United States
Environmental Protection
Agency

Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268

Research and Development

EPA/600/S-94/017 _ September 1994

EPA

ENVIRONMENTAL

RESEARCH BRIEF

Waste Minimization Assessment for a
Manufacturer of Caulk

Harry W. Edwards", Michael F. Kostrzewa", 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ment has been superseded by the Facility Pollution Prevention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
Colorado State University performed an assessment at a plant
that manufactures latex and acrylic caulk. Raw materials, such
as water, latex, and dry ingredients for latex caulk, and sol-
vents and thermoplastic rubber for acrylic caulk, are blended
and mixed. The resulting product is packaged and shipped.
The assessment team's report, detailing findings and recom-
mendations, indicated that the greatest quantity of waste was
generated by cleaning of equipment. The greatest cost saving
opportunity recommended to the plant involved using a solvent
recovery unit to recover water from waste cleaning water/caulk.
The recovered water can be reused.

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 that is fully documented in a separate report of the
same title available from University City Science Center.

* Colorado State University, Department of Mechanical. 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
Risk Reduction Engineering Laboratory, the Science Center
has established three WMACs. This assessment was done by
engineering faculty and students at Colorado State Universi
(Fort Collins) WMAC. The assessment teams have consider-
able direct experience with process operations in manufactur-
ing 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 $75 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.

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

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in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.

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 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 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 water-based latex caulk and solvent-
based acrylic caulk. It operates approximately 2,800 hr/yr to
produce more than two million pounds of caulk annually.

Manufacturing Process

Latex caulk is produced from a mixture of water, latex, and dry
ingredients. The raw materials are blended together and mixed
for several hours. After mixing, the caulk is pumped into tubes
or larger buckets and packaged in boxes for shipping.

An abbreviated process flow diagram for latex caulk production
is shown in Figure 1.

Acrylic caulk is made from dry ingredients, including a thermo-
plastic rubber, and liquid solvents, including toluene. The raw
materials are blended together and mixed for several hours
under vacuum and heat in an isolated explosion-proof room.
The product is stored in heated silos prior to packaging. During
the packaging process, the caulk is pumped through heated
pipes to the filling machinery. Then the caulk is packaged and
boxed for shipping.

The process for acrylic caulk manufacturing is shown in Figure
2.

Existing Waste Management Practices

This plant already has implemented the following techniques to
manage and minimize its wastes.

+ Aqueous wastes from the latex caulk manufacturing process
are shipped offsite instead of being sewered. The plant has
set zero discharge of aqueous wastes as an eventual goal.

Plant personnel are investigating methods to evaporate
water from the aqueous wastes generated by the latex caulk
manufacturing process.

Plant personnel are investigating alternate production tech-
niques to reduce cleanup between latex caulk color changes,
improve production efficiency, and reduce product inventory.

Citrus-based cleaning agents used instead of mineral spirits
to clean product display tubes.

Solid and
liquid
raw Blending
materials

Mixing

| Equipment
cleaning waste
shipped offsita as non-
hazardous waste
Filling eo
Packaging

Latex caulk to customers

Figure 1. Abbreviated process flow diagram for latex caulk.

Solid and
liquid '
y+ Blending
materials
Spent activated
Mixing |_____» ( carbon regenerated
offsite and retumed
for reuse
Equipment
Fillin cleaning waste
[> \_ shipped offsite as.
hazardous waste
Packaging

Le Acrylic caulk to customers

Figure 2. Abbreviated process flow diagram for acrylic caulk.

+ Mineral spirits are used instead of perchloroethyleneto clean
floors in the acrylic caulk mixing room.

+ Anaggressive data collection and management system has
been implemented to track production and productivity.


Waste Minimization 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 waste minimization that the
WMAC team recommended for the plant. The minimization
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 pos-
sible 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 hazardous 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 the savings achiev-
able when implementing each waste minimization opportunity
independently and do not reflect duplication of savings that
would 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 were consid-
ered. These measures were not analyzed completely because
of insufficient data, implementation difficulty, or a projected
lengthy payback. Since one or more of these approaches to

Table 1. Summary of Current Waste Generation

waste reduction may, however, increase in attractiveness with
changing conditions in the plant, they were brought to the
plant's attention for future consideration.

+ Develop colorizing equipment that can add and mix the
coloring agents with the caulk during packaging, in a just-in-
time fashion. This measure would reduce the amount of
cleaning wastes generated and improve product quality
thereby reducing off-specification products.

Replace toluene and perchloroethylene used in cleaning
operations with safer, less volatile solvents.

Distill the waste cleanup solvent onsite and use the recov-
ered solvent for further cleaning.

Install liquid level detectors and a control system to prevent
‘spills in the mixing room for the acrylic caulk production line.

Replace Stoddard solvent used for equipment and tool
cleaning with a less volatile solvent.

Develop a stronger quality assurance/quality control pro-
gram to inspect raw materials prior to mixing in caulk batches.

Reduce the amount of powdered raw material that is spilled
from the mixing tanks.

Reuse cleaning water in subsequent caulk batches. (Be-
cause of the low water content of caulk, this recommendation
was found to be impractical.)

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.

Annual Quantity Annual Waste
Waste Generated Source of Waste Waste Management Mathod Generated (Ib) Management Cost!
Cleaning water Cleaning of mixing and Shipped offsite for disposal as 59,500 $4,23
filling equipment in latex nonhazardous waste
caulk production line
Mixed solvent wastes Cleaning of acrylic caulk Shipped offsite for recycling 10,700 6,800
production line incineration
Evaporated solvents Cleaning of acrylic caulk Evaporates to plant air 130 0
production line
Waste Stoddard solvent Cleaning of tools and filling Shipped offsite for recovery 1,160 460
‘equipment in acrylic caulk by distillation; reused
production line
Spent activated charcoal Collaction of solvent Shipped offsite for regeneration; 1,050 1,875
emissions from mixing of reused onsite
raw materials in acrylic
caulk production line
Waste Stoddard solvent Cleaning in maintenance Shipped offsite for racovery 1,160 460
area by distillation; reused
Waste soybean oi! Production of an obsolete product Stored onsite pending disposal 6,198 9709

1 Includes waste treatment and disposal costs.
? Nota recurring stream.
3 Estimated cost to dispose of waste.