 |
URBAN
RECYCLED WOOD
CHARACTERIZATION STUDY Final Report |
Acknowledgment
ReTAP is a venture of the Clean Washington Center, Washington State's lead agency for the market development of recycled materials, and an organization committed to maximizing the benefits of recycling. ReTAP is an affiliate of the national Manufacturing Extension Partnership (MEP), a program of the U.S. Commerce Department's National Institute of Standards and Technology. The MEP is a growing nationwide network of extension services to help smaller U.S. Manufacturers improve their performance and become more competitive. ReTAP is also sponsored by the U.S. Environmental Protection Agency and the American Plastics Council.
ReTap and the Clean Washington Center disclaim all warranties to this report, including mechanics, data contained within and all aspects, whether expressed or implied, without limitation on warranties of merchantability, fitness for a particular purpose, functionality, data integrity, or accuracy of results.
This report was designed for a wide range of commercial, industrial and institutional facilities and a range of complexity and levels of data input. Carefully review the results of this report prior to using them as the basis for decisions or investments.
TABLE OF CONTENTS
Executive Summary............................................................................................................ 1
1.0 INTRODUCTION...................................................................................................................
1.1 BACKGROUND................................................................................................................... 4
2.0 METHODOLOGY.................................................................................................................. 5
2.1 END USER SURVEY............................................................................................................ 5
2.2 URBAN RECYCLED WOOD CHARACTERIZATION.......................................................... 5
3.0 END USER SURVEY RESULTS.........................................................................................
3.1 BACKGROUND................................................................................................................. 10
3.2 BIOMASS FUEL END USE............................................................................................... 12
3.2.1 Summary................................................................................................................... 12
3.2.2 Issues Regarding Size and Shape..............................................................................
3.2.3 Contaminant Issues..................................................................................................
3.3 COMPOSITE WOOD MANUFACTURING....................................................................... 15
3.3.1 Summary...................................................................................................................
3.3.2 Issues Regarding Size and Shape..............................................................................
3.3.3 Contaminant Issues.................................................................................................. 17
3. 4 PULP AND PAPER MANUFACTURING........................................................................ 19
3.4.1 Summary...................................................................................................................
3.4.2 Issues Regarding Size and Shape..............................................................................
3.4.3 Contaminant Issues..................................................................................................
4.0 URBAN RECYCLED WOOD CHARACTERIZATION RESULTS................................
4.1 URBAN RECYCLED WOOD PROCESSING FACILITY DESCRIPTIONS........................
4.1.1 Facility 1...................................................................................................................
4.1.2 Facility 2...................................................................................................................
4.1.3 Facility 3...................................................................................................................
4.1.4 Facility 4...................................................................................................................
4.2 CHARACTERIZATION RESULTS..................................................................................... 33
4.2.1 Facility 1...................................................................................................................
4.2.2 Facility 2...................................................................................................................
4.2.3 Facility 3...................................................................................................................
4.2.4 Facility 4...................................................................................................................
5.0 END USER TECHNICAL DISCUSSIONS........................................................................
5.1 INTRODUCTION.........................................................................................................
5.2 URBAN RECYCLED WOOD CONTAMINANT CONTENT AND QUALITY.............. 44
5.3 HANDLING AND PROCESSING ISSUES...................................................................
5.4 ECONOMICS..................................................................................................................................................... 48
