Is pressure treated wood safe to use in the construction of compost containers in the yard?
Question:
I read the Cornell ‘Composting to Reduce the Waste Stream’ on your site. I do not like the idea it includes about using ‘pressure treated’ wood to construct compost containers in the yard. I wonder if you agree?
Answer:
Kate Garland, Horticultural Professional
When the Cornell document was written (1991) pressure treated lumber was made using CCA (Chromated Copper Arsenate). The chromium and copper weren’t really a problem but the arsenic certainly had issues. For years pressure treated wood was not recommended for raised beds because of the arsenic and potential to leach. Plants really don’t absorb arsenic. More commonly gardeners get exposure directly from breathing soil dust and ingestion of soil particles.
In the early 2000’s the method for manufacturing pressure treated wood changed and CCA was no longer permitted. They now use ACQ (Alkaline Copper Quat (Quaternary ammonia)). These products are not known to have toxicity issues or to leach into soils. Most people don’t know these changes were made and still think of pressure treated wood as potentially toxic. It has always been a personal choice to use or not use pressure treated wood, but there is significantly less risk now with the change in production methods. Hemlock or cedar can be used as an alternative to pressure treated lumber in raised bed or compost bin construction.