Methods of Pretreating Raw Materials Containing Organic Compounds before Anaerobic Digestion

Abstract

Introduction. The volume of accumulated organ-containing non-recyclable waste products in Russia is increasing. Existing technologies make it possible to recycle these waste products through using anaerobic digestion to produce biogas and fertilizers. The organic portions of waste consist mostly of hard-to-degrade lignin, cellulose, and extracellular polymers, which make anaerobic digestion difficult. Pretreating is necessary to make the raw materials available to microorganisms for bioavailability and deeper degradation. There are many different types of pretreating with their own specific effects on the raw materials. To improve understanding the process of pretreating organic raw materials prior to anaerobic digestion, and to improve the quality of the decisions made, pretreatment methods need to be identified and systematized. Materials and Methods. The subject of the study is the relationship between the effects of methods, techniques and specific operations of pretreatment for anaerobic digestion. The main method of this study is the analysis of data on the application of different methods to increase the bioavailability and degree of decomposition of organic matter of waste products during anaerobic digestion. Results. The scheme of preparatory operations and methods for pre-treatment of organic waste products before anaerobic digestion is developed. It is revealed that each method (mechanical, thermal, electromagnetic, chemical, biological and combined) contains many practices, which are divided into particular techniques. The mechanisms of influence that improve further processing are described. Discussion and Conclusion. The choice methods of pretreatment depends on the purpose and tasks performed, the physical and chemical composition of raw materials, access to energy, biological and chemical resources. Advantages and disadvantages of various methods should be studied in more detail and ranked into private methods according to energy costs and the effect they produce. The comparison of the research results reveals disadvantages and difficulties.

Keywords

• organ-containing waste products
• pre-treatment
• biogas
• anaerobic fermentation
• biodegradability
• hydrolysis
• acidogenesis
• acetogenesis
• methanogenesis