[USCC] Rate of composting

Jim McNelly compost@cloudnet.com
Wed Mar 22 18:57:27 2000

List members,

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 


Jim~ McNelly

At 03:47 PM 03/21/2000 -0500, Phuong Nguyen <pnguyen@uoguelph.ca> 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.

cheers, Phuong

Hi Phuong,

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 
years ago.

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.