I understand that sustainably harvested western red cedar shingles and shakes are a very low environmental impact choice for walls and roofs. However the articles I’ve seen on the subject seem only to be considering untreated shingles/shakes.

My concern is regarding treatment for decay and/or fire resistance. In particular how do the various treatments complicate the issue of disposal at the end of their working lives? Untreated shingles/shakes have the advantage of  being compostible.

Can any of my fellow readers direct me toward resources that clarify the best disposal methods for treated products and how this impacts their life cycle analysis compared to other siding and roofing options?

My question is in the context of specifying for new construction projects, not for dealing with old products that may have been treated with chemicals such as CCA which are no longer commonly used.

Thanks!