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Is it safe to mulch with paper?

Shredded paper mulch
"Aren't you concerned about the heavy metals and dioxin that are found in papers and inks?" --- Organic Gardener

"I was actually wondering about this recently.  I am somewhat leery of the chemicals in the paper and inks (even if it is soy based ink there are other chemicals in it that may not be great)." --- Sharon


I put this question to Tradd Cotter at his talk on mycoremediation (using mushrooms to deal with chemical pollutants) and the upshot is that fungi can break down nearly anything we throw at them as long as the fungi are healthy.  Since Mark and I work hard to create fungus-friendly soils (by not tilling, never adding pesticides or herbicides, always applying organic matter to the soil surface, and so forth), I trust our fungi to break down everything except heavy metals.

Black raspberry

The question becomes --- will paper used as mulch in the garden contain heavy metals?  A study by West Virginia University showed that glossy paper may contain heavy metals while, in contrast, paper with only black ink is quite safe in the garden.  The study didn't address the middle ground, though --- non-glossy paper with color ink.

What do we do in our own garden?  Glossy paper hits the trash can (since it makes plants grumble even before you consider the heavy metals issue), black-and-white paper is used without concern in the garden, and non-glossy paper with colored ink goes in one place or the other, depending on how desperate I am for mulch material.  I figure that, given the relatively low quantities of paper we use for mulch, simply using my paper to mulch different areas each year will keep heavy metals from building up to toxic levels.  (My junk mail mulch probably amounts to about 1% of our annual mulch, if that.)

Mulched garden

As a side, note, neither of the questioners addressed the C:N ratio issue, but I think this is an important point for gardeners to understand if they're using paper in or on their soil.  Paper has a C:N of between 50:1 and 175:1, which means that decomposing bacteria will suck nitrogen out of your soil while breaking the paper down if you're not careful.  How do you get around this issue?  Only use paper as mulch in parts of your garden where you aren't going to till in the near future, since mulch doesn't steal much nitrogen from the soil but paper worked into your dirt definitely will.  Or, if you must till in paper mulches, be sure to apply some extra nitrogen (compost, manure, urine, etc.) at the same time so the paper won't steal important nutrients from your plants.

I hope that helps you decide whether or not to use paper as mulch in your own garden.  In the end, it comes down to a personal decision about how careful you want or need to be, and how much you want to save a buck and keep waste materials out of the landfill.  (Or to avoid a trip to the recycling center if you have one nearby, which we don't.)  We try to use up as much of our "waste" as possible, so paper mulch, within reason, is acceptable on our farm.



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The source states that paper with black ink is safe. I am concerned about paper with black toner, and that is quite different than ink. Do you have any thoughts on toner? Thanks!!

Comment by Robert Thu Jun 12 09:19:38 2014

Newsprint contains a good deal of pine resin, which is bacteriocidal. That's why newspapers were often used as bedsheeting for home birthing in the old days. I don't know if they're also fungicidal or if the effect is big enough to affect its use as mulch.

In regards soil bacteria "sucking up N," is it really that important? It's not like they're eating their lunch and leaving the field, carrying the N away.

Comment by doc Thu Jun 12 10:01:31 2014

Chlorinated dioxins (the dangerous kind, simply said) can a by-product of bleaching paper with elemental chlorine (Cl2). As you can see here, in the US and Europe, paper production had almost totally shifted to processes that don't use elemental chlorine (and don't form chlorinated dioxins) by 2005.

So modern paper produced in the US would probably be OK in that regard.

Comment by Roland_Smith Thu Jun 12 15:11:43 2014

It seems that chromium (often in combination with lead) is what you could expect to find in some inks. This probably comes from lead(II) chromate.

Not sure about the situation in the US, but in Europe lead chromate will be banned from 2015 by the REACH legislation. Some pigment manufacturers have phased it out already and others are in the process of doing so.

But it hard to be sure that a printing ink doesn't contain this stuff without testing. So I guess the prudent path would be to avoid colored inks until some years after the US and Europe have completely banned it and until China starts enforcing existing regulations on it.

Comment by Roland_Smith Thu Jun 12 17:31:56 2014
I have just recently been thinking about using some shredded paper for mulch. I thought of mixing it in with some compost mainly to stop it being compressed and not allowing rainwater to soak through to the soil. That might help with nitrogen drawdown as well.
Comment by Gillian Thu Jun 12 21:18:25 2014

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