6.0 CONCLUSIONS AND RECOMMENDATIONS..............................................................
Appendices:
Appendix A: End User Survey
Appendix B. End User Technical Discussions
List of Tables
Table l Brightness Rating Scale
Table 2 URW End Use Survey Results: Size and Shape Specifications
Table 3 URW End Use Survey Results: Contaminant Content (%) Specifications
Table 4 URW End Use Survey Results: Moisture & Brightness Requirements
Table 5 Size and Shape Specifications - Biomass Energy End Use
Table 6 Contaminant Content (%) Specifications - Biomass Energy End Use
Table 7 Size and Shape Specifications - Composite Wood Manufacturing End Use
Table 8 Contaminant Content (%) Specifications - Composite Wood Manufacturing
Table 9 Moisture, Brightness, and Species Requirements - Composite Wood Manufacturing
Table 10 Size and Shape Specifications - Pulp and Paper Manufacturing End Use
Table 11 Contaminant Content (%) Specifications - Pulp and Paper Manufacturing
Table 12 Moisture, Brightness, and Species Requirements - Pulp and Paper Manufacturing
Table 13 Facility 1 Overview
Table 14 Facility 2 Overview
Table 15 Facility 3 Overview
Table 16 Facility 4 Overview
Table 17 Facility 2 URW Characterization Results (Biomass Energy End Use)
Table 18 Facility 2 URW Characterization Results (Biomass Energy End Use)
Table 19 Facility 2 URW Characterization Results (Manufacturing End Use)
Table 20 Facility 3 URW Characterization Results (Biomass Energy End Use)
Table 21 Facility 3 URW Characterization Results (Manufacturing End Use)
Table 22 Facility 4 URW Characterization Results (Manufacturing End Use)
Table 23 Effect of Specific Contaminants on the Manufacturing Process
Table 24 Effect of Specific Contaminants on Product Function
Table 25 Effect of Specific Contaminants on Product Aesthetics
List of Figures
Figure 1 Sample Collection and Analysis Flow Chart
Figure 2 Facility 1 Processing Schematic
Figure 3 Facility 2 Processing Schematic
Figure 4 Facility 3 Processing Schematic
Figure 5 Facility 4 Processing Schematic
Executive Summary
Over the last several years, the amount of urban wood waste recycled in Washington State has increased from 100,000 tons per year to over 640,000 tons per year. Considerable success has been achieved in developing end uses and markets for this material. The pulp and paper and composite wood manufacturing industries have used this material as a manufacturing feedstock. However, market development has been curtailed by a poor understanding of product quality, end-user requirements, perception about demolition wood, and regulatory constraints.
In recognition of these constraints, the Clean Washington Center sponsored a project to:
1. Determine end-use specifications for use of urban recycled wood (URW) as a biomass fuel and feedstock for pulp and paper and composite wood manufacturing.
2. Characterize URW produced by four processors in Washington State.
3. Convene end users discussion groups with end user industry representatives.
A survey was conducted to determine end-user specifications in the composite wood, pulp and paper and biomass energy industries. Results indicated that many of the respondents who had used URW as a manufacturing feedstock experienced problems with excessive contamination. Few of these companies use URW as a manufacturing feedstock because of the low cost of virgin fiber but indicated that URW would be an important source of fiber in the future.
The URW characterization component of the project involved collecting and characterizing URW samples from four URW processing facilities. A sampling procedure was developed to ensure the collection of a representative sample. The collected URW samples were analyzed for inert contaminants (i.e. plastic, metal, painted wood, etc.), sieve analysis, moisture, ash, heat energy and trace metal content. The results were analyzed to determine feedstock variability, potential methods for improving the quality of the product, and how well the various URW products met end use specifications.
In addition, end-users and composite wood and pulp and paper manufacturing industry representatives met to discuss the constraints of using URW as a manufacturing feedstock. A main concern was the quality of processed URW and the significant affect of various contaminants on the manufacturing process and the quality of the manufactured product. Contaminants such as plastic, sand and grit, metals and other inert materials have a significant effect on the manufacturing process and product quality. The consensus was that contaminated URW was a constraint to its use.
The contamination issue was prevalent several years ago when URW was first used in composite wood and pulp and paper manufacturing processes and when both the URW processors and the end-users were first learning how to process and use URW. Since that start-up period, the remaining URW processors have developed more sophisticated techniques for sourcing clean materials and removing contaminants. Manufacturers using URW have also learned how to better utilize URW as a manufacturing feedstock.
Project results indicated that many firms had some experience using URW as a biomass fuel or manufacturing feedstock. The specifications and technical requirements for using URW as a biomass fuel are less stringent than for manufacturing end-uses. Consequently, this market has been the easiest to access. Currently, most URW is placed in this market and the end-users seem satisfied with the quality and performance of the product.
Based on the findings of this project, the market for biomass fuel is expanding and should provide a stable market for URW in the future. However, in order for this market to remain substantial, URW processors need to work closely with the end-user to provide a product that meets their end-use requirements.
