Question of the Week
Answer: The authorities that govern biodynamic and organic certification are the Biodynamic Standard and the USDA National Organic Program (NOP) Regulations, respectively. Both prohibit the use of treated wood in certified production systems, as detailed below:
Biodynamic: A producer must not use lumber treated with arsenate or other prohibited materials – for new installations or replacement purposes – that comes in direct contact with soil used in certified production or certified livestock¹.
Organic: A producer must not use lumber treated with arsenate or other prohibited materials for new installations or replacement purposes in contact with soil or livestock².
Some certifiers will allow treated wood on certified farms if the wood exists prior to certification. If this is the case, you will need a barrier to prevent the wood from coming into contact with soil or animals. For fence posts, certifiers will usually accept an electric wire (polytape, etc.) as a barrier to prevent animals from coming in contact with the treated wood. Ask your certifier if he or she has an allowance for this practice.
For new construction, you will need to use non-treated wood. I recommend the ATTRA publication Pressure-Treated Wood: Organic and Natural Alternatives. Included in this publication are sections on preservatives applied before purchase, preservatives applied after purchase, and alternatives to treated lumber.
1. Biodynamic Farm Standard, Demeter Association, September 2005.
2. National Organic Program Regulations, CFR Title 7, Apr 2017
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