United States
                         Environmental Protection
                                     Risk Reduction
                                     Engineering Laboratory
                                     Cincinnati OH 45268
                         Research and Development
                                    EPA/600/S-92/004  May 1992
        Waste Minimization Assessment for a Manufacturer of Chemicals
                                  Gwen P. Looby and Phylissa S. Miller*
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small- and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers, Waste Minimization Assessment Centers (WMACs) were
established  at selected universities  and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). The WMAC
team at the University of Tennessee performed an assessment
at a plant manufacturing acrylic emulsions, low molecular weight
resins, herbicides, and specialty chemicals-approximately 300
million Ib/yr. In general, monomers, additives, activators, and
catalysts are metered and mixed in tanks then pumped  se-
quentially into reactor vessels. Once the product is formed, the
solution is pumped into a blend tank where  more chemicals,
such as binders, emulsifiers, and thickeners,  are added. From
the blend tank the product is passed through filters for clump
removal then pumped into either storage tanks or drums for
shipping. The team's report, detailing findings and recommen-
dations, indicated that the majority of waste was generated in
the wastewater treatment system and that the greatest savings
could be obtained by installing a natural gas-fired dry-off oven
in the wastewater treatment system to reduce (by 81%) the
amount of sludge removed to the landfill.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing  research
project. This brief provides only summary information and is
•University City Science Center, Philadelphia, PA 19104.
                         not intended for use as a thorough analysis. A fully docu-
                         mented report of the same title is available from the authors.

                         The amount of  waste generated by industrial plants has be-
                         come an increasingly costly problem for manufacturers and an
                         additional stress on the environment. One solution to the prob-
                         lem of waste is to reduce or eliminate the waste at its source.

                         University City Science Center (Philadelphia, PA) has begun a
                         pilot project to assist small- and medium-size manufacturers
                         who want to minimize their formation of waste but who lack the
                         in-house expertise to do so. Under agreement with EPA's Risk
                         Reduction Engineering  Laboratory, the Science Center  has
                         established three WMACs. This  assessment was done by
                         engineering faculty and students at the University of
                         Tennessee's (Knoxville) WMAC. The assessment teams have
                         considerable direct experience with process operations in manu-
                         facturing plants and also have the knowledge and skills needed
                         to minimize waste generation.

                         The waste minimization assessments are done for small- and
                         medium-size manufacturers at no out-of-pocket cost  to the
                         client. To  qualify for the assessment,  each client must  fall
                         within Standard  Industrial Classification Code 20-39, have gross
                         annual sales not exceeding $50 million, employ no more than
                         500 persons, and lack in-house expertise in waste minimiza-

                         The potential benefits of the pilot  project include minimization
                         of the amount of waste generated by manufacturers and reduc-
                         tion of waste treatment and disposal costs for participating
                         plants. In addition, the project provides valuable experience for
                         graduate and undergraduate students who participate in  the
                         program and a cleaner environment without more  regulations
                         and higher costs for manufacturers.
                                                                                Printed on Recycled Paper

Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures  outlined  in the EPA Waste  Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC
staff locates the sources of waste in the plant and identifies the
current disposal or treatment  methods and their associated
costs.  They then identify  and analyze a variety of ways to
reduce or eliminate the waste. Specific measures to achieve
that goal are recommended and the  essential supporting tech-
nological and economic information is developed. Finally, a
confidential report that details the WMAC's findings and recom-
mendations (including cost savings, implementation costs, and
payback times)  is prepared for each  client.

Plant Background
This plant manufactures acrylic emulsions, low molecular weight
resins, herbicides,  and other specialty chemicals. The plant
operates 8,400  hr/yr  to  produce approximately 300  million
pounds of chemicals.

Manufacturing Process
The processes are complex and vary extensively in the exact
methods used in order to produce the final product. The pro-
duction of one particular low molecular weight dispersant prod-
uct generates significant quantities of wastes and therefore will
be considered a separate process in this evaluation. The pro-
cess lines are described below in detail.

Acrylic Emulsion Production
Approximately 400 different acrylic emulsion formulations  are
produced by this plant. The actual sequence of steps required
varies  greatly from  product to product. However, the  overall
process sequence  is similar in  most cases and is described
below. Raw materials for the emulsion line include monomers,
additives, activators, and catalysts in either liquid or solid form.
Some monomers have been pre-mixed with inhibitors for stabi-
lization. Catalysts are used to activate the  monomers and
initiate the desired  reactions. Activators increase the activity
level of the catalysts and allow reactions to overcome  the
effects of the inhibitors. Additives include  detergents, disper-
sants,  and pH-adjustment ingredients.

