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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. 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That document has been superseded by the Facility Pollution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 the University of Louisville performed an assessment

at a plant that manufactures carbon and stainless steel products, primarily conveying and transportation equipment. Raw

steel is cut, machined, welded into subassemblies, and sandblasted. Expanded metal is coated. All parts are painted, assembled, inspected, packaged, and shipped. The team’s report,

detailing findings and recommendations, indicated that the plant

could achieve significant cost savings and waste reduction by

replacing its current airless paint spraying system with a low

pressure, airmix system.

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.

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 (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 the University of Louisville’s

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

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 proceWaste Minimization Assessment for a Steel Fabricator

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-95/006 April 1995

Marvin Fleischman*, Clay Hansen*,

Eric Daley**, and Gwen P. Looby**

* University of Louisville, Department of Chemical Engineering.

** University City Science Center, Philadelphia, PA.

E AP
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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 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 manufactures carbon and stainless steel products,

primarily conveying and transportation equipment. It operates

approximately 2,040 hr/yr to process 1,500,000 lb of raw steel

annually.

Manufacturing Process

The major raw materials used by the plant are stainless and

carbon steel. Additional components used include pumps, wheel

assemblies, controls and instrumentation, labels, and light assemblies.

Raw steel is cut by oxyacetylene gas torches, an automatic

plasma system, or a water cutting system. Bending, drilling,

turning, shaping, milling, punching, and sanding operations are

performed as required. Machined parts are welded and sandblasted.

Expanded metal is coated with Penetrol (rust preventative)

prior to joining raw steel parts in the paint area. Parts are

wiped down, primed, and painted with an airless spray system.

Painted parts undergo final assembly where additional components are attached. These include pumps, assemblies, and

instrumentation.

The finished product is inspected and shipped. An abbreviated

process flow diagram is shown in Figure 1.

Existing Waste Management Practices

This plant already has taken the following steps to manage and

minimize its wastes:

• Steel scrap is segregated by type and sold to a scrap dealer

for recycling.

• A nonhazardous, biodegradable cutting fluid has replaced

the previously used 1,1,1-trichloroethane-containing cutting

fluid.

• The plant is working directly with a paint manufacturer to

lower the barium concentration of the primer used.

• The plant has set a goal to become a limited or zero quantity

generator by the first quarter of 1992.

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 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 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 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 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, several 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.

• Employ galvanic or cathodic corrosion protection to eliminate

the need for barium-based paint. Paint waste is currently

considered hazardous because the barium level exceeds the

allowable Toxicity Characteristic Leaching Procedure (TCLP)

level.

• Purchase a chip wringer to remove tramp oil from small metal

chips to prevent any future scrap metal recycling problems.

• Attach a drip board to the Penetrol dip tank to reduce lost

dragout.

• Build an enclosure for steel storage or set up sediment traps

with a weir system to eliminate storm water from washing oil

off the steel and into the ground.

• Apply a polyurethane coat to the cement slab under the

maintenance vehicle gas pump to prevent spillage from

seeping through the cement and into the ground.

• Use a paint dipping system for expanded metal and rails to

decrease the amount of paint overspray.

• Use a solvent recirculating paint gun washer.

• Give overpurchased paint to the community.

• Use a variable aperture paint gun to apply paint to the rails.

• Convince paint supplier to accept empty paint cans.

• Improve plant layout to facilitate efficient collection and

segregation of wastes for recycle or pollution control.

• Use a centralized coolant sump for individual machining

equipment.

• Skim and filter coolant, regularly clean the sump, and maintain the proper coolant-to-water ratio.

• Use acid treatment, ultrafiltration, centrifugation, coalescence, or evaporation for onsite treatment of coolant.

• Replace disposable paint booth filters with dissolvable

styrofoam filters.

• Compact short metal scrap to reduce the cost of transporting

to a recycler.

• Use sand waste as a raw material in manufacture of rock

wool, as construction sand, or as an encapsulant for hazardous waste disposal.

• Sandblast in an enclosed or draped area to reduce dispersion of dust.
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• Recycle empty sand bags.

• Investigate recycling of tires, pallets, batteries, and office

trash.

