Valorization of animal manure via pyrolysis for bioenergy: A review

The continuous development of the economy and the constant improvement of living standards have stimulated the development of animal husbandry. This development has been accompanied by the massive production of animal manure with various bad odors and high heavy metal content, constituting severe damage to ecological security and human health. Traditional disposal methods, including composting and anaerobic digestion, are difficult to achieve satisfactory results due to long processing time, water and soil eutrophication, and toxic gas emissions. However, converting animal manure into bioenergy through pyrolysis is a clean, safe, and promising technique to reduce the amount of waste and produce valuable products. Co-pyrolysis with other materials can decrease the content of heavy metals in biochar and ameliorate the properties of products. The application of catalysts influences the pyrolysis process and product properties positively. The objective of this review is to analyze the properties of animal manure and discuss the recovery of biofuel from harmful animal manure by pyrolysis. A comprehensive analysis of animal manure pyrolysis and related product characteristics will provide a foundation for the sustainable management and scientific disposal of hazardous manure waste.