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Other Treatment Alternatives

Alternative lumber treatments are available. These alternatives are free of arsenic, chromium, and other preservatives classified by the EPA as hazardous. However, they may contain ingredients that are synthetic or that are not yet evaluated by the National Organic Standards Board (NOSB).

Borates (boric acids and borax) have long been used for alternative wood protection and are used in all types of lumber, logs, and plywood. Boric acid is a synthetic substance allowed for use in organic crop production as a “structural pest control, [not in] direct contact with organic food or crops.”

Borate wood treatments will penetrate to the center of the wood when the wood is dipped, especially when the wood is freshly cut, or when seasoned wood is re-wetted. However, because borates are water soluble, they will leach from the wood when in contact with water in the soil, leaving the wood unprotected. Thus, borate-treated lumber is commonly used only in locations that are at least six inches above the ground and protected from excessive rain. Borate-treated wood is not considered suitable for unprotected outdoor use, such as for fence posts or poles, but is suitable for most building construction purposes.

Ammoniacal Copper Citrate (CC) is a recently developed wood preservative that has 62.3% copper as copper oxide and 35.8% citric acid dissolved in a solution of ammonia in water. The treated wood initially will have a slight ammonia odor, but the odor dissipates soon after treatment. The copper protects against decay and insects, and the citric acid helps distribute the copper inside the wood.

Copper azole (CBA) is a wood preservative with active ingredients of copper, boric acid, and tebuconazole (azole), a synthetic organic carbon product used in fungicides. Copper azole has 49% copper as CU, 49% boron as boric acid, and 2% azole as tebuconazole dissolved in a solution of ethanolamine in water. CBA lumber use must be discussed with your certifying agents before any application and use, and written into your Organic System Plan. The EPA has not yet established use and handling precautions for wood treated with copper azole.

Alkaline Copper Quaternary Ammonium (ACQ®) is a wood preservative—containing copper and quaternary ammonium compound (quat) as active ingredients — that protects against rot, decay, and termite attack. It is the most common CCA replacement. Quat is a product commonly used in commercial disinfectants and cleaners. It acts as a co-biocide. Some copper does leach from ACQ-treated lumber, making it unsafe for garden use. And because copper is highly toxic to marine life, ACQ is not recommended for aquatic environments.