United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/008 August 1995
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of Iron Castings
and Fabricated Sheet Metal Parts
Marvin Fleischman*, Jennifer J. Harris*, Allan Handmaker*,
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. Waste Minimization Assessment Cen-
ters (WMACs) were established at selected universities and
procedures were adapted from the EPA Waste Minimization
Opportunity Assessment Manual (EPM625/7-88/003, 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That document has been superseded by the Facility Pollution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 iron castings and fabricated sheet
metal parts. Foundry operations include mixing and mold for-
mation, core making, metal pouring, shakeout, finishing, and
painting. Cutting, shaping, and welding are the principal metal
fabrication operations. The team's report, detailing findings and
recommendations indicated that paint-related wastes are gen-
erated in large quantities, and that significant waste reduction
and cost savings could be realized by installing a dry powder
coating system or by replacing conventional air spray paint
guns with high-volume low-pressure spray guns.
This research brief was developed by the principal investiga-
tors and EPA's National Risk Management Research Labora-
tory, 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 be-
come an increasingly costly problem for manufacturers and an
* University of Louisville, Department of Chemical Engineering
"University City Science Center, Philadelphia, PA
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
National Risk Management Research 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 pollution prevention opportunity 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 pollution
prevention.
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 participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
Methodology of Assessments
The pollution prevention opportunity assessments require sev-
eral site visits to each client served. In general, the WMACs
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follow the procedures outlined in the EPA Waste Minimization
Opportunity Assessment Manual (EPM625/7-88/003, 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 support-
ing technological and economic information is developed. Fi-
nally, 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 performs casting of gray iron and ductile iron, fabri-
cates heavy metal plate parts, and fabricates sheet metal
parts. It operates 4,000 hr/yr to cast approximately 25,000 tons
of metal and fabricate over 4 mil ft2 of metal annually.
Manufacturing Process
Foundry Operations
Three basic departments—large moldings, medium moldings,
and small moldings—make up the foundry. Mixing and mold
formation, core making, metal pouring, shakeout, finishing, and
painting operations take place in each of the three depart-
ments.
Patterns produced onsite are made from wood boards and are
used to form the sand molds for casting. Saws, planes, drills,
senders, band-saws, and a press are used to shape the wood.
Sand that is used to form the molds and cores is mixed with a
binding agent so that the sand will set into a mold. The sand is
then pumped into the pattern, compacted, and allowed to
harden. Small, molded spacers called cores are made onsite in
a similar manner.
Metals used include virgin pig iron, old rails, and purchased
slitter scrap (from metal cutting). In addition, all of the internally
generated scrap metal is remelted and reused. No metal pre-
treatment is performed prior to melting. Weighed amounts of
metal are placed in one of three electric induction furnaces.
Once the metal is placed in the furnace, some alloying agents
are added. As the metal melts, slag (impurities and dirt) sepa-
rates from the metal and is skimmed off. After the metal leaves
the furnace, silicon and other alloying agents are added to
produce either gray cast iron or ductile iron.
The melted metal is collected in ladles and transported via
crane to the assembled mold and poured. The mold is then
allowed to cool.
After the metal has cooled, the mold is moved to the shakeout
(a large vibrating metal grating). The vibration causes the
casting to separate from the sand mold. If necessary, employ-
ees dig the sand core out of the casting. Remaining sand is
removed from the casting surface with steel shot. Some of the
castings are painted before they are shipped.
An abbreviated process flow diagram for the foundry opera-
tions is shown in Figure 1.
Metal Fabrication Operations
Heavy metals fabrication operations include cutting, shaping,
and welding plates of low carbon steel from 3/8 to 8 in. thick.
Parts requiring painting are sent offsite and returned.
The light metals fabrication department produces metal cabi-
nets and similar products from 4 by 8 ft sheets of 1/4 in. or
smaller thickness. After metal shaping operations, oil present
on the sheets is removed using a mixture of phosphoric acid
and steam.
All parts fabricated in this area receive a primer coat and 90%
of products receive a topcoat onsite.
An abbreviated process flow diagram for the metal fabrication
operations is shown in Figure 2.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
• All scrap metal generated in the foundry operations is re-
melted and reused.
• The plant recently replaced the binder used to make large
molds with one that does not contain methanol.
• Sand from the molds is collected and reused.
• High-volume low-pressure paint spray guns are used for
large painting jobs.
• Onsite painting is limited in order to control volatile organic
compound (VOC) emissions.
• Pallets received with raw material shipments are reused for
shipping products.
• Sand used for making molds contains a lesser amount of
chromium than the sand used previously.
Pollution Prevention 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 waste management cost for each waste
stream identified are given in Table 1.
Table 2 shows the opportunities for pollution prevention that
the WMAC team recommended for the plant. The opportunity,
the type of waste, the possible waste reduction and associated
savings, and the implementation cost along with the simple
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 opportuni-
ties, in most cases, results from the need for less raw material
and from reduced present and future costs associated with
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New Metal
- Finished castings
Shipped to customers
Figure 1. Abbreviated process flow diagram for foundry operations.
Metals
Metal working
Oven drying
Light metal
parts shipped
Offsite painting
Steam cleaning
Top-coating
Heavy metal parts shipped
Light metal
parts shipped
Figure 2. Abbreviated process flow diagram for fabrication operations.
