Dynamics of physical and chemical properties of the composting process with different doses of efficient microorganisms

Abstract

Composting is the process of decomposition of organic solid waste by mixed populations of microorganisms under controlled conditions. The objective of this research is to evaluate the effect of the addition of efficient microorganisms in different doses and the dynamics of their physical and chemical properties during the whole composting process. Four treatments T1 (0L EM/5L H2O), T2 (0.1L EM/5L H2O), T3 (0.5L EM/5L H2O), T4 (1L EM/5L H2O) with 110 days duration were evaluated. The results showed that the temperature control shows that the treatment with the highest dose of efficient microorganisms remained longer in the thermophilic phase, unlike the control treatment (T1), therefore a greater sanitization. As for pH, the treatments started with a slightly acid pH and later increased to 9-10 and then decreased to values of 9-8 in the treatments T2, T3 and T4. For EC, treatments T1, T2 and T3 presented values higher than 5.00 dS m^-1, however, treatment T4 presented values of 4.78 dS m^-1, which would be within the acceptable range according to different regulations. As for total organic carbon (TOC), a higher percentage of mineralization is evidenced in treatment T4 and a lower percentage in T1 with respect to initial carbon. In the case of total nitrogen, there is evidence of an increase in treatments T2, T3 and T4 with microbial inoculant over the control treatment, attributing this to the nitrogen-fixing bacteria present in the efficient microorganisms. Finally, it can be evidenced that CO2 emissions are an important parameter to identify the biological activity and stability of the compost, as well as the CO2 emissions produced by the transformation of TOC is directly proportional to the temperature. This shows that the incorporation of efficient microorganisms benefits the composting processes causing higher biological activity as a consequence; increase of temperature for an adequate sanitization, an increase of the TOC mineralization percentage, improvement of pH and conductivity conditions, an increase of the total nitrogen percentage and the stability of the final compost.