Evolution of carbon compounds during municipal solid waste composting: suitability of chemical and biochemical parameters in defining the stability and maturity of the end product

In this review we discuss the transformation of organic matter during municipal solid waste (MSW) composting and the suitability of chemical and biochemical parameters in defining the stability and maturity of the end product. The dynamics of chemical and biochemical parameters, such as several hydrolase activities and water-soluble fractions (i.e. water soluble carbon, water soluble nitrogen, water soluble carbohydrate) during MSW composting is discussed along with their suitability as tools for compost characterization. Besides, the evolution during the MSW process of the molecular structure of humic acids (HA), based on Fourier transform infrared (FTIR), 13C NMR spectroscopy and thermal analysis, is also discussed. The data presented highlight the suitability of several enzymatic activities and water soluble fractions as indicators of the evolution of the organic matter during MSW composting. However, since the extent of each enzyme activity at the end of composting depends on the starting material used, single point determinations appear inadequate for compost characterization. Moreover, the importance of the characterization of the dynamics of enzymatic activities and water-soluble fractions during the process has been emphasized. FTIR and 13C NMR spectra appeared useful tools reflecting the rate of change in HA structure during MSW composting. Thermoanalitical analyses (TG/DTG and DSC curves) also revealed valuable in order to characterize the organic matter during composting and distinguish between well and poorly stabilized organic matter.