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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. 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That document has been superseded by the Facility Pollution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 paints and coatings. Raw materials are received and staged appropriately for batches of product. Processing in this plant includes mixing of raw materials,

filtering, pumping and milling. Additional materials may be

added in letdown tanks prior to product filling, packaging, and

shipping. The team’s findings and recommendations indicated

that the plant generated waste wash water and solvent from

equipment cleaning in large quantities and that significant waste

reduction and cost savings could be achieved by removing

more of the product from the letdown tanks prior to cleaning

them.

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 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.

Methodology of Assessments

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

Pollution Prevention Assessment for a Manufacturer of

Paints and Coatings

United States

Environmental Protection

Agency

National Risk Management

Research Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-95/009 August 1995

Marvin Fleischman*, Patrick A. Schmidt*,

and Gwen P. Looby**

E AP

 *University of Louisville, Department of Chemical Engineering.

 **University City Science Center, Philadelphia, PA.
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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

The plant manufactures oil- and water-based interior and exterior architectural coatings, coatings for metal surfaces, and

other specialty coatings. It operates 4,125 hr/yr to produce

over 6 million gal/yr of product.

Manufacturing Process

Bulk liquids, including solvents, liquid resins, glycols, and powders, including pigment, are received and stored. As customer

orders are received and scheduled for production, the required

raw materials are collected according to a specific batch recipe

and staged.

Appropriate raw materials are mixed in the tank. The proper

particle size distribution in the final product is achieved using

either specially equipped dispersion tanks or mixing tanks in

conjunction with a milling process afterward. Once the proper

particle size is obtained in the batch, it is fed to a letdown tank

directly or indirectly through a filter, a pump, a mill, or any

combination of these pieces of equipment.

Once a batch from a dispersion tank is transferred to a letdown

tank, additional solvent and rheological additives are added in

order to adjust the batch’s viscosity. Additives for other desirable product properties are also added in the letdown tank.

After the batch is approved by the quality control department, it

is sent to a filling machine.

Large batches are packaged automatically and small batches

are packaged semi-automatically or manually.

Lower quality paint is manufactured using waste products such

as quality control samples and customer returns. This paint is

used when color matches are not critical or when the presence

of metal-containing compounds does not pose a significant

hazard.

An abbreviated process flow diagram for this plant is shown in

Figure 1.

Existing Waste Management Practices

This plant already has taken the following steps to manage and

minimize its wastes:

• Most metal drums are returned to the supplier, sent to be

reconditioned, or used for hazardous waste disposal.

• Pallets from raw material shipments are reused, returned to

the supplier, or given away.

• Bulk liquid storage tanks are equipped with conservation

vents.

• Process equipment is dedicated to either oil-based or waterbased production in order to minimize cleaning waste.

• Long runs and light-to-dark runs are scheduled sequentially

to minimize cleaning waste.

• Mercury-containing paint has been phased out of production.

• Caustic and alkaline cleaners are not used by the facility.

• Pigment dust from three of the baghouses is returned to the

appropriate batch.

• Buckets are reused as long as possible in the prebatching

area.

• Equipment is cleaned immediately after a batch is finished in

order to reduce the amount of water or solvent required.

Some of the wash solvent and water is incorporated into the

batch being made.

• Foam plugs or “pigs” are used for cleaning some of the lines

and recovering product.

• Cardboard layers separating the cans used for the product

packaging are used as spill absorbents, reducing the quantity of absorbents purchased. A portion of the separators is

returned to the supplier for reuse.

• Oil-based and water-based wastes are segregated.

• Reusable wire strainers are used for filtration instead of

cartridge filters.

• Several potential waste streams are reused in formulating

lower-quality paint.

• Damaged dry metal product cans are recycled offsite.

• Waste cardboard and office paper are recycled offsite.

• Styrofoam “popcorn” received with shipments is reused in

outgoing shipments.

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 annual 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 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 opportunity, in most cases, result from reductions in raw materials and

waste treatment and disposal costs. 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

are for each pollution prevention opportunity independently and
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Figure 1. Abbreviated process flow diagram for paint formulation.

Incoming materials

Receiving

Prebatching

Mixing

Filtering

Letdown

Filtering

Bulk storage

Milling Mill tank

Automatic

filling

Semi-automatic

filling

Manual

filling

Products shipped to customers
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Table 1. Summary of Current Waste Generation

Waste Management Annual Quantity Annual Waste

Waste Generated Source of Waste Method Generated (lb/yr) Management Cost1

Pigment bags and residual powder Raw materials handling Compacted; shipped 507,000 $225,000

offsite to landfill

Fiber drums, paper bags, and buckets Raw materials handling Shipped offsite to landfill 5,100 3,810

Metal drums Raw material handling Shipped offsite for reconditioning 683,000 125,000

Solvent drum heels Raw material handling Shipped offsite 272,000 42,600

(lost with drums shipped offsite)

Dispersed pigment dust Raw material handling Collected in baghouses; 750 770

shipped offsite to landfill

Evaporated solvent Raw material handling Evaporated to plant air and 2,000 300

atmosphere

Packaging/shipping wastes Received with raw materials Shipped offsite to landfill 55,000 1,160

(shrink wrap and binding straps)

Pallets Received with raw materials Reused onsite, returned to 1,400,000 -

supplier, or given away

Cardboard Received with raw materials Shipped offsite for recycling n/a n/a

Raw material samples Quality control sampling Blended into maintenance paint 14,400 -

Raw material sample cans Quality control sampling Shipped offsite to landfill 1,600 30

Drip bucket liquid Leaks from product formulation Blended into maintenance paint 2,500 -

