POLLUTION PREVENTION
FOR THE
WOOD FINISHING
INDUSTRY
DEVELOPED BY:
U.S. EPA/SEDESOL
POLLUTION PREVENTION
WORKGROUP
OCTOBER 1994
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TABLE OF CONTENTS
Section Page
LIMITATIONS OF THIS MANUAL iv
INTRODUCTION v
SECTION I GOALS AND BENEFITS OF POLLUTION PREVENTION
Pollution Prevention Goals I-1
Benefits of a Pollution Prevention Program I-1
What is Pollution Prevention? 1-4
SECTION II POLLUTION PREVENTION IN THE WOOD FINISHING INDUSTRY
Chapter 1 The Wood Finishing Industry II-l
Chapter 2 Pollution Prevention Options for the Wood Finishing Industry II-5
Bibliography 11-30
SECTION III CASE STUDIES
CASE STUDYNO. 1—Conversion to HVLP III-l
CASE STUDYNO. 2—Solvent Recycling III-3
CASE STUDYNO. 3—Wood Waste to Energy III-5
CASE STUDYNO. 4—Switching to Water-Based Inks III-6
CASE STUDYNO. 5—Conversion to HVLP III-7
CASE STUDYNO. 6—Reusing Overspray III-8
Appendix
ADDITIONAL INFORMATION
Attachments
A INFORMATION ON ACCESSING POLLUTION PREVENTION INFORMATION
CLEARINGHOUSES
B SURVEY
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LIST OF TABLES
Table Page
1-1 SOURCE REDUCTION: PROCESS CHANGES 1-6
1-2 WASTE MANAGEMENT STRATEGIES THAT ARE NOT POLLUTION
PREVENTION 1-7
II-1 REDUCTIONS IN VOC EMISSIONS POSSIBLE FOR EACH STEP WHEN
NITROCELLULOSE IS REPLACED WITH AN ALTERNATIVE COATING 11-13
11-2 COATINGS 11-14
II-3 SAVINGS PER $1,000 SPENT ON COATING MATERIALS WITH
IMPROVED TRANSFER EFFICIENCIES 11-16
II-4 APPLICATION METHODS 11-20
LIST OF FIGURES
Figure Page
1-1 METHODS OF SOURCE REDUCTION 1-5
1-2 WASTE MANAGEMENT HIERARCHY 1-9
II-l TYPICAL WOOD FINISHING SEQUENCE II-2
II-2 TYPICAL FURNITURE SPRAY BOOTH II-4
II-3 TYPICAL TRANSFER EFFICIENCIES 11-21
II-4 OPTIONS FOR MANAGING SOLVENT 11-27
TABLE OF CONTENTS 111
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LIMITATIONS OF THIS MANUAL
This manual provides an overview of the pollution prevention and recycling alternatives
that are available in the wood finishing industry. This report is intended only to assist
the user in his or her preliminary research and development of pollution prevention
options. Each company is responsible for identifying, evaluating, and implementing
pollution prevention practices that are appropriate to its specific situation. By
compiling and distributing this manual, EPA and SEDESOL are not recommending the
use of any particular processes, raw materials, products, or techniques in any particular
industrial setting. Compliance with U.S. and Mexican environmental laws,
occupational health and safety laws, and all applicable federal, state, and local laws and
regulations is the responsibility of each individual business. It is not the focus of this
document.
The information in this manual is intended to be a relatively comprehensive overview
of the documented information on pollution prevention and recycling practices for the
wood finishing industry. However, the collection, organization, and dissemination of
pollution prevention information is a relatively new undertaking, as well as an ongoing
and evolutionary process. In addition, there are limits to any manual, including this
one. Therefore, this summary may not contain every relevant piece of information on
pollution prevention and recycling for wood finishing companies. EPA encourages all
users who discover, in the literature or in the field, pollution prevention options that are
not cited in this report to share this information with EPA. Please submit any
corrections, updates, or comments on this report to the following:
Robert D. Lawrence (6M-PP)
Pollution Prevention Coordinator
U.S. EPA Region 6
1445 Ross Avenue
Dallas, TX 75202
(214)665-6580
This manual is an assimilation of existing research and case studies of waste
minimization and pollution prevention principles. Because of the voluminous amount
of such information, referencing sources in the text as and when they are used would
make the manual cumbersome to the reader. Therefore, the authors of this manual wish
to acknowledge the authors of all of the articles referenced throughout the text and
listed in the bibliography section.
IV Pollution Prevention for the IVood Finishing Industry
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INTRODUCTION
The production of economically competitive products is the driving force behind any
successful business. Manufacturing frequently requires the use of various chemicals.
The purchase and storage of these chemicals, their use in the process, and the ultimate
disposal of the waste generated by the manufacturing process can present many
problems. These problems include financial concerns, environmental management, and
worker health and safety.
Pollution prevention (also referred to as waste minimization or source reduction)
is the use of materials, processes, or practices that reduce or eliminate the
generation of pollutants or wastes at the source. It includes practices that reduce the
use of hazardous and nonhazardous materials, energy, water, and other resources, in
addition to practices that protect natural resources through conservation or more
efficient use.
Because of the enormous potential for pollution prevention along the U.S.-Mexico
border, the U.S. Environmental Protection Agency (EPA) and Secretaria de Desarrollo
Social (SEDESOL) established the Pollution Prevention Workgroup in February 1992.
EPA and SEDESOL also began promoting and coordinating the reduction of pollution
through a broad range of approaches: technical assistance, training, public and private
sector programs in pollution prevention awareness, assessment of pollution prevention
opportunities, policy development and institutional support, and technology
development and investment activities.
The purpose of this manual is to provide pollution prevention information for the
wood finishing industry. This manual builds on the effort of the first manual
—"Waste Minimization for the Metal Finishing Industry." That manual was the first
in this series of bilingual pollution prevention manuals prepared jointly by EPA and
SEDESOL. Future manuals will include other industries that are typical in the border
area. The manual contains the following sections:
Section I Goals and Benefits of Pollution
Prevention
In this general introduction, the term "pollution prevention" is clarified. This
section also includes an overview of the benefits of applying pollution
prevention techniques.
Section II Pollution Prevention in the Wood
Finishing Industry
This technical section describes various processes associated with the wood
finishing industry and pollution prevention options for that industry.
INTRODUCTION
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Section III Case Studies
This section includes specific examples of companies that have used pollution
prevention techniques. These case studies describe the benefits, particularly
cost savings, that these companies have achieved.
Appendix Additional Information
This section lists additional technical documents pertaining to pollution
prevention opportunities for the wood finishing industry, and other
information. These documents are currently available only in English.
Attachment A Information on Accessing Pollution
Prevention Information
Clearinghouses
This section describes how to access the International Cleaner Production
Information Clearinghouse (ICPIC) database, which is an international
clearinghouse for pollution prevention information. Information is also
included on how to access the Pollution Prevention Information Exchange
System (PIES).
Attachment B Survey
PLEASE COMPLETE THE SURVEY INCLUDED IN THIS SECTION.
Your response provides valuable information for evaluating the usefulness of
this manual. Additionally, when your survey is returned, your name will be
placed on a mailing list for updates to the manual and other documents as they
become available.
VI Pollution Prevention for the IVood Finishing Industry
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Section I
Goals and Benefits
of Pollution Prevention
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GOALS AND BENEFITS OF POLLUTION PREVENTION
POLLUTION PREVENTION GOALS
The goal of a pollution prevention program is to improve the quality of the environment
through eliminating, preventing, and/or reducing all waste generation. Pollution
prevention includes any action by a company to reduce the amount of waste generated
by a manufacturing process prior to off-site recycling, treatment, or disposal of the
waste. To effectively accomplish this, the program must include an ongoing,
comprehensive assessment of the operations at a facility.
BENEFITS OF A POLLUTION PREVENTION PROGRAM
Businesses and governments have strong incentives to reduce the toxicity and volume
of the waste that they generate. As pollution prevention activities lower operating
costs, production costs will decrease. Therefore, companies with an effective,
ongoing pollution prevention plan will have a significant competitive edge.
As discussed in detail below, a pollution prevention program can achieve the following
benefits:
! Protect human health and environmental quality.
! Reduce operating costs.
! Improve employee morale and participation.
! Enhance the company's image in the community.
! Assist in compliance with environmental laws.
Protect Human Health and Environmental Quality
Reducing the waste released to air, land, and water will enhance the environment and
protect human health. Typical harmful pollutants that can be reduced significantly by
pollution prevention techniques include the following:
! Air emissions, including solvent fumes, fine particulates, and carbon
monoxide
GOALS AND BENEFITS OF A POLLUTION PREVENTION PROGRAM
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! Land disposal, including ash from incineration, waste solvents, and
debris
! Water disposal, including wastewater contaminated with solvents and
other toxic materials
Volatile organic compounds (VOC) typically comprise a significant amount of the
solvents used in wood finishing. VOCs are central nervous system depressants. High
exposures (hundreds to thousands parts per million in the air) may result in giddiness,
confusion, unconsciousness, paralysis, and death from respiratory or cardiovascular
arrest. Long-term exposure may result in behavioral effects. Some VOCs are
suspected carcinogens.
The health and safety of employees can be affected by poor ventilation, mishandling
of chemicals, and a lack of proper safety equipment. An informative employee training
program is an important way to reduce accidents. Reducing the amount of chemical
materials and wastes at a facility is also beneficial, because it reduces the amount of
space required for storage and the potential for accidental spills. Furthermore,
hazardous waste transportation requirements may be reduced if the volume of pollution
is minimized.
Reduce Operating Costs
An effective pollution prevention program can yield cost savings that will more
than offset program development and implementation costs. Cost reductions may
be immediate savings that appear directly on the balance sheet or anticipated
savings based on avoiding potential future costs. Cost savings are particularly
noticeable when the costs resulting from the treatment, storage, or disposal of wastes
are allocated to the production unit, product, or service that produces the waste.
Materials costs, or the costs of purchasing materials, can be reduced by adopting
production and packaging procedures that consume fewer resources. This approach
uses resources more efficiently and reduces the quantity and toxicity of waste
generated. As wastes are reduced, the percentage of raw materials converted to finished
products increases. This results in a proportional decrease in materials costs.
Waste management and disposal costs may be reduced when less waste is produced.
Required procedures for proper handling of the waste at the facility —in addition to
specific treatment, disposal, and transportation methods - are typically labor—intensive
and very costly. These requirements and their associated costs are expected to increase.
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Production costs can be reduced through a pollution prevention assessment. When
people examine production processes from a fresh perspective, they find opportunities
for increasing efficiency that might not, otherwise, have been noticed. Production
scheduling, material handling, inventory control, and equipment maintenance are all
areas in which facilities can work to reduce the production of waste of all types, thereby
controlling the costs of production.
Energy costs will decrease as the facility implements pollution prevention measures in
various production lines. In addition, by thoroughly assessing how operations interact,
companies can reduce the energy used to operate the overall facility.
Improve Employee Morale and Participation
Employees are likely to feel better about their company when they believe that
management is committed to providing a safe work environment and is acting as a
responsible member of the community. By participating in pollution prevention
activities, employees have an opportunity to be part of a "team," and interact positively
with coworkers and management. Helping to implement and maintain a pollution
prevention program will normally increase each employee's sense of commitment to
company goals. This positive atmosphere helps to retain a competitive work force and
to attract high-quality new employees.
Enhance the Company's Image in the Community
The quality of the environment has become an issue of critical importance to society.
Your company's policy and practices for controlling waste increasingly influence the
attitudes of the local community at large.
Community attitudes are more positive toward companies that operate and publicize
a thorough pollution prevention program. If a company creates environmentally
compatible products and avoids excessive use of material and energy resources, the
company's image will be enhanced both in the community and with potential customers
and consumers.