In contrast to the URW specifications for the end-use option of biomass fuel, specifications and technical requirements for using URW as a manufacturing feedstock are more stringent. As a result, it has been more difficult for URW processors to place materials in this end-use market. Part of this problem is due to the learning curve the processors and manufacturers experienced several years ago. Unaware of the challenges in using URW, many manufacturers experienced difficulties and quickly discontinued using URW when virgin feedstocks became more readily available at low prices.
Since URW was first used as a manufacturing feedstock, processors still in the business have made modifications to their manufacturing process and have learned how to better use this material. Consequently, they are producing a very clean, consistent product.
1.0 INTRODUCTION
1.1 BACKGROUND
Over the last several years, the amount of urban wood waste recycled in Washington State has increased from approximately 100,000 tons per year to 640,000 tons per year. A large fraction of the urban (and suburban) wood being recycled is “clean” wood waste and consists primarily of mill residuals, land clearing debris, and pallets and crates. A smaller quantity of construction and demolition (C&D) wood waste is recycled. A primary barrier to recycling C&D wood waste is market development, which has been inhibited by a poor understanding of product quality, end user requirements, negative perceptions about "contaminated" demolition wood, and regulatory constraints.
In recognition of these constraints for developing markets for urban recycled wood (URW), the Clean Washington Center’s Recycling Technology Assistance Partnership sponsored a project to determine end use specifications, characterize URW and establish the opportunity for placing URW in various manufacturing processes. The results of this project will increase the competitiveness of wood waste products by:
· Helping processors understand the characteristics of their product relative to the specifications and constraints of the marketplace;
· Providing processors with technical and market information needed to initiate processing or increase processing capacity;
· Providing end users with feedstock quality data; and
· Providing regulatory officials with technical information that will encourage the development of reasonable regulations.
A survey was conducted to determine end-user specifications in the composite wood, pulp and paper and biomass energy industries. Two of the primary barriers indicated by survey respondents include: 1) many of the respondents who had used URW as a manufacturing feedstock experienced problems with excessive contamination; and (2) few of the companies use URW as a manufacturing feedstock because of the low cost of virgin fiber but indicated that URW would be an important source of fiber in the future.
The URW characterization component of the project involved collecting and characterizing URW samples from four URW processing facilities. A sampling procedure was developed to ensure the collection of a representative sample. The collected URW samples were analyzed for contaminants, sieve analysis, moisture, ash, heat energy and trace metal content. The results were analyzed to determine feedstock variability, potential methods for improving the quality of the product, and how well the various URW products met end-use specifications.
2.0 METHODOLOGY
2.1 END USER SURVEY
The primary focus of this report was to define the end users specifications and known constraints to using urban wood debris. A survey tool was developed (Appendix A) for eliciting information from end users about their experience with URW. A database was developed of potential major end users of URW. The survey was mailed to 35 potential and current users of URW. Of those surveyed, 9 manufacture pulp and paper, 12 manufacture composite wood products, and the remaining 14 generate energy from biomass. Within two weeks of mailing the survey, all of the firms were contacted by telephone (even if they returned the survey). The firms contacted in the survey are not identified in this report.
2.2 URBAN RECYCLED WOOD CHARACTERIZATION
Samples were collected for analysis from four processing facilities. An overview of the sample collection and analysis procedure is presented in Figure 1. Between September 16, 1996, and February 2, 1997, four URW samples were collected from the following URW processing facilities located in Washington State:
· Waste Management, Inc., Seattle
· H&H Wood Recyclers, Inc., Vancouver
· Horizon Wood Recyclers, Sultan
· Northwest Fiber and Wood Recovery, Auburn
At each facility, an initial representative, composite sample was collected and prepared. The sample was at least 2.8 cubic feet and from a stockpile containing at least 50 cubic yards of processed URW. In order to obtain a representative sample, it was collected from at least four different locations and at a minimum depth of six inches. The green weight and volume of the initial sample was determined.
The inert contaminant content was determined by examining the entire sample in one gallon subsamples and then manually removing any inert contaminants. Inert contaminants included all non-wood items (rocks, plastic, metals, roofing material, and styrofoam), composite wood products (oriented strand board, plywood, and particleboard), painted wood, and treated wood. The weight of each contaminant category was determined with a triple beam balance to the nearest gram and the percentage of contaminant content was calculated.