Drip buckets Used to contain leaks Shipped offsite to landfill 100 negligible

Wash water/paint solids Equipment cleaning for Sewered 11,300,000 358,320

water-based paint

Supernatant from metal-containing Equipment cleaning for metal- Decanted from sludge; sewered 280,000 8,680

wash water containing water-based paint

Sludge from metal-containing Equipment cleaning for metal- Blended into fence paint 271,800 -

wash water containing water-based paint

Spent wash solvent/paint solids Equipment cleaning for Shipped offsite to be 967,000 2,877,000

oil-based paints used as fuel

Solvent-based filter/strainer solids Filtering during solvent-based Shipped offsite as hazardous 12,000 20,300

paint production waste; landfilled or burned

Water-based filter/strainer solids Filtering during water-based Shipped offsite to landfill 37,200 780

paint production

Clean-up waste (rags, floor Clean-up Shipped offsite to landfill 16,300 340

sweepings, pigment dust)

Damaged metal containers Product handling Shipped offsite to landfill 513,000 353,820

or for recycling

Damaged plastic containers Product handling Shipped offsite to landfill 184,000 143,880

Damaged cardboard boxes Product packaging Shipped offsite for recycling 77,000 -

Damaged packaging material Product packaging Shipped offsite to landfill 40,400 850

Miscellaneous wastewater Various sources Sewered 20,800,000 5,140

1Includes waste treatment, disposal, and handling costs, and applicable lost raw material value.
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do not reflect duplication of savings that would result when the

opportunities are implemented in a package.

Additional Recommendations

In addition to the opportunities analyzed by the WMAC team,

several additional measures were considered. These measures were not completely analyzed because of insufficient

data, minimal savings, implementation difficulty, or a projected

lengthy payback. Since one or more of these approaches to

pollution prevention may, however, increase in attractiveness

with changing conditions in the plant, they were brought to the

plant’s attention for future consideration.

The measures considered include the following:

• Obtain raw materials in dissolvable bags to reduce packaging wastes.

• Use pastes or slurries instead of powdered pigment to reduce

the quantity of waste paper bags generated.

• Purchase raw materials in reusable containers.

• Reuse “empty” powder bags in prebatching instead of shipping them to landfill.

• Find an appropriate method of recycling empty paper bags.

• Reduce pigment dust losses by installing deflector curtains

on the tank lids attached to the mixers.

• Use currently discarded pigment dust in fence paint when

possible.

• Recover solvent losses by using chillers, adsorbers, or

compressors on the bulk storage tank vents.

• Install and use lids on process tanks to prevent evaporative

losses.

• Replace splash filling of tanks with submerged filling.

• Install high-pressure low-volume nozzles to reduce the amount

of cleaning water used.

• Use hydrocyclone to remove suspended solids from wash

water thereby reducing water quality surcharges.

• Use countercurrent solvent rinsing of tanks for cleaning.

• Investigate the possibility of sending damaged labels back to

the supplier for recycling.

This research brief summarizes a part of the work done under

Cooperative Agreement No. CR-814093 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 2. Summary of Recommended Pollution Prevention Opportunities

Annual Waste Reduction

Net Annual Implementation Simple

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

Recover additional pigment raw material from paper Pigment bags and 205,000 40 $190,000 0 immediate

bags by increased shaking of the bags over the tanks. residual powder

Currently, a considerable amount of unused pigment is

sent to the landfill along with the “empty” paper bags.

Coat the letdown tanks with a lining that will cause the Wash water/paint solids 2,532,000 22 169,320 281,6001 1.7

product to bead and drain more effectively, thereby Spent wash solvent/ 218,000 22

reducing the amount of product wasted and the paint solids

quantity of water or solvent used during equipment

cleaning.

Use rubber squeegees to remove product from the Wash water/paint solids 2,532,000 22 154,920 120 immediate

sides of the letdown tanks before using liquid Spent wash solvent/ 218,000 22

cleaning agents. paint solids

Install drain valves at the lowest points of nondraining Wash water/paint solids 900,140 8 26,970 2,000 0.1

pipes between the letdown tanks and the filling tanks, Spent wash solvent/ 32,020 3

thereby reducing the amount of product wasted and paint solids

the quantity of water or solvent used during equipment cleaning.

Store spent wash solvent/paint waste in containers Spent wash solvent/ 871,000 90 358,310 3,700 immediate

and reuse in the formulation of future product batches. paint solids

Request that suppliers of raw materials use specially Solvent drum heels 269,610 99 42,240 0 immediate

designed drums that drain more completely in order

to reduce the plant’s drum heel losses.

Allow spent wash solvent/paint waste to settle for Spent wash solvent/

one day. Decant supernatant and reuse in cleaning paint solids 193,000 20 28,500 0 immediate

operations.

Install an onsite solvent recovery unit to recover Spent wash solvent/ 537,000 55 80,460 56,000 0.7

spent wash solvent for reuse. paint solids

Install an ultrafiltration system to recover some of the Spent wash solvent/ 415,000 43 79,500 27,000 0.4

spent wash solvent for reuse. paint solids

Send waste paint, powder dust, and solvent-based Solvent-based filter/

filter cake that is not contaminated with dirt to a strainer solids 6,600 55 6,000 0 immediate

paint recovery plant to be reprocessed instead of

shipping it to a hazardous waste facility for landfilling or burning.

Reduce losses of pigment used as a raw material. Pigment bags and

Install bulk storage silos for the pigments used in residual powder 101,000 20 47,900 115,000 2.4

largest quantities. Use a pneumatic conveying

system to deliver the pigments to the mixing or

letdown tanks.

1 It is possible that a less expensive coating method can be used. This implementation cost estimate is based upon vendor information for an epoxy resin coating. Testing should be done in order to

identify a suitable coating material.
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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-95/009

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35