Evaluation of Parameters During Composting of Two Contrasting Raw Materials

Abstract

The aims of this work were: i) to evaluate, during a composting process, some parameters in two contrasting raw materials: one a ligneous material (C1) and the other (C2) a mixture of horse and poultry manure with a low straw percentage and ii) to compare results from microbiological and chemical analyses of both composting material during the process. Total carbon, total nitrogen, C: N ratio, ash, organic matter, organic matter destroyed, CEC, soluble organic carbon, soluble ammonium and nitrate, ammonium: nitrate ratio and respiration rate were evaluated during 18 weeks. C1 material showed a lower rate of organic matter mineralization probably due to the high proportion of ligneous material. This material reached a greater CEC during the experiment. Increase in CEC during composting is due to conversion of the remaining organic material into humic substances. These results would imply that C1 presented a greater humification level and consequently, a better quality. On the other hand, the greater decrease in soluble organic carbon and NH4+-N values in C2 is in accordance with greater organic matter mineralization. A high decrease in soluble fractions, especially the more degradable ones (water soluble components) indicates a high mineralization of the organic matter during composting and a lower humification level. According to the data obtained in our experiment, some parameters such as CEC, soluble organic carbon and soluble NH4+-N seem to achieve the stability level for both studied materials, while those parameters or indices such as C: N ratio, NH4+-N: NO3−-N ratio indicated stability/maturity only in C2 material during the experimental time.