Umbra on composting paper
Two questions: Does the colored ink in newspapers still contain chemicals bad for a compost pile? Also, what about the colored ink printed on cardboard boxes? I want to have a safe compost pile to use in a garden.
Dearest Mysterious Reader,
Some readers may find gardening questions in February a bit jarring. By choosing to answer this one, I’m taunting those of you who don’t live in the Pacific Northwest. True, we may be moistly imprisoned under an unrelenting steely sky, daylight may be a dim memory, and mildew may be our constant companion, but at least we can consider composting in February. Ahh, compost. So helpful in relieving Seasonal Affective Disorder.
Pigments combine with a “vehicle” and a “binder” to create specific inks for various printing projects. The pigment and the vehicle are the bad boys. Paper composting and mulching is haunted by the specter of the heavy metals used as pigment in commercial inks in the past. For years, the vehicle was petroleum-based, but the industry is slowly switching over to soy- or vegetable-based inks. However, inks labeled “soy-based” are still permitted (and likely) to contain some amount of petroleum.
Pigments themselves still contain heavy metals such as zinc and copper, although overall amounts of heavy metals have been reduced. Although toxins are present in quite small amounts, all the sources I consulted agreed that contemporary printed newsprint, including colored newsprint, and cardboard boxes are safe for garden use. Glossy inserts, shiny ink of any sort, magazines, and colored paper do not make appropriate compost or mulch materials, due to a higher prevalence of toxics within the paper and ink, and likelihood of “de-inking” (ink sliding off the paper into your garden).
One further thing: If you’re gardening in an urban or suburban area, ink is a drop in the contamination bucket. It’s far more likely that your soil will be contaminated by other sources, such as lead paint, pavement runoff, or car exhaust that washes from building walls into the soil. Get your soil tested for heavy metals before food gardening and avoid food gardening within 10 feet of a building. What is toxic is often invisible to the eye.