Assist In Compliance With Environmental Laws
Mexico's environmental laws include administrative penalties that entitle
government inspectors to require temporary or permanent closure of businesses
that are not in environmental compliance. A pollution prevention plan that includes
standard operating procedures that comply with environmental laws and regulations is
very helpful. By following the plan, a company increases its chances of avoiding
violations and associated penalties.
GOALS AND BENEFITS OF A POLLUTION PREVENTION PROGRAM
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WHAT IS POLLUTION PREVENTION?
1-4
Pollution prevention (also known as source reduction and waste minimization) is any
action that reduces the production of wastes (at their source) that may be released to the
air, land, or water. Two general methods of pollution prevention are (1) process
changes, and (2) product changes. Various source reduction changes are presented
on Figure 1-1.
Process changes allow resources to be used more efficiently during the manufacturing
process. Process changes include the following:
! Prudent purchasing, in which the company buys the most
appropriately sized container of new material rather than buying too
much and disposing of the unused portion
! Operational changes, such as reusing input materials during
production and reducing water consumption in the process lines
! Technology changes, such as using a safer process material
! Increased energy efficiency
Table 1-1 summarizes specific examples of process changes.
Product changes reduce the volume of pollution by reducing the impact of the finished
product on the environment. Product changes include the following:
! Development of a less chemical-intensive product
! Development of a higher-quality product that lasts longer
! Incorporation of a life-cycle analysis including the use and disposal
options for the product
Other Environmental Management Strategies
There are a numerous pollution control measures that are applied only after wastes are
generated. They are, therefore, not correctly categorized as pollution prevention. Table
1-2 provides some examples of procedures that are waste management measures but are
not pollution prevention.
Companies should recognize that transferring hazardous wastes to another
environmental medium is not pollution prevention. Many waste management practices
to date have merely collected pollutants and moved them from one environmental
medium to another. For example, solvents can be removed from
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GOALS AND BENEFITS OF A POLLUTION PREVENTION PROGRAM
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TABLE 1-1
SOURCE REDUCTION: PROCESS CHANGES
The process changes presented here are pollution prevention measures, because they reduce the amount of waste
generated during production.
Examples of input material changes
! Switch to nonsolvent-based coatings and finishes.
! Use a less hazardous or toxic solvent for cleaning, coating, or finishing.
! Purchase raw materials that are free of trace quantities of hazardous or toxic impurities.
Examples of technology changes
! Redesign equipment and piping to reduce the volume of material contained, thereby reducing losses
during batch or color changes or when equipment is drained for maintenance or cleaning.
! Change to mechanical stripping and cleaning devices to avoid solvent use.
! Use spray systems with higher transfer effectiveness.
! Install a hard-piped vapor recover system to capture and return emissions.
! Use more efficient equipment.
Examples of improved operating practices
! Train operators.
! Cover solvent tanks when not in use.
! Segregate waste streams to avoid cross-contaminating hazardous and nonhazardous materials.
! Increase control of operating conditions (including flow rate, temperature, pressure, residence time,
and stoichiometry) and change maintenance scheduling, recordkeeping, or procedures to increase
efficiency.
! Optimize purchasing and inventory maintenance methods for input materials. Purchasing in
quantity can reduce costs and packaging material if care is taken to ensure that materials do not
exceed their shelf life. Reevaluate shelf life characteristics to avoid unnecessary disposal of stable
items.
! Prevent leaks, drips, and spills and use drip pans and splash guards.
! Turn off electrical equipment such as lights and copiers, when not in use.
! Place equipment in a manner that will minimize spills and losses during transport of parts or
materials.
GOALS AND BENEFITS OF A POLLUTION PREVENTION PROGRAM
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TABLE 1-2
WASTE MANAGEMENT STRATEGIES THAT ARE NOT POLLUTION PREVENTION
Off-site recycling
! Off-site recycling (for example, solvent recovery at a central distillation facility) is an excellent
waste management option. However, because it does not reduce the actual amount of pollution
generated, it is not a pollution prevention measure.
Waste treatment
! Waste treatment involves changing the form or composition of a waste stream, through controlled
reactions, to reduce or eliminate the amount of pollutant. Examples include pretreatment,
detoxification, incineration, decomposition, stabilization, and solidification or encapsulation.
Concentration of hazardous or toxic constituents to reduce volume
! Volume reduction operations, such as dewatering, are useful treatment approaches, but they do not
eliminate or reduce the amount of pollutants being generated. For example, pressure filtration and
drying of a heavy metal waste sludge before disposal decreases the sludge water content and waste
volume, but it does not decrease the number of heavy metal molecules in the sludge.
Diluting of constituents to reduce hazard or toxicity
! Dilution is applied to a waste stream after it is generated. Dilution does not reduce the absolute
amount of hazardous constituents entering the environment.
Other control technologies
! Control technologies are generally "end-of-pipe" approaches to pollution. Many control
technologies that have been used have only collected pollutants and moved them from one
environmental medium (air, water, or land) to another. For example, filters that collect paint
overspray may prevent air pollution, but they create a solid waste problem.
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wastewater using activated carbon. However, regenerating the activated carbon
requires using another solvent or heating, which transfers the contaminants to the air.
In some cases, this type of waste management strategy is a valid treatment option.
However, too often the purpose has been to shift a pollutant to a medium that is
regulated less stringently.
For example, waste treatment prior to disposal reduces the toxicity and/or disposal-site
space requirements but does not eliminate all pollutant materials. Frequently, the effect
is to transfer pollution from air or water to land. Conventional waste treatments
include processes such as volume reduction, dilution, detoxification, incineration, and
stabilization.
Off-site recycling, which is another waste management strategy, is vastly preferable to
other forms of off-site waste handling, because it helps to preserve raw materials and
reduce the amount of material that will require disposal. However, compared with
closed-loop recycling (reuse) performed at the production site, off-site recycling is
likely to have more residual waste that requires disposal. Furthermore, waste
transportation and the recycling process carry the risk of worker exposure and release
to the environment.
The pollution prevention hierarchy, represented on Figure 1-2, prioritizes waste
management options from those that are most environmentally beneficial to those that
are least environmentally beneficial. Specific technical information on pollution
prevention options for the wood finishing industry is in Section II of this manual.
GOALS AND BENEFITS OF A POLLUTION PREVENTION PROGRAM
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1-10
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Section II
Pollution Prevention in the
Wood Finishing Industry
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Chapter 1
THE WOOD FINISHING INDUSTRY
This manual is targeted mainly toward wood finishing as it applies to the following
industries: (1) wood household furniture, (2) wood office furniture, (3) wood kitchen
cabinets, (4) wood office and store fixtures, partitions, shelving, and lockers, and
(5) any industries closely related to these. Wood finishing companies range in size.
Most employ fewer than 50 people. The wood finishing process is often
labor-intensive. It usually includes sanding and staining, followed by coating (used
interchangeably with "finishing" in this manual), drying, and resanding in repeated
steps until the desired finish is obtained. The function of the finishing is to provide the
end product with the final appearance and resiliency that satisfies the customer.
Facilities vary greatly in product type and quality.
The three grades of furniture—the main product of the wood finishing industry —are
often described by the industry as high-end, medium-end, and low-end. Generally,
high-end furniture is constructed of solid wood and wood veneers, with the wood grain
showing through the finish. A high-end piece might require 30 to 35 finishing
operations. Low-end furniture is often made of medium-density fiberboard with some
plastic components and some natural wood. The piece often has a colored or printed
wood grain finish and might require only six to 12 finishing operations. Figure II-1
shows a typical wood finishing sequence.
In small facilities, wood stock is often moved manually between stations. However, in
larger facilities, the wood is moved mechanically along the finishing line. In some
cases, pallets—with the wood product on them—are pulled by cables or chains. In
other cases, various types of conveyor belts are used. Many facilities use a
combination of these methods. Generally, furniture is assembled first; the finish is then
applied. Cabinets, on the other hand, are frequently finished before being assembled.
The processes generally involved in manufacturing a value-added wood product -for
example, apiece of furniture—include (1) shaping raw stock, (2) assembling parts, (3)
applying a finish, and (4) packaging and shipping. Of these processes, application of
a finish is the major source of pollution in the wood products industry. This manual
focuses on the means of economically minimizing this pollution. Wastes from the
remaining operations are mainly nonhazardous. For the purposes of this manual, the
wood finishing process is defined to comprise (1) sanding, (2) coating, and (3) the
ancillary operations of equipment cleaning and coating preparation.
The wood finishing
industry
manufactures a
THE WOOD FINISHING INDUSTRY
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Because finishing materials have traditionally been solvent-based, the issue of pollution
prevention in the wood finishing industry is closely tied to the issue of reducing
emissions of volatile organic compounds (VOC).
The emission of VOCs—including methyl ethyl ketone, methyl isobutyl ketone
methylene chloride, toluene, andxylenes—into the atmosphere is the most serious
hazardous waste issue currently confronting the industry. Solvents with high VOC
content are commonly used in stains, paints, finishes, and glues, in addition to stripping
and cleaning operations. The U.S. wood finishing industry is dominated by the use of
nitrocellulose lacquers, which—apart from their high VOC content—are hazardous
also because of their high flammability.
Most VOC emissions generated by the wood finishing process are from (1) the spray
booths, where the coatings are applied; (2) the flashoff areas and ovens, where the
finish hardens; and (3) cleanup operations.
Depending on the line of products being manufactured, different sizes and types of
spray booths are used. A typical spray booth for a facility manufacturing residential
furniture is shown on Figure II-2. Most spray booths of this type are open. Other types
of booths are mainly enclosed.
Flashoff areas are either between spray booths or between a spray booth and an oven.
Some flashoff areas use forced air circulation to increase solvent evaporation. When
fast-drying finishes are used, pieces may be completely cured in these areas. Other
finishes may require ovens. Depending on the type of finish used, the ovens are heated
to between 38°C and 121 °C (100°F to 250°F) or may use infrared or ultraviolet
energy sources.
Solvents are often used to clean application equipment, piping, and spray booths, and
to strip cured coating from wood parts or equipment. Emissions can be reduced
economically in each of these segments of the wood finishing process. Chapter 2
covers various options for pollution prevention. Some options may reduce emissions
from several segments of the wood finishing process. For example, changing to a
coating material with a lower VOC content will reduce emissions from the spray booth,
flashoff areas, ovens, and cleanup activities.
VOC emissions is the
most serious
pollution problems.
POLLUTION PREVENTION OPTIONS IN THE WOOD FINISHING INDUSTRY
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Chapter 2
POLLUTION PREVENTION OPTIONS FOR THE
WOOD FINISHING INDUSTRY
The list of pollution prevention options presented in this chapter is extensive but not
exhaustive. Research is ongoing in the areas of coating composition and application
methods. Also, the best solutions to problems are often original, discovered by
creative employees and resourceful management. Additionally, this manual was
prepared as an overview of pollution prevention in the wood finishing industry. The
manufacturers within the industry vary widely in size and product; consequently, not
every option presented will be appropriate for every company. Each company should
implement the options that reduce pollution the most while maintaining or improving
product quality goals and the company's bottom line. Pollution prevention presents not
only an opportunity to improve worker health and safety, and the quality of your
environment, but also many opportunities for increased profitability. A manufacturing
company's finances may be approximated by the following simple equations:
Product = Raw Material — Waste
and
Income = Product x Price
Any waste produced by a company is potential product wasted. For example, any
finish that ends up on the floor instead of on the wood is a raw material that was
purchased and could have been part of a finished product; instead, it is merely
waste material Not only is the wasted finish material never sold as part of the
product, but it now costs money to clean up and dispose of. Additionally, whether you
are in the U.S. or Mexico, this disposal cost will only increase.
As mentioned in Section I, there is a hierarchy of options that deal with waste. The
most preferable is source reduction—decreasing the amount of hazardous material
used, then recycling or reusing the material, followed by treating the waste and finally
disposing of it. Although recycling is not necessarily a method of pollution prevention,
some aspects of recycling are covered in this chapter. Source reduction and recycling
involve many alternatives. Throughout this chapter, options are given in a roughly
descending order of desirability.
