$EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/M-91/023 July 1991
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Paint Manufacturing Plant
F. William Kirsch and Gwen P. Looby*
Abstract
The U.S. Environmental Protection Agency (EPA) has
funded a pilot project to assist small- and medium- size manu-
facturers who want to minimize their generation of hazardous
waste but 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). The WMAC team at Colorado State Univer-
sity inspected a plant blending and mixing raw materials into
paints, coatings, stains, and surface-treating products. For
water-based paints, water, latex, resins, extenders, and pig-
ments are mixed and blended. For oil-based paints, solvents
replace water and latex, and plasticizers, tints, and thinners are
also added. These batches are then transferred to let-down
tanks where additional ingredients are incorporated. After
testing, the paints meeting specifications are filtered, canoed,
labeled, and packaged for shipping. Hazardous wastes result
when the mixing vessels, let-down tanks, and lines are cleaned.
For example, cleaning a let-down tank after a water-based
paint has been blended requires about 35 gal water; after a
400-gal tank for a solvent-based paint, about 5 gal mineral
spirits. Because the spirits are sent off-site for recovery, most
of the waste results from cleaning up after mixing water-based
paint. This waste is hazardous because it contains mercury
used as the bactericide. Although the plant reuses rinse water,
recovers solvent, and has adopted other measures to reduce
waste, the team report, detailing findings and recommenda-
tions, suggested that additional savings could result from
installing a pipe cleaning system, using a solvent-recovery
system based on distillation, and substituting an organic mate-
rial for the mercury bactericide.
This Research Brief was developed by the principal inves-
tigators and EPA's Risk Reduction Engineering Laboratory,
Cincinnati, OH, to announce key findings of an ongoing re-
search project that is fully documented in a separate report of
the same title available from the authors.
Introduction
The amount of hazardous waste generated by industrial
plants has become an increasingly costly problem for manufac-
turers and an additional stress on the environment. One solu-
tion to the problem of hazardous 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 manu-
facturers who want to minimize their formation of hazardous
waste but lack the inhouse expertise to do so. Under agreement
with EPA's Risk Reduction Engineering Laboratory, the Sci-
ence Center has established three WMACs. This assessment
was done by engineering faculty and students at Colorado
State University's (Fort Collins) WMAC. The assessment teams
have considerable direct experience with process operations in
manufacturing plants and also have the knowledge and skills
needed to minimize hazardous waste generation.
•University City Science Center, Philadelphia, PA 19104
Printed on Recycled Paper
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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 an-
nual sales not exceeding $50 million, employ no more than 500
persons, and lack inhouse expertise in waste minimization.
The potential benefits of the pilot project include minimiza-
tion of the amount of waste generated by manufacturers, re-
duced waste treatment and disposal costs for participating
plants, valuable experience for graduate and undergraduate
students who participate in the program, and a cleaner environ-
ment without more regulations and higher costs for manufactur-
ers.
Methodology of Assessments
The waste minimization 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 locates the sources of hazardous 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 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 and Operations
This plant produces paints, coatings, stains, and surface-
treating products at an overall rate of about 1.1 million gal/yr for
regional distribution on a schedule of 2080 hr/yr for 52 wk. Its
operations primarily involve blending and mixing of raw materi-
als, followed by product testing and packaging and by cleaning
of vessels and lines. Color separation in the product is obviously
important, and each lot must meet a variety of other customer
specifications.
Individual bts of water-based and solvent-based paints are
mixed in a variety of tanks from 200- to 1000-gal capacity. For
this initial step, ingredients for water-based paints include water,
latex, resins, extenders, and dispersed pigments. For solvent-
based paints, the materials are generally similar in type, but
obviously solvent replaces water and latex. Other new ingredi-
ents include plasticizers, tints, and thinners.
After batches are made up, they are transferred to so-called
let-down tanks, where additional water (or solvent), resins,
preservatives, anti-foaming agents, thinners, and bactericides
are added. Batch testing encompasses at least color, viscosity,
and gloss, and those tots that meet specifications are filtered
and charged to cans for labeling, packaging, and shipping.