• Clean rags onsite instead of using an outside laundry service.

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.

Figure 1. Abbreviated process flow diagram for conveying and transportation equipment manufacture.

Raw steel Expanded

metal

Cutting,

machining

Arc

welding

Sandblasting

Cleaning

Parts

Spent

petroleum

naphtha

recycled

offsite Conveying and

transportation equipment

Contaminated

hydraulic oil

recycled

offsite

Speny xylene

from paint gun

cleaning

recycled

offsite

Paint

overspray,

plastic, and

filters

Final

assembly

Painting Spent sand

Spent welding

rods and slag

Spent coolant

recycled

offsite

Scrap metal

recycled

offsite

Coating

Spilled

rust

preventative
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Table 1. Summary of Current Waste Generation

Waste Generated Source of Waste Waste Management Method Annual Quantity Annual Waste

Generated (lb/yr) Management Cost1

Scrap metal, paint cans Machining, painting Sold to metal recycler 420,000 -$17,160

Sand Sandblasting Shipped to nonhazardous landfill 3,650,000 55,030

Rags Cleaning sandblasted parts Laundered offsite unknown 13,520

Paint wastes (overspray, Paint line Shipped offsite as hazardous waste 6,000 6,000

filters, plastic sheets, rags)

General trash Welding, packaging, and office activities Shipped to nonhazardous landfill 1,500,000 18,300

Coolant Machining Shipped to waste oil reclaimer 9,600 3,720

Grease/sludge Machining Shipped to waste oil reclaimer 45 negligible

Petroleum naphtha Cleaning of small parts Reclaimed offsite by supplier 4,220 3,600

Hydraulic oil Contaminated during assembly Shipped to waste oil reclaimer 10,500 5,040

Motor oil Vehicle maintenance Shipped to waste oil reclaimer 19,440 1,470

Xylene and paint solids Cleaning of paint guns Offsite reclamation 4,750 2,550

Unused paint Paint line Shipped offsite as hazardous waste 195 1,200

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

Annual Waste Reduction

Net Annual Simple Payback

Minimization Opportunity Waste Reduced Quanity (lb/yr) Per cent Savings Implementation Cost (yr)

Modify the paint spray sys- Paint wastes 2,000 50 $8,860 $12,000 1.4

tem by using a low pressure, airmix system.

Implementation of this opportunity would

lead to reduced overspray.

Replace the naphtha-based parts washer Petroleum naphtha 4,220 1 100 3,100 5,080 1.6

with a mechanical agitation system utilizing

an aqueous biodegradable non-toxic detergent. The proposed unit should include an

oil skimmer for oil removal; following skimming, the spent detergent solution can be

sewered.

Use di-basic esters instead of naphtha in Petroleum naphtha 4,220 2 100 1,340 750 0.6

the parts washer. Di-basic esters have a

lower volatility than naphtha and are nontoxic, thereby lowering costs associated

with evaporative losses and disposal. A dibasic ester waste stream will be generated

if this WMO is implemented.

Use cheese cloth pre-filters to cover Filters 1,240 71 1,110 0 0

currently used paint booth filters. Because

cheese cloth is thinner than the filters,

the volume of waste to be disposed of

would decrease.

Recover spent paint gun cleaning Xylene and paint 3,000 63 760 3,700 4.9

solvent onsite using a batch distillation

unit. A small quantity of still bottoms

will be generated and shipped offsite

for disposal if this opportunity is

implemented.

Use an electrostatic precipitator and a Hydraulic oil 10,500 100 4,280 15,000 3.5

filtering system to reclaim contaminated

hydraulic oil onsite for reuse. A small

quantity of residual dirt will be disposed

of offsite if this WMO is implemented.

Replace the coolant with a biodegradable Coolant 9,600 100 2,020 4,000 2.0

and nonhazardous coolant. Purchase a

ultrafiltration unit to remove oils so that the

spent coolant can be discharged to the

septic system. Oily residue will be shipped

offsite if this WMO is implemented.

1 A small quantity of spent detergent solution and skimmed oil will be generated.2 Waste di-basic ester (approximately 3,170 lb/yr) will be generated.
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United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-95/006

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35