Making smart use of milling byproduct

Smart Bark is produced by heat treating discarded Douglas fir bark, a byproduct of the milling industry. Photo: After Image Visual Services

A half million dry ton of Douglas fir bark is an annual byproduct of the milling process in Washington state. It is the most readily available bark in the Pacific Northwest, where it is commonly used for decorative purposes, burned as “hog fuel” or becomes a disposal issue for mills.

Recent research has shown that heat treating tree bark to produce a “Smart Bark” may serve as a suitable substitute for vermiculite and/or perlite. The bark is first screened to remove any debris and wood particles. It is then ground into uniform sized particles. The bark is then ready to be heat treated.

The bark represents an organic material devoid of toxic resins and low moisture content after the heat treatment. The treated bark could serve as a natural cellulosic sponge capable of absorbing and retaining water and plant nutrients.