Survey on kinetic decomposition of organic matter and bio-fertilizer synthesis by composting sawdust, vegetable waste and sewage sludge

Abstract

Kinetic degradation of organic matter was investigated in this work by composting mixtures of organic wastes with bulking agent (sawdust) to produce biofertilizer. In-vessel method of composting was performed with three plastic drums each of 120 L capacity. Temperature, microbial population, and pH were used to monitor the rate of organic matter degradation during composting. Turning over of the compost piles was done twice every week for aeration. Various physical, chemical, and biological parameters were monitored at every 5 days interval till the end of composting. The organic matter degradation data was used to determine the kinetic parameters according to the four kinetic models; Petric and Selimbasic, Michaelis menten, Contois, and Xi et al. model. Physiochemical properties of the compost extracts demonstrated that Organic matter and Carbon content decreased significantly with time in all the compost, nitrogen content of the composts increased significantly except in the control. The highest average temperature reached during the composting process was 61.4$°\mathrm{C}$ after 20 days of composting of substrates in compost 2. Error analysis conducted on the models showed that Xi et al. model best described the degradation of organic matter during composting.

Keywords:

• Composting
• vegetable waste
• sawdust
• sewage sludge
• kinetics

Acknowledgments

The authors want to thank in a special way Energy research center University of Nigeria Nsukka for making their equipment’s available for this research and also to Dr. C.N Eze of the department of microbiology University of Nigeria Nsukka for providing the technical assistance in counting the organisms and to everyone who contributed in one way or the other to the success of this work.

Disclosure statement

No potential conflict of interest was reported by the authors.