Biodegradation Activity of Eight Organic Substrates: A Correlation Study of Different Test Methods

The biological activity of eight organic substrates was assessed using different techniques under aerobic and anaerobic environments at different scales. The used substrates included simulated fresh to actual stabilized composts. Experiments included dynamic respiration (with 30 and 5.5 L reactors), static respiration (with 1 L reactors) and biochemical methane potential (BMP) tests (with 1.1 L flasks). The indices evaluated were: the 24-h dynamic respiration index (DRI24) and the cumulative dynamic respiration indices at 4 and 7 days (DCRI4 and DCRI7, respectively) measured with two different methods, the maximum dynamic CO2 generation rate (D-CO2_24) at 24 h and a dynamic cumulative CO2 generation after 7 days (D-CO2_7), the maximum static O2 consumption rate in 12 and 24 h (SRI12 and SRI24), the static cumulative O2 consumptions after 4 and 7 days (SCRI4 and SCRI7) and the static CO2 generation after 7 days (S-CO2) and the BMP after 30 days. The DRI24 ranged from 25 to 3000 mg O2 kg−1 VS h−1 in one lab and from 150 to 3500 mg O2 kg−1 VS h−1 in the other. A positive statistically significant correlation was achieved between the two types of dynamic indices. In addition, the CH4 production after 30 days showed a strong positive correlation with both DRI24 indices and DCRI4 and DCRI7, as measured in both labs. The static respiration indices did not correlate well with the dynamic respiration ones. The practical implications of the use of the biodegradation activity indices were also analysed and discussed.