Wood recycling transforms discarded timber into new materials, diverting significant waste from landfills. Construction and demolition (C&D) debris often includes large volumes of wood, accounting for a considerable percentage of the overall waste stream. When wood decomposes in a landfill, it produces methane, a potent greenhouse gas, making recovery environmentally sound. Recycling wood also conserves natural resources and reduces the energy required to manufacture virgin products.
Sorting Wood Waste Streams
The recycling process begins by classifying the incoming wood materials into categories. This initial separation determines the eventual end-use of the recycled product and ensures quality control. Wood waste is typically classified based on its source and level of contamination, ranging from clean, untreated dimensional lumber to mixed industrial scrap.
Clean wood, often sourced from pallets or manufacturing offcuts, is kept separate from demolition wood, which is more likely to contain paint, metal fasteners, or adhesives. Manual inspection is employed at the receiving facility to identify and remove obvious non-wood contaminants like large pieces of plastic, drywall, or metal brackets. This preliminary sorting creates usable wood streams before the material enters the mechanical processing stage.
Processing Wood for Reuse
Sorted wood waste is fed into industrial machinery for size reduction and cleaning. Large, bulky pieces are processed through powerful shredders or grinders, which break the material down into smaller, uniform chips or particles. Low-speed shredders are used for heavily contaminated material as they are more tolerant of foreign objects, while high-speed grinders are utilized for cleaner wood to achieve a finer particle size efficiently.
Following grinding, the material moves through a series of screening stages, typically using trommel or vibrating screens, to separate the wood chips by size. Oversized pieces are returned to the grinder, while the finer material proceeds to contaminant removal systems. Magnetic separators extract ferrous metals like nails and screws. Air classifiers use a stream of air to separate lighter wood fiber from heavier non-wood materials such as rocks, grit, or paint chips. This mechanical process creates the various grades of clean wood fiber needed for new product manufacturing.
New Products Created from Recycled Wood
The processed wood fiber is a versatile raw material used across several industries. Its final application depends on the cleanliness and size of the recovered chips. Low-grade, mixed-fiber material is often directed toward biomass fuel, where it is combusted in specialized power plants to generate heat and electricity. This energy recovery is a significant market for fiber too contaminated for material reuse.
Clean, fine-grade wood fiber is used extensively in the creation of engineered wood products, such as particleboard and medium-density fiberboard (MDF). These composite panels are manufactured by binding the recycled wood particles together with resins under heat and pressure. Using recycled fiber in these products reduces the demand for virgin timber.
The medium-grade chips are frequently used for landscaping materials, including colored mulch, compost additive, or playground surfacing. For applications like playground material and animal bedding, the wood must meet strict cleanliness standards to ensure it is free of chemicals and sharp metal fragments. Wood fiber can also be combined with recycled plastic to create composite decking, offering a durable, low-maintenance alternative to traditional lumber.
Types of Wood That Cannot Be Recycled
Certain types of wood are excluded from recycling due to hazardous chemical treatments or excessive contamination. Pressure-treated wood, which contains preservatives like chromated copper arsenate (CCA) or creosote, cannot be recycled into new products that might contact people or animals. These chemicals can pose a health hazard.
Materials like railway ties, utility poles, and agricultural fencing are typically treated with industrial-strength preservatives, classifying them as hazardous waste that requires specialized disposal. Additionally, older painted wood, particularly materials from construction predating 2007, may contain heavy metals like lead. Heavily contaminated wood mixed with excessive dirt, concrete, or non-removable plastics often cannot be salvaged, as the cost and effort of cleaning the material exceed its market value.