Waste Generation and Present Waste Minimization
The principal waste streams are the result of equipment
cleaning, especially from water-based paints. For example,
rinsing the let-down tanks ordinarily requires about 35 gal of
rinse water, but that amount increases to 53 gal if light paint is
to be blended after dark paint. The hazardous nature of water
rinses results from the mercury used as a bactericide in the
paint.
In some instances, rinse water from the mixing tanks is held
in 500-gal tanks and used in the let-down tanks (instead of fresh
water) to formulate future batches of water-based paint. The
rinses are separated according to the color intensity of paint in
the tanks from which they were derived. For example, rinses
from white paint formulation amount to about 70% of the total,
and they are invariably used again.
Waste rinses not used again are piped to holding and
flocculatton tanks; alum is added to lower the pH, flocculant is
added to precipitate some solids, and supernatant liquid is
removed for reuse in other paint formulations.
Tanks used for solvent-based paints are rinsed with mineral
spirits at a rate of about 5 gal/400-gal tank. These washings are
sent off-site for recovery, followed by recycling or sale as fuel.
In addition to reusing rinse water and recovering solvent,
this plant has adopted the following measures to reduce waste
generation:
cleaning equipment before the paint dries and
hardens;
eliminating hazardous materials, except for
mercury in the bactericide added to outdoor water-
based paint;
• avoiding hazardous container waste by purchasing
the bactericide in water-soluble bags that dissolve
during paint formulation;
• scheduling batch formulations so that light colored
paints precede dark ones and thereby reduce the
total volume of rinses;
reducing the inventory of raw materials to avoid
degradation and spoilage and to ensure a high-
quality product that can be sold; and
• using bag filters to collect dust.
Table 1 summarizes the principal sources of waste, their
amounts, and the associated costs.
Waste Minimization Opportunities
Table 2 offers a brief description of current plant practice,
the recommended waste minimization opportunity, and savings
and cost data. Considered individually, the three recommended
WMOs could save over $22,000/yr, which represents about
25% of current waste management costs. Each has a simple
payback time less than 1 yr.
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 Brian A.
Westfall.
The EPA contact, Emma L. George, can be reached at:
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Table 1. Summary of Currant Waata Generation
Source of Waste Hazardous Waste Generated
Annual Quantify Annual Waste Management Costs
Generated Treatment Disposal
Equipment cleaning by water
washing
Equipment cleaning by solvent
washing
Mercury water and paint
Mineral spirits
26,700 gal
27,200 gal
$3,740
$48,040'
37,080'
'Off-site
Table 2. Summary of Recommended Waste Minimization Opportunities
Present Practice
Proposed Action
Waste Reduction and
Associated Savings
Water rinses remove paint from tanks
and pipes
About 15 gal solvent per batch of paint
is drummed and sent off-site for
disposal.
A bactericide containing mercury is
being used in water-based paints.
Install a pipe-cleaning system
consisting of 3 different-sized foam
plugs or "pigs" to be sent throughout
the pipes by compressed air. Paint is
thus forced from the lines and to the
canning line filter. The use of water
and amount of waste are lower. (This
WMO is applicable to nonwhite paints.)
Use a solvent recovery system based
on distillation, and ship the small
amount of remaining solid to a
hazardous waste disposal site.
Eliminate the bactericide from water-
based interior paints and substitute
an organic material. (This WMO is
applicable to nonwhite paints.)
There is no cost difference between
these additives.
Waste reduction = 1,780 gal/yr
Cost reduction = $11,110/yr
Implementation cost = $1,600
Simple payback * 2 mo
Waste reduction « 3,300 gal/yr
Cost reduction = $5,420/yr
Implementation cost * $4,950
Simple payback = 11 mo
Waste reduction = 3,100 gal/yr
Cost reduction = $5,580/yr
Implementation cost = none
Simple payback is immediate.
£ll.S. GOVERNMENT PRINTING OFFICE: t994 • 5S4MK7/«OI70
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United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
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EPA/600/M-91/023
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