Nick Kitchener wrote:The risk of formaldehyde contamination from cardboard in sheet mulching has been well and truly discussed. What I have not seen anywhere is a discussion about using this same cardboard as a growing medium for mushrooms.
We know that mycelium are very good at absorbing toxins, and corrugated cardboard is a widely used growing medium for cultivating oyster mushrooms and other culinary strains.
People seem to assume that failure to decompose is direct proof that Formaldehyde is present in a sample of cardboard. Firstly, we need to be much more concerned about its persistence in the air of our homes. If my cardboard actually did have Formaldehyde in it, then I would want it OUT of my house. I'll gladly place it outdoors where it can off-gas! But secondly, and more importantly, try researching the chemical itself. How does the compound react in the environment? "Given its physical-chemical properties,
formaldehyde is degraded by various processes in air, with very small amounts transferring into water. When released to water or soil, formaldehyde is expected to remain primarily in the original compartment of release, where
it undergoes various biological and physical degradation processes. Formaldehyde is not bioaccumulative or persistent in any compartment of the environment." -
https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/contaminants/psl2-lsp2/formaldehyde/formaldehyde-eng.pdf (page 49)
I don't particularly want any extra exposure to it than is necessary. Even still, I'm not going assume that few poorly decomposed cardboard sheets means there is a highly concentrated level of Formaldehyde that has stalled all biological activity. That's completely baseless. "Low levels of formaldehyde occur naturally in a variety of foods, such as fruits." -
https://www.atsdr.cdc.gov/ToxProfiles/tp111-c1-b.pdf So should we stop composting old fruit for fear that we'll disrupt the ecosystem?
