Is the ink in newsprint safe for the soil. Many gardeners advocate using newspaper and cardboard as part of a layering system. Is the ink in black and white newspaper okay and is the glue in cardboard okay?
Clackamas County Oregon
Newsprint and cardboard are generally considered safe for the soil, though glossy prints are not recommended. Soy and water-based inks are used on newsprint. I'm not finding research based specifically on the glue used in cardboard.
Here are articles with more information:
FAQ Cornell University Waste Management System, Composting in Schools, (third question) http://compost.css.cornell.edu/faq.html#newspaper
The Garden Professors, Extension, "Why I don't like cardboard mulch" http://blogs.extension.org/gardenprofessors/2012/06/20/why-i-dont-like-cardboard-mulch/ and "Sheet mulching--benefit or barrier?" http://blogs.extension.org/gardenprofessors/2010/09/16/sheet-mulching-benefit-or-barrier/.
Yes, black newspaper ink is soy-based and may be used as a soil mulch. Cardboard? I don't know, but I have used cardboard mulches and wouldn't hesitate to do so. But I don't have any science to back that up.