The article below is written by a man in Montana (paul wheaton) who is studying the effects of cardboard and newspaper as it applies to gardening. I am not a gardener but the information is disturbing thus opening Denver’s Moving Boxes. We have been moving with cardboard since the beginning of time and it has to change; soon and fast.
concerns with using cardboard/newspaper as a mulch
“This is a massive area of study. Somebody could fill a few chapters in a book on this. So I’m gonna take some shortcuts and say:”
1) the wood lignins that make up most paper could get okay paper with mechanical smashing, but better paper comes from a chemical process. Hence, chemical process is preferred. Some papers/cardboards contain a lot more gick (to make it look nice longer) than what folks will usually see for mulch.
2) Cardboard is usually several layers of paper glued together (or a very thick paper) sandwiching a corrugated layer of paper. These layers are glued together. Usually the glue is corn starch based – enhanced with a variety of petroleum chemicals.
Another problem is that newspaper/cardboard tends to not break down particularly fast. And since the mission is usually to smother something that is already there, it is placed in sheets. If too thick, it could make a layer that cannot be penetrated by water or air – maybe for many years.
Last spring I visited somebody’s garden where an apple tree was doing poorly. After digging around a little, a layer of newspaper was found about an inch under the soil. It was about a quarter of an inch thick and had apparently been put down to kill weeds about five years earlier. It killed the weeds. And it was making the tree sick. And it wasn’t breaking down.