The chapter "Biogas production: current state and perspectives" by Peter Weiland discusses the increasing importance of anaerobic digestion of energy crops, residues, and wastes to reduce greenhouse gas emissions and promote sustainable energy supply. Biogas, a renewable energy carrier, can be used for heat and power generation and as a vehicle fuel. Various process types, including wet and dry fermentation systems, are employed for biogas production, with wet digesters being the most common. Biogas is primarily utilized in engine-based combined heat and power plants, while microgas turbines and fuel cells are more expensive alternatives requiring further development. Upgrading biogas to renewable vehicle fuel or injecting it into the natural gas grid is gaining interest for more efficient use. The digestate from anaerobic fermentation is a valuable fertilizer due to its increased nitrogen availability and reduced pathogen content. The paper reviews the current state and future prospects of biogas production, focusing on biochemical parameters and feedstocks that influence the efficiency and reliability of microbial conversion and gas yield. The global energy demand and the rise in greenhouse gas concentrations highlight the need for alternative energy sources, making biogas an attractive option. Germany has become the largest producer of biogas, with a significant number of agricultural biogas plants. The biochemical process of methane fermentation is detailed, including the four phases: hydrolysis, acidogenesis, acetogenesis/dehydrogenation, and methanation, each involving different microorganisms and environmental conditions. The balance between these stages is crucial for efficient biogas production, and the process design must be adapted to the substrate properties to ensure complete degradation without failure.The chapter "Biogas production: current state and perspectives" by Peter Weiland discusses the increasing importance of anaerobic digestion of energy crops, residues, and wastes to reduce greenhouse gas emissions and promote sustainable energy supply. Biogas, a renewable energy carrier, can be used for heat and power generation and as a vehicle fuel. Various process types, including wet and dry fermentation systems, are employed for biogas production, with wet digesters being the most common. Biogas is primarily utilized in engine-based combined heat and power plants, while microgas turbines and fuel cells are more expensive alternatives requiring further development. Upgrading biogas to renewable vehicle fuel or injecting it into the natural gas grid is gaining interest for more efficient use. The digestate from anaerobic fermentation is a valuable fertilizer due to its increased nitrogen availability and reduced pathogen content. The paper reviews the current state and future prospects of biogas production, focusing on biochemical parameters and feedstocks that influence the efficiency and reliability of microbial conversion and gas yield. The global energy demand and the rise in greenhouse gas concentrations highlight the need for alternative energy sources, making biogas an attractive option. Germany has become the largest producer of biogas, with a significant number of agricultural biogas plants. The biochemical process of methane fermentation is detailed, including the four phases: hydrolysis, acidogenesis, acetogenesis/dehydrogenation, and methanation, each involving different microorganisms and environmental conditions. The balance between these stages is crucial for efficient biogas production, and the process design must be adapted to the substrate properties to ensure complete degradation without failure.