Potential for biogas production from anaerobic digestion of animal manure: A systematic review

Abstract

Anaerobic digestion of animal manure is a sustainable alternative for livestock waste management due to its capacity to mitigate greenhouse gas emissions and generate renewable energy. This systematic review analyzes 34 studies published between 2020 and 2025 to evaluate biogas production potential, the influence of the carbon-to-nitrogen (C/N) ratio, the quality of the biogas obtained, and the yields achieved under different operating conditions. The results show that bovine and poultry manure exhibit high biogas and methane production values, while swine manure improves its performance through strategies such as co-digestion or thermal pretreatment. The C/N ratio, with optimal values ​​between 20 and 30, is confirmed as a key parameter for maintaining microbial stability and preventing ammonia inhibition, especially in manures with high nitrogen content. Despite scientific progress in this field, methodological limitations persist among the analyzed studies, hindering direct comparisons and affecting the reproducibility of results. Furthermore, knowledge gaps have been identified regarding the utilization of generated carbon dioxide and the evaluation of digestate as an agricultural fertilizer. The available evidence confirms that the anaerobic digestion of animal manure represents a viable and strategic technology for promoting the circular economy and the energy transition in the agricultural sector.