[USCC] Rate of composting
Wed Mar 22 18:57:27 2000
I fielded this question from the website. I thought the group might like
to discuss the issue or perhaps someone else might want to contact Phuong
At 03:47 PM 03/21/2000 -0500, Phuong Nguyen <firstname.lastname@example.org> wrote:
My name is phuong, and I have one or two questions about composting.
1. how long does it take for food waste to transform into the stuff that
is referred to as 'hummus'?
2. Is there any way to speed up the process?
thank you for your time.
This is Jim McNelly, Vice President of the Composting Council.
How about sharing some more information about yourself? It is hard to
answer your question without knowing if you are working on a back yard or
commercial scale. It appears from your e-mail that you are from the
University of Guelph in Canada. I will try to answer your question with
the assumption that you are a university student.
First let me tell you a story. In college, I was studying Anthropology and
the professor told us an account of an archaeological dig he conducted in
Central America. In the process of looking for artifacts, they were
digging out dried, ancient sloth manure from a cave. The manure was
stockpiled outside the cave where it was rained upon. This pile
consequently heated up and started to compost. Sloths went extinct 20,000
What is the lesson? Composting can be delayed up to 20,000 years if the
organic material is fully dried.
When I was studying the composting process many years ago, I heard
Professor Mel Finstein from Rutgers University make the comment,
"Composting can not be accelerated or sped up, it can only be delayed".
He went on to say that most people do not optimize the composting process,
and therefore have delayed, or slow composting rates. It is natural for
them to believe that composting is a "slow" process because they don't have
an understanding of the optimum conditions for composting. So when the
question is asked "How can composting be accelerated", we have to ask the
question, "Compared to what?"
When leaves fall in the forest, for example, it takes them a year to
decompose. But layers of leaves in the forest is not the same thing as a
compost pile, which is a human construct. I have seen giant piles of dry
leaves that remain unchanged for at least ten years without signs of
Personally, I believe that the optimum rate of composting is a geometric
pattern of seven days in the initial "hot" phase, fourteen days in an
active composting period, twenty-eight days in a mesophilic initial curing
phase, and then a final fifty-six days of curing. 7+14+28+56 = 105 days.
This assumes that everything is optimized at each phase. Any condition out
of balance results in delayed rates of composting.
You use the term "humus" as a measure of composting being finished. By
humus, I take you to mean stable organic matter. This is a difficult term
to quantify. Many great minds in the composting field argue with each other
as to the terms "stability" and "maturity". The Composting Council has
initiated a program where we do not try to define the rate of composting or
the measure of stability, except as it is appropriate to the plant being
grown in the compost.
A mulch spread under trees needs a different maturity specification than a
compost blended into planter mixes where seeds and cuttings are
started. Compost applied to a field in the spring requires different
properties than compost applied in the fall. Every case is unique.
I have probably provided more information than you were looking for, but I
hope that I have given you some ideas to stimulate your thinking and that
you continue your interest in composting and write back.