Anaerobic Digestion for Treatment and Resource Recovery

Anaerobic digestion (AD) is the most primitive form of metabolism. The process typically involves the breakdown of complex organic compounds into fatty acids by bacteria, which work in tandem with methanogens to produce carbon dioxide and methane, collectively known as biogas. Biogas has been widely considered as one of the most promising renewable energy sources for the past several decades. Apart from biogas generation, mineralising organics of higher molecular weight organics is particularly interesting to environmental scientists and engineers. It is possible as AD can be replicated in engineered vessels to treat organic wastes and wastewater. In addition, tailored AD of specific substrates can yield other valuables, such as hydrogen through dark fermentation, as well as nitrogen and phosphorus-rich liquid fertiliser recovery from the digestate supernatant liquid of the anaerobic digester. A revisit to the concepts and the translation of these concepts into resource recovery, solid organic waste stabilisation and wastewater treatment is imperative. This chapter, therefore, collates the fundamental principles of AD, emphasising its potential and limitations in wastewater/waste treatment and resource recovery.