United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/011 August 1995
&EPA ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment for a Manufacturer of
Automotive Battery Separators
Marvin Fleischman*, Patrick Schmidt*, David Roberts*,
and Gwen P. Looby**
Abstract
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). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at the
University of Louisville performed an assessment at a plant
that manufactures automotive battery separators. Two types of
separators—polyethylene/silica sheet and vinyl rib—are pro-
duced. Processes used in polyethylene/silica sheet production
include blending, extruding, extraction, drying, and slitting. Mix-
ing, dipping, extrusion, and cutting are required in vinyl rib
separator production. The team's report, detailing findings and
recommendations, indicated that waste spill absorbents are
generated in large quantities and at a significant waste man-
agement cost, and that waste reduction could result from using
wringable, reusable absorbents.
This Research Brief was developed by the principal investiga-
tors and EPA's National Risk Management Research Labora-
tory, Cincinnati, OH, to announce key findings of an ongoing
research project that is fully documented in a separate report
of the same title available from University City Science Center.
University of Louisville, Department of Chemical Engineering.
"University City Science Center, Philadelphia, PA.
Introduction
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
problem of waste generation 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 generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
National Risk Management Research Laboratory, the Science
Center has established three WMACs. This assessment was
done by engineering faculty and students at the University of
Louisville's WMAC. The assessment teams have considerable
direct experience with process operations in manufacturing
plants and also have the knowledge and skills needed to
minimize waste generation.
The pollution prevention opportunity 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 $75 million, employ no more
than 500 persons, and lack in-house expertise in pollution
prevention.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, and
reduction of waste treatment and disposal costs for participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
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Methodology of Assessments
The pollution prevention opportunity assessments require sev-
eral site visits to each client served. In general, the WMACs
follow the procedures outlined in the EPA Waste Minimization
Opportunity Assessment Manua/(EPA/625/7-88/003, July 1988).
The WMAC staff locate the sources of waste in the plant and
identify 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 support-
ing technological and economic information is developed. Fi-
nally, a confidential report that details the WMAC's findings
and recommendations (including cost savings, implementation
costs, and payback times) is prepared for each client.
Plant Background
This plant manufactures two types of automotive battery sepa-
rators. It operates approximately 8,400 hr/yr to produce almost
3.5 bil ft2 of polyethylene/silica separators and over 2 bil vinyl
rib separators annually.
Manufacturing Process
Automotive battery separators, which are thin sheets placed
between battery electrodes to prevent the electrodes from
shorting out, are manufactured by this plant. The production
processes for the two types of separators manufactured—
polyethylene/silica sheet and vinyl rib—will be described here.
Polyethylene/silica Sheet
Polyethylene/silica sheet is manufactured from a mixture of
high density polyethylene, ultrahigh molecular weight polyethyl-
ene, silica, oil, and other ingredients. The raw materials are
blended together and the resulting mixture is extruded through
a die bar into a sheet and calendered. The oil, which prevents
the silica from damaging the extruder and provides porosity to
the product when extracted, is then removed by countercurrent
extraction with trichloroethylene (TCE). After oil removal, the
sheet passes through a drying oven for TCE removal and
enters a water bath where a wetting agent is added to change
the electrical properties of the sheet. The sheet is then dried
again for water and further TCE removal and is inspected,
wound onto a roll, and slit.
Countercurrent extraction of oil generates a mixture of oil and
TCE that is known as miscella. The miscella is distilled to
separate the oil and TCE so that both can be reused.
An abbreviated process flow diagram for polyethylene/silica
sheet production is shown in Figure 1.
Vinyl Rib Separators
A latex batch containing latex, silane, water, and other ingredi-
ents is mixed in two steps and placed in a dip tank. Plastisol,
which is composed of diethylhexyl phthalate (DEHP), polyvinyl
chloride, mineral spirits, and other ingredients, is mixed sepa-
rately for use in extrusion through the rib die bar.
In order to produce the vinyl rib separators, fiberglass sheet
paper is dipped into the dip tank, squeezed between rollers to
remove excess latex, and then passed under the rib die bar
where plastisol is extruded onto the sheet to form the ribs. The
resulting product sheet is dried in an oven, cut into squares,
inspected, and packaged.
An abbreviated process flow diagram for the manufacture of
vinyl rib separators is shown in Figure 2.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
• Waste fiberglass paper from vinyl rib production is used to
adsorb spills from polyethylene/silica sheet production thus
reducing the quantity of adsorbents purchased.
