Compost Maturity Test:

More Than Just One Factor

The Solvita® Compost Maturity Test employs both CO2 and NH3 probes simultaneously to measure compost, a protocol recognized worldwide for validating compost stability and maturity. The simple, dual procedure is based on the concept of “triangulating” maturity, since single tests may not necessarily correctly identify true stability. Miscalculating when compost is mature should be avoided since customers rely on a product being stable and compost manufactures need to properly determine when compost activities may be terminated.

Composting organic matter produces large quantities of carbon dioxide (CO2) which is released into the atmosphere. At the same time, the decomposition of proteins and urea often creates large quantities of free ammonia (NH3) which also escapes as a gas. The end-stage of composting is signified when both these factors have declined to reasonably low levels.

While the cycles of CO2 and NH3 often occur together during composting they are not necessarily closely linked. It is common that the NH3 cycle may outlast the CO2 cycle somewhat (see chart). True stability happens when both these two factors converge at low levels.

Solvita® is perhaps the only commercial method to measure these combined traits in the form of a simple field-test.  For laboratories wishing to perform the test and report actual quantitative values, the is available to improve precision of color determination. The Compost Maturity Index has been traditionally determined by using a simple coordinate-lookup table printed in the .