The determination of biological stability of composts using the Dynamic Respiration Index: the results of experience after two years.

Biological stability was ascertained by using the Dynamic Respiration Index (DRI) on 144 samples of compost during the years 2003 and 2004, as a routine service for private subjects. Data obtained were collected and are critically discussed in this paper by using other parameters registered during tests, i.e., biomass temperature (T), specific airflow rate (Qs) and biomass analytical data (pH). Good linear correlations were obtained for DRI vs. T, DRI vs. Q(s) and DRI vs. pH, confirming expected results based on the theoretical discussion. Consequently, using the analytical method proposed in this paper means both T and Q can be used as additional parameters for measurement of the biological stability of compost. As a result, T values of 25.8 and 30.5 degrees C, and specific airflow rate of 8.6 and 13.4 m3 Mg(-1) VS h(-1) were found corresponding to 500 and 1000 mg O2 kgVS(-1) h(-1), which, respectively, indicate a high and a medium degree of biological stability.