>A
United States
Environmental Protection
Agency
Risk Reduction Engineering
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/M-90/017 Dec. 1990
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Printed Plastic Bags
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
manufacturers who want to minimize their generation of
hazardous 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). The
WMAC team at the University of Tennessee performed an
assessment at a plant manufacturing printed plastic bags
for snack foods—approximately 1.8 million Ib/yr. Plastic
stock is ink printed and oven cured. To make single-layer
bags, a heat seal process is used, and the bags are then
packaged and shipped. For certain products, a plastic or
metalized film is laminated to the printed plastic film, the
rolls are slit to obtain individual bags, and the bags are
packaged and shipped. The team's report, detailing
findings and recommendations, indicated the most waste
was generated in the lamination process and that the
greatest savings could be obtained by installing an
automatic adhesive/solvent mixing system to reduce (75%)
the waste from the unused metalized film adhesive/solvent
mixture.
This Research Brief was developed by the principal
investigators and EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce key findings of an
University City Science Center, Philadelphia, PA 19104
ongoing research project. For additional information please
contact the authors.
introduction
The amount of hazardous 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 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
manufacturers who want to minimize their generation of
hazardous waste but who lack the inhouse 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 the University of
Tennessee's (Knoxville) 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.
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 a gross annual sales not exceeding $50 million,
employ no more than 500 persons, and lack inhouse
expertise in waste minimization.
Printed on Recycled Paper
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The potential benefits of the pilot project include
minimization of the amount of waste generated by
manufacturers, reduced waste treatment and disposal
costs for participating plants, 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 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 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 produces printed plastic bags for snack foods.
The plant operates 6,240 hr/yr to produce approximately
1.8 million Ib of bags.
Manufacturing Process
This plant prints designs onto plastic roll stock and then
forms the plastic into bags for snack foods and other
consumer products. The raw materials include
polypropylene and metallic films, inks, adhesives, and
solvents. The adhesives include clear film adhesive,
metalized film adhesive, and thermostripping adhesive; the
solvents are ethyl acetate, ink solvent, and thermostripping
solvent.
The following steps are involved in making the bags:
• Ink printing of plastic stock followed by oven curing.
Unused and contaminated ink/solvent mixture is
collected and transferred to the onsite distillation unit.
Waste ink resulting from run color changes is
disposed of offsite as hazardous waste. Solvent vapor
is emitted directly to the outdoor atmosphere by three
of the four curing ovens. In the remaining curing oven,
50% of the vapor is recycled to the oven and the
remaining is ducted to an incinerator outside of the
plant building.
• Single-layer bag-making. A heat seal process is used,
and then these bags are packaged and shipped.
• For certain products, lamination to form multi-layered
plastic rolls followed by oven curing. A clear plastic or
metalized film is laminated to the printed plastic film,
or a special kind of lamination called thermostripping
is done. Unused adhesive/solvent mixture from the
metalized film application are disposed of offsite as
hazardous waste. Half of the stack gases from the
curing oven, which contain evaporated solvents, are
directed back into the oven. The remaining gases are
ducted to the outside incinerator.
• Slitting of laminated plastic rolls to obtain individual
bags. These bags are then packaged and shipped.
Existing Waste Management Practices
• Recovery of ink-contaminated solvent using an onsite
distillation unit. The recovered solvent is reused in the
inking operation or is used for cleanup. Ink still
bottoms are disposed of offsite as hazardous waste.
• Incineration of oven stack vapor in the outdoor gas-
fired incinerator.
Waste Minimization Opportunities
The type of waste currently generated by the plant, 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
that the WMAC team recommended for the plant. The type
of waste, the minimization opportunity, the possible waste
reduction and associated savings, and the implementation
cost along with the payback time are given in the table.
The quantities of hazardous 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
minimization opportunity, in most cases, results 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 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 implemented in a
package.
Additional Recommendations
In addition to the opportunities recommended and
analyzed by the WMAC team, two additional measures
were considered. These measures were not completely
analyzed because of insufficient data or minimal savings
as indicated below. They were brought to the plant's
attention for future reference, however, since these
approaches to waste reduction may increase in
attractiveness with changing plant conditions.
• Mix the ink and solvent in a smaller container directly
at the presses to reduce the generation of ink/solvent
waste. Minimal savings are projected for this measure.
• Possibly recover solvent on the used cleanup rags
through some type of evaporation process. This
opportunity was not analyzed further because of a lack
of detailed data and limited field experience with such
systems.
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Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Annual Quantity
Generated
Annual Waste
Management Cost
Unused ink
Evaporated ink solvent
Unused metalized film adhesive/solvent
mixture
Evaporated adhesive solvents
Spent Ink
Spent solvent on rags
Ink presses. 60 gal
Ink that cannot be used because of
changes in run color is collected and
disposed of as hazardous waste.
Ink presses. 8,550 gal
Solvent evaporates in the curing ovens
associated with the ink presses. A portion
of the solvent is lost to the atmosphere.
The remainder is fed to the onsite
incinerator.
Laminator. 2,490 gal
Unused adhesive/solvent required for
metalized film application is discarded
daily, collected, and disposed of as
hazardous waste.
Laminator. 39,100 gal
So/vents in the adftestVes evaporate in the
curing oven associated with the laminator.
The vapor is fed to the onsite incinerator.
Solvent recovery distillation unit. Ink still 195 gal
bottoms from the distillation unit are
disposed of as hazardous waste.
Equipment and plant cleanup. Soiled rags 7,000 Ib1
wetted with solvent are disposed in 1,850 gal3
municipal trash.
$970
720
43,690
3,280
4,880
'flags
2 Plant personnel report no incremental cost associated with present disposal in municipal waste,
3 Solvent
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste
Generated
Evaporated
solvents
Unused
metalized film
adhesive/
solvent
mixture
Spent solvent
on rags
Minimization Opportunity
Install a condensing system on
each of the oven stacks to
recover evaporated solvents.
Remove any water collected
along with the solvents in a
distillation unit. Reuse the
solvents
Install an automatic
adhesive/solvent mixing
system. The amount of unused
adhesive/solvent will be
reduced as will evaporation of
the solvent.
Use solvent as a cleaning
agent only for equipment. For
all other cleanup use a
nonhazardous detergent.
fviuuai wdait
Quantity
23,900 gal
1,860 gal
1,750 /to*
463 gal6
, ncuuouu,/ Nat Annual Implemenfatinn Payhrtr.k
Percent Savings Cost Years
50 $69,800' $ 63,800 0.9
75 75.9002 27,900 0.4
25 204 0 0
1 Total savings reduced by annual operating cost of the condensing systems and distillation unit.
2 Includes savings on raw materials.
3 Rags
4 Total savings reduced by the purchase price of the new detergent.
^ Solvent
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This research brief summarizes a part of the work done
under Cooperative Agreement No. CR-814903 by the j
University City Science Center under the sponsorship of I
the U.S. Environmental Protection Agency. The EPA
Project Officer was Brian A. Westfall.
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/M-90/017
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US EPA KEGILh
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