After determining the contaminant content, subsamples were obtained for laboratory analysis. The contaminants were mixed back into the initial sample and the entire sample was mixed. Using a “cone and quarter” sampling procedure, representative subsamples of the sample were collected for analysis. The cone and quarter procedure entailed the homogenization of the primary sample followed by the formation of a cone that was split into quarters. One of the quarters was discarded and the remaining three quarters were mixed. This procedure was repeated until the desired sample volume remained. The subsamples included a 0.7 cubic foot (cf) gallon sample for sieve analysis, a 0.1 cf gallon sample for laboratory analysis, and a 0.1 cf gallon sample for archiving. The brightness of each sample was determined by E&A Environmental Consultants, Inc. (E&A) according to the brightness index presented in Table 1.
Table 1: Brightness Rating Scale |
|
|
Brightness Rating |
Brightness Description |
|
1 |
Very bright, no dirty or dark wood present |
|
2 |
Moderately bright, less than 10% of the surface area is dirty or dark wood |
|
3 |
Dark, more than 10% of the surface area is dirty or dark wood |
|
4 |
Very dark, more than 50% of the surface area is dirty or dark wood |
The sieve analysis conducted by E&A was performed by hand, using six, eight-inch diameter ASTM standard sieves with square hole openings measuring 1-inch, 5/8-inch, 3/8-inch, 5/16-inch, 3/16-inch, and 1/25-inch. The top sieve was loaded to approximately three-quarters capacity and the entire stack of sieves was manually shaken back and forth 50 times on a horizontal plane. Limiting the sieve shaking time reduced the amount of long thin particles “spearing” through the sieves. Fraction larger than one-inch was manually measured and all pieces larger than three inches were segregated and identified as the greater than three-inch fraction.
A single subsample from each sampling event was forwarded for analysis to Columbia Analytical Services in Kelso, Washington. Prior to analysis, the laboratory mechanically ground a representative subsample (of the received sample) to pass a quarter-inch sieve. This procedure is necessary because many analytical testing procedures use less than a gram of sample. A representative one-gram sample was obtained for analysis by grinding and homogenizing the large-sized wood debris samples. The wood debris samples were analyzed for the following parameters:
· Total solids
· Volatile solids
· BTU content* (hog fuel only)
· Trace metal* content (arsenic, cadmium, chromium, copper, lead, nickel, and zinc).
* The BTU content and trace metal content are only important for characterizing URW to be used as hog fuel only.
During the site visits to each facility, the following information was obtained on how the facility was being operated:
· Sources of urban wood debris
· Pre-sorting activities at generation and processing sites
· Age of stockpile
· Intended market
· Description of process train and primary processing equipment
3.0 END USER SURVEY RESULTS
3.1 BACKGROUND
The purpose of the urban recycled wood (URW) end user survey was to collect information regarding the use of URW materials by specific end users. One of the survey objectives was to obtain specifications for procuring URW as energy and manufacturing feedstocks. Results of the survey are discussed according to the end uses. Of those surveyed, 9 manufacture pulp and paper, 12 manufacture composite wood products, and the remaining 14 generate energy from biomass. Tables 2, 3 and 4 summarize the survey results. Note: In this report of survey results, the term URW refers to all types of urban wood debris, including mill residuals and construction and demolition and land clearing debris (CDL).
