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Re: Newspaper Mulch

Denise, 
On Sunday, May 04, 1997 12:36 AM
you wrote:
> Thinking so does not MAKE it so. I would simply like to point out that
> there is a BIG difference between animals lying on paper products and
those
> same paper products with their attendant ink, coatings and printer/copier
> toners decomposing and being absorbed by the vegetables I eat! 

I should have foreseen that response.  Frankly, I have not seen any recent
literature regarding the migration of anything nasty from newsprint into
plants grown in composted newsprint.  (And I would like to see it, if it's
out there.  I suspect the COMPOST list may have opinions here, but I do not
watch that one).  There used to be toxic organics in printer's ink a decade
or more ago: inks are now almost exclusively soy-oil based, not
petroleum-derived.  The colors used to be toxic metal based (i.e., cadmium,
chromium, lead) but not anymore.  The colors are now due to complex organic
molecules, just like the dyes that color clothing.  

Are these a problem?  Yes, it's possible.  But not after composting, or
after decomposition in the soil.  The soil flora (fungi, bacteria) and the
flora in the gut of the soil decomposition fauna (worms, insects) that
would chew on the paper would chew up those organic molecules and use them
for energy.  Seriously.  There's actually a sub-discipline in environmental
engineering called bioremediation, in which microflora are introduced into
a system in order to speed up the decomposition of organic pollutants in
natural systems.  And it works.  

Consider a sewage treatment plant.  If the plant is working properly, and
within design limits for capacity, the effluent water coming out of the
plant is clean.  That's essentially bioremediation.  Similar degradation
processes are going to occur in a compost heap, or in the soil in your
garden, as long as you work to maintain a high level of organic matter in
that soil.  

Why is OM important?  Worm food, for one.  Worms lead to aeration, and the
oxygen is good for the process.  Aeration encourages soil flora and fauna,
which can only help the breakdown process.

OM also binds things that could otherwise be a problem.  There are heavy
metal-contaminated sites in the eastern US where the soil SHOULD be too
toxic to support plants, but people safely garden in those areas.  How?  By
keeping the OM content high (the residents typically fertilize with lots
and lots of cow manure).  The OM ties up the heavy metals, reducing the
availability of the metals to the plants to a non-toxic level, and keeping
them in the soil.  And because the metals are tied up to the OM, they are
NOT available to the plant, and do NOT get into the part you eat.  

The problem is that the OM needs to remain high in these areas.  If you
quit adding OM, the OM content decreases (over a period of years), and the
heavy metal levels can become toxic to the plants. 

Rick Grazzini
rickg@centrelab.com
"It's ALL chemistry" -- Dr. R. O. Mumma
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