Abstract
Anaerobic digestion (AD), a proven and widely adopted technology, is used in life cycle analyses of energy systems. AD has been widely adopted for the management and treatment of both waste and wastewater. The product of this process is biogas, a mixture of methane gas (55-75% by volume) and carbon dioxide gas (25-45% by volume). This study contributes to ongoing research on renewable energy generation from waste and provides valuable insights into innovative waste processing. Biogas can be used for various energy production purposes, such as heating, converting it to high-quality natural gas, or generating electricity and heat together. AD plants are characterized by their technical simplicity and minimal energy and space requirements. The classification of anaerobic treatment systems is based on two categories: “high-speed” systems, which involve the retention of biomass, and “low-speed” systems, which do not involve the retention of biomass. High-speed systems have a relatively short hydraulic retention time and a long mass retention period, making them suitable for the treatment of many types of wastewater. Low-speed systems have traditionally been used for the degradation of slurries and solid wastes. This difference in retention times affects the types of waste each system is best suited for. AD reduces the amount of waste and generates valuable products, such as biogas. These systems were characterized by an extended hydraulic retention period, equivalent to the mass retention period. The biogas production process was subject to fluctuations depending on factors such as the nature and concentration of the raw materials as well as the prevailing process conditions. Biogas yields for the organic fraction of municipal solid waste and animal manure ranged from 80 to 200 m3/t and from 2 to 45 m3/m3, respectively. The co-digestion practice played an important role in enhancing the efficiency of the reactors and ensuring their economic viability. Improving the sale of all derivative products enhanced the economic efficiency of anaerobic treatment. Moreover, the implementation of financial incentives to promote renewable energy production significantly enhanced the competitiveness of anaerobic digestion compared to anaerobic composting, providing an optimistic outlook for the future of this technology.

Key words: Anaerobic digestion, Biogas production, municipal solid waste, Wastewater treatment.