vvEPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-94/017 September 1994
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ment has been superseded by the Facility Pollution Prevention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 University's
(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
Printed on Recycled Paper
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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 WMAGs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manual {EPAJ625/7-88/QQ3, 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.
Solid and
liquid
raw
materials
Blending
Mixing
Filling
Equipment
cleaning waste
shipped oraste as non
hazardous waste
Packaging
Latex caulk to customers
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 red uce cleanup between latex cau Ik color changes,
improve production efficiency, and reduce product inventory.
* Citrus-based cleaning agent is used instead of mineral spirits
to clean product display tubas.
Figun 1. Abbreviated process flow diagram for latex caulk.
Solid and
liquid
raw
materials
Blending
Mixing
Filling
f Spent activated
carbon regenerated
^offsite and returned
for reuse
Equipment
cleaning waste
shipped offsite as
^hazardous waste_
Packaging
Acrylic caulk to customers
Figun 2. Abbreviated process flow diagram for acrylic caulk.
Mineral spirits are used instead of perchloroethyleneto clean
floors in the acrylic caulk mixing room.
An aggressive data collection and management system has
been implemented to track production and productivity.
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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
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 priorto 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 watercontent 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.
Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Waste Management Method
Annual Quantity Annual Waste
Generated (Ib) Management Cost'
Cleaning water
Mixed solvent wastes
Evaporated solvents
Waste Stoddard solvent
Spent activated charcoal
Waste Stoddard solvent
Waste soybean oil
Cleaning of mixing and
filling equipment in latex
caulk production line
Cleaning of acrylic caulk
production line
Cleaning of acrylic caulk
production line
Cleaning of tools and filling
equipment in acrylic caulk
production line
Collection of solvent
emissions from mixing of
raw materials in acrylic
caulk production line
Cleaning in maintenance
area
Shipped off site for disposal as
nonhazardous waste
Shipped off site for recycling
incineration
Evaporates to plant air
Shipped off site for recovery
by distillation; reused
Shipped off site for regeneration;
reused onsite
Shipped off site for recovery
by distillation; reused
Production of an obsolete product Stored onsite pending disposal
59,500
10,700
130
1,160
1,050
1,160
6,790"
$4,23
6,800
460
1,575
460
9703
' Includes waste treatment and disposal costs.
s Not a recurring stream.
3 Estimated cost to dispose of waste.
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