Monomers are pumped from tanker trucks to  monomer tanks
for storage. From the storage tanks,  monomers are pumped to
holding/premixing tanks, and  in some cases  to the additive,
activator, and catalyst holding tanks  where mixing occurs. The
additives, activators, and catalysts may be added directly to
the reactors without being  mixed with monomers in their re-
spective holding tanks.

From the holding tanks, raw materials are mixed together using
certain proprietary  recipes  in one of three temperature- and
pressure-regulated reactors where polymers are formed. Chemi-
cal reactions are initiated  by addition of catalysts  and  are
regulated with additives or by pressure and temperature  ad-

Next,  the resulting acrylic emulsion  polymers  are pumped to
blend tanks where other  ingredients are added. At this point
approximately 40% to 60% of the emulsion is water. Formalde-
hyde is added as a preservative to  control bacteria and mold
growth, and ammonia is added to  approximately half of  the
product for pH  adjustment. Another pH-adjustment chemical
that is added in the blend tanks is sodium hydroxide. Other
ingredients such as emulsions, emulsifiers, surfactants,  bind-
ers, and thickeners are added to modify monomer viscosity, to
stabilize the polymers, and to hold the polymers in suspension.
De-ionized water is added to lower the solids content.  After
each polymer batch is processed, the blend tanks are flushed
with de-ionized water that is then pumped to the plant's waste-
water treatment system.

Wastes generated up to this point  in  the  process  include
composited absorbed monomers, burnable  liquids,  and off-
grade methylolacrylamide/acrylamide. Most of the composited
absorbed monomer waste generated occurs from spillage dur-
ing loading and unloading of the railcars or from batch  spills
and reactor clean-ups. Burnable liquids waste results from off-
spec  mixtures or reactions  resulting  from incorrect tempera-
tures  or incorrect batch weights of solutions in the feed tanks
and reactors.  Some of the burnable liquids waste from the off-
spec batches  are recovered and mixed with good batches. Off-
grade methylolacrylamide/acrylamide results from bad batches
of a particular commercial product. In addition, some waste is
generated because of a product's relatively short shelf life.
Equipment and/or operator error also accounts for a portion of
off-grade material.

From the blend tanks, the acrylic emulsion polymers are pumped
through tightly woven cloth filters that separate unwanted clumps
of product from the water phase. The used filters, which con-
tain clumps of product,  are shipped  offs'rte to a landfill. (An
estimated 0.25% of actual product is trapped in  the filters.)
After  filtering,  the emulsions  are pumped either to  storage
tanks or directly into drums for shipping.

Low  Molecular Weight Resin Production
Production processes and raw materials for the low molecular
weight (LMW) resins are identical to those of the acrylic emul-
sions  until the product is pumped into the blend tanks.

Following batch polymerization in the reactor vessels, the  LMW
resin  product  is pumped to  one of  six blend  tanks where
different additives including water, sodium hydroxide, ammo-
nia, detergents,  and  emulsifiers are  added.  These additives
provide pH adjustment, solids adjustment, and preservation of
the product. From the blend tanks, the LMW resin polymers
are pumped  either to storage  tanks for future shipping or
directly to drums for immediate shipping.

One waste generated from this production line is an unsalable
product, which is shipped offsite as a hazardous waste.  Addi-
tional waste generated  by this line  is a result  of off-grade

Other wastes generated  in this process are similar to those in
the emulsion line  and include composited absorbed mono-
mers,  burnable  liquids,  and off-grade methylolacrylamide/
acrylamide. These wastes are generated in the same  manner
mentioned above. An abbreviated flow diagram for acrylic
emulsion and the LMW resin  process  is shown in Figure  1.

Dispersant  Process
The production of one particular low molecular weight  resin
product (a proprietary dispersant) results in the  generation of
two significant waste streams and will  be considered here as a
separate process description.


