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Originally published Friday, June 15, 2012 at 6:11 PM

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Recycling old wood is tricky, but demand high for certain types

As an organic material, wood is eminently recyclable or compostable.

Special to The Seattle Times

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How much wood would a woodchuck recycle in the Northwest?

With all the trees here in our woodsy region, you would think wood recycling would have a higher profile. As an organic material, wood is eminently recyclable or compostable, but wood recycling does not show up on the radar screen for many consumers.

Q: Let's start with the basics then. What types of wood can we recycle?

A: Any "clean" used wood that is untreated, unstained and unpainted can be recycled. This includes lumber, plywood, pallets and tree branches.

Q: How exactly should consumers recycle wood?

A: That's the tricky part. Although a strong demand exists for recycled wood, programs and companies that collect it may only want certain types.

Most area residential curbside-collection programs accept tree branches in the yard-waste cart. The city of Seattle allows branches and other clean wood scraps up to 4 inches in diameter and 4 feet in length to be put in the cart.

The city of Auburn, as another example, has the same size criteria for branches but asks that no lumber or fencing be placed in the residential yard-waste cart. Check with your program to confirm what they take.

Solid-waste transfer stations in Seattle, Shoreline and Enumclaw accept a wider variety of clean wood for recycling, at a lower rate than the fee charged for garbage. Those transfer stations will take wood with nails and staples.

King County's "What Do I Do With?" website lists more than 25 site, mostly privately operated, where the public can take wood waste. For details visit and click on "wood" and "residence."

Q: Since no recycling programs want pressure-treated wood, how do you identify it?

A: Pressure-treated lumber, which contains pesticides, typically has staple-sized slits lining the wood. One end may have a greenish tint.

Because much of the pressure treatment of lumber before 2004 used a hazardous chemical called chromated copper arsenate, or CCA, you should generally avoid reusing pressure-treated waste wood in yard projects.

Q: How does waste wood actually get recycled?

A: Recyclers turn wood waste into compost or mulches used for soil improvement, landscaping, erosion control and animal bedding. One of the main types of waste wood is a coarse mix of ground-up wood and bark called "hog fuel."

Large industrial operations such as paper mills may burn hog fuel to make heat or steam for internal energy needs, and at the same time they may generate electricity that goes back into the regional power grid.

Wood waste, crop waste and manures are known as biomass, and burning them has been controversial because of air pollution concerns.

However, using biomass for fuel has advantages because it is not a fossil fuel such as oil, coal or natural gas. Biomass is considered a renewable energy source.

Q: Why do they call it hog fuel?

A: The most common explanation is that a machine used to grind up the wood is called a "hog," but some sources say it comes from the Norwegian word "hogge," which means "chop."

Q: What about reusing wood?

A: Utilizing salvaged wood in home and yard projects is much more common than it was 20 years ago. Many contractors and do-it-yourselfers reuse timbers, beams, planks, flooring, doors and wood scraps.

Used building-materials stores such as the RE Store ( and Second Use ( in Seattle accept drop-offs of usable lumber and other salvaged wood they can resell. Call first to make sure they can use the materials.

You can offer lumber and other usable wood online on or, and you will probably get some takers.

Also consider using salvaged wood yourself. Turn old stakes from campaign yard signs into garden stakes, for example, or make a raised garden bed from unpainted, untreated boards.

Think of recycling or reusing wood as the ultimate act of respect toward a tree. Don't just knock on wood. Use it again.

Tom Watson is project manager for King County's Recycling and Environmental Services.

Reach him at, 206-296-4481 or

On Twitter @ecoconsumer.

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