Market Farming

[Alex McGregor <waldenfarm AT sprintmail.com>]

Here's an article form Science News that talks about hormone breakdown
in composting processes.  The antibiotics come through, too, but are
chemicals produced by fungi.  These can be broken down in a good
composting operation.

BTW, Science News had an article last month on androgen (mainly
testosterone) contamination of water from manure in feed lots.


Livestock naturally excrete large amounts of estrogen and testosterone,
hormones that can harm crops and wildlife when farmers use manure as
fertilizer (SN: 7/15/95, p. 44). A study now shows that farmers can rid
chicken manure of much of this unwanted hormonal baggage by composting
the wastes.

Heldur Hakk of the Agriculture Department's Biosciences Research
Laboratory in Fargo, N.D., and his colleagues collected manure from
egg-laying chickens and mixed it with hay, straw, decomposing leaves,
and some starter compost. Then, they added water and heaped the mix atop
impermeable pads in long compost piles. Periodically, they turned the
compost to maximize the bacteria-driven degradation, which generates
heat.

Although the manure's starting concentrations of testosterone and
estrogen averaged 187 parts per billion (ppb) and 95 ppb, respectively,
amounts of both hormones fell gradually over 19 weeks—to a mere 13 ppb
for testosterone and 16 ppb for estrogen. Initially, Hakk notes, the
breakdown of testosterone proceeded at three times the rate of that of
estrogen.

The heaped compost cooled before either hormone fully disappeared, which
means that some could have leached out and flowed downstream if the
compost were spread as fertilizer. Hakk's team didn't assay the finished
compost for any breakdown products of estrogen or testosterone, some of
which are hormonally active. Hakk said his group plans to investigate
such hormone-breakdown residues in new compost heaps containing manure
from cattle and swine.

--
Alex McGregor
Walden Farm