Energy and economic implications of anaerobic digestion pasteurisation regulations in Ireland

•The use of anaerobic digestion to treat organic wastes is spreading throughout Europe.•AD facilities are successful only if they produce a significant energy output.•EU and national legislation impose pasteurisation controls which consume energy.•EU and Irish national standards and a number of alternate treatments were examined.•Most efficient treatments are 60 °C for 1 h, 70 °C for 1 h or 80 °C for 30 min.

The use of anaerobic digestion for the treatment of organic wastes is spreading throughout Europe. A number of restrictions on organic wastes which can be treated in anaerobic digestion facilities and the subsequent handling of the digested material are specified in European legislation. Regulation 1774/2002/EC as amended states that after reduction the material must be heated to either 70 °C or 90 °C for a minimum of 60 min. An alternative Irish national standard of 60 °C for 48 h twice has been introduced in place of the EU standard. Anaerobic digestion systems are successful only if they produce a significant energy output. The aim of this research was therefore to examine both the EU and Irish national standards as well as a number of alternative treatment scenarios to determine their respective pasteurisation efficiency and energetic requirement. Post-digestion pasteurisation above 60 °C was found to satisfactorily remove all viable Escherichia coli bacteria from the test feedstock. It was determined that the most energy and economically efficient heat treatments were 60 °C for 1 h, 70 °C for 1 h (EU standard), and 80 °C for 30 min. The Irish national standard was found to be prohibitively energy inefficient and expensive.