Pollution prevention
improves worker
health and safety,
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
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SANDING
Dust collection
systems extend
equipment life.
Wood waste can be
used for decorative
landscaping or
Source Reduction
As the cost of raw materials increases, manufacturers must seek more effective uses of
timber and veneer. Because thinner veneers are often being used, sanding with minimal
stock removal is becoming more important. This has resulted in the use of segmented
polishing platens. Platens may be controlled electronically or pneumatically. The
electronic sanding platen is more sensitive, but the pneumatic sanding platen is much
cheaper. Sanding with air pressure helps to dissipate heat, allowing a more uniform
finish at a higher grit without varnishing the panel. Dust collection is important for
worker health and for extending equipment life. Without a dust collection system, dust
becomes embedded in the sanding belt, thereby shortening belt life and reducing the
quality of the finish. Wood dust also tends to work its way into machinery, increasing
maintenance costs.
Proper Technique
Paper belts, rather than cloth belts, should be used on hardwoods. Paper belts cost
about one-half as much as cloth belts and give a better finish, because the abrasive
is more uniform on paper belts than on cloth belts. Another simple tip for sanding
efficiency is to never skip more than one belt. If grit is changed by too much, removing
the scratches left by the larger grit will be difficult.
Recycling—Wood Waste to Energy
Traditionally, wood waste has merely been dumped into landfills. Because the cost of
disposal will only increase, businesses need to seek more productive alternatives than
throwing away so much of their raw materials. Wood waste recycling options include
(1) grinding to reduce volume of waste stored; (2) shredding to form animal bedding,
mulch, or decorative landscaping; and (3) burning for energy production. Wood by-
products are a cheap fuel Consequently, using wood waste as fuel potentially
solves two problems: (1) it eliminates problems associated with disposal, and (2) it
saves money as an inexpensive fuel source. Wood waste, especially waste from
unfinished wood, may be used in a wood boiler, typically operating at around 1,600°K,
to convert the wood into energy with minimal hydrocarbon emissions. However,
burning wood with plastic laminate, containing chlorides, is a problem because of
concern over possible formation of chlorinated hydrocarbon. The operator should be
familiar with all applicable regulations before a wood boiler is used.
To take full advantage of wood waste as an energy source, a company should automate
its feed system to the greatest extent possible. Controlled feeding
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yields more efficient combustion, and labor costs for hand feeding will only increase.
In many cases, there are enough waste and scrap to not only produce enough power for
the whole facility, but also to heat or cool the facility. If there are a few small wood
finishing operations in one area, it would be possible for these companies to combine
wood waste so that they could have sufficient quantities to generate power or to sell or
distribute for other purposes.
FINISHING
Variations in the finishing procedure are too numerous to list exhaustively, but wood
finishing usually consists of some combination of the following materials being applied
in the following order:
1. Size, coat and/or bleach to prepare the wood and ensure uniform color
2. Stain to achieve the desired color
3. A washcoat to smooth the wood
4. Filler, fill-glaze, or oil sealer
5. Wood sealers
6. Glaze and/or shading stains
7. Topcoats
Each of these materials is available in various general formulations. For example,
stains, sealers, and topcoats are available in water-based and nitrocellulose-based
formulations. This section will discuss these general types of formulations, rather than
individual materials (such as stains, sealers, and fillers).
The most significant source of pollution in the wood finishing industry is the VOC
content of the finishes used to provide the product's final appearance. Two main
areas to consider when developing your pollution prevention plan are the materials of
which your coatings are made and the application methods used. The type of coating
is important, because available materials vary widely in their VOC content—the lower
the VOC content, the less pollution will be generated. Application methods are also
very important—the better a process transfers the coating to the wood, the more money
a company will save and the less pollution it will generate.
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Choosing the best
finish is important
for environmental
Source Reduction
Alternative Coatings
Switching to a different coating material can reduce or even possibly eliminate
hazardous waste. It requires a strong organizational commitment to change finishing
materials. Such a change, however, can eliminate many health and environmental
problems and result in a comparable or even superior finish. Of course, not every
alternative finish is right for every product. Time must be spent to find the acceptable
alternative. This section first discusses the properties of traditional nitrocellulose-
based coatings and then presents several types of alternative coatings.
Nitrocellulose-Based
Nitrocellulose-based coatings are by far the most frequently used type of finish in the
U.S. wood finishing industry. The properties of nitrocellulose-based coatings are
presented here to establish a standard against which the alternative coatings may be
judged.
Nitrocellulose is a resin that acts as a binder in the coating material. Different types of
organic solvents must be mixed with nitrocellulose. Some solvents are added because
of their evaporative properties, and some are added because of their ability to dissolve
the nitrocellulose. This blend causes the coatings to dry quickly and gives them a
desired viscosity. Nitrocellulose coatings are nonconvertible coatings, meaning that
film formation occurs via solvent evaporation—no chemical reaction, or curing, takes
place. The resulting finish has low resistance to heat and solvents. Because of this, the
finishes are easy to damage and relatively easy to repair. Nitrocellulose-based coatings
are classified as fast-drying. They contain about 6 pounds of VOCs per gallon of
coating, not including water. The solids content of the nitrocellulose-based lacquers
is about 16 percent by volume. This relatively low solids content is necessary to
achieve the needed viscosity.
Finishing with nitrocellulose-based coatings is a familiar, well-developed procedure.
Nitrocellulose coatings are (1) easy to apply, (2) dry quickly at ambient temperature,
and (3) perhaps most important—produce the final appearance that manufacturers
believe customers want. However, these coatings have several major drawbacks.
First, nitrocellulose is highly flammable. Second, it requires the use of organic
solvents that are expensive, toxic, and quick to volatilize. Finally, the resulting
finish is not very durable, and it yellows in sunlight. Switching to alternative
coatings has many benefits. However, when considering a switch, an organization must
remember to adapt its equipment; perhaps even more important, it must adapt its
personnel training to the new finishing material.
II-8
Pollution Prevention for the Wood Finishing Industry
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Waterborne
Waterborne coatings are widely considered the future of the wood finishing industry.
There are many types of water-based coatings. What all of these coatings have in
common is that water is the major solvent or carrying liquid for the film-forming
polymers. Within waterborne coatings are three types of polymer systems: (1) water
emulsions, (2) water-reducible resins (solutions), and (3) colloidal dispersions.
Coatings formulated with water-emulsion polymers contain water-insoluble spherical
particles of high molecular weight uniformly dispersed in water. Water-reducible resins
are completely soluble in water or water-solvent mixtures. Colloidal dispersions
contain medium molecular weight polymers that combine the properties of the water-
emulsion polymers and the water-reducible polymers.
Depending on the type of polymer in their formulation, each type of waterborne coating
exhibits different film properties. Understanding the advantages and disadvantages of
each type makes coating selection easier. Water-emulsion formulations produce
finishes that are durable and stain-resistant.
Water-reducible formulations offer high gloss, clarity, and good application properties.
However, the film is not as durable as the water emulsions. Viscosity depends on
molecular weight, making the water emulsion formulations the most viscous. Colloidal
dispersion formulations offer high gloss, good application properties, durability, and
resistance to chemicals and staining. Different waterborne coatings require a different
drying method; some require air or forced air, and others require elevated temperature.
The VOC content of water-based coatings varies substantially. Cosolvents are usually
added to allow adequate coalescence and film formation, and aid penetration of
pigmented materials. Most waterborne coatings have a VOC content of from 1.3 to 2.3
pounds per gallon, less water. The coatings range from 26 to 30 percent solids by
volume. These waterborne finishes represent a 90 to 95 percent reduction in VOC
emissions per volume of solids applied. The total emission reduction for a facility
depends on how many steps, formerly using nitrocellulose coatings, can be converted
to using water based finishes. The major disadvantage of water is that it evaporates at
a slower rate than solvents.
Each type of coating material is associated with a different set of concerns. The
following factors that should be considered when using waterborne coatings:
! Waterborne coatings should generally be stored at temperatures above
freezing.
! Equipment must be cleaned immediately after use, because the dry
coatings are no longer water-soluble.
Waterborne coatings
may be the future of
the industry.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
II-9
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Today, Waterborne
formulations give
finishes comparable
Equipment can be
cleaned with soap
and water.
\ Sagging and grain raising are potential problems that must be
addressed.
! Equipment pumps, containers, and application equipment should be
corrosion-resistant.
! Humidity has a large effect on the drying rate and must be accounted
for.
! Current water-based finishes are available and satisfactory for most
applications, but there are often subtle differences in the final
appearance.
! Waterborne coatings are generally more susceptible to air
entrainment; consequently, aeration should be minimized by returning
coating material to the tank below the fluid level and minimizing the
splash caused by agitators.
! For the coating to adhere well, surfaces must be free of oil films.
Waterborne finishing materials are used by a growing number of companies.
Water-based coatings are generally 25 to 50 percent more expensive than traditional
materials, but—because they have twice the solids content—they are at least as cheap
to use. In the past, the water-based coatings were suitable only for low-end products.
The first water-based finishes had problems with grain raising and with clarity, but
these problems are diminishing as new formulations are generated. Waterborne
lacquers are now durable and offer good clarity and sandability. Water-based finishes
currently offer many benefits over conventional nitrocellulose lacquers, including
(1) greater resistance to moisture, chemicals, impact and reverse impact, and
abrasion, (2) adaptability to a wide range of application methods, (3) low toxicity,
(4) low VOC content, and (5) cleaning of equipment with soap and water.
Waterborne coating can usually be applied with the same methods as traditional
solvent-based finishes. The main cost of conversion is for installing corrosion
resistant equipment. An added incentive is the decrease in insurance costs that
results from switching to a water-based system. Insurance for facilities that use
only water-based coatings averages 50 percent less than for shops that use
solvent-based formulations.
Polyester
Nitrocellulose lacquers dominate the U.S. wood finishing industry. However, this is
not the case in all countries. In other parts of the world, polyester-based and
polyurethane-based coatings predominate.
11-10
Pollution Prevention for the Wood Finishing Industry
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Two types of polyester coatings are available. The first type is a styrene-derived
polyester. Here, styrene is used as a solvent and reactant for unsaturated alkyd resins
contained in the coatings. The formulations also contain a drying agent, usually a
heavy metal, and may be cured through a catalytic reaction or by ultraviolet (UV)
radiation. Acrylic polyesters comprise the second type of polyester coatings. These
contain organic solvents and cross-linking acrylics. They are cured either by catalytic
reaction or exposure to UV radiation.
Both types of polyester coatings are fast-drying with films that are durable and resistant
to heat, chemicals, and impact. Because the polyester films are so durable, they are
also very difficult to repair after curing. Styrene-based polyesters are usually 100
percent solids VOC emissions of near zero. The acrylic polyesters have a VOC
content of about 3 pounds per gallon, less water, with a solids content of 30 to 50
percent by volume. Each step converted from nitrocellulose-based coatings to
polyester coatings would result in an 85 to 100 percent reduction in VOC emissions.
However, polyester finishes are chemically incompatible with nitrocellulose; mixing
these compounds is a potential explosive hazard. Polyesters and nitrocellulose finishes
should never be used on the same piece. The aesthetic and chemical compatibilities of
different coatings should always be considered before coating types are mixed on the
same piece.
Polyurethane
As with polyester coatings, polyurethane finishes are used infrequently in the U.S. but
are common in other countries. Polyurethane coatings are formed through the reaction
of a polyhydric alcohol with an isocyanate cross-linking resin. Classification of
polyurethane finishes depends on the formulation or cure process, as follows: (1) one-
component products, (2) two-component products, and (3) moisture-cured materials.
The two-component products are convertible coatings; film formation occurs through
polymerization. Moisture-cured coatings are not fully cured through polymerization;
rather, the final curing occurs when moisture in the environment reacts with the
material to form a dry film. Moisture-cured coatings can take up to several months to
cure. Once cured, all polyurethane coatings are very durable and are characterized as
good for polishing, providing a high-gloss finish. As with polyester finishes, the high
durability of polyurethane coating means that it is very difficult to repair after curing.