Table 2: Urban Recycled Wood End Use Survey Results: Size and Shape Specifications
End-Use
|
Dimensions (inches) |
|||||
|
Length |
Width |
Thickness |
||||
|
Range |
Avg |
Range |
Avg |
Range |
Avg |
|
|
Biomass Fuel |
1.0 – 24.0 |
4.4 |
1.0 - 6.0 |
2.9 |
1.0 - 4.0 |
2.6 |
|
Composite Wood |
0.38 - 3.0 |
1.63 |
0.38 - 3.0 |
1.35 |
0.13 - 3.00 |
0.66 |
|
Pulp & Paper |
0.88 - 3.0 |
1.50 |
0.88 - 3.0 |
1.50 |
0.13 - 0.39 |
0.26 |
|
Maximum % Allowed |
Size (inches) |
||||
|
Range |
Avg |
Range |
Avg |
Range |
Avg |
|
|
0 – 10.0 |
7 |
5.0 – 33.0 |
14 |
0.13 - 0.25 |
0.18 |
|
|
0 – 20.0 |
8.2 |
2.0 – 40.0 |
10.3 |
0.02 - 0.25 |
0.15 |
|
|
Pulp & Paper |
0.5 10.0 |
5.2 |
1.5 – 5.0 |
3.3 |
0.12 - 0.19 |
0.15 |
Table 3: URW End Use Survey Results: Contaminant Content (%) Specifications
End-Use |
Contaminants (Range of Percent by Weight) |
|||||||
|
Bark |
OSB |
MDF |
Painted Wood |
Treated Wood |
Soil & Rocks |
Metals |
Plastics |
|
|
Range |
Range |
Range |
Range |
Range |
Range |
Range |
Range |
|
|
Biomass |
nl |
0 – nl |
0 – nl |
0 – nl |
0 - nl |
0 – 1 |
0 – 1 |
0 – 1 |
|
Composite Wood |
0 - 18 |
0 – 25 |
0 – 5 |
0 – 0 |
0 – 0 |
0 - 1 |
0 - 1 |
0 - 0.001 |
|
Pulp & Paper |
0.2 – 5.0 |
0 - 0 |
0 - 0 |
0 – 0 |
0 – 0 |
0 - 1 |
0 - 1 |
0 - 0 |
|
nl – No Limit |
||||||||
Table 4: URW End Use Survey Results: Moisture and Brightness Requirements
Min. 0 – 50Max. 12 – 90 |
17 47 |
25% of respondents do require minimum brightness level |
|
|
Pulp & Paper |
Min. nl Max. nl |
--- --- |
67% do require minimum brightness level |
3.2 BIOMASS FUEL END USE
3.2.1 Summary
Fourteen firms who use biomass fuel supplied information. Eighty-six percent of the respondents have used URW as a fuel and 79% are currently using URW as a fuel. The majority of end users experienced minor problems using URW as a fuel; these problems are discussed in respective section topics below.
3.2.2 Issues Regarding Size and Shape
Most end users accept a fairly coarse material as a fuel feedstock (Table 2). About 70% of the respondents can use a URW feedstock that is three inches in length or greater. One respondent uses a hog mill to process incoming URW and can accept larger-sized material as long as two feet. All of the respondents indicated that a shred material is acceptable, as long as it meets the size specifications.
The primary issue regarding the size of URW as a hog fuel is the conveyance of feedstocks from the fuel storage area into the boiler combustion chamber. System shutdown can occur when a large portion of oversized materials clog the conveyors and other equipment used to move the URW. Most of the facilities can handle URW having overs content of 5-10%. Several firms indicated that handling problems could result if the overs content exceeds a specified level.
The fines content of a fuel feedstock is of less concern than the oversized fraction. About 60% of the respondents indicated that fines are of no concern or only require periodic attention when fine content gets too high. Dust control is a primary issue regarding fines because of the health impacts on workers. Combustibility of the feedstock is also an issue, as several respondents indicated that fine material does not burn as well in their boiler as does coarser material.
