Enzymatic activity as a parameter for the characterization of the composting process

Enzymatic activity (EA) was explored as a possible tool for composting characterization. Three composts (yard wastes, cotton wastes and a mixture of the two) were sampled during different phases of the process and divided in two fractions. The first was immediately analysed for microbial biomass C (BC) and EAs (β-glucosidase, arylsulphatase, acid and alkaline phosphatase). The second fraction was air-dried prior to analysis for the same EAs and for organic C (CORG), total N (NTOT), dissolved organic C (DOC), extractable C (CE) and humic-like C (CH). reased throughout the composting period (149 days), whereas EA in moist fractions stabilized between 50 (β-glucosidase, alkaline phosphatase) and 90 (arylsulphatase, acid phosphatase) days of composting. always reduced by air‐drying (β-glucosidase: 40–80%; arylsulphatase: 10–50%; acid phosphatase: 10–70%; alkaline phosphatase: 50–90%), but this effect was less prominent as composting proceeded, especially for β-glucosidase and alkaline phosphatase. air-dried samples displayed the same trend as in moist ones, except that there was a marked difference (47–66%) between initial and final activities of all four enzymes. air‐dried compost and content of humic-like substances showed a similar trend: a marked increase in the first 90 days of the process and no significant variations afterwards. This suggests that the formation of humic–enzymatic complexes has taken place and indicates that this process occurs almost totally during the first stage of composting. adiness in air-dried samples occurred concurrently with the achievement of compost stability, as indicated by the conventional indexes (i.e. CH, CORG/NTOT). Therefore, the development of a stable enzyme activity in air-dried compost could represent a simple measure of compost stabilization in routine analysis of composting process.