vvEPA
United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/060 October 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Reduction Activities and Options for a
Manufacturer of Plastic Containers by Injection Molding
Hanna Saqa and Daniel J. Watts*
Abstract
The U.S. Environmental Protection Agency (EPA) funded a
project with the New Jersey Department of Environmental
Protection and Energy (NJDEPE) to assist in conducting waste
minimization assessments at 30 small- to medium-sized busi-
nesses in the state of New Jersey. One of the sites selected
was a facility that manufactures plastic containers by injection
molding. The manufacturing process involves melting of a
plastic resin and injection of the melt into molds in the shape of
the container to be manufactured. The cooled and solidified
container is removed from the mold, the mold is cleaned with
solvent when required and the injection process is repeated. A
portion of the containers are also made by blow molding which
involves use of compressed gas to move the resin melt onto
the walls of the mold. The rest of the operation is similar. A site
visit was made in 1990 during which several opportunities for
waste minimization were identified. Options identified for pollu-
tion prevention include change in equipment to eliminate use of
hydraulic oil, change in mold cleaning procedures, and modifi-
cations to metal machining operations. It should be pointed out
that this facility had already initiated an aggressive pollution
prevention program. Implementation of the identified waste
minimization opportunities was not part of the program. Percent
waste reduction, net annual savings, implementation costs and
payback periods were estimated.
This Research Brief was developed by the Principal Investiga-
tors and EPA's Risk Reduction Engineering Laboratory in Cin-
cinnati, OH, to announce key findings of this completed as-
sessment.
* New Jersey Institute of Technology, Newark, NJ 07102
Introduction
The environmental issues facing industry today have expanded
considerably beyond traditional concerns. Wastewater, air
emissions, potential soil and groundwater contamination, solid
waste disposal, and employee health and safety have become
increasingly important concerns. The management and dis-
posal of hazardous substances, including both process-related
wastes and residues from waste treatment, receive significant
attention because of regulation and economics.
As environmental issues have become more complex, the
strategies for waste management and control have become
more systematic and integrated. The positive role of waste
minimization and pollution prevention within industrial operations
at each stage of product life is recognized throughout the
world. An ideal goal is to manufacture products while generat-
ing the least amount of waste possible.
The Hazardous Waste Advisement Program (HWAP) of the
Division of Hazardous Waste Management, NJDEPE, is pursu-
ing the goals of waste minimization awareness and program
implementation in the state. HWAP, with the help of an EPA
grant from the Risk Reduction Engineering Laboratory, con-
ducted an Assessment of Reduction and Recycling Opportuni-
ties for Hazardous Waste (ARROW) project. ARROW was
designed to assess waste minimization potential across a
broad range of New Jersey industries. The project targeted 30
sites to perform waste minimization assessments following the
approach outlined in EPA's Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003). Under contract to
NJDEPE, the Hazardous Substance Management Research
Center at the New Jersey Institute of Technology (NJIT) assisted
in conducting the assessments. This research brief presents
an assessment of the manufacturing of plastic containers by
injection molding (1 of the 30 assessments performed) and
Printed on Recycled Paper
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provides recommendations for waste minimization options re-
sulting from the assessment.
Methodology of Assessments
The assessment process was coordinated by a team of techni-
cal staff from NJIT with experience in process operations,
basic chemistry, and environmental concerns and needs. Be-
cause the EPA waste minimization manual is designed to be
primarily applied by the inhouse staff of the facility, the degree
of involvement of the NJIT team varied according to the ease
with which the facility staff could apply the manual. In some
cases, NJITs role was to provide advice. In others, NJIT
conducted essentially the entire evaluation.
The goal of the project was to encourage participation in the
assessment process by management and staff at the facility.