Table 5: Size and Shape Specifications - Biomass Energy End Use |
|||||||
|
Company |
Dimensions (inches) |
Overs |
Fines Content |
Shred Wood Acceptable ? |
|||
|
Length |
Width |
Thick |
Max (%) |
Max (%) |
Size (in.) |
||
|
End User 1 |
2.5 |
2.5 |
2.5 |
10 |
nl |
--- |
Yes |
|
End User 2 |
24.0 |
6.0 |
2.0 |
0 |
15 |
3/16 |
Yes |
|
End User 3 |
4.0 |
4.0 |
4.0 |
10 |
nl |
--- |
Yes |
|
End User 4 |
4.0 |
1.0 |
1.0 |
10 |
nl |
--- |
Yes |
|
End User 5 |
4.0 |
4.0 |
4.0 |
5 |
10 |
1/4 |
Yes |
|
End User 6 |
3.0 |
3.0 |
3.0 |
ns |
a |
a |
Yes |
|
End User 7 |
3.0 |
3.0 |
3.0 |
10 |
nl |
--- |
Yes |
|
End User 8 |
1.0 |
1.0 |
1.0 |
ns |
ns |
--- |
Yes |
|
End User 9 |
3.0 |
3.0 |
3.0 |
0 |
nl |
--- |
Yes |
|
End User 10 |
1.5 |
1.5 |
1.5 |
10 |
nl |
--- |
Yes |
|
End User 11 |
2.0 |
2.0 |
2.0 |
5 |
5 |
3/16 |
Yes |
|
End User 12 |
3.0 |
3.0 |
3.0 |
10 |
33 |
1/8 |
Yes |
|
End User 13 |
3.0 |
3.0 |
3.0 |
10 |
nl |
--- |
Yes |
|
End User 14 |
3.0 |
3.0 |
3.0 |
5 |
5 |
1/8 |
Yes |
|
Average |
4.4 |
2.9 |
2.6 |
7 |
14 |
0.18 |
|
|
5.7 |
1.3 |
1.0 |
4 |
12 |
0.05 |
||
|
Maximum |
24.0 |
6.0 |
4.0 |
10 |
33 |
0.25 |
|
|
Minimum |
1.0 |
1.0 |
1.0 |
0 |
5 |
0.13 |
|
|
ns - Not specified nl - No limit a - Fines can cause dust problems, evaluated on a case by case basis |
|||||||
3.2.3 Contaminant Issues
Contaminants affect two major facets in the attempt to use URW as a fuel; regulations and boiler operation. Data obtained for this report came from facilities that are permitted to burn wood only. Burning other materials such as paper and plastic would require the facility to be permitted as an incinerator and would require a significant upgrade in emissions control equipment and a lengthy, expensive permitting process. According to Jim Knudsen of the Washington Department of Ecology, each facility (regardless of size) is allowed to burn up to 12 tons of URW per day from a source contaminated with waste materials (i.e. demolition debris that contains plastic). Contaminants such as dirt, sand, rocks, and metal can affect the performance of the boiler. In addition to having no BTU value, these contaminants increase the amount of ash disposal and also can clog grates to cause a shutdown.
Respondents indicated that their facilities have no tolerance for dirt, metals, plastic, and painted URW, as shown in Table 3. However, they were aware that a certain amount of these contaminants are received. There is no regular testing of incoming fuel feedstocks and it would be difficult to obtain and analyze representative samples. To reduce the amount of incoming contaminants, several of the facilities have specifications that state “Wood waste must be free of dirt, rocks, and metals” or a similar statement. All of the firms using URW as a fuel, frequently observe shipments as they are unloaded and moved by conveyor. A supplier is warned if a significant amount of dirt, metal, plastic or paint is observed. If the supplier continues to provide poor quality feedstock, they are no longer allowed to bring URW to the facility. A few of the respondents have specifications for dirt and metals. One firm addresses this issue by allowing a maximum ash content of 90%.
Table 6: Contaminant Content (%) Specifications - Biomass Energy End Use |
||||||||
|
Company |
Bark |
OSB |
MDF |
Painted Wood |
Treated Wood |
Soil & Rocks |
Metals |
Plastics |
|
End User 1 |
nl |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
End User 2 |
nl |
nl |
nl |
nl |
0 |
0.5 |
0.5 |
0 |
|
End User 3 |
nl |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
End User 4 |
nl |
nl |
nl |
0 |
0 |
0 |
0 |
0 |
|
End User 5 |
nl |
0 |
0 |
0 |
0 |
a |
a |
0 |
|
End User 6 |
nl |
nl |
nl |
b |
0 |
c |
c |
0 |
|
End User 7 |
nl |
nl |
nl |
0 |
0 |
0 |
0 |
0 |
|
End User 8 |
nl |
nl |
nl |
nl |
nl |
0 |
0 |
0 |
|
End User 9 |
nl |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
End User 10 |
nl |
nl |
nl |
0 |
0 |
0 |
0 |
0 |
|
End User 11 |
nl |
nl |
nl |
d |
0 |
0 |
0 |
0.5 |
|
End User 12 |
nl |
nl |
nl |
0 |
0 |
0 |
0 |
0 |
|
End User 13 |
nl |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
End User 14 |
nl |
e |
e |
e |
0 |
1 |
||