vvEPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-94/003 September 1994
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment
for a Manufacturer of Screwdrivers
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ment has been superseded by the Facility Pollution Prevention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 screwdrivers—over 30 miilion/yr. Plastic
handles are fabricated from virgin and recycled plastic beads.
Five plastic extruders are used to form plastic rods that are cut
to length and machined into handles. The finished handles are
painted and then assembled into screwdrivers with metal blades
forged in another plant. The team's report, detailing findings
and recommendations, indicated that the waste stream gener-
ated in the greatest quantity is waste plastic and that significant
cost savings could be realized by pelletizing the plastic scrap
before its sale to a recycler.
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
* Colorado State University, Department of Mechanical Engineering,
Fort Collins, CO
" University City Science Center, Philadelphia, PA
same title available from University City Science Center, Phila-
delphia, 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 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 Reduc-
tion Engineering Laboratory, the Science Center has estab-
lished 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 ex-
perience with process operations in manufacturing 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 re-
duction of waste treatment and disposal costs for participating
plants. In addition, the project provides valuable experience for
Printed on Recycled Paper
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graduate and undergraduate students who participate in the
program, and a cleaner environment without more regulations
and higher costs for manufacturers. j
Methodology of Assessments ;
The waste minimization assessments require several site visjts
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 tpe
current disposal or treatment methods and their associatad
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,1 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
Thfs plant manufactures screwdrivers for national distribution.
It operates 8,760 hr/yr to produce more than 30 million scre;w-
drivers annually.
Manufacturing Process ;
The plant produces plastic-handled screwdrivers from plastic
handles that are formed in this plant and metal blades that are
forged in another plant. Clear and colored plastic beads are the
principal raw materials used by this plant to make the handles.
A mixture of 70% virgin and 30% recycled plastic is dried! in
desiccant dryers and fed to an auger that moves the plastic
through the heated barrel of one of five extruders. The heated
plastic is forced through dies to create the desired shape.
Upon leaving the extruder, the resulting plastic rod is immersed
In a water bath for cooling. A puller or tractor at the end of the
cooling bath is adjusted as needed to maintain or reduce the
diameter of the rods. The rods are cut to workable lengths
using a saw, and cooled further on an automated rack for 20
min or on a separate rack for 24 hr depending on the crc>ss
section of the rod. !
The rods are cut to the appropriate size for handles on special-
ized screw machines and lathes. Both types of machine us$ a
mixture of oil and water as a spray-on coolant. Next, drilling
and doweling operations are performed on the handles. After
the handles have been cut to shape and machined, they are
sent through a washer for removal of shavings, dust, and
residual machine coolant. i
The finished handles are then treated with liquid isobutyl ac-
etate (ISA) and acetone. First, the handles are dipped in IBA1 to
remove the dullness from the machined plastic. Next, \he
handles are exposed to acetone vapor, which serves to soffen
the plastic, remove blemishes, and generate a smooth, shiny
surface. !
After the IBA/acetone treatment, the ends of the handles are
painted using solvent-based paint. Product names are stamped
on the barrels of the dried handles using foil tape.
The blades of the screwdrivers, which are forged in another
plant, undergo minor processing such as sandblasting end
cleaning in this plant. Then the blades are pressure-fitted i|ito
the handles. The assembled screwdrivers are inspected, pack-
aged, and shipped.
An abbreviated process flow diagram that also describes the
waste generation in this plant is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes:
« Waste plasticf rom machining of product handles is baled and
shipped offsite for recycle.
• Dry machining that generates no cutting oil waste is used in
drilling/doweling operations.
• Waste oil from screw machines and lathes is shipped offsite
to be reblended into boiler fuel.
• Aqueous cleaners are used instead of solvents for cleaning
screwdriver handles and blades.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, the waste management
method, and the annual waste management cost 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 payback time are given in the table. The quantities of
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 financial savings of the minimization
opportunities result from the need for less raw material and
from reduced present and future costs associated with waste
management. Other savings not quantifiable by this study in-
clude a wide variety of possible future costs related to chang-
ing emissions standards, liability, and employee health. It also
should be noted that the savings given for each opportunity
reflect the savings achievable when implementing each waste
minimization opportunity independently and do not reflect du-
plication 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, minimal savings, 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.
• Install a solvent recovery unit to recover spent acetone for
reuse onsite.
• Replace solvent polishing of plastic handles with ultraviolet
painting coatings.
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Plastic beads
Extrusion
Machining
Waste plastic solid
for reuse
Waste oil shipped
to recycler
Drilling,
doweling
Cleaning
IBA/acetone
curing
Painting
Blades
Assembly
Packaging,
shipping
Waste plastic
landfilled
C'leaner and rinse
evaporated
Spent cleaner and rinse
sewered
IBA/acetone evaporated
Waste IBA/acetone shipped
offsite for incineration
Waste paint/acetone shipped
offsite for incineration
Figure 1. Abbreviated process flow diagram that describes the waste generation in this plant
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.
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Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Annual Quantity
I Generated (Ib)
Waste Management
Method
Annual Waste
Management Cost*
Wasto plastic
Wasta plastic
Waste plastic/metal
Waste oit
Cutting and machining
of extruded plastic
Spilled from bales of
waste plastic
Drilling and doweling
of plastic handles
500,640
24,960
10,960
Machining 19,100
Baled; shipped offsite
for reuse
Landfilled
Landfilled
Shipped offsite;
$545,800
39,990
17,590
10,130
Spont cleaner
Rinse water
Spent acetone
Evaporated acetone
Spont Isobutyl acetate
Evaporated isobutyl acetate
Solvent-based paint
Evaporated solvent
Cooling water
Petroleum naphtha
Washing of handles
Rinsing of handles
Curing of handles
Curing of handles
Curing of handles
Curing of handles
Painting of handles
Painting of handles
Plastic extruders
Cleaning of blades
and maintenance
21,660
21,660
11,870
90,850
1,300
32,920
26,380
19,270
5,392,240
8,850
reused as fuel
Sewered 490
Sewered 490
Shipped offsite; 13,020
incinerated
Evaporates to plant air 29,980
Shipped offsite; 2,250
incinerated
Evaporates to plant air 18,730
Shipped offsite; 51,980
incinerated
Evaporates to plant air 6,360
Sewered 12,900
Shipped offsite; recycled 4,550
Includes waste treatment, disposal, and handling costs and applicable raw material costs.
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