Anaerobic digestion (AD) or Methanogenesis is the breakdown of organic matter by microorganisms in the absence of oxygen. Humans can exploit this process to reduce waste volumes and produce renewable biogas.
There are 4 stages of AD, hydrolysis, acetogenesis, acidogenesis and methanogenesis. In these stages a variety of microbes breakdown molecules resulting in Carbon dioxide (CO2) and Methane (CH4). Both CO2 and CH4 are greenhouse gases and can be damaging to the environment, trapping heat. when AD takes place in a controlled environment such as a bioreactor (digestor) the gas produced known as biogas can be captured and stored. Biogas can then be used to create heat or combined heat and power. When CO2 is removed biomethane is created which can be used in the transport sector or injected into the gas grid.
European countries such as Germany and Sweden are leaders in the use of AD for energy production and assists in meeting their emissions target. Ireland has a unique opportunity to engage in the use of AD due to large livestock numbers and optimal grass growth. Animal manure and other organic matter such as crops and food waste are suitable feedstocks for a digestion. AD reduces the waste volume, kills pathogens, diverts emissions while producing renewable gas and nutrient rich digestate.