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 manufacturers, 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). That document has been superseded by the Facility Pollution Prevention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 million/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 generated 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 investigators and EPA’s Risk Reduction Engineering Laboratory, Cincinnati, 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, Philadelphia, PA.

Introduction

The amount of 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 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 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 considerable direct experience 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 minimization.

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 participating

plants. In addition, the project provides valuable experience for

Waste Minimization Assessment

for a Manufacturer of Screwdrivers

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-94/003 September 1994

Harry W. Edwards*, Michael F. Kostrzewa*,

and Gwen P. Looby**

* Colorado State University, Department of Mechanical Engineering,

Fort Collins, CO

** University City Science Center, Philadelphia, PA

E AP
2

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 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 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

This plant manufactures screwdrivers for national distribution.

It operates 8,760 hr/yr to produce more than 30 million screwdrivers 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 cross

section of the rod.

The rods are cut to the appropriate size for handles on specialized screw machines and lathes. Both types of machine use 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.

The finished handles are then treated with liquid isobutyl acetate (IBA) and acetone. First, the handles are dipped in IBA to

remove the dullness from the machined plastic. Next, the

handles are exposed to acetone vapor, which serves to soften

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 and

cleaning in this plant. Then the blades are pressure-fitted into

the handles. The assembled screwdrivers are inspected, packaged, 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 plastic from 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 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 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, 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.
3

Plastic beads

Extrusion

Machining

Drilling,

doweling

Cleaning

IBA/acetone

curing

Waste plastic solid

for reuse

Waste oil shipped

to recycler

Waste plastic

landfilled

Cleaner 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

Painting

Assembly

Packaging,

shipping

Blades

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. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.
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Table 1. Summary of Current Waste Generation

Annual Quantity Waste Management Annual Waste

Waste Generated Source of Waste Generated (lb) Method Management Cost*

Waste plastic Cutting and machining 500,640 Baled; shipped offsite $545,800

 of extruded plastic for reuse

Waste plastic Spilled from bales of 24,960 Landfilled 39,990

 waste plastic

Waste plastic/metal Drilling and doweling 10,960 Landfilled 17,590

 of plastic handles

Waste oil Machining 19,100 Shipped offsite; 10,130

 reused as fuel

Spent cleaner Washing of handles 21,660 Sewered 490

Rinse water Rinsing of handles 21,660 Sewered 490

Spent acetone Curing of handles 11,870 Shipped offsite; 13,020

 incinerated

Evaporated acetone Curing of handles 90,850 Evaporates to plant air 29,980

Spent isobutyl acetate Curing of handles 1,300 Shipped offsite; 2,250

 incinerated

Evaporated isobutyl acetate Curing of handles 32,920 Evaporates to plant air 18,730

Solvent-based paint Painting of handles 26,380 Shipped offsite; 51,980

 incinerated

Evaporated solvent Painting of handles 19,270 Evaporates to plant air 6,360

Cooling water Plastic extruders 5,392,240 Sewered 12,900

Petroleum naphtha Cleaning of blades 8,850 Shipped offsite; recycled 4,550

 and maintenance

* Includes waste treatment, disposal, and handling costs and applicable raw material costs.
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Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction

Net Annual Implementation Simple

Minimization Opportunity Waste Stream Reduced Quantity (lb) Per cent Savings Cost Payback (yr)

Install an automatic plastic pelletizer to Waste plastic —-1 —- $85,590 $67,000 0.8

 replace the baler used for plastic scrap

 collection. Currently, the scrap plastic is

 shipped overseas to a recycler after it is

 collected and baled. The pelletizer will

 compact the waste plastic and thus re-

 duce the volume of the waste shipments

 to the recycler. Secondly, the pelletizer

 will eliminate the current breaking of

 bales that leads to landfilling of scrap

 plastic. Lastly, a higher price can be ob-

 tained from national markets that recycle

 plastic pellets.

Eliminate use of isobutyl acetate for Spent isobutyl acetate 1,300 100 20,980 0 Immediate

 screwdriver handle curing. Trial operat- Evaporated isobutyl acetate 32,921 100

 ions at the plant have shown that pro-

 duct quality will be maintained without

 the polishing.

1 The waste plastic spilled from bales that is currently landfilled (24,960 lb/yr) will be shipped to the recycler instead of being landfilled.
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-94/003