Within the last few years, a two-component waterborne polyurethane resin has been
developed. It combines the finish properties of the traditional solvent-based
polyurethanes with the advantage of a zero VOC content. The traditional
polyurethanes have a VOC content of about 3.4 pounds per gallon, less water. They
are between 40 and 60 percent solids by volume. Overall, traditional polyurethanes
would represent about an 80percent reduction in VOC emissions
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-11
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from those of nitrocellulose-based finishes. As with all coating types, the overall
pollution reduction depends on how many steps could be converted to the alternative
coating.
Carbon Dioxide rCO.VBased
Union Carbide has developed the Unicarb™ coating system for minimizing VOCs.
This system uses supercritical COy instead of organic solvents or water, to dissolve
the coatings. The Unicarb™ coatings contain polymers and coalescing solvents,
whereas the cutting solvents are omitted. In most formulations, cutting solvents are
used to decrease viscosity and enhance atomization. The Unicarb™ system uses CO2
to decrease viscosity and enhance atomization. The viscous coating and supercritical
carbon dioxide are blended in a mixing chamber. Generally, compared to traditional
coatings, 1 pound of carbon dioxide "replaces" 1 pound of cutting solvents. The
mixture is released as an atomized paint through an airless spray gun. The CO2
evaporates from the atomized coating. The deposited paint, still containing the
coalescing solvents, cures conventionally, either by air drying or baking. The quality
of the atomized coating is considered superior to conventional airless atomization and
similar to that obtained by conventional air atomization.
The Unicarb™ coatings contain about 4.7 pounds per gallon, less water, of VOCs and
they are about 34 percent solids by volume. Overall, VOCs are reduced by about 50
percent. The exact properties depend on the type of coating used in the system. A
company using the Unicarb™ system has the advantage of not having to completely
reformulate its finishes, while it is still reducing VOC emissions. A nitrocellulose
Unicarb™ coating, for example, will produce a film with the same advantages and
disadvantages as the traditional film but will have lower VOC emissions. The main
disadvantages of Unicarb™ are the lack of demonstrated performance by
manufacturers and the royalties that must be paid.
Ultraviolet OJVVCurable
The main components of UV-curable coatings are polymers, diluent monomers, and
photoinitiators. UV curing uses high-intensity UV light to react with the
photosensitizers, thereby creating free radicals that initiate crosslinking to form the
solid film. Consequently, UV-curable coatings are convertible. Much of the diluent
UV curin? is
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emissions is from 80 to nearly 100 percent Curing three-dimensional pieces remains
difficult, because all of the finish must be exposed to the UV radiation. Some UV
ovens have been designed to accommodate three-dimensional pieces. However,
because the UV lamps need to be arranged for each type of furniture, these ovens would
be practical only for a product line that manufactured the same design for a reasonable
length of time. Currently, UV curing is still used mainly for flat products. However,
the curing is rapid, and the product is heated little during curing, resulting in higher
productivity and lower space requirements. Curing also uses less energy than thermal
curing. UV curing will typically use one-fifth of the energy used by a comparable
thermal curing line. Energy is absorbed only by the coating and is not wasted by
heating the air or workpiece. All UV coating materials are, basically, single-component
systems that do not require the addition of catalyst. UV curing is one form of radiation
curing; radiation curing is also accomplished by using infrared radiation and electron
beams. The cost of a UV curing system varies from $4,200 to $200,000.
Table II-1 shows overall reductions in VOC emissions possible for each step where
nitrocellulose-based coatings are replaced by an alternate coating. The total VOC
reduction depends on how many steps can be converted to using an alternate coating
material.
TABLE II-l
REDUCTIONS IN VOC EMISSIONS POSSIBLE FOR
EACH STEP WHERE NITROCELLULOSE IS
REPLACED WITH AN ALTERNATIVE COATING
Coating Material
Nitrocellulose
Water-based
Polyester
Polyurethane
CO2-based
UV-Curable
Percent Reduction in VOCs
0%
90 - 95%
85 - 100%
80 - 100%
~ 50%
80 - 100%
Table II-2 summarizes the advantages and disadvantages of each type of coating.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-13
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TABLE II-2
COATINGS
Coating
Advantages
Disadvantages
Water-based
Durable
At least as cheap to use as
conventional coatings
Low VOC content
Equipment cleans with soap and
water
Decreased insurance costs,
because fire hazard is eliminated
Lower volume of material to
store
Need for corrosion-resistant
equipment
Evidence of grain raising on
some types of wood from
some formulations
Possible need for air
movement or heat to facilitate
drying
Surface must be free of oily
films
Higher viscosity, possibly
requiring changes in piping
and pump system
Need for better temperature
and humidity control
Polyester and
Polyurethane
! High gloss
! Very durable
! Low VOC content
Difficult to repair
Requires a "clean room"
environment
CCvbased
! Low VOC content
! Elimination of the cost, odor,
flammability, toxicity, and oven
sagging associated with cutting
solvents
Royalty costs
Special sprayer and delivery
system needed
Pumps and mixers required to
handle the viscous Unicarb™
formulations
Limited industrial experience
UV-curable
! Low energy costs
! Very low VOC content
! Very durable finish
! Rapid curing
Higher coating costs
Difficult to cure
irregular-shaped pieces
Limited to clear or semiclear
finishes and thin films
Nitrocellulose
! Established methods
! Easy repair
! Fast drying
Average to poor durability
High VOC content
Toxic and flammable
11-14
Pollution Prevention for the Wood Finishing Industry
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Application Methods
The following techniques are used for coating applications: (1) flat line finishing,
(2) spray application, (3) brushing, and (4) dipping. Within each technique there are
many variations. Flat line finishing is used to coat only flat stock. Dipping is usually ^QW transfer
not used for hollow pieces. Spraying is the most commonly used technique. One way efficiency = money
of measuring the efficiency of coating usage is to examine transfer efficiency (TE). TE wasted
is defined as the ratio of the solid coating deposited on a surface to the total amount of
coating used, expressed as a percentage. For example, if one-half sprayed of the
coating stays on the target, the system has a TE of 50 percent. Although 50 percent TE
is almost twice that usually achieved by conventional spray guns, one-half of all
material purchased is still wasted. Examples of savings from improved TE (for
example, by better equipment or operator training) are shown in Table II-3.
Electrostatic
During electrostatic finishing, coating particles are atomized and given a negative
charge, whereas the piece to be finished is either grounded or given a positive charge.
Electrostatic attraction pulls the particles to the product. This attraction results in a
high TE, which allows each piece to be finished with fewer passes, thereby using less
coating material and saving time and money. The main advantage of using this type
of system is the high TE. One effect of electrostatic finishing responsible for increased
TE is called "wraparound." This is the tendency of the charged coating particles to
effectively cover the sides of the piece being sprayed and even for particles that go past
the piece to be attracted to the back of the piece. Another property of electrostatic
finishing, the Faraday cage effect, causes the particles to deposit only around the
entrance of a cavity, often making touchup painting necessary. The particles must
possess sufficient momentum to overcome the Faraday cage effect but not so much that
the attractive forces are completely negated. Therefore, balancing particle velocity with
electrostatic voltage is essential to optimizing TE. Another consideration is that the
workpiece must be a conductor. Obviously, this is no problem for metal finishing, but
it is a concern for wood finishing. When the wood has a sufficient moisture content,
it is a reasonably effective conductor. However, when the wood is very dry, it does not
conduct well enough on its own. Nonconductive surfaces must be treated with a
coating that increases the electrical attraction between the charged coating particles and
the piece to be finished. One common type of treatment is to apply sensitizers to the
wood surface. Sensitizer formulations are applied in a thin colorless film that picks up
moisture from the surrounding air. This moisture makes the piece conductive enough
to spray electrostatically and the sensitizer dissolves into the applied coating. Using
a sensitizer is a process that is sensitive to humidity and is not
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-15
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TABLE II-3
SAVINGS PER $1,000 SPENT ON COATING MATERIALS WITH IMPROVED
TRANSFER EFFICIENCIES (TE)
NewTE
45% 50% 60% 70% 80% 90%
Old
TE
20%
25%
30%
35%
40%
45%
556
444
333
222
111
0
600
500
400
300
200
100
667
583
500
417
333
250
714
643
571
500
429
357
750
688
625
563
500
438
778
722
667
611
556
500
Note:
Example—A company uses 100 gallons of finish per month spraying cabinet doors ($10 per
gallon for a total of $1,000). The conventional spray guns that the company uses are 30 percent
efficient. If company switches to an air-assisted airless spray system which is 60 percent
efficiently, the company would save $500 per month.
11-16
Pollution Prevention for the Wood Finishing Industry
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effective when relative humidity is below 40 percent. The rewards of using electrostatic
finishing may be worth the effort, however, because the coating cost may be reduced by
about 40 percent.
The two main types of electrostatic equipment are rotary atomizers and electrostatic spray
guns. Some rotary atomizers use rotating disks, and others use balls. Disks are best for
long thin parts and flat pieces, whereas balls are better for shorter, wider pieces. Low-speed
rotary atomizers rely on electrostatic force to atomize the coatings, whereas the high-speed
versions use centrifugal force to atomize the coatings. Both apply a negative charge to the
particles. Electrostatic spray guns may be of either the air or airless variety. These spray
guns operate in a manner similar to that of conventional guns, using air or fluid pressure for
atomization. Additionally, the particles are charged by an electrode at the tip of the gun.
The overall TEs are generally better with the rotary atomizers than with the electrostatic
spray gun. Electrostatic spray guns produce particles with greater momentum, tending to
increase overspray. Also, they are less efficient at electronically charging the paint particles
than the rotary atomizers. Electrostatic spraying equipment can cost over $60,000 and,
consequently, may be too expensive for smaller shops.
High-Volume/Low-Pressure (HVLP) Spray
HVLP spray guns use a high volume of air at low pressure—no greater than 10 pounds per
square inch (psi)—to atomize a stream of coating material. At low pressures, coating
materials are propelled at lower velocities than with conventional systems. At these lower
velocities, "bounce-back" is minimized, and TE is improved. This softer spray is also good
at penetrating recessed areas. However, this higher TE is achieved at the cost of a lower
fluid flow rate. The finish achievable with HVLP is comparable to finishes with increasing transfer
conventional spray, when efficiency from 30%
low- to medium-viscosity coatings are used. As with all spray gun techniques, TEs t ^QO/ w/-// cu+
depend on operator skill level, type of equipment, coating formulation, and operating
pressure. HVLP systems typically have TEs in the 40- to 70-percent range. As
described in a later section, operator skill level is the most reliable predictor of TE.
Nevertheless, it is also vitally important that gun performance is optimized, for example,
with proper system pressure and the optimal spray gun tip.
There are two basic types of HVLP systems; one is operated with a compressor; the other
is operated with a turbine. When a compressor is used a conversion kit is purchased to
allow the use of HVLP. This kit contains filters to clean the air and a regulator to control
air pressure. Turbines are ideal for use with HVLP systems, because they are designed to
produce a high volume of warm, dry, low-pressure air. The heated air produced by most
turbines can improve the ability of coating to flow and speed drying.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-17
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Airless Spray
11-18
As the name implies, this method of atomizing coatings does not use compressed air.
Instead, hydraulic pressure is used to force the material through the small opening of the
spray gun nozzle to atomize the coating. The system can be adjusted either by adjusting
the viscosity or changing the fluid pressure. Airless systems have several advantages.
First, airless systems have better TEs than conventional systems. Second, when heavy
films are desirable, a single coating with airless spray often yields results that would
require two coats, applied conventionally. Also, because the airless guns deposit material
faster, a gun may be moved faster to produce a given film thickness. This results in
greater productivity and less operator fatigue. Other reported benefits are (1) fewer
rejections, because of a more consistent finish, and (2) as much as 15 percent savings
in material costs.