• Trichloroethylene fugitive emissions are reduced as a result
of the extraction pans, turnaround, drier, wetting agent bath,
and water drier being welded together.
• Disposable cotton wound cartridge filters are being replaced
by reusable metal mesh strainers on the miscella recovery
still feed lines.
• Recovered materials such as oil and TCE are reused exten-
sively onsite.
• Equipmentto regrind blacksheettrim for reuse in the polyeth-
ylene/silica sheet production line has been purchased.
• Roll cores from the fiberglass sheet used in the vinyl rib
production line are returned to the supplier for reuse.
Pollution Prevention Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the waste management cost for each waste
stream identified are given in Table 1.
Table 2 shows the opportunities for pollution prevention that
the WMAC team recommended for the plant. The opportunity,
the type of waste, the possible waste reduction and associated
savings, and the implementation cost along with the simple
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 the economic savings of the opportuni-
ties, in most cases, result from the reduction in raw material
and costs associated with waste treatment and disposal. Other
savings not quantifiable by this study include a wide variety of
possible future costs related to changing emissions standards,
liability, and employee health. It also should be noted that the
savings given for each opportunity reflect that pollution preven-
tion opportunity only and do not reflect duplication of savings
that may result when the opportunities are implemented in a
package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, several additional measures including the
following were considered. These measures were not analyzed
completely because of insufficient data, implementation diffi-
culty, or a projected lengthy payback. Since these approaches
to pollution prevention may, however, increase in attractive-
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Polyethylene,
Silica
I*- Mix tower
screening
Oil
_ f _
Mixing
Extruding
Calendering
TCE
Extraction
Miscella
Miscella *• TCE
recovery p-*- O//
Drying
Addition of
wetting ' **' Drying
agent \
- . I i.
Inspection
Slitting
Sheet
Shipped
Winding I
Figure 1. Abbreviated process flow diagram for polyethylene/silica sheet production.
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Latex,
Silane,
Water,
Other
ingredients
Latex
mixing
Dip tank
Roller
_i
Diethylhexyl phthalate,
PVC,
Mineral spirits,
Other ingredients
Plastisol
mixing
Rib die
bar
Finished
separators
shipped to
customers
Packaging
Slitting/
I cutting
,!
Drying
Figure 2. Abbreviated process flow diagram for vinyl rib separator production.
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ness with changing conditions in the plant, they were brought
to the plant's attention for future consideration.
• Identify a suitable alternative for trichloroethylene currently
used for oil removal.
• Identify an alternative oil for use in the process, thereby
making it possible to use a different solvent for extraction.
• Grind waste black sheet for reuse onsite. (The plant is in the
process of implementing this measure.)
• Replace the steam stripper used for oil recovery on one of the
process lines with a newer, more efficient unit.
• Install a back-up centrifuge to take the place of the primary
centrifuge when it is not working.
• Regenerate the carbon beds with nitrogen instead of steam
in orderto eliminate the generation of wastewater containing
TCE.
• Recover dioctyl phthalate from stack gases priorto incinera-
tion by carbon bed adsorption and condensation.
• Reuse empty Gaylords internally and/or substitute ship-
ments currently received in paper bags with shipments in
returnable bulk bags.
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. Environ-
mental Protection Agency. The EPA Project Officer was Emma
Lou George.
