Anaerobic digestion of biomass for biogas production has been developed for a long period of time. In recent years, anaerobic co-digestion in which two or more substrates are treated together has been applied worldwide since the biogas production is improved through this combined process. The book is divided into two parts. Chapter one introduces the biochemical process of anaerobic digestion, anaerobic digesters, feedstocks and recent studies in anaerobic co-digestion. Chapter two illustrates a batch study of anaerobic co-digestion of swine wastewater with switchgrass and wheat straw under mesophilic conditions and studies the effect of total solids concentration on methane production. The book will be a good reference for researchers in related areas.