Although materials do not need to be reformulated for use with an airless system, heating
the coatings is one way to improve the system. Heating coating materials for an airless
system provides three main advantages: (1) because of increased atomization, finer
finishes are possible; (2) because of the lower viscosity of heated liquids, hydraulic
pressures necessary for atomization may be lowered, and (3) the heated spray facilitates
solvent evaporation for faster drying. The main disadvantage of airless spray is that the
quality of the finish is usually lower than with conventional spray. This is not true in
applying thicker coats, however, in which airless spray is quite effective.
Air-Assisted Airless Spray
In an air-assisted system, air jets assist in the final break-up of a pressurized liquid stream.
Air-assisted, airless spray systems use a pressurized stream of coating, as with airless
spray, with air jets assisting in the atomization of the coating material. This system wastes
less paint and achieves a higher quality finish than an airless spray. In fact, the finish
achieved with air-assisted airless spray is comparable to the finish obtained with
conventional air spray, and a 5 percent reduction in annual feedstocks has been
documented.
Vacuum Coating
Vacuum coating is another application method with a TE of near 100 percent, but it is also
limited in the shapes of pieces that it can accommodate. The application is performed in
a coating chamber. This chamber has openings on opposite sides that are the same shape
as, but slightly larger than, the piece to be finished. Coating material fills the chamber to
above the openings. Because the chamber is under a vacuum, coating material does not
spill out of the openings. The workpiece is passed through the chamber. After the
workpiece exits the chamber, a stream of air removes the excess finish. Film thickness is
controlled by varying the coating's viscosity, the magnitude of the vacuum, and the
intensity of the air jet. The major
Pollution Prevention for the Wood Finishing Industry
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limitation of this technology is that it can accommodate only pieces possessing the same
silhouette dimensions over the entire length of the part. The system is intended mainly for
use with waterborne coatings, because the vacuum would tend to deplete solvent-based
finishes.
A few advantages that a company could receive from using this technology are
(1) significantly lower material costs, resulting from very high TE, (2) improved
coating quality, (3) higher productivity, and (4) lower direct labor costs.
Flat Line
As the name implies, flat line finishing is the coating method of choice for finishing
essentially flat workpieces. Prior to finishing, the pieces are sanded to uniform thickness,
and a filler is applied to function as a base for the subsequent coatings. Roll coaters apply
the finishes and are often engraved to produce a wood-grain effect on panels made from
particle board. Applying the finish with rollers results in a very high TE and allows the use
of high solids coatings that are difficult or impossible to spray. UV curing is an excellent
option after flat line finishing, because it is efficient at curing flat pieces. If a company
manufactures flat pieces, it can use materials much more efficiently, with significant
savings, by converting from conventional spray finishing to flat line finishing or another
technique designed for flat pieces, for example, curtain coating or vacuum coating.
Curtain Coating
Curtain coating, or "pouring," is a high-speed production process for applying smooth films
to flat or moderately curved workpieces. This is related to the older principle of flow
coating—moving an object through a continuous falling stream of material. In curtain
coating, however, the piece is passed through a pressure head or over a weir-head at very
high production rates, about 150 meters per minute. The excess coating material is trapped
in a reservoir and recirculated with minimal losses.
Dipping
Dipping is another direct application technique. A workpiece, which may be of any shape,
is submerged in a tank of the desired coating material. The object is removed from the tank,
and the excess is allowed to drain back into the coating tank. It is crucial that the viscosity
of the coating material be optimized to achieve the desired film thickness. It is also vital
that the piece be allowed sufficient time for excess material to drain off while the piece is
still above the tank. Without sufficient time, material will be wasted.
In summary, various acceptable application methods are available, and every organization
should evaluate its application methods periodically and make modifications when
necessary. Table II-4 summarizes the advantages and disadvantages of the various
application methods.
Choice of
appropriate coating
methodology will
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-19
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TABLE II-4
APPLICATION METHODS
Application
Technologies
Conventional
Low- Volume/
High-Pressure
Spray
HVLP Spray
Air- Assisted Airless
Spray
Airless Spray
Electrostatic Spray
Electrostatic Rotary
Atomizers
Dip Coating
Flow Coating
Curtain Coating
Vacuum Coating
Advantages
! Excellent atomization
! High production rate
! Low overspray and good transfer efficiency
! Reduced waste
! Lower booth cleaning costs
! Lower filter replacement costs
! Decreased VOC emissions
! Lower worker exposure
! Good atomization
! Good transfer efficiency
! High coating flow rate
! No air hose
! Good transfer efficiency
! Able to handles viscous fluids
! Good transfer efficiency
! Uniform film thickness
! Edge cover
! Excellent atomization
! Excellent transfer efficiency
! Handles any type of finish
! Uniform film thickness
! High production rates
! Low labor costs
! Excellent transfer efficiency
! Excellent transfer efficiency
! High production rates
! Low labor costs
! Low maintenance
! Excellent transfer efficiency
! Uniform film thickness
! Very high production rates
! High production rates
! Excellent transfer efficiency
! Lower labor costs
Disadvantages
Extensive overspray — poor TE
Booth cleanup costs
Filter replacement costs
Hazardous waste disposal costs
High VOC emissions
Less complete atomization
Need for clean dry air
Slower application rate
! Increased maintenance
! Increased training required
! Skin injection dangers
! Reduced spray pattern coated
! Relatively poor atomization
! Skin injection danger
! Increased training and maintenance
required
! Bulky delicate guns
! High equipment and maintenance costs
! Faraday cage effect
! Importance of cleanliness
! Safety and fire hazard
! Part must be conductive
! Cost
! Faraday cage effect
! Importance of cleanliness
! Safety and fire hazard
! Parts must be conductive
! Cost
! Importance of coating viscosity
! Not suitable for hollow pieces
! Fire hazard
! Below-average appearance
! Below-average appearance
! Importance of coating viscosity
! Viscosity-dependent
! Only for flat work
! Suitable only for pieces with uniform
silhouettes
! Based for use with waterborne coatings
11-20
Pollution Prevention for the Wood Finishing Industry
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Application Technique
Because spray painting allows fast and even coverage with relatively low labor costs, it is
often the application method of choice in the wood finishing industry. However, applying
coatings with a spray gun tends to waste much more material than brushing, rolling, or
dipping, which typically have TEs of over 90 percent. Conversely, spray application can
result in TEs of as low as 20 percent. Any coating material that does not stay on the
product is wasted. If the TE of a system is 30 percent, you are wasting 70 percent of
your money spent on coating materials! Many factors affect TE, including (1) spray
equipment type, (2) equipment maintenance and optimization, (3) size and shape of the
target, (4) type of coating, (5) air pressure and velocity, and (6) fluid flow rate. One way
to improve TE is to use the spray equipment as it was meant to be used. People frequently
increase air and fluid pressure beyond recommended limits. This produces a mist that is
easier for unskilled workers to apply uniformly. Unfortunately, high velocities increase
bounce-back, and the ventilation system tends to carry off most of the coating mist,
resulting in low TEs. Consequently, overspray is directly related to air and fluid pressure;
these pressures should be as low as possible. Figure II-3 shows typical TEs of various
application methods.
Material that does
not stay on product
is material wasted.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-21
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Good training is the
easiest way to save
money.
Air and fluid pressure and spray gun type are very important; however, according to a 1992
study by the Pacific Northwest Pollution Prevention Research Center, the factor most
consistently influencing TE is the skill level of the operator. Therefore, training operators
in proper spray technique is the easiest way to significantly decrease pollution and save
money.
Proper Spray Technique
The following are fundamentals of good spray technique:
Fifty percent overlap of the spray pattern
Spray gun held 6 to 8 inches from the workpiece
Constant gun speed of about 250 feet per minute
Holding the spray gun perpendicular to the workpiece surface
Triggering the gun at the beginning and end of each pass
If less than a 50 percent overlap is used, the workpiece will become streaked.
If more is used, coating material is wasted, and the operator makes more passes than
necessary to finish the piece, requiring excessive time spent on each piece. To maintain a
50 percent overlap, the painter, on the first pass, aims the spray gun nozzle at the edge of
the workpiece. On each subsequent pass, the painter aims the spray gun at the bottom edge
of the previous pass.
The distance between the spray gun and the workpiece must remain constant for a uniform
finish. A separation of 6 to 8 inches is usually ideal. As the separation increases, the width
of the spray pattern on the workpiece increases, and the thickness of the film decreases.
Also, a separation of more than 8 inches often results in some of the finishing material
drying before it reaches the surface. This dry material either bounces off the surface,
thereby wasting material, or sticks to the surface, thereby producing a grainy finish. Spray
guns should be adjusted for the separation that will be used, and operators then need to
maintain that distance.
A consistent finish also requires a constant gun speed. Changing the speed varies the
amount of material being applied to the surface. Low gun speeds may result in the
application of too much finish, causing runs. High gun speeds may result in poor aiming,
improper gun control, and a distorted spray pattern. All of these demonstrate inefficient use
of materials. Gun speeds that are too high may also lead to inadequate coating thickness.
11-22
Pollution Prevention for the Wood Finishing Industry
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&&&*
Maintaining the gun perpendicular to the surface is also important. Failing to hold the gun
perpendicular to the workpiece results in uneven coating, and the increased angle of
incidence of the spray increases the amount of material that rebounds off the surface.
Arcing or fanning the gun constantly changes the gun distance and the gun angle, making
a uniform finish unlikely.
Training Operators
A company can derive the following benefits from a formal training program for spray
operators:
\ Reduced material costs
! Higher quality finish
! Reduced VOC emissions
! Less overspray and reduced cleanup costs
! Higher production rate
Training is often conducted on the shop floor by a coworker who shows spray techniques
to a new operator. This method of training is inefficient at best. The trainee will often pick
up and repeat the bad habits of the coworker. Also, the coworker will often neglect to
convey important points that seem obvious to an experienced operator but are not obvious
to a new employee.
Formal training, however, should include an explanation of the fundamentals of good spray
technique and how these techniques can benefit the operator. First, good technique makes
the job easier for the operator. Through proper spraying, the operator can spray the piece
faster and use fewer strokes. For example, if an operator can reduce the number of strokes
needed to finish a piece of furniture by just five, and the operator sprays 200 pieces each
day, the operator would save 1,000 strokes per day. Second, good spray technique will
result in a higher quality finish. Generally, people take pride in their work and will
appreciate the opportunity to make a better product.
Ideally, each operator should be videotaped periodically. The operator should then meet
with the supervisor and technical personnel to review the tapes. Because spray operators
are usually very knowledgeable, they can often identify poor techniques by watching
themselves on tape. Constructive advice and "hands-on" instruction under production
conditions should follow the videotape review. Next, the operators should be retaped and
given an opportunity to compare the two tapes. This allows the operators to see their
improvement. One company, conducting this training twice a year, reported an 8 to 10
percent reduction in the amount of finishing material being used, resulting in annual
savings of $50,000 to $70,000.
Proper supervision
will ensure that
principles learned in
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-23
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Even with good training, supervision is necessary to ensure that operators do not revert to
bad habits. To maximize TE, regardless of the type of system used, excessive air or fluid
pressure must be avoided to maximize TE.
Also, training must be specific to the equipment and materials being used. For instance,
because of their higher solids content, waterborne coatings do not need to be applied as
thickly as solvent-based finishes.
Operation and Maintenance
Direct Transfer of Coatings to the Spray Guns
A system that transfers coatings directly to the guns, instead of by hand with a bucket,
offers many advantages. It may be economically justified even if your shop uses as little
as 30 to 40 gallons a week.
A direct transfer system eliminates the need to fill a can from a drum each time a coating
is needed. The following savings can be expected:
! Discounted costs from bulk purchases
! Less material waste from minimizing spills, evaporation, and loss of
skimmings on the side of the drum
! Lower labor costs because of less time spent collecting paint from the
storage area, adjusting the coating's viscosity, and filling pressure pots
and gravity containers
! Lower solvent costs, because containers no longer need to be cleaned at
the end of the shift
The savings in time increase productivity. Finish quality is also improved, because the
finishing material that reaches the gun is more consistent.
