4>EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S-92/022 May 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer Producing
Treated Wood Products
F. William Kirsch and J. Clifford Maginn, Jr.*
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 Assess-
ment Centers (WMACs) were established at selected universi-
ties and procedures were adapted from the EPA Waste Minimi-
zation Opportunity Assessment Manual (EPA/625/7-88/003, July
1988). The WMAC team at Colorado State University per-
formed an assessment at a plant producing treated wood
products—approximately 1,700,000 ft 3/yr. Railroad crossties
and poles are treated with creosote in pressure cylinders to
increase their serviceability under conditions that promote de-
cay, weathering, insect destruction, or exposure to fire. Lum-
ber is treated by Wolmanizing, a closed loop process in which
a 2% chromated copper arsenate solution is used for treatment
in a pressure cylinder. The team's report, detailing findings
and recommendations, indicated that most waste was gener-
ated in the creosote treatment process, and also that cost
savings could be obtained by arranging an exchange of accu-
mulated bark and wood chips with others who use wood scrap
as a raw material.
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
same title available from the authors.
• University City Science Center, Philadelphia, PA 19104
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 formation of hazardous waste but
who lack the in-house expertise to do so. Under agreement
with EPA's Risk Reduction Engineering Laboratory, the Sci-
ence 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 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 gross
annual sales not exceeding $50 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.
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 Opportu-
nity 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, imple-
mentation costs, and payback times) is prepared for each
client.
Plant Background
The plant produces treated wood products. It operates 8,760
hr/yr to process approximately 1,700,000 ft 'Vyr of wood.
Manufacturing Process
The plant treats crossties and poles with creosote and No. 6 oil
in heated pressure cylinders. Lumber is treated with 2%
chromated copper arsenate solution in a pressure cylinder.
The raw materials used are the wood products, creosote, No. 6
oil, and chromated copper arsenate. Steam is used for clean-
ing the surface of the wood in the creosote treatment cylinders,
and ozone is used to destroy phenols in the steam conden-
sate.
The following steps are involved in treating the wood products:
• Crossties and poles are trimmed on the ends and
stacked on rail trams which are pushed into a pres-
sure treatment cylinder.
• A heated mixture of 50% (v/v) creosote and No. 6 oil
is pumped into the cylinder and pressured to force the
liquids into the wood cells.
• The liquid is drained from the cylinder and held for re-
use.
• The cylinder is flooded with steam to clean excess
creosote and oil from the surface of the wood. A
vacuum is drawn on the cylinder to enhance removal
of the liquid from the wood and the cylinder.
• Steam condensate drains to a blowdown tank. Re-
sidual creosote and oil that drains when the cylinder is
opened is pumped to the blowdown tank. The creo-
sote is separated from the condensate and held for
re-use.
These steps are involved in treating lumber:
• Lumber is stacked on rail trams which are pushed into
a pressure treatment cylinder.
• A closed-loop Wolmanizing process with 2% chromated
copper arsenate is used for treatment. The cylinder is
pressurized to 125 psig.
• Solution drained from the cylinder is held for re-use.
Steam condensate from creosote treatment is treated with a
flocculant to settle contained creosote, and the pH is adjusted
to 3.6 - 4.0. An ozone treatment is used to break down
phenols in the steam condensate before it is discharged as
industrial wastewater. Creosote wastes are also generated
from periodic steam cleaning of the treatment cylinders. No
steam is used in cleaning the Wolmanizing cylinders. Accumu-
lated waste containing chromated copper arsenate is disposed
of as hazardous waste.
Existing Waste Management Practices
• Cylindrical tanks holding creosote and chromated cop-
per arsenate have been fitted with conical bottoms for
accumulation of sludge, minimizing the need for peri-
odic cleaning.
• The Wolmanizing pressure cylinder does not require
steam cleaning, lessening the quantity of contami-
nated waste.
• Storage tanks are heated to maintain proper viscosity
and reduce sludge formation.
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 man-
agement 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 hazard-
ous 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.'
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, three additional measures were considered.
These measures were not analyzed completely because of
insufficient data or low projected savings. Since one or more
of these approaches to waste reduction may, however, in-
crease in attractiveness with changing conditions in the plant,
they were brought to the plant's attention for future consider-
ation.
• Use steam condensate from creosote treatment as
boiler feedwater.
• Collect creosote drainage generated when the cylin-
ders are opened for removal of crossties and poles.
• Preclean the crossties and poles before treatment to
reduce the quantity of creosote sludge generated when
the cylinders are cleaned.
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
Generated
Annual Waste
Management Cost
Spent chromated copper
arsenate solution
Water and creosote mixture
Creosote sludge
Bark and wood chips
Residual solution collected when cleaning 280 gal
the Wolmanizing pressure cylinder used for
treatment of lumber is disposed of as
hazardous waste.
Steam condensate from cleaning of creosote-treated 720,000 gal
crossties and poles to remove excess creosote is
treated with a flocculant, settled and decanted,
treated with ozone and caustic soda, and •
discharged as industrial wastewater.
Cleaning of the creosote treatment cylinders 16,550 gal
results in a creosote sludge. Part of the
sludge is shipped for use as boiler fuel,
and the remainder is disposed of as
hazardous waste.
Chips, bark, and wood trimmings are stored 9,750 yd3
in an open area on leased property awaiting
disposal.
$700
4,175
16,625
1,200
Table 2. Summary of Recommended Waste Minimization Opportunities
Minimization Opportunity
Waste
Generated
Annual Waste Reduction
Quantity Percent
Net Annual Implementation Payback
Savings Cost Years
Bark and wood
Arrange a waste
exchange with
others who use
wood scraps as
raw material.
9,750 yd3
100
$1,200
•itV.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40273
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United States Center for Environmental BULK RATE
Environmental Protection Research Information POSTAGE & FEES PAID
Agency Cincinnati, OH 45268 EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S-92/022
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