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Table 1. Summary of Current Waste Generation
Waste Stream Generated
Oversize silica
Bad batches and leaks
Vacuum pump liquid
Centrifuge sludge
Waste black and gray sheet
Solid wastes (e.g., filter
cartridges)
Spill absorbents
Fiberglass paper used as
absorbent
Paper filters
TCE emissions
TCE emissions
Skimmed waste oils
Sump sludge
WWTP sludge
Foamed plastisol (unneeded
or unacceptable)
Nonfoamed plastisol
Iron scrap
(revenue received)
Stainless steel scrap
(revenue received)
Diethylhexyl phthalate emissions
Phenol and formaldehyde
emissions
Unusable fiberglass paper
Latex sludge
Process wastewater
Process wastewater
Sanitary wastewater
Blowdown
Pallets
Cardboard
Empty drums
Paper bags
Plastic-lined bags
Spent solvent
Gear oil
Source of Waste
Screening of raw material
Mixing of recycled oil with polyethylene and silica
Extruder knockout drum (disposed of when
centrifuge is not operating)
Extruder knockout drum
Start-up of polyethylene/silica sheet production
and trimming of sheet
Extraction, extrusion, and oil/TCE recovery
Clean-up of spills from extractor and oil/TCE
recovery
Clean-up of spills from extractor and oil/TCE
recovery
Carbon adsorption system for vented process
gases
Fugitive emissions
Stack emissions
Sump in conjunction with floor drains
Sump in conjunction with floor drains
Onsite WWTP
Vinyl rib production line
Vinyl rib production line
Worn out belts from drying ovens
Worn out belts from drying ovens
Stack emissions
Stack emissions
Vinyl rib production line
Onsite WWTP
Various
s-line
Cooling towers
Raw material delivery
Raw material delivery
Raw material delivery
Raw material delivery
Raw material delivery
Parts washer
Waste Management Method
Landfilled as special waste
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Landfilled as special waste
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Evaporated to plant air
Vented from plant
Shipped offsite for disposal
as hazardous waste
Shipped offsite for disposal as
hazardous waste
Accumulating onsite
Shipped offsite for disposal as
hazardous waste
Shipped offsite for disposal as
hazardous waste
Sold to scrap recycler
Sold to scrap recycler
Vented from plant
Vented from plant
Compacted; landfilled
Landfilled
Treated onsite; sewered
Treated onsite; sewered
Sewered
Sewered
Landfilled
Given to recycler
Shipped to reconditioner
Landfilled
Landfilled
Removed by supplier for offsite
recycling
Recycled offsite
Annual Quantity
Generated (Ib/yr)
73,600
33,840
18,280
2,990
4,684,000
1,250
7,620
8,930
80
211,000
266,500
9,060
4,910
208,100
660
31,110
17,900
16,900
106,800
6,900
196,000
280,000
124,000,000
87,736,000
8,263,000
103,283,000
20,000
122,000
9,000
20,000
350
1,890
6,680
Annual Waste
Management Cost
$44,9401
76.0001
18.9001
5,000
2,856,8001
1.7501
22.2901
96.9301
3501
52.9001
66.6001
8,900
8,300
—2
1.6701
78,1 401
-1,360
-1,630
53.4001
—
3,960
700,000
31,410
200
0
300
200
10
960
200
Includes applicable lost raw material value.
Not yet disposed.
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Table 2. Summary of Recommended Pollution Prevention Opportunities
Annual Waste Reduction
Pollution Prevention Opportunity
Waste Stream Reduced
Quantity
(Ib/yr)
Percent
Net Annual Implementation Simple
Savings Cost Payback (yr)
Replace TCE solvent extraction operation
with supercritical carbon dioxide extrac-
tion. Implementation of this measure
would eliminate all TCE-related wastes
and waste management operations.
Oil recovery using supercritical CC>2
extraction should be easier than the
current method. Further investigation
and testing is necessary in order to
determine if this option is technically
feasible.
Replace the currently used single-use
absorbents with wringable, reusable
absorbents for clean-up of spills and
leaks. The oil/TCE recovered by the
wringer could be processed onsite in
the recovery system. A small quantity
of wringable pads will be disposed of
periodically, as the pads lose their
effectiveness.
Reduce fugitive emissions and leaks
and spills of TCE from pumps by up-
grading the driveshaft seals on the
current pumps using magnetic fluid
seals. The proposed seals would
act as backup for the existing me-
chanical seals; the space between
the seals can be vented to the on-
site carbon adsorption system for
TCE recovery.
Give wooden pallets received with
incoming shipments to a local re-
cycler or rebuilder instead of shipp-
ing them to the landfill.
Give empty non-plastic-lined bags
from raw material shipments to a local
recycler instead of shipping them to
the landfill.
Ship oversize silica currently
disposed of in a landfill to a cement
manufacturer for use as an additive.
Transfer clean wasted fiberglass
paper to a supplier or recycler in-
stead of shipping it to a landfill.
TCE fugitive emissions
TCE stack emissions
TCE containing wastes
211,000
266,500
87,000
100
100
100
$365,000 $1,500,000
Spill absorbents
7,620
100
21,400
990
0.1
TCE fugitive emissions 95,000
Spill absorbents 640
Fiberglass paper absorbent 1790
45
8
20
43,850
248,000
5.7
Pallets
Paper bags
Oversize silica
Fiberglass paper
200
200
10,300
1,760
immediate
immediate
immediate
immediate
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United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/011
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