The three main types of transfer systems are (1) dead-end, (2) simple flow, and (3) fully
recirculating. A dead-end system merely supplies the material to the end point with no
return line. This type should be used only for materials in which settling is not a problem.
A simple flow system has a return line to the storage tank from the farthest point of use.
This continuous circulation prevents settling in most materials. The fully recirculating
transfer system is designed to circulate the material even in the hose of the spray gun. This
type of system is used only for coating materials with very high settling rates.
11-24
Pollution Prevention for the Wood Finishing Industry
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&&&*
Caring for Spray Equipment
All equipment, especially the spray equipment, must be maintained regularly to minimize
replacement costs and optimize performance. This, in turn, helps prevent pollution. The
following measures, among others, will help ensure reliable spray operations:
! Place compressor where it gets fresh air, and clean and lubricate it
regularly.
! To avoid spray gun clogging, keep feed tanks free of dried finish particles
by cleaning them properly, and use proper agitation to prevent skin from
forming.
! Never mix air in material hoses.
! Optimize selection of needle, nozzle, and air cap for each type of finish.
! Do not spray lacquer and varnish in the same booth, because this can
result in spontaneous combustion.
Use Heat Instead of Solvents to Thin Coatings
The viscosity of coatings must often be adjusted before the coating can be sprayed.
Traditionally, this has been accomplished by adding organic solvents. The cost of solvents
is a significant part of the overall cost of materials, and solvents are sources of air
pollution. An alternative to solvent thinning is to use heat to reduce coating viscosity.
Benefits include lower solvent usage, fewer emissions, viscosities that are more consistent,
and faster curing rates.
Closed-Loop Recycling of Lacquer
HisStrand Chemical ofLenoir, North Carolina, has developed a method of recycling
lacquer dust. For this program, the dust must come from conventional nitrocellulose
lacquers. Lacquer dust is the flammable overspray residue in spray booths, on baffles, and
in filters. The only cash outlay required is a sifter, which can be bought for about
$1,500. Depending on the size of the facility, this cost can typically be recovered in a
few weeks to a few months. The process is closed-loop recycling, the lacquer dust is
eventually resprayed onto product. The lacquer dust becomes a basic ingredient in
formulating the sealers, and coatings for backs and drawers. Usually, each pound of lacquer
dust yields 1 gallon of sealer. This reduces disposal costs and material costs, with a
minimal change in labor costs.
Treat equipment as if
it is your own.
Thinning with heat
means faster curing.
Recycling
nitrocellulose
lacquers saves
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-25
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&&&&&&&&&&&&&&&&&&&
Inventory Management
Improved inventory control can reduce costs and minimize waste. If too much finishing
material is purchased, (1) the production of that piece could end, leaving a large quantity
of material unused, and (2) the material may deteriorate before it can be used. Companies
should work with their suppliers to accurately determine inventory needs so that excess is
minimized. Stock stored beyond its shelf life, or stock that becomes unusable because
production has been completed, results in two preventable costs: (1) costs from unneeded
material purchase, and (2) costs associated with disposal of the waste material.
If there is excess finishing material at the end of a production run, a company has several
options. The best option is, obviously, to find another project on which to use the material.
Other options include (1) returning unused containers to the original vendor, (2) contacting
other finishers about their potential needs, and (3) contacting a waste or materials exchange.
Options for managing waste or excess solvents are shown on Figure II-4.
Recycling
Recycling solvents by purifying through distillation is an attractive alternative that will
reduce material cost and minimize waste. Distillation is a proven technology with
equipment available in a variety of sizes. It may be performed on site or by off-site
vendors. On-site recycling that occurs as part of the coating process, closed-loop recycling,
is considered a pollution prevention technique. An example of closed-loop recycling is
recovering coating material from, and returning it directly to, an application unit. Another
option to extend solvent life is to remove particulate matter from the solvent by settling or
filtration so that the fluid may be reused in a rough cleaning of materials.
Another form of on-site recycling is capturing overspray in the spray booth and returning
it to the process. A water wall flowing over a series of baffles at the back of the spray
booth can capture overspray from the air. The coating and water mixture forms a sludge.
If the coating material is immiscible with water, the coating can be easily separated and
recycled. If the coating material cannot be easily separated from water, ultrafiltration can
be used to separate the water from the coating material. Ultrafiltration uses membranes
with small (about 0.01-micron) pores to filter the mixture. Water passes through the
membrane, but coating particles are too large to pass through the membrane pores.
11-26
Pollution Prevention for the Wood Finishing Industry
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&&&*
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-27
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&&&&&&&&&&&&&&&&&&&
Leave containers
open, and watch your
profits evaporate!
Used solvent should
be reused for product
formulation or for a
EQUIPMENT CLEANING
Equipment cleaning is required when a process is completed, a color change is needed, or
maintenance is required. When assessing the pollution prevention opportunities in the
cleaning process, a facility should use good operation practices to minimize the frequency
of cleanings. For instance, production may be sequenced so that pieces requiring light-
colored paint or stain are sent through the finishing line first, followed by the pieces that
require darker finishes. This minimizes the need for cleaning between runs. Also, it should
be determined whether cleaning is even necessary. For some low-cost items, the cost of
replacing the item may be less than the costs associated with cleaning solvent, solvent waste
disposal, and additional labor. However, the cost of properly disposing of the item must
be considered.
When cleaning is necessary, facilities should incorporate mechanical cleaning (scraping and
wiping) into cleanup procedures. Floors should be cleaned with squeegees instead of rags,
brooms, or mops. Where possible, Teflon-lined tanks can be used to improve drainage and
reduce coating deposits. When tanks are cleaned, operators should use rubber wipers to
manually scrape the sides to remove coating deposits.
If cleaning with solvents is necessary, alternative solvents are available, the use of
which results in lower VOC emissions than the use of conventional solvents. Dibasic
esters are one class of alternative solvents. Solvents with low volatility should be used to
minimize emissions. When conventional solvents are used, there are still a few options that
reduce pollution and save money. The easiest and most obvious way is to fully use the
solvents that are purchased. Most companies dispose of their solvents long before they
should do so. Solvents should be disposed of or recycled only because they have lost
their cleaning effectiveness, not just because they look "dirty. " Also, leaving solvents
open to the air creates unnecessary VOC emissions, and the money spent on the solvent
evaporates. A way to use solvent more efficiently is to flush solvent into a trap for reuse
in swishing the pressure pot. Also, solvent pumps should be maintained and replaced, as
needed, to prevent leakage.
When considering what type of finish to use, remember that using water-based finishes
eliminates the need to use solvents in equipment cleaning.
Regardless of whether aqueous or solvent solutions are used to clean equipment, there are
a few techniques that will minimize the volume of the waste. First, if lines are being
cleaned, use air to blow residue back into the pots before final cleaning with water or
solvent; this reduces the amount of coating material wasted and helps to minimize the
amount of cleaning fluid used. Second, when using water or solvent to clean, use high
velocities instead of large volumes; this cleans more efficiently so that less cleaning fluid
is required. Third, spray cleaning solvent into a container, preferably below the fluid line,
for reuse instead of spraying the cleaning solvent into the air; this "used" solvent can be
used for rough cleaning or for product formulation.
11-28
Pollution Prevention for the Wood Finishing Industry
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&&&*
COATING PREPARATION
Proper coating material preparation is important for waste and cost minimization. Too
much reduction may result in sagging, whereas too little can cause poor flow, orange peel,
and other defects. These problems can, in turn, result in rejects and wasted or unusable
material. Here are a few tips to enhance the formulation:
! Always add the reducer to the material (instead of the reverse), and add it
slowly while stirring vigorously.
! Test for complete mixing by taking a few drops from the top of the
container and a few from the bottom; put each on a separate piece of
glass, and watch for differences in color or rate of flow down the glass;
noticeable differences probably indicate that additional mixing is needed.
! Mix materials well before use; some need to be mixed while in use to
ensure the uniformity of the finish.
! Cover tanks to prevent evaporative losses.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-29
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BIBLIOGRAPHY
Sheet 1 of 5
Adams, Larry. 1991. "Finishing Materials: Must Compliance Mean an Inferior Product?" Wood &
Wood Products. December. Pages 113-119.
Akzo Coatings Inc. (no date). "Useful Facts & Figures." Fourth edition. Industrial Wood Coatings
Business Unit.
Artistic Finishes, Inc. 1992. "Investigation of Low-Volatile Organic Compound (VOC) Coatings and
Methods for Finishing Wood Substrates." Thomas Leach. Roseville, Minnesota. December
11.
Bankert, Peter J. 1990. "Waterborne Paint Circulation." Industrial Finishing. July. Pages 42-43.
Battelle. (no date). "Draft Training Manual on Techniques for Reducing or Eliminating Releases of
Toxic Solvents in Wood Finishing Operations."
Blackman, Ted. 1991. "Recycling: Not Just for Papers and Bottles Anymore." October. Pages 19-20.
Christiansen, Rich. 1991. "Pennsylvania House Scores a Finishing First." Wood & Wood Products.
October. Pages 53-55.
Dambele, Paul, and others. 1992. "A Guide to Pollution Prevention for Wood Furniture Finishing."
August.
Dunne, Beverly. 1993. "Environmental, Educational Concerns Affect Sanding." Wood & Wood
Products. May.
Furniture Design & Manufacturing. 1993. "Recycling Program Delivers Finishing Savings." March.
Heltzer, Josh. 1992. "Wooden Furniture Finishing: A Pollution Prevention Assessment." Tufts
University. April 30.
Higgins, Thomas. 1989. "Hazardous Waste Minimization Handbook." Lewis Publishers, Inc., Chelsen,
Michigan.
Hunag, Eddy, Carry Watkins, and Robert McCrillis. 1993. "Development of Ultra-Low VOC Wood
Furniture Coatings." For U.S. Environmental Protection Agency (EPA) Pollution Prevention
Conference on Low- and No-VOC Coating Technologies, San Diego, California. May 25-27
11-30
Pollution Prevention for the Wood Finishing Industry
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&&&*
BIBLIOGRAPHY
Sheet 2 of 5
Indiana Department of Environmental Management. 1993. Pollution Prevention for Industrial Coating.
Office of Air Management, Office of Pollution Prevention and Technical Assistance. December
Industrial Finishing. 1990. "How Rapid Rack Raised Transfer Efficiency." October. Pages 20-24.
Koeing, Karen Malamud. 1991. "Terra on Firm Ground with VOC Safety Compliance." Wood &
Wood Products. August. Pages 126-130.
Kohl, Jerome. 1986. "Managing and Recycling Solvents in the Furniture Industry." Industrial
Extension Service, School of Engineering, North Carolina State University. Raleigh, North
Carolina. May.
Marg, Ken. 1989. "HVLP Spray Puts You into Compliance." Metal Finishing. March. Pages 21-23.
Minnesota Technical Assistance Program (MnTAP). 1991. "Intern Project Summary; Water-Based
Substitutes for Wood Finishing Lacquers." Minneapolis, Minnesota. December.
MnTAP. 1993a. "Waste Reduction Alternatives for Spray Painting and Coating." Minneapolis,
Minnesota.
MnTAP. 1993b. "Case Study; Reuse of Wood Finishing Overspray." Minneapolis, Minnesota.
January.
MnTAP. 1993c. "Intern Summary; Increasing Transfer Efficiency through Part Placement, Spray
Adjustment, and Overspray Reuse." Minneapolis, Minnesota. April.
North Carolina Department of Environment, Health, and Natural Resources, (no date). "Overview of
Coating Technologies." Sharon M. Johnson.
North Carolina Department of Environment, Health, and Natural Resources. 1989. "Companion
Document for the Conference on Waste Reduction for Industrial Air Toxic Emissions."
