Wood Recycling

Published guidelines provide guidance on specifications for C&D biomass

Editor’s Note:
The Construction Materials Recycling Association worked with the National Solid Waste Management Association to develop the document below. The specifications are based on industry experience, permit requirements for boilers using C&D wood as a fuel stock and regulatory requirements governing the use of this material. The specifications provide real world guidance on what works in the marketplace for C&D wood fuel buyers (boiler owners and operators) and sellers (C&D wood processors).

C&D wood is generated at construction and demolition sites and processed throughout the U.S. by dedicated C&D processors. The processed wood is turned into a variety of end products, one of the most valuable of which is a fuel stock. The specifications are designed to serve as a starting point in negotiations between potential buyers and sellers of C&D wood fuel and to aid governmental regulators and legislators better understand workable and proven specifications for C&D wood fuel.

The Construction & Demolition Wood-Derived Product Specifica-tions are intended to provide a guide of differing grades of C&D wood-derived (C&D wood) product. These specifications provide categorization of C&D wood to encourage standardization and promote marketability. The specifications serve as a starting point in negotiations between purchasers and suppliers. C&D wood suppliers will need to work with purchasers to ensure the C&D wood meets the purchaser’s specific needs. 

Disclaimer: The EPA issued the “Identification of Non-hazardous Secondary Materials that are Solid Waste” March 21, 2011, per 40 CFR Part 241 which must be addressed independently by suppliers and sellers of C&D wood.
http://edocket.access.gpo.gov/2011/pdf/2011-4492.pdf (last visit April 18, 2011)

Definition
C&D wood-derived product—a renewable, biomass product prepared from wood materials generated at construction and demolition sites that is processed to create a commodity that can be used as fuel for a boiler and/or other energy generation technology (e.g. gasification). This product can also include other biomass materials such as boxes, crates, pallets and other wood products from industrial and post-consumer sources.

Unwanted Materials
Certain substances should be discouraged from entering the C&D wood processing operation. Limiting these materials will improve the characteristics of the (e.g, fuel heat content) final product. These include materials such as scrap metal, PVC piping, drywall and non-combustibles such as rocks and aggregate, can create operational problems with the C&D wood used as fuel. In addition, processors must take care to ensure prohibited substances (such as lead-based painted wood or certain treated woods) and asbestos-containing materials are prevented from entering the fuel processing.

Fuel purchasers may have specific limits or prohibitions on particular substances and materials. C&D wood suppliers may be required through contractual obligations to further prevent and also, restrict these or other materials from entering the processing system. The limitation may be specified through standards or specifications from common standardization entities such as American Standards and Testing Methods (ASTM). This document does not address such levels of specific requirements between individual purchaser-supplier agreements. The CMRA and NSWMA encourage all C&D wood suppliers to strive to ensure the highest quality product for the C&D wood application. The C&D wood supplier must comply with all federal, state and local regulations. This document does not address such regulations. Suppliers and/or purchasers may need to comply with additional state, federal and facility testing procedures and protocols and sizing procedures.

Product Grade System
Process material is categorized for Grade and sizing. Grade defines the acceptable amount of undesirable materials. Sizing defines the range of acceptable particle nominal sizing from processing (i.e., grinding) of materials. All sizing fractions are based on measures of mass.

Size A: 3 inches or less in any dimension.

Size B: A minimum of 90% is 3 inches or less in any dimension. All material is 6 inches or less in any dimension. A minimum of 85% is greater than ¼ inch size in their smallest dimension.

Size C: A minimum of 90% is between 3 inches and 6 inches in any dimension. All material is 10 inches or less in any dimension. A minimum of 85% is greater than ¼ inch in any dimension.

Size D: A minimum of 90% are 6 inches or greater in any dimension. All material is 10 inches or less in any dimension. A minimum of 85% is greater than ¼ inch in any dimension.

Grade Number—The following materials are restricted within the following grades: lead-based painted wood, CCA-treated wood, plastic, plaster and all non-combustibles such as rocks, concrete and aggregate.

Grade 1: 1% or less

Grade 2: 1% to 5%

Grade 3: 5% or more

Notes for C&D Wood–Desirable Properties for Fuel
Boilers and other energy generation technologies have operational specifications for fuels (e.g., moisture content, ash, fuel particle size and fines). These operational specifications are needed to ensure the combustion system is well operated to ensure the fuel is suitable to be used in the boiler. 

In general, high quality fuels have low moisture, low ash content and high heating value. These qualities encourage efficient and complete combustion. C&D wood suppliers should strive to limit the moisture exposure such as rain water, of process materials, reduce noncombustible materials and maximize the carbon content of the C&D wood (e.g., increase organic content). The purchaser may request fuel to be processed to a less than nominal diameter (e.g., 3 inch or less) in order for the material to properly burn in a specific combustion system.

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