                                                                                     Absorbed:, ,
                                                                                         - v- 4
                      Depending on
                      the Product
                     Used Filters,
                     Clumps, Waste water
                                              Storage Tanks or
             Unsalable Product
Figure 1.  Abbreviated flow diagram for the acrylic emulsion and LMW resin process.
Xylene, diisobutylene (DIB), and other monomers  and addi-
tives are pumped to the reactors in the LMW resin production
line. In a batch production, polymers are formed in the reac-
tors. The product is  pumped to a separation tank where the
unwanted heavier DIB settles to the bottom of the tank and the
lighter-fraction product is decanted from the top. An emulsion-
like interface composed of DIB  and product is formed between
the product and the DIB layers and  is removed from the tank
and shipped offsite as a hazardous waste. Some of the DIB
solvent from the separation tank is drained to a storage tank
where further separation by settling occurs. Product/DIB inter-
face is removed from this storage tank and is shipped offsite as
hazardous waste. The DIB wet solvent from this tank is pumped
to the boiler and  burned. Recovered xylene/DIB mixture from
the separation tank is returned  to the reactor.
From the separation tank, the upper layer product fraction is
decanted into another separation  tank. Water is separated
from the product and pumped to the plant's water treatment
system. The  product is  pumped to a blend tank from which
more DIB wet solvent is removed and burned in the boiler. The
product is then pumped either to storage tanks or to drums for
shipping. An  abbreviated flow diagram for the dispersant pro-
cess is shown in Figure 2.

Herbicide/Specialty Chemical Production
Ingredients are mixed together in a pressure- and temperature-
regulated reactor where a specified reaction occurs. Absorbed
propionic acid waste is generated from the loading and unload-
ing of material. High- and low-acidic content  propionic  acid
wastes are generated by the reactions. Highly acidic propionic

                      Raw Material
                     Separation Tank
              pH and Solids
                                                                        /Excess DIB\
                        Blend Tank
                                               Decanted DIB
                       Storage Tanks
                         or Drums
   Figure 2.  Abbreviated flow diagram for the dispersant process.
acid is recycled back into the reactors for use in further pro-
cessing. The low-acidic content propionic acid is  pumped to
the wastewater treatment system where it is used to neutralize
caustic wastewater from other plant operations.

From the  reactor, the product is pumped to a blend tank to
which other chemicals and emulsifiers are added; these sub-
stances reduce the viscosity of the product. Several wastes are
generated from the annual cleaning of the reactor and blend
tank including wastewater that is pumped to the wastewater
treatment  system, herbicide  residue, and herbicide articles
(contaminated employee clothing). From the  blend tank, the
products are loaded onto railcars and shipped. An abbreviated
flow diagram for the herbicide/specialty chemical process is
shown in Figure 3.

Pollution Abatement (PA) System
This plant uses a  pollution abatement system to remove va-
pors from various  areas of the plant including the monomer
storage area, tanks in the resin  production area, and the
reactors and holding/premixing tanks in the emulsion produc-
tion line. This system was installed mainly to remove vapors
with persistent irritating odor from the plant.

A blower located down the line creates a pressure difference
and pulls  fresh air over the tanks mentioned above. Vapors
collected from the monomer storage area and resin area tanks
are blown to separate liquid knock-out tanks. These tanks act
as  condensers and  use ambient air cooling to condense a
portion  of the vapors. The resulting condensate  from these
tanks is directed  to the water  treatment facility. From the
knock-out tanks, the vapors are ducted through separate lower
explosive  limit (LEL) monitors that evaluate the flammability of
the vapors. From the monitors, the vapors are directed through
backfire preventers that act as safety valves and prevent va-
pors from being drawn back through the system.

Vapors from the reactors and feed tanks in the emulsion line
follow a similar route through the PA system;  however, they
are first ducted through a caustic scrubber. Caustic solution is
added  to this scrubber as well  as 150 gal/min  of  water  to
remove particulates from the fumes. This solution is dumped to
the water treatment system  every 11  days. The vapors are
then directed through a liquid knock-out tank (from which water
is  pumped to water treatment), through a backfire preventer,
and then through an LEL monitor.

From that monitor, the vapors pass through a blower, another
backfire preventer, and finally most of the vapors  (99.97%)
enter a natural gas-fired thermal oxidizer at MOOT.

