There was a recent questionon the USGBCs Green Home Guide asking, “Is there pressure-treated wood that isn’t treated with chemicals?” Unfortunately, the answer only listed a number of conventional (ie chemically treated) options, and made no mention of the other alternatives that are available.
But there are other materials, though they may not be as widely known. I posted an additional reply to the question, which I’ve reposted here below. Since I have written about Kebony before, I’m pretty familiar with it already. (It was also one of the things I covered in my presentation this past weekend.) I’ve also heard about Timbersil and Accoya, though I haven’t written about them, yet.
These alternatives are somewhat pricey. They’re going to get value-engineered out of a lot of projects. But this is a starting point for a couple alternatives for use especially for things like decks that might be in frequent contact with bare feet or where otherwise you really would like not to have conventionally treated wood.
There are several treated wood options that use alternatives that are far safer than the preservatives in Anthony’s list. They are “treated with chemicals” in one fashion or another, but fundamentally, even wood (and everything else) is made up of chemicals.
All three of these are natural wood that is treated, but is non-toxic and does not leach any noxious chemicals the way that more conventionally treated lumber will. They can be worked without special protective gear for the workers (other than what would normally be prudent for woodworking tasks). A couple of them can even be composted at the end of their working life if there is not another use for them.
Kebony (kebony.com) is wood treated with a food grade material that is a byproduct from sugar cane processing to make wood resistant to decay. According to the company, decks will last, without any maintenance needed, for 30 years. There are also examples of it being used as roofing and building siding, with similar life expectancy.
Accoya (accoya.com) is another wood treatment that changes the wood so that it is far more resistant to decay. There is nothing in the wood that is not already naturally found there (although presumably more than what is normally present)
Timbersil (timbersilwood.com) has a technology that treats wood with an amorphous glass to produce a more decay resistant material, as well as increasing fire resistance.
Both Kebony and Accoya can be sourced from FSC certified forests, as well, so the origin of the wood is responsibly managed. All of these products are going to be more expensive than conventional treated wood. But, if they will last for many more years, it may be worth the extra cost.