To do this, the participants were encouraged to proceed through
the organizational steps outlined in the manual. These steps
can be summarized as follows:
• Obtaining corporate commitment to a waste minimization
initiative
• Organizing a task force or similar group to carry out the
assessment
• Developing a policy statement regarding waste minimiza-
tion for issuance by corporate management
• Establishing tentative waste reduction goals to be achieved
by the program
• Identifying waste-generating sites and processes
• Conducting a detailed site inspection
• Developing a list of options which may lead to the waste
reduction goal
• Formally analyzing the feasibility of the various options
• Measuring the effectiveness of the options and continuing
the assessment.
Not every facility was able to follow these steps as presented.
In each case, however, the identification of waste-generating
sites and processes, detailed site inspections, and development
of options was carried out. Frequently, it was necessary for a
high degree of involvement by NJIT to accomplish these steps.
Two common reasons for needing outside participation were a
shortage of technical staff within the company and a need to
develop an agenda for technical action before corporate com-
mitment and policy statements could be obtained.
It was not a goal of the ARROW project to participate in the
feasibility analysis or implementation steps. However, NJIT
offered to provide advice for feasibility analysis if requested.
In each case, the NJIT team made several site visits to the
facility. Initially, visits were made to explain the EPA manual
and to encourage the facility through the organizational stages.
If delays and complications developed, the team offered assis-
tance in the technical review, inspections, and option develop-
ment.
No sampling or laboratory analysis was undertaken as part of
these assessments.
Facility Background
The facility is a manufacturer of approximately 1.5 million
plastic containers every day. The facility melts pellets of plastic
resin and using either injection molding or blow molding pro-
duces the containers. The containers are typically sold to other
manufacturers for use in packaging their products.
The facility is located in a suburban area and employs about
320 people. This facility has already undertaken an aggressive
pollution prevention and energy conservation program.
Manufacturing Processes
The production of the plastic containers requires melting of the
starting plastic resin which is purchased. For injection molding,
mechanical force, presently hydraulically produced, is used to
push the melt into molds in the shape desired for the product.
Blow molding uses compressed gas, frequently compressed
air, to move the melt onto the walls of the mold. The type of
mold is different for the two procedures. When necessary, the
molds are cleaned with a solvent, currently 1,1,1-trichloroethane,
to assure ease of movement of the melt and to facilitate good
surface characteristics in the molded product.
The facility also makes and maintains the molds themselves
which entails some metal machining.
Existing Waste Management Activities
The company has already instituted an aggressive program of
pollution prevention and energy conservation. Many changes
in practice have either been made or are planned in the near
future.
The process for producing the plastic containers produces
relatively little waste or pollution. The resin is purchased and is
completely used. Occasionally, a color change may result in a
few containers which are off-specification or incomplete mold-
ing occurs resulting in a poor quality product. In these situations,
the flawed containers can be ground and used as feed stock
for later production runs. On the rare occasions where such
reuse is not possible, the material is handled as nonhazardous
industrial waste. The hydraulics of the injection molding pro-
cess leak and the resulting waste oil becomes contaminated
with cooling water, metal fragments and dirt. Approximately
26,000 gal of such waste is generated annually. Presently the
stream is passed through a separator and the water is sent to
the POTW for treatment, while the oil is shipped offsite as a
hazardous waste. Approximately 13,000 gal of such oil is
produced annually.
The molds and the lines through which the melt passes are
cleaned with solvent, currently 1,1,1-trichloroethane. Current
practice is to undertake this cleaning judiciously on an as
needed basis. Minimum volume of solvent is used. This is a
change from past practice which required use of large volumes
of solvent at regular intervals. This type of change has signifi-
cantly reduced solvent usage. Currently 2300 Ib of the solvent
is sent for disposal offsite annually.
The mold machining operation uses a water-based vegetable
oil mixture as a metal-working fluid for lubricating and cooling
during machining operations. This fluid is recirculated and is
estimated to have a life span of six months. Approximately
1200 gal of this material are produced each year and are
disposed of offsite as hazardous waste.
The appearance of the facility shows that the management and
employees recognize the waste reduction value of ease of
movement of raw materials, good maintenance of equipment,
and spill control and spill prevention activities.
