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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 manufacturers Waste Minimization Assessment Centers (WMACs) were

established at selected universities and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention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 produced. Processes used in polyethylene/silica sheet production

include blending, extruding, extraction, drying, and slitting. Mixing, 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 management cost, and that waste reduction could result from using

wringable, reusable absorbents.

This Research Brief was developed by the principal investigators and EPA’s National Risk Management Research Laboratory, 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.

Introduction

The amount of waste generated by industrial plants has become 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 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.

Pollution Prevention Assessment for a Manufacturer of

Automotive Battery Separators

ENVIRONMENTAL

RESEARCH BRIEF

Marvin Fleischman*, Patrick Schmidt*, David Roberts*,

and Gwen P. Looby**

* University of Louisville, Department of Chemical Engineering.

** University City Science Center, Philadelphia, PA.

E AP

United States

Environmental Protection

Agency

National Risk Management

Research Laboratory

Cincinnati, OH 45268

Research and Development EPA/600/S-95/011 August 1995
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Methodology of Assessments

The pollution prevention opportunity assessments require several site visits to each client served. In general, the WMACs

follow the procedures outlined in the EPA Waste Minimization

Opportunity Assessment Manual (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 supporting technological and economic information is developed. Finally, 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 separators. 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 polyethylene, 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 ingredients 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 separately 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 extensively onsite.

• Equipment to regrind blacksheet trim for reuse in the polyethylene/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 opportunities, 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 prevention 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 difficulty, or a projected lengthy payback. Since these approaches

to pollution prevention may, however, increase in attractive-
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Figure 1. Abbreviated process flow diagram for polyethylene/silica sheet production.

Slitting Winding

Sheet

Shipped

Drying Inspection

Addition of

wetting

agent

Drying

Miscella

recovery Miscella

Extraction

TCE

TCE

Oil

Mixing Extruding Calendering Mix tower

screening

Polyethylene,

Silica Oil
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Figure 2. Abbreviated process flow diagram for vinyl rib separator production.

Latex,

Silane,

Water,

Other

ingredients

Latex

mixing Dip tank Roller

Diethylhexyl phthalate,

PVC,

Mineral spirits,

Other ingredients

Plastisol

mixing

Rib die

bar

Packaging

Finished

separators

shipped to

customers

Slitting/

cutting Drying
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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 order to eliminate the generation of wastewater containing

TCE.

• Recover dioctyl phthalate from stack gases prior to incineration by carbon bed adsorption and condensation.

• Reuse empty Gaylords internally and/or substitute shipments 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. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.
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Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Stream Generated Source of Waste Waste Management Method Generated (lb/yr) Management Cost

Oversize silica Screening of raw material Landfilled as special waste 73,600 $44,9401

Bad batches and leaks Mixing of recycled oil with polyethylene and silica Shipped offsite for disposal as 33,840 76,0001

hazardous waste

Vacuum pump liquid Extruder knockout drum (disposed of when Shipped offsite for disposal as 18,280 18,9001

centrifuge is not operating) hazardous waste

Centrifuge sludge Extruder knockout drum Shipped offsite for disposal as 2,990 5,000

hazardous waste

Waste black and gray sheet Start-up of polyethylene/silica sheet production Landfilled as special waste 4,684,000 2,856,8001

and trimming of sheet

Solid wastes (e.g., filter Extraction, extrusion, and oil/TCE recovery Shipped offsite for disposal as 1,250 1,7501

cartridges) hazardous waste

Spill absorbents Clean-up of spills from extractor and oil/TCE Shipped offsite for disposal as 7,620 22,2901

recovery hazardous waste

Fiberglass paper used as Clean-up of spills from extractor and oil/TCE Shipped offsite for disposal as 8,930 96,9301

absorbent recovery hazardous waste

Paper filters Carbon adsorption system for vented process Shipped offsite for disposal as 80 3501

gases hazardous waste

TCE emissions Fugitive emissions Evaporated to plant air 211,000 52,9001

TCE emissions Stack emissions Vented from plant 266,500 66,6001

Skimmed waste oils Sump in conjunction with floor drains Shipped offsite for disposal 9,060 8,900

 as hazardous waste

Sump sludge Sump in conjunction with floor drains Shipped offsite for disposal as 4,910 8,300

hazardous waste

WWTP sludge Onsite WWTP Accumulating onsite 208,100 —-2

Foamed plastisol (unneeded Vinyl rib production line Shipped offsite for disposal as

or unacceptable) hazardous waste 660 1,6701

Nonfoamed plastisol Vinyl rib production line Shipped offsite for disposal as

hazardous waste 31,110 78,1401

Iron scrap Worn out belts from drying ovens Sold to scrap recycler 17,900 -1,360

(revenue received)

Stainless steel scrap Worn out belts from drying ovens Sold to scrap recycler 16,900 -1,630

(revenue received)

Diethylhexyl phthalate emissions Stack emissions Vented from plant 106,800 53,4001

Phenol and formaldehyde Stack emissions Vented from plant 6,900 —-

emissions

Unusable fiberglass paper Vinyl rib production line Compacted; landfilled 196,000 3,960

Latex sludge Onsite WWTP Landfilled 280,000 100,000

Process wastewater Various Treated onsite; sewered 124,000,000 31,410

Process wastewater s-line Treated onsite; sewered 87,736,000

Sanitary wastewater Sewered 8,263,000

Blowdown Cooling towers Sewered 103,283,000

Pallets Raw material delivery Landfilled 20,000 200

Cardboard Raw material delivery Given to recycler 122,000 0

Empty drums Raw material delivery Shipped to reconditioner 9,000 300

Paper bags Raw material delivery Landfilled 20,000 200

Plastic-lined bags Raw material delivery Landfilled 350 10

Spent solvent Parts washer Removed by supplier for offsite 1,890 960

recycling

Gear oil Recycled offsite 6,680 200

1Includes applicable lost raw material value.

2Not yet disposed.
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Table 2. Summary of Recommended Pollution Prevention Opportunities

Annual Waste Reduction

Quantity Net Annual Implementation Simple

Pollution Prevention Opportunity Waste Stream Reduced (lb/yr) Percent Savings Cost Payback (yr)

Replace TCE solvent extraction operation TCE fugitive emissions 211,000 100 $365,000 $1,500,000 4.1

with supercritical carbon dioxide extrac- TCE stack emissions 266,500 100

tion. Implementation of this measure TCE containing wastes 87,000 100

would eliminate all TCE-related wastes

and waste management operations.

Oil recovery using supercritical CO2

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 Spill absorbents 7,620 100 21,400 990 0.1

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 TCE fugitive emissions 95,000 45 43,850 248,000 5.7

and spills of TCE from pumps by up- Spill absorbents 640 8

grading the driveshaft seals on the Fiberglass paper absorbent 1790 20

current pumps using magnetic fluid

seals. The proposed seals would

act as backup for the existing mechanical seals; the space between

the seals can be vented to the onsite carbon adsorption system for

TCE recovery.

Give wooden pallets received with Pallets —- —- 200 0 immediate

incoming shipments to a local recycler or rebuilder instead of shipping them to the landfill.

Give empty non-plastic-lined bags Paper bags —- —- 200 0 immediate

from raw material shipments to a local

recycler instead of shipping them to

the landfill.

Ship oversize silica currently Oversize silica —- —- 10,300 0 immediate

disposed of in a landfill to a cement

manufacturer for use as an additive.

Transfer clean wasted fiberglass Fiberglass paper —- —- 1,760 0 immediate

paper to a supplier or recycler instead of shipping it to a landfill.
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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

EPA/600/S-95/011

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35