Wastewater Treatment System
Another onsite waste treatment facility this plant has installed
is  its wastewater treatment system. Wastewater from the emul-
sion line and the resin line, laboratory wastewater, and air
compressor and other cooling water are directed to this facility
for treatment. All incoming water passes through a roto-strainer
that removes suspended solid particulates. The solid waste
falls into two  hoppers and  is eventually hauled offsite  to a

From the roto-strainer, the water enters a neutralization tank
where  carbon dioxide and low acidic propionic acid from the
herbicide line are added for neutralization. The water  then
enters a second neutralization tank where the water is agitated
to promote further neutralization. Next, the wastewater enters
three open-air  mixing  basins in which sludge is allowed  to
settle to the  bottom. Sludge is removed  quarterly to landfill.

                                 Excess Low
                                 Propionic Acid
                                 to Wastewater
Figure 3.  Abbreviated flow diagram for the herbicide/speciality chemical process.
The effluent wastewater is released to the municipal sewer.
Total water discharged from the plant on an annual basis is
approximately 126 million gal/yr.

Existing Waste  Management Practices
  • A pollution abatement  system removes noxious and odor-
    ous vapors from the plant and incinerates them.

  • Off-grade monomers and polymers are reused in an effort
    to produce salable products.

  • Diisobutylene wet solvent is burned in an onsfte boiler.

Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity  of the waste, and the annual treat-
ment and disposal costs are given in Table 1.

Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The type of  waste,
the minimization  opportunity, the possible waste reduction and
associated savings, and the implementation cost along with the
payback time are given  in the table. The quantities of waste
currently generated by the plant and possible waste reduction
depend on the production level of the plant. All values should
be considered in that context.

It should be noted that, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
material and from reduced present and future costs associated
with waste treatment and disposal. Other savings not quantifi-
able  by this study include a  wide  variety of  possible future
costs  related to changing emissions  standards, liability, and
employee health. It should also be noted that the savings given
for each opportunity reflect the savings achievable when imple-
menting each waste minimization  opportunity independently
and do not reflect duplication of sayings that would result when
the opportunities are  implemented in a package.

This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency. The EPA Project Officer was Emma Lou
George.                              ;

Tsble 1.  Summary of Waste Generation
Waste Generated
 Source of Waste
Annual Quantity       Annual Waste
   Generated      Management Cost ($)
Burnable liquids
Composited absorbed monomers
Off-grade methylolacrylamide/
Used filters and trapped product
Unsalable low molecular weight

Diisobutylene (DIB) wet solvent
Off-grade mixtures and bad reactions in the
acrylic emulsion and low molecular weight resin
production lines.

Spillage and clean-up of reactors in the
acrylic emulsion and low molecular weight resin
production lines.

Off-grade batches of product in the acrylic
emulsion and low molecular weight resin
production lines

Filtering process in the acrylic emulsion
production line.

Expired products and off-grade batches of products
in the low molecular weight resin production line.

Spent solvent from the dispersant production line.
DIB wet solvent is sent to an onsite thermal
     15,400 Ib

     15.400 Ib

      5,100 Ib

     44,800 Ib

     20,880 Ib

    316,220 Ib





Product/DIB Interface
Absorbed proplonic acid
Contaminated employee clothing
Herbicide residue
Cold stack gases (noxious,
odorous, and organic vapors
drawn from monomer storage
area, tanks in resin line, and resin
reactors and tanks)
Wastewater sludge
Separation tank in the dispersant production line.
Spillage in the herbicide/specialty chemical
production line.
Herbicide/specialty chemical production line.
Cleaning of the reactor and blend tank in the
herbicide/specialty chemical production line.
Thermal oxidizer and heat exchanger in the
Pollution Abatement System.
Onsite wastewater treatment system.
Onsite wastewater treatment system.
25,750 Ib
6,000 Ib
394,200 ff
300,000 Ib
126,000,000 gal
 'New waste; no data available.
"There are no direct costs reported for handling evaporative waste.

Table 2.  Summary of Waste Minimization Opportunities

Unsalable product
                                                           Annual Waste Reduction
                                                            Net Annual    Implementation    Payback
Waste Generated
Burnable liquids
Composited absorbed
Minimization Opportunity
Upgrade the redundant
sensing and control
devices on the reactor
raw material lines to
reduce the amount of off-
specification product
7 1,550 to
2,890 Ib
3,480 to
Savings ($) Cost ($)
139,810 365,480
                                   3,130 Ib
Wastewater sludge
Install a natural gas-fired
dry-off oven in the waste-
water treatment system to
reduce the amount of
sludge removed to the
244,030 Ib
                                                                            •&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40271

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Research Information
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