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Table 1. Summary of Current Waste Generation
Waste Stream Generated Source of Waste
Waste Management Method
Annual Quantity
Generated (Ib/yr)
Annual Waste
Management Cost
Empty drums and totes
Pallets and scrap wood
General trash
Paint and solvent wastes
Dirt slag and waste sand
Metal scrap
Dirt and broken refractory
Waste acid and binder
Waste corewash
Chromium emissions
Spent shot and sand
Metal and sand dust
Fugitive emissions
VOC emissions
Paint solids
Exhaust filters and paint overspray
Air intake filters
Wastewater
Wastewater treatment sludge
Waste oils
Office waste
Sanitary Wastewater
Spent solvent
Raw material receiving
Raw material receiving
Various operations
Painting operations
Metal preparation and foundry operations
Metal fabrication
Metal charging and metal pouring
Cleaning of storage tanks
Cleaning of dip tank
Emitted from sand
Removal of molds and cores
Shakeout and finishing
Painting
Painting
Painting (filtered from water)
Paint booth
Paint booth
Various operations
Onsite Wastewater treatment
Maintenance of machinery
Office operations
Plant and office
Parts washer
Reconditioned or recycled offsite 52,200
Recycled offsite 200,000
Shipped to landfill 75,240
Shipped to fuels program 89,350
Shipped to landfill 8,720,000
Sold to recycler 4,132,000
Shipped to landfill 868,000
Disposed of as hazardous waste 1,080
Shipped to landfill 13..200
Vented from plant 600
Shipped to landfill 400,000
Shipped to landfill 130,620
Evaporated to plant air 7,200
Evaporated to plant air 43,000
Shipped to fuels program 825
Shipped to landfill 43,650
Shipped to landfill 1,250
Treated onsite; sewered 13,694,280
Shipped to landfill 134,000
Recycled offsite 4,680
Shipped to landfill 40,000
Sewered 5,404,320
Removed by supplier 2,060
$2,720
3,950
9,740
25,250
49,270
-92,160
13,080
800
500
0
3,540
2,740
0
0
300
1,000
12,000
1,730
10,400
0
3,150
630
2,420
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 em-
ployee health. It also should be noted that the savings given for
each opportunity reflect the savings achievable when imple-
menting each pollution prevention opportunity independently
and do not reflect duplication of savings that may 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 consid-
ered. These measures were not analyzed completely because
of insufficient data, implementation difficulty, or a projected
lengthy payback. Since these approaches to pollution preven-
tion may, however, increase in attractiveness with changing
conditions in the plant, they were brought to the plant's atten-
tion for future consideration.
Install a sewer meter to measure the volume of wastewater
discharged to the sewer. Current sewer charges are based
on the amount of water that enters the plant.
Explore the possibility ofshipping sawdusttoan area nursery
or to a local cement or brick kiln.
Give scrap wooden crates and pallets to employees for use
as kindling.
Use the scrap metal from machining and trimming operations
in the sheet metal shop in the foundry operations. Use of the
scrap metal would require removal of the rust-preventing oil
from its surface.
Recycle waste cardboard and paper sacks.
This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-819557 by the University City
Science Center under the sponsorship of the U. S. Environ-
mental Protection Agency. The EPA Project Officer was Emma
Lou George.
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Table 2. Summary of Recommended Pollution Prevention Oppi
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Replace all conventional air spray paint guns with either high-
volume low-pressure or airless-air assisted spray guns. Imple-
mentation of this recommendation would reduce paint
purchases, VOC emissions, disposal of paint filters, and
disposal of paint solids. The plant is currently investigating
the purchase of an afterburner to reduce VOC emissions.
This recommendation could eliminate the need for an after-
burner or decrease the size of the afterburner required. It is
possible that the spent filters and paint overspray will be re-
classified as hazardous waste in the future. In that case,
cost savings will be higher than estimated here. The eval-
uation presented assumes filters will continue to be disposed
of as nonhazardous waste and that high-volume low-pressure
guns will be installed. This analysis does not include the
avoided purchase of an afterburner. A more detailed tech-
nological and financial feasibility analysis of this recommen-
dation should be done prior to implementation.
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Install automatic gun cleaners for cleaning paint spray guns.
Implementation of this recommendation will lead to reduced
solvent purchase and disposal costs.
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Install a solvent recovery still to recover solvent from the paint
wastes shipped offsite. Reuse the recovered solvent for
paint gun cleaning.
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Pollution Prevention Opportunity
Pack the wood-waste dumpster more efficiently. Carefully
screen the wastes placed in the dumpster to evaluate
whether some of the pallets could be returned to the
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supplier for reuse. Wood waste should be stacked in the
dumpster neatly in order to decrease the volume occupied
in the dumpster.
Negotiate with a cement company to accept the plant's
waste sand for use in cement manufacture.
Sell non-reconditionable drums to a solid waste recycler.
Replace the currently used paint application system with
a dry powder coating system. Implementation of this recom-
mendation will lead to reduced paint/solvent wastes and
reduced VOC emissions. This recommendation could
eliminate the need for an afterburner. The paint booth can
be equipped to capture and recirculate powder that does
not adhere to parts during spraying. This analysis assumes
that the waste filters will continue to be classified as non-
hazardous waste and that the powder will be recycled.
The avoided cost of an afterburner is not included in this
analysis. A more detailed technological and financial
feasibility analysis of this recommendation should be done
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Replace the currently used paint application system with super-
critical CO2 spraying. In supercritical CO2 spraying, the super-
critical fluid replaces as much as 80% of the organic solvents
required for ordinary paint spraying. In addition, the proposed
system offers improved transfer efficiency. This recommenda-
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1 Net waste reduction
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United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/008
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