[USCC] technical definitions of finished compost

Wed Dec 5 12:11:17 CST 2007

Cathy,

There is also a "very un-scientific" way to tell if your compost is finished, mature and stable if you don't have a microscope or an expert to certify it:

1) it is dark CHOCOLATE brown in color 
2) it smells like the forest floor
3) you can't tell what the starting materials were

If it stinks, is black or has pieces that you can tell what they are (ie: pine bark, chunks of wood, etc.) the answer is DON'T USE IT to grow plants.

Have a GREAT day!
Jennifer Appel RLA, LI, CSFIA
Landscape Architect # 1930
Licensed Irrigator # 4951
Certified Soil Food Web Advisor
713.263.1682 office

---------- Original Message ----------------------------------
From: "David Schellinger" <david_schellinger at bresnan.net>
Reply-To: Compost Discussion List <compost at mailman.cloudnet.com>
Date:  Tue, 4 Dec 2007 18:32:20 -0700

>Join us at the US Composting Council's 16th Annual Conference & Trade Show
>Oakland Marriott City Center, Oakland, CA | February 9-12, 2008. The National forum for those involved in the development and expansion of the composting and organics recycling industry. 
>Conference Highlights, Registration forms, Exhibitor information and Sponsorship Opportunities available at the USCC website: www.compostingcouncil.org or call the USCC at 631.737.4931
>_________________________________________
>Hi Cathy.  
>
>Definitions of composting processes and compost will differ significantly
>between educators and industry personnel.  This has a lot to do with the
>fact that no two composting processes are the same.  Feedstocks compost
>differently, and numerous environmental, chemical and physical factors
>combine to influence the composting process.  Slight changes in composting
>process management also influence the rate of composting and the properties
>of the end product.  However, two fundamental principals are discussed in
>most composting educational materials:  compost stability and compost
>maturity.    
>
>A simple way to express the science of compost stability when feedstock
>nutrient balance is optimized in the initial feedstock mix (Carbon:Nitrogen
>= 30:1 to 40:1):  when the readily available organic carbon sources for
>microbiological energy production have been depleted from the feedstocks to
>the point where microbiological populations and metabolic activity are not
>sufficient to maintain thermophilic conditions in the materials.  In short,
>as materials become stable, the average temperature in the materials
>decreases over time, and pore space oxygen usually increases due to reduced
>microbiological use.  If insufficient nitrogen is added to the initial
>feedstock mix, elevated degradable organic carbon may remain in the finished
>compost.  When added to soils or potting mixes, the organic carbon may
>degrade in the soil and utilize nutrients that are meant for plant use.  
>
>Though many experts may differ with this assessment, maturity of composted
>materials can only occur after compost has become relatively stable.  Some
>experts determine immature compost as containing significant concentrations
>of organic acids produced during composting.  Because these acidic compounds
>are readily available organic carbon sources for microbiological use, the
>presence of the organic acids denotes instability.  However, significant
>concentrations of ammonia or sulfur compounds, elevated or low pH levels, or
>excessive electrical conductivity (soluble salts) may be expected in stabile
>compost, and these properties will influence the ability of plant seeds to
>germinate and plants to survive in the compost.  Feedstock mixes with low
>C:N (<30:1) will typically contain more elevated plant toxins in the stable
>compost.  The curing process relies on low levels of microbiological
>activity, activity from slow growing microorganisms and increased aeration
>properties in the compost to reduce the harmful levels of the phytotoxic
>compounds.  The cured compost is also called mature compost.  
>
>Typically, large scale composting operations will observe temperatures in
>composting materials in excess of 145 degrees F for periods of time and over
>several turning cycles.  This temperature and turning activity is important
>for reducing the viable weed seed in the finished compost.  Temperatures of
>131 degrees various periods and turning cycles is used to destroy pathogenic
>microorganisms in feedstocks containing animal mortalities, food waste,
>human or animal excrement, or other materials.  In small scale processes
>such as backyard composting systems it is often difficult to achieve even
>130 degrees F.  Therefore, backyard composting of animal wastes or meat
>products is not recommended.  
>
>For further assistance I would recommend obtaining the valuable literature
>available on the US Composting Council web site.  I hope I've been of some
>assistance.
>
>Dave Schellinger
>
>
>
>-----Original Message-----
>From: Cathy Gill [mailto:cathy at athenaes.com] 
>Sent: Wednesday, November 28, 2007 2:58 PM
>To: Compost Discussion List
>Subject: [USCC] technical definitions of finished compost
>
>Hi all! 
>
>You've been so helpful in the past so I was wondering if you wouldn't mind
>answering a couple of more questions for me.
>
>What is the technical definition of when compost is "finished"? does it have
>to reach a certain temperature and then cool? Or is it based on levels of
>microorganisms that are active? I am very interested in knowing the science
>behind this.
>
>Also, I have read somewhere that, at least in a home setting, compost that
>is finished may still need to be cured. How does one know when it is cured?
>What happens during the curing process? 
>
>Thanks in advance!
>
>Cathy Gill
>
>AthenaES
>1450 S. Rolling Road
>Baltimore, MD 21227
>410-455-6319
>www.athenaes.com
>cathy at athenaes.com
>
>Join us at the US Composting Council's 16th Annual Conference & Trade Show
>Oakland Marriott City Center, Oakland, CA | February 9-12, 2008.
>The National forum for those involved in the development and expansion of the composting and organics recycling industry.
>Conference Highlights, Registration forms, Exhibitor information and Sponsorship Opportunities available at the USCC website: www.compostingcouncil.org or call the USCC at 631.737.4931 
>______________________________________________________________________________
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