Advances in Hydrothermal Carbonization of Livestock Manure

In order to meet the needs of modern people for protein food, livestock farming has developed rapidly. In the process of livestock breeding, a great deal of livestock manure will be produced, and the number of livestock manure is growing rapidly every year. Safe, economical, and effective treatment of livestock manure is a crucial link affecting the sustainable development of livestock breeding industry. Hydrothermal carbonization is an available technology for livestock manure treatment, which could transform livestock manure into hydrochar and solve the environmental pollution problem of livestock manure at the same time, such as odor, pathogens, greenhouse gas emission, and water/soil pollution. Hence, the study of hydrothermal carbonization of livestock manure has attracted extensive attention from researchers all over the world in recent years. In this chapter, the basic process of the hydrothermal carbonization of livestock manure is firstly introduced. Then, the effects of main process conditions, including reaction temperature, catalyst, reaction time, heating mode, solid-liquid ratio, and feedstock, on hydrochar production are analyzed. Next, the transport and conversion behaviors of heavy metals in the hydrothermal carbonization of livestock manure are summarized. Last, the application and treatment of process water are discussed. Microwave heating, catalyst application, and co-carbonization are effective ways to improve the hydrothermal carbonization of livestock manure. This chapter can provide an essential reference for relevant researchers or managers to understand and promote the hydrothermal carbonization technology of livestock manure.