Greensboro, North Carolina. Pollution Prevention Pays Program. April 24-25.
North Carolina Department of Environment, Health, and Natural Resources. 1993. "Case Studies; A
Compilation of Successful Waste Reduction Projects Implemented by North Carolina
Businesses and Industries." Office of Waste Reduction. Pollution Prevention Pays Program.
September.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
11-31
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BIBLIOGRAPHY
Sheet 3 of 5
North Carolina State University, School of Engineering. 1986. "Managing and Recycling Solvents in
the Furniture Industry." May.
Pacific Northwest Pollution Prevention Research Center. 1992. "Transfer Efficiency and VOC
Emissions of Spray Gun and Coating Technologies in Wood Finishing."
Robinson, Frank, and Dennis Stephens. 1990. "Understanding Electrostatic Finishing." Industrial
Finishing. September. Pages 34-37.
Ross, Vincent. 1989. "Pollution Prevention Waste Reduction for Industrial Air Toxic Emissions; Waste
Reduction—Pollution Prevention in the Furniture Industry." Ross Associates, Inc. Greensboro,
North Carolina. April 24-25.
Scharfenberger, James A. (no date). "Automated Electrostatic Equipment for the Wood Industry."
Electrostatic Equipment Division, Ransburg Corporation. Indianapolis, Indiana.
Schneberger, Gerald. 1991. "The Basics of Statistical Process Control (SPC)." Industrial Finishing.
June. Page 28-30.
Schrantz, Joe. 1989. "New CO2 Spray Finishing Technology!" Industrial Finishing. September.
Pages 27-32.
Schrantz, Joe. 1990. "Exciting Infrared and Ultra Violet (UV) Developments." Industrial Finishing.
September. Pages 14-21.
Schrantz, Joe. 1991. "Intense Resin R&D Bearing Fruit." Industrial Finishing. January. Pages 20-
24.
Toxics Use Reduction Institute, (no date). "Massachusetts Toxics Use Reduction Program, Curriculum
for Toxics Use Reduction Planners." University of Massachusetts. Lowell, Massachusetts.
Toxics Use Reduction Institute. 1992. "Toxics Use Reduction Research Directory." University of
Massachusetts. Lowell, Massachusetts.
U.S. Environmental Protection Agency (EPA). 1987. "Project Summary; Evaluation of the Problems
Associated with Application of Low-Solvent Coatings to Wood Furniture." Air and Energy
Engineering Research Laboratory. Research Triangle Park, North Carolina. May.
EPA/600/52-87/007.
U.S. EPA. 1989. "Pollution Prevention Benefits Manual, Volumes I and II, Phase II." Office of Policy
Planning and Evaluation and Office of Solid Waste. October.
11-32
Pollution Prevention for the Wood Finishing Industry
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BIBLIOGRAPHY
Sheet 4 of 5
U.S. EPA. 1991a. "SWAMI Version 2.0." May.
U.S. EPA. 199Ib. "Industrial Pollution Prevention Opportunities for the 1990s." EPA/600/8-91/052.
August.
U.S. EPA. 1991c. "Guideline Series; Control of VOC Emissions from Wood Furniture Coating
Operations, Draft." Chapters 1-5. Office of Air and Radiation, Office of Air Quality Planning
and Standards. Research Triangle Park, North Carolina. October.
U.S. EPA. 1992a. "User's Guide: Strategic Waste Minimization Initiative (SWAMI) Version 2.0, A
Software Tool to Aid in Process Analysis for Pollution Prevention." January. EPA/625/11-
91/004.
U.S. EPA. 1992b. "Pollution Prevention Options in Wood Furniture Manufacturing; A Bibliographic
Report." Office of Pollution Prevention and Toxics. Washington, D.C. February. EPA/560/8-
92/001C
U.S. EPA. 1992c. "Facility Pollution Prevention Guide." Risk Reduction Engineering Laboratory,
Office of Research and Development. Ohio. May.
U.S. EPA. 1992d. "PIES Quick-Reference Guide." Office of Pollution Prevention and Toxics.
September.
Walberg, Arvid C. 1990. "Boost Overall Transfer Efficiency." Industrial Finishing. May. Pages 20-
30.
Washington State Department of Ecology, (no date). "Success Through Waste Reduction; Proven
Techniques from Washington Businesses, Volume II." Olympia, Washington.
Washington State Department of Ecology. 1991. "Success Through Waste Reduction; Proven
Techniques from Washington Businesses." Olympia, Washington. May.
Wood & Wood Products. 1989. "Material Makeup Changing to Meet Finishing Rules." November.
Pages 101-105.
Wood & Wood Products. 1990. "Waterborne Lacquers Help Solve Emissions Problems." Pages 42
and 43. October.
POLLUTION PREVENTION OPTIONS FOR THE WOOD FINISHING INDUSTRY
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BIBLIOGRAPHY
Sheet 5 of 5
Wood & Wood Products. 1992. "EPA Studies Economic Impact of VOC Reductions." May. Pages
74-81.
Wood & Wood Products. 1993. "Reduce Hazardous Waste by On-Site Distillation." May. Pages 114-
115.
11-34
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Section III
Case Studies
-------
&&&*
CASE STUDY NO. 1—Conversion to HVLP
Introduction
Tiz's Door Sales, Inc. (IDS), is located in Everett, Washington, and employs over 60 people.
IDS manufactures wood products for both remodeling and new home construction. Its product
line includes interior and exterior doors and frames, window and base moldings, and stained
railings.
Process Prior to Pollution Prevention
The company was using conventional spray guns, which were about 20 percent efficient
manual-spray lines. High-quality finishes were obtained by using conventional solvent-based
coatings.
Current Process
IDS was very aggressive in its source reduction efforts. IDS installed automated flat line spray
equipment, which provides maximum application efficiency and recycles overspray, thereby
saving 220 gallons of lacquer per week.
Where possible, solvents and coatings have been switched from toluene-based solutions to less
hazardous blends. Heat, instead of solvents, is used to thin coatings for application.
IDS has converted all manual-spray lines to high-volume/low-pressure (HVLP) spray guns,
which provide a high transfer efficiency (TE) and result in less overspray. This not only reduces
the amount of waste generated but also provides immediate dividends by reducing the amount
of coating material needed to finish each piece. Less overspray also means lower maintenance
of equipment and lower labor costs. IDS found that using HVLP even resulted in a faster
production rate—that is, although the application rate is slower, the drying time was less.
Using dedicated pumps and lines for each type of coating was another simple change that
resulted in a large reduction in the amount of solvent needed. This reduced the cleaning required
between coats. When cleaning is required, operators block gun nozzles and blow air back
through the guns and delivery systems to reduce waste material even further.
Savings
TDS has reduced the amount of its coatings use by one-half. In 1991, 18,000 gallons were
saved. At $10/gallon, this was a savings of $180,000! In addition, the company
experienced significant savings in labor costs from less time spent on cleanup,
maintenance, and material handling. Also, waste disposal costs were reduced dramatically.
The improved working environment is cleaner and safer, which has led to lower absenteeism and
injury.
CASE STUDIES
III-l
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&&&&&&&&&&&&&&&&&&&
Taken from "Success Through Waste Reduction; Proven Techniques from Washington
Businesses, Volume II," Washington State Department of Ecology.
III-2
Pollution Prevention for the Wood Finishing Industry
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&&&*
CASE STUDY NO. 2—Solvent Recycling
Introduction
The Doling Company, located in Mt. Olive, North Carolina, manufactures wood office furniture
with four different style lines and seven different finishes.
Process Prior to Pollution Prevention
Until January 1983, the company was burning spent solvents from the wood finishing process
for fuel.
Current Process
In considering ways to reclaim spent solvents, Boling found it difficult finding commercial
recyclers in its region. In 1983, Boling installed a "Little Still" to recycle spent lacquer thinners
from the plant's washoff operations.
Early in the operation of the still, Boling encountered a few problems because of improper
washoff collection practices. Boling realized that, in addition to problems associated with the
washoff collection practices, Boling realized that the composition of the seven-component
washoff solvent blend changed with distillation. It could not be reused in the washoff operation.
However, by mixing one part acetone with three parts reclaimed solvent, the reconstituted
mixture could be used as a thinner in the spray coating operation.
The plant's washoff operation generates about 10 to 15 gallons of spent solvent per day. Forty
to 60 gallons per week are reclaimed for the spray operation. The still is operated four times
per week to avoid accumulation of spent solvents. It operates on a 7-hour distillation/1-hour
cooldown cycle. The rest of the solvents and the still bottoms remain in the plastic liner. The
plastic bag liner is removed about once a week and burned in the plant's wood-chip fueled boiler
for heat recovery. The boiler provides steam to the drying ovens and the drying kilns. In the
winter, the boiler provides space heat for the plant.
Savings
In 1983, the cost of the still was $4,825. It was estimated that (1) the labor cost was
$0.02 per gallon of solvent recovered, (2) the power cost was $0.05/gallon, and (3) the cost of
the plastic bag liner containing the still bottoms was $0.05. This resulted in a total still
operation cost of $0.12 per gallon of solvent reclaimed. With the addition of acetone to the
seven-component washoff solvent blend, the mixture is reconstituted as a thinner. This reuse
reduces the amount of virgin-blend solvent purchased for the spray mix. In 1985, the cost of
the virgin-blend solvents was $2.67/gallon. The cost of reclaiming the solvent and adding
acetone was $1.00.
The net savings is about $100per week. In addition, the cost of disposal is avoided. Another
CASE STUDIES III-3
-------
&&&&&&&&&&&&&&&&&&&
Doling plant pays $0.40 per gallon to dispose of the same spent solvent. The still paid for
itself in about 1 year of operation.
Taken from "Managing and Recycling Solvents in the Furniture Industry," Industrial Extension
Service, School of Engineering, North Carolina State University. May 1986.
III-4
Pollution Prevention for the Wood Finishing Industry
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&&&*
CASE STUDY NO. 3—Wood Waste to Energy
Introduction
Stanley Furniture (previously known as Burlington Furniture) is a furniture manufacturing
company located in Lexington, North Carolina.
Process Prior to Pollution Prevention
The furniture maker shipped spent solvents to a landfill in South Carolina.
Current Process
Stanley installed an in-house incinerator to burn its spent solvents for heat recovery. The
incinerator has a lower chamber and an upper chamber. Plant wastes are segregated into four
groups: solids, heavy liquids (such as stains and glazes), sludges, and solvents. The solids and
sludges are burned in the lower chamber. Wastewater from the rag wash is treated, and the
residue is mixed with sawdust, in addition to water wash curtain sludges, and is burned in the
lower chamber. The solvents are burned in the upper chamber, which uses No. 2 fuel oil as its
primary fuel. The upper chamber runs at a temperature of 1,800°F. The heat from the
incinerator fires a boiler to make steam, which is used to wash and dry rags. During winter,
excess heat is used to supplement the plant's space heat. The incinerator ash is considered
nonhazardous and is sent to the county landfill.
Savings
The incinerator was installed at an initial cost of $1.5 million. The facility anticipates a 3-year
payback period. The incinerator burned 4,000 gallons of spent solvent, which was part of the
1.5 million pounds of waste burned in the incinerator. In addition to saving money in-house,
Stanley made additional income by charging other small local furniture companies $29.00 per
drum of spent solvents for incineration. Because of the high energy content of spent wash-off
solvents, measured in British thermal units (Btu), Stanley finds that it is easier and cheaper to
send its wastes to be used as fuel than to have solvents recycled.
Taken from "Managing and Recycling Solvents in the Furniture Industry," Industrial Extension
Service, School of Engineering, North Carolina State University. May 1986.
CASE STUDIES
111-5
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CASE STUDY NO. 4—Switching to Water-Based Inks
Introduction
Kemp Furniture Industries is a furniture manufacturing facility located in Goldsboro, North
Carolina.