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Waste Minimization Opportunities
The type of waste currently generated by the facility, the
source of the waste, the quantity of the waste and the annual
treatment and disposal costs are given in Table 1.
Table 2 shows the opportunities for waste minimization recom-
mended for the facility. The type of waste, the minimization
opportunity, the possible waste reduction and associated sav-
ings, and the implementation cost along with the payback time
are given in the table. The quantities of waste currently gener-
ated at the facility and possible waste reduction depend on the
level of activity of the facility.
It should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with waste treatment and disposal. It should also be
noted that the savings given for each opportunity reflect the
savings achievable when implementing each waste minimization
opportunity independently and do not reflect duplication of
savings that would result when the opportunities are imple-
mented in a package. Also, no equipment depreciation is
factored into the calculations.
Regulatory Implications
* Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
There are no significant regulatory implications to pollution
prevention initiatives at this facility. The management of the
facility, without regulatory pressure, has moved strongly in the
area of pollution prevention and energy conservation because
of economic considerations and for personal environmental
concerns. However, international agreements addressing ozone
depletion and global warming may further inhibit the use of
1,1,1-trichloroethane. Also, 1,1,1-trichloroethane is 1 of 17
chemicals which EPA has targeted under a voluntary program
with industry (the 33/50 Industrial Toxics Program) to reduce
releases to the environment. This program may lead to re-
duced use of the solvent.
This Research Brief summarizes a part of the work done under
cooperative Agreement No. CR-815165 by the New Jersey
Institute of Technology under the sponsorship of the New
Jersey Department of Environmental Protection and Energy
and the U.S. Environmental Protection Agency. The EPA Project
Officer was Mary Ann Curran. She can be reached at:
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Table 1. Summary of Current Waste Generation
Waste Generated Source of Waste
Waste Hydraulic Oil
Waste Machining Oil
Annual Quantity
Generated
Annual Waste
Management Costs
Leaks from the hydraulic
system on the injection
molding machines
Mold machining lubrication
and cooling after reaching
the end of its useful life
13,000 gal
1,200 gal
Spent 1,1,1-Trichloroethane Cleaning of molds and injection 2,300 Ib
lines
$6,500
4,500
1,500
•fru.S. GOVERNMENT PRINTING OFFICE WM - 5SO-067/MI45
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Table 2. Summary of Recommanded Waste Minimization Opportunities
Waste Stream
Reduced
Waste Hydraulic Oil
Waste Machining Oil
Mold Cleaning Solvent
Minimization Opportunity
Filtration or centrifugation
of oil allowing reuse
(Potential use of this option
will require some investigation
of whether or not the reclaimed
oil will have the necessary
performance characteristics
as a hydraulic fluid.)
Find and repair leaks more
expeditiously
Replace hydraulic molding
machines with direct electrical
drive
(This option had been selected
by the company prior to the
assessment. While exact replacement
costs are not known, they are substantial.
Although there are savings of about
75% on electrical costs with the new
equipment, the capital costs suggest
that a change of this magnitude occur
primarily when it is time to change
equipment anyway.)
Prolong useful life by
cleaning and biocide addition
Change to biodegradable terpene-
based solvent
Annual Waste Reduction
Quantity Percent
Net Implementation Payback
Annual Savings Cost Years'
6,500 gal
50
$13,000
$10,000
0.8
1,300 gal
13,000 gal
10
100
2,600
23,450
immed.
substantial
capital
investment
400 gal
33
1,670
5,000
2,300 Ib 100
(Obviously, a different
waste stream will be
generated and will present
reduced levels of environmental
risk. Without a comparison
of the relative effectiveness
of the two solvent system
it is difficult to estimate
the volume of waste from this
new approach. It is possible
that this material can be recycled.
If we assume that the volumes are
the same and that the purchase
prices are the same we can estimate
a savings in treatment cost of approximately
$1000 per year.)
* Savings result from reduced raw material and treatment and disposal costs when implementing each minimization opportunity independently.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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