The Effect of Vermicomposting Process on Organic Matter of Cattle Manure Compost and Municipal Solid Waste Compost

Background & Aims of the Study: Considering the importance of solid waste disposal and the possibility of conversion them into rich organic fertilizers, the objectives of this study were to evaluation of effect of vermicomposting process (VP) on organic matter of cattle manure compost (CMC) and municipal solid waste compost (MSWC) by record changes of the elemental contents of C, N, H, S, and O, organic matter content and their parameter ratios that the substrates. Also, an empirical equation was developed for each substrate and vermicompost products as a function of their elemental composition and describe the stoichiometry of aerobic bioprocessing. Material and Methods: This study is interventional. The thermal elemental analyzer was used for measurement of elemental contents and organic matter was measured by weight loss between 105°C and 550°C in a muffle furnace. Results: Based on the results of this study, significant reduction in contents of C (69.1%, 45.6%), N (45.6%, 18.2%), H (90%, 77.5%), and S (100%, 100%) and also, significant increase in content of O (26.9%, 26.2%) was observed during VP in CMC and MSWC vermibeds, respectively. During vermicomsting of CMC and MSWC with P value of less than 0.05 between treatments, the H/C ratio was decreased from 0.13 to 0.04 and 0.07 to 0.03, the C/O ratio was increased from 0.5 to 2.22 and 0.5 to 1.25, the C/N ratio was decreased from 21.56 to 12.24 and 13.55 to 9, the C/OM ratio was decreased from 58.3 to 29.9 and 60.3 to 41.9 respectively. Also, approximate empirical formula was C83N3O31H133S, C177N11O67H143S, C14NO24H7, and C11NO10H4 for CMC, MSWC, CMC vermicomposted (CMCV), and MSWC vermicomposted (MSWCV), respectively. Developing of stoichiometry equation for each material indicated that oxygen requires for complete aerobic biodegradation of organic fraction in vermicompost products was significantly lower than substrates.