Waste wood materials are generated in virtually all urban areas as a consequence of urban and suburban growth. While this material is often overlooked as a raw material resource or feedstock, it has the potential to add tangible market value in a number of ways while providing environmental benefits.
Primary sources of urban waste wood include wood generated while clearing timber tracts for expanded urban development, dunnage, which is wood used to secure goods as they are transported to manufacturing or distribution facilities, and wood waste generated as a byproduct of home ownership or municipal maintenance activities.
Other urban wood waste materials that are often referred to as “yard waste” include landscaping debris, land clearing and right-of-way (ROW) waste, and clean construction and demolition (C&D) waste that includes pallet waste. The volume of this material is not related to market demand for waste wood; rather this type of waste must be disposed of. Generally speaking, the flow of urban waste wood begins at the point of generation before arrival at a landfill, which charges a tipping fee to accept these materials.
What is a tipping fee?
Disposal facilities charge tipping fees to cover the immediate cost of handling the materials, as well as any future costs that may be incurred for a period of 30 years after the facility closes, which is the standard regulatory requirement in the solid waste industry. Tipping fees can range from a $15.00 per ton minimum (for wood waste entering an inert landfill) to a $75.00 per ton maximum if materials are directed to a Municipal Solid Waste (MSW) landfill.
Who collects urban wood waste?
Typically, there are two types of landfills that will collect urban waste wood:
- Land-clearing and inert landfill: Collects land-clearing and inert waste that is not chemically or biologically reactive, and will not decompose.
- MSW landfill: Collects solid waste resulting from the operation of residential, commercial, industrial, governmental, or institutional establishments.
How is urban wood waste used?
Oftentimes, permitted landfills bury all the waste wood that crosses their scales. However, some facilities divert clean waste wood to an on-site processing area where the materials are ground and made available to the public. Typically, landfills that grind wood waste then use these materials in a few ways:
- Sell it in the open market as boiler fuel or mulch
- Use it in their own on-site processing efforts (e.g., mix wood waste with bio-solids from water reclamation facilities to produce a commercial grade compost to be sold to the public)
- Use it to aid with daily facility operational needs (e.g., on-site soil erosion issues, or daily/ intermediate cover, if a site is “dirt poor”)
Urban tree debris being chipped and collected.
In addition to landfills, urban wood processors and/or wood dealers have the capability to supply boiler fuel to the market for a fee per ton. The different types of urban wood processors include:
- Land clearing companies
- Yard trash processing facilities
- Tree/arborist companies
- Wood dealers
- Mulching operations
These processors source the waste wood material by intercepting a portion of the flow of urban material that would otherwise go to landfills. Urban wood processors secure their waste wood by charging a lower tipping fee, which in turn drives a portion of the material to their facilities rather than to the landfills. The processors can also control the volume of material they receive by adjusting their tipping fee lower when they require more material, and increasing the fee when they require less.
The economics of waste disposal drive the diversion of wood waste from burial at a landfill to a repurposed, more efficient use such as boiler fuel and landscaping mulch. The price paid per ton for boiler fuel is based on:
- The cost of disposal at the landfill (which is a negative cost to the landfill receiving a tipping fee for the material)
- The cost of processing the material (which may include sorting, grinding and screening)
- The cost of material handing at the processing site
- The cost of transportation to the boiler fuel consumer
Are there any regulations in place for the collection of urban wood waste?
Solid waste regulations are typically separated into either a collection or disposal category. Regulations for the proper disposal of municipal solid waste are extremely stringent as the process is costly, which has led many local government-owned landfills to close or simply sell out to the private sector. Regulations are more relaxed for Class 1 (inert) and Class 2 (C&D) landfills due to their constituents. However, as states have adopted waste reduction goals, many cities and counties have been encouraged to increase the diversion of reusable materials from local landfills and direct them into the marketplace. As a result, many states have established guidelines under which these reusable processing facilities may operate.
Current economics favor funneling wood waste into the market, whether the market is for fuel, mulch or other uses. This is because the disposal of wood waste into a landfill adds zero net value. Rather, introducing wood waste into the market adds value as it can become a feedstock for a biomass power facility, for example. Using this material in the market will also result in direct and indirect economic effects (e.g. new jobs, added construction, etc.).
Urban waste wood converted and used as mulch.
The economic factors driving a landfill’s decision to shift wood waste into the market are contingent upon the following:
- The landfill’s need for daily or intermediate cover (cover dirt is expensive and often difficult to find)
- State waste reduction goal credits the landfill might secure by using the wood waste for daily or intermediate cover
- A desire to save valuable landfill space for materials which have no alternative disposal options
- An end-market consumer with feedstock demand requirements
In general (and depending on location), there are a few regulations and/or challenges that affect urban wood waste collection:
- Yard trimmings may not be placed in plastic bags for collection in curbside programs, as plastic bags do not decay and become litter if yard trimmings are ground instead of buried.
- Many cities and counties have contracted the collection of waste (MSW and yard trimmings) to the private sector which, unless directed, does not provide separate collection of yard trimmings. When not collected, these materials represent a lost opportunity.
- Curbside collection programs are often funded with General Fund tax dollars. In difficult economic times, local governments may shift funding away from these programs, which can create some instability in the wood waste market.
- Reduction (i.e. grinding) equipment is expensive, which can make entry into the wood fuel market difficult.
For a biomass power operation, urban wood waste material can be a viable supply source for a current or new-project facility. While it may not be a facility’s primary feedstock source, considering it as a supplemental option may reduce costs, improve efficiencies and add value to the supply chain. Unsustainable raw materials costs can be the undoing of a renewable energy project. Many parts of the country have access to quality urban wood waste material, which can help drive the success of a biomass power facility while helping to close the carbon loop by creating new energy.