Process Prior to Pollution Prevention
Kemp Furniture has a five-stage printer for printing wood grain on fiberboard and plywood
pieces before assembly and final finishing. Solvent-based inks were used in the printing line.
Spent solvent from equipment cleanup was sent to a recycling company to be distilled and sold
back to Kemp.
Current Process
Kemp Furniture's printing division switched from using solvent-based inks to water-based inks.
The only adjustments needed for changing to water-based inks were a higher drying oven
temperature and minimal operator training. The water-based inks are nontoxic, and wastes from
press cleanups may be flushed into the city sewer without treatment.
The printing operation still requires the use of solvent-based finishes before and after printing;
also, to keep the wood from showing through, some solvent-based coatings are still required
when putting on a white finish. Kemp has made housekeeping improvements in its use of
solvent-based finishes, including keeping waste streams segregated and effectively using
solvents in a countercurrent manner. Virgin solvent is first used to flush out the pump and lines
of the application equipment. This "spent" solvent is then used as a thinner for the finishing
material. The solvent reclaimed by the recycling company is used for cleaning the dirtier parts
of the equipment, such as rollers and belts. When this reclaimed solvent is too dirty for reuse,
it is sent back to the recycler.
When there is no viable alternative to solvent-based finishes, Kemp reduces the use of solvents,
thereby reducing the amount of spent solvent generated, by using different spraying equipment.
Savings
Water-based inks cost about one-half of the price of solvent inks. Kemp estimates that the
change to water-based inks has reduced the printing line's spent solvents stream by 30 to 40
percent.
Taken from "Managing and Recycling Solvents in the Furniture Industry," Industrial Extension
Service, School of Engineering, North Carolina State University. May 1986.
III-6
Pollution Prevention for the Wood Finishing Industry
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&&&*
CASE STUDY NO. 5—Conversion to HVLP
Introduction
Thomson Crown Wood Products, Inc. (Thomson Crown), manufactures wood and wood-finished
television cabinets in Mocksville, North Carolina.
Process Prior to Pollution Prevention
Thomson Crown sprayed its cabinets by using an air-assisted airless spray gun. These guns used air
pressure of up to 55 pounds per square inch (psi) to atomize the coating material. This high pressure
resulted in poor TEs.
Current Process
Thomson Crown tested four different HVLP spray guns using penetrating stain
(no-wipe), glaze, sap stain, equalizer, toner, shade, and water-based black paint. Because of its specific
product line, Thomson Crown chose a spray gun that would work well with a heavier finish. Each
manufacturer produces a spray gun with slightly different properties—underlining the necessity of
customizing equipment choice to product goals.
Using the HVLP spray guns, Thomson Crown has experienced the following reductions in material:
(1) 65 percent for equalizer, (2) 65 percent for stain, (3) 65 percent for toner, (4) 35 percent for glaze,
(5) 35 percent for no-wipe, and (6) 53 percent for water-based black paints.
In addition to using different spray guns, Thomson Crown has also altered its printing process room to
incorporate roll-on finishings of all top and end panels of the outside cabinet. This modification
resulted in 60 percent of the company's spray operations being diverted to the printing room. This
reduced purchases of coatings by an additional 50 percent.
Savings
The material use reductions resulting from the change to HVLP guns total over 13,300 gallons per
year of coatings, translating to an annual savings of over $137,000. The pollution prevention
project cost of about $21,000 was recovered in 2 months.
Taken from "Pollution Prevention Case Studies," North Carolina Department of Environment, Health,
and Natural Resources, Office of Waste Reduction. September 1993.
CASE STUDIES
III-7
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CASE STUDY NO. 6—Reusing Overspray
Introduction
Medallion Kitchens, located in Waconia, Minnesota, is a leading woodworking company that
manufactures kitchen cabinets and bathroom vanities. Medallion Kitchens was interested in using
materials more efficiently to (1) reduce raw material costs, (2) reduce VOC emissions, (3) minimize
hazardous waste disposal costs and the liabilities associated with hazardous waste disposal, and (4)
decrease labor costs related to sludge removal, dewatering, and handling.
Process Prior to Pollution Prevention
Wooden cabinet pieces are stained and then finished with a solvent-based catalyzed sealer and topcoat
before the pieces are assembled into the complete cabinets. Sealer and topcoat applications are
automated. A central conveyor belt, two water-wash spray booths, and two drying ovens are all
automated. Sensor-triggered automated spray guns apply coatings to cabinet parts in each spray booth.
Overspray waste has been a problem. Before any changes were made, about 75 gallons of sealer were
used per day, and the process generated about 50 gallons of hazardous waste sludge per day.
Process Changes
Medallion Kitchens decided to invest in a reclamation system to collect sealer overspray. The system
consists of two holding reservoirs and minor plumbing. It was designed to catch most of the overspray
before it fell into the water-wash tank.
Innovative features of the final reclamation system include the following:
! Cooling water was added under the collection trays to minimize solvent
evaporation.
I
Collected material is agitated to prevent "skinning."
! The reclamation tray and support assembly were designed to fit well into the
spray booths and provide for easy removal.
! A nonstick coating was applied to the collection trays to decrease labor and
material costs required for cleaning.
Collected solvents are recirculated through a pumping system to prevent curing. After about 5 gallons
of overspray have accumulated, the overspray is manually removed and transferred to the mixing area.
Solvent and catalyst are added to the material, as needed, to obtain the desired coating properties, and
material is added back to the spray system to be reused. Some time is required for employees to
maintain the new reclamation system. However, time is also saved, because the spray booth now
requires less maintenance. The effective solids TE has increased from 40 percent before installation
to about 80 percent. The system cost about $2,500 per booth to install, about $2,000 for materials,
III-8
Pollution Prevention for the Wood Finishing Industry
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&&&*
and about $500 for labor.
Savings
An average of 11.5 gallons of overspray was collected each day during October and November 1992.
Assuming a raw material cost of $8 per gallon, Medallion Kitchens will save about $23,000
annually on raw materials as a direct result of collecting its overspray.
Also, hazardous sludge generated by operations in the sealer spray booth has decreased from 50 to 25
gallons per day. Related waste disposal costs have been halved, saving the company around
$30,000 per year, resulting in a total annual savings of $53,000.
Taken from "Case Study: Reuse of Wood Finishing Overspray," Minnesota Technical Assistance
Program. 1993.
CASE STUDIES
III-9
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&&&*
APPENDIX
ADDITIONAL INFORMATION
The following are additional documents on pollution prevention that you may find useful.
Unfortunately, they are available only in English. Copies of documents with an U.S. Environmental
Protection Agency document number may be obtained from the EPA Center for Environmental
Research Information (CERI) or the Pollution Prevention Information Clearinghouse (PPIC). Some
documents are available, without charge, from PPIC. For a current list of these documents, please
contact PPIC.
EPA CERI Publications Unit
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7562
GENERAL INFORMATION
PPIC
401M Street
Mail Code PM221A
Washington, DC 20460
(202)260-1023
PIES
Technical Support Office
SAIC
7600-A Leesburg Pike
Falls Church, VA 22043
(703) 821-4800
Akzo Coatings Inc. (no date). "Useful Facts & Figures." Fourth edition. Industrial Wood Coatings
Business Unit.
Battelle. (no date). "Draft Training Manual on Techniques for Reducing or Eliminating Releases of Toxic
Solvents in Wood Finishing Operations."
Higgins, Thomas. 1989. "Hazardous Waste Minimization Handbook." Lewis Publications, Inc. Chelsen,
Michigan.
Kohl, Jerome. 1986. "Managing and Recycling Solvents in the Furniture Industry." Industrial Extension
Service, School of Engineering, North Carolina State University. Raleigh, North Carolina. May.
Toxics Use Reduction Institute, (no date). "Massachusetts Toxics Use Reduction Program, Curriculum for
Toxics Use Reduction Planners." University of Massachusetts. Lowell, Massachusetts.
U.S. Environmental Protection Agency (EPA). 1989. "Pollution Prevention Benefits Manual, Volumes I and n,
Phas
eH."
Offi
ce of
Polic
y
Plan
ning
and
Eval
uatio
n
and
Offi
ce of
Solid
ADDITIONAL INFORMATION
A-l
-------
&&&&&&&&&&&&&&&&&&&
Wast
e.
Octo
her.
U.S. EPA. 1991. "Guideline Series; Control of Volatile Organic Compound Emissions from Wood Furn
iture
Coat
ing
Oper
ation
s,
Draf
t."
Cha
pters
1-5.
Offi
ce of
Air
and
Radi
ation
Offi
ce of
Air
Qual
ity
Plan
ning
and
Stan
dard
s.
Rese
arch
Tria
ngle
Park
Nort
h
Caro
lina.
Octo
her.
U.S. EPA. 1992. "Facility Pollution Prevention Guide." Risk Reduction Engineering Laboratory, Office of Rese
arch
and
Dev
elop
ment
Ohio
A-2
-------
&&&*
May.
SANDING
Dunne, Beverly. 1993. "Environmental, Educational Concerns Affect Sanding." Wood& WoodProducts. May.
ADDITIONAL INFORMATION
A-3
-------
&&&&&&&&&&&&&&&&&&&
ALTERNATIVE COATING AND APPLICATION METHODS
Bankert, Peter J. 1990. "Waterborne Paint Circulation." Industrial Finishing. July. Pages 42-43.
Christiansen, Rich. 1991. "Pennsylvania House Scores a Finishing First." Wood & Wood Products.
October. Pages 53-55.
Industrial Finishing. 1990. "How Rapid Rack Raised Transfer Efficiency." October. Pages 20-24.
North Carolina Department of Environment, Health, and Natural Resources, (no date). "Overview of Coat
ing
Tech
nolo
gies.
Shar
on
M.
John
son.
Marg, Ken. 1989. "HVLP Spray Puts You into Compliance." Metal Finishing. March. Pages 21-23.
Pacific Northwest Pollution Prevention Research Center. 1992. "Transfer Efficiency and VOC Emissions of
Spray Gun and Coating Technologies in Wood Finishing."
Robinson, Frank, and Dennis Stephens. 1990. "Understanding Electrostatic Finishing." Industrial Finishing. Sept
emb
er.
Page
s34-
37.
Scharfenberger, James A. (no date). "Automated Electrostatic Equipment for the Wood Industry."
Electrostatic Equipment Division, Ransburg Corporation. Indianapolis, Indiana.
Schrantz, Joe. 1989. "New CO2 Spray Finishing Technology!" Industrial Finishing. September.
Pages 27-32.
Schrantz, Joe. 1990. "Exciting Infrared and UV Developments." Industrial Finishing. September.
Pages 14-21.
Schrantz, Joe. 1991. "Intense Resin R&D Bearing Fruit." Industrial Finishing. January. Pages 20-24.
Walberg, Arvid C. 1990. "Boost Overall Transfer Efficiency." Industrial Finishing. May. Pages 20-30.
Wood & Wood Products. 1989. "Material Makeup Changing to Meet Finishing Rules." November.
Pages 101-105.
Wood & Wood Products. 1990. "Waterborne Lacquers Help Solve Emissions Problems." Page 42 and 43.
October. Page 42-43.
RECYCLING
Blackman, Ted. 1991. "Recycling: Not Just for Papers and Bottles Anymore." October. Page 19-20.
A-4 Pollution Prevention for the Wood Finishing Industry
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&&&*
Furniture Design & Manufacturing. 1993. "Recycling Program Delivers Finishing Savings." March.
Wood & Wood Products. 1993. "Reduce Hazardous Waste by On-Site Distillation." May. Pages 114-115.
COMPUTER SOFTWARE
U.S. Environmental Protection Agency (EPA). 1992. "User's Guide: Strategic Waste Minimization
Initiative (SWAMI) Version 2.0, A Software Tool to Aid in Process Analysis for Pollution Prevention.'
January. EPA/625/11-91/004.
U.S. EPA. 1991. "SWAMI Version 2.0." May.
ADDITIONAL INFORMATION
A-5
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