann report. Pp. 344-357 in Antibiotics and Anti-
biotics in Agriculture. W. Woodbine, ed. Boston: Butterworths.
Snedecor, B., and C. L. Cooney. 1974. Thermophilic mixed culture for bacteria utilizing
methanol for growth. Appl. Microbiol. 27: 1112- 1117.
OCR for page 68
68 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS
Sonoda, Y., and H. Ono. 1965. Anaerobic digestion of antibiotic waste water. I. On
kanamycin, streptomycin, penicillin waste water and mycelium cake. J. Ferm. Technol.
43(1 1):842-846.
Tabata, S., and G. Terui. 1963. Studies on microbial enzyme active in hydrolizing yeast
cell wall. III. On the protease fraction of the yeast cell wall-lytic enzyme of Streptomyces
albidoflavus. J. Ferm. Technol. 43(10):777-782.
Tannenbaum, S. R., and D. I. C. Wang. 1975. Single-Cell Protein II. Cambridge, Mass.:
MIT Press.
U.S. Department of Commerce. 1980. Statistical Abstract of the United States, 100th ed.
Washington, D.C.: U.S. Government Printing Office.
U.S. Department of Energy. 1979. The Report of the Alcohol Fuels Policy Review Raw
Fuels Availability Reports. Report No. ET-01 14/1. Washington, D.C.: U.S. Government
Printing Office.
U.S. Environmental Protection Agency. 1973. Development Document for Effluent Lim-
itations Guidelines and Standards of Performance. EPA Report for Contract No. 68-01-
1509. Washington, D.C.: U.S. Government Printing Office.
U.S. Tariff Commission. 1970. Synthetic Organic Chemicals. United States Production
and Sales. TC Publication 327. Washington, D.C.: U.S. Government Printing Office.
Wilcox, R. P., L. B. Evans, and D. I. C. Wang. 1978. Experimental behavior and math-
ematical modeling of mixed cultures on mixed substrates. AIChE Symp. Ser. 74:236-
240.
Wodzinski, R. S., and M. J. Johnson. 1968. Yields of bacterial cells from hydrocarbons.
Appl. Microbiol. 16:1886-1891.
Yakinov, P. A., O. V. Krusser, and Y. E. Koney. 1960. Investigations of Penicillium
chrysogenum mycelium as a possible protein source for feeding domestic animals. I.
Leningr. Khim. Farmatsevt. Inst. 9:212-219.
Representative terms from entire chapter:
nonfood industrial
