Evaluation of Compost Maturity Indices

Outline of Evaluation of Compost Maturity Indices

Outline of Evaluation of Compost Maturity Indices

The progress of biodegradation, and hence the state of compost maturity is often difficult to judge. Immature compost is rapidly decomposed and fermented in soil to release heat and damage plants if not completely decomposed. It is presumed that the compost maturity is selected depending on the type of plants to be fed such as crops, fruits, bedding plants, and potting plants as well as on its objectives of use. Demand for monitoring the compost maturity is increased for better management of manufacture of the consistent compost without quality fluctuation.


Requirements for Evaluation of the Compost Maturity

  • Components in compost are varied with progress of decomposition. JEF-TEC quantitatively evaluates the compost maturity index by determining the molecular weight change of the compost and its molecular weight distribution.
  • JEF-TEC's method can evaluate the maturity index of compost without evaluating carbon (C) and nitrogen (N), thus allowing for determination of the maturity index in compost from municipal solid waste, organic compost, and waste compost of which accurate determination of the maturity index is believed to be difficult.

Evaluation Method of Compost Maturity Index

A compost sample is dried, pulverized, extracted, and fractionated according to the molecular mass using the gel permeation chromatography (GPC) and each component is quantified by the high performance liquid chromatography.

Reference Standard for the Compost Maturity Index

Compost Maturity Index Based on GPC Method

Maturity index GPC value
Immature 10.1% or higher
Moderately mature 2.1-10.0%
Mature 0.5-2.0%
Completely mature Less than 0.5%

Analysis Example of Various Composts

Analysis Example of Various Composts

Evaluation of Maturity Index by Seed Germination and Growth

Seed germination test

Control: Water (4 days after starting the seed germination test)
Control: Water
(4 days after starting
the seed germination test)
Z fungus, 3 weeks, in box approximately 40 cm Control: Water (4 days after starting the seed germination test)
Z fungus, 3 weeks,
in box approximately 40 cm
Control: Water (4 days after
starting the seed germination test)

Fig.7 GPC pattern of various composts and raw materials

Sawdust Farm wastes compost Sewage sludge compost
Leftovers compost Human excrement compost Tsuna wastes compost

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