Hey Mr. Green,
Help! Our plans to replace our rapidly rotting fence have been delayed for 3 years, as we have been unable to decide on the greenest option. I listened to your podcast about this topic, but unfortunately a "living fence" is not feasible because we need to contain a dog. In particular, what materials are the best option for the posts, which will be in the ground and subject to rotting more quickly than the rest of the fence? Obviously, pressure treated wood is far too toxic and not an option for us. –-Kim, in Seattle
If you want absolutely, teetotaling, chemical-free fenceposts, then choose a highly rot-resistant wood such as redwood or cedar. But if you go this route, please, please, please obtain posts that are certified by the Forest Stewardship Council http://info.fsc.org/, an organization that helps to insure that timber companies follow environmentally sound forestry practices. After all, nefarious forestry can be every bit as devastating to the environment as toxic chemicals, if not more so.
Other reasonably green choices are posts made of metal, recycled plastic, or composite synthetic lumber made , although these options might not suit your tastes.
Regarding chemicals, the EPA has okayed wood that is pressure-treated with alkaline copper quat (ACQ types B and D) and copper azole (CBA-A, CA-B), so if you are willing to compromise your standards, you might consider these, though they are not 100 percent benign. For example, there is some concern that copper compounds can leach into water and harm aquatic creatures.
These preservatives replace a once widely used arsenic-laced preservative known as in copper chromated arsenic (CCA). The EPA deemed it too toxic, and banned its application to wood intended for consumer and residential use after 2003. By now, it is unlikely to remain in a dealer’s inventory, but you never know. So if you do decide to default to the less-toxic treated posts, look very closely at the tags on the ends of the lumber to make sure they were not treated with CCA. If the tags are missing, ask the dealer what the wood has been treated with.
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