Production of biofuel from AD digestate waste and their combustion characteristics in a low-speed diesel engine

Abul Kalam Hossain, Vikas Sharma, Clara Serrano, Anand Krishnasamy, Duraisamy Ganesh

Research output: Contribution to journalArticlepeer-review


Anaerobic digestion biogas plants generate large amounts of digestate that cannot always be valorised as fertilizer. This study proposes an alternative use through pyrolysis of the digestate for the production of liquid fuels for compression ignition engines. The digestate pyrolysis oil (DPO) and two types of biodiesel were produced and mixed with different alcohols. A total of five blends of DPO, biodiesel and alcohol were prepared and characterized, showing that their acidity and viscosity were higher than for pure diesel, and their heating value was lower. Blends containing 60 % biodiesel, 20 % DPO, and 20 % butanol were then tested in an engine, showing that the maximum in-cylinder pressure and heat release rate were 4.6 % and 3 % lower, respectively, compared to diesel, and the engine thermal efficiency at full load was 6–8% lower. The nitric oxide and smoke emissions were 7 % and 40 % lower, respectively, but the carbon dioxide emissions were 7–10 % higher than with diesel. The blends showed retarded start of combustion by 1.5° crank angle, which delays the ignition by about 6.4 %. This study concludes that blends can be used as a fuel for agriculture and marine diesel engines, although their viscosity should be reduced by improving the pyrolysis conditions.
Original languageEnglish
Article number119884
JournalRenewable energy
Early online date22 Dec 2023
Publication statusPublished - Feb 2024

Bibliographical note

This is an open access article distributed under the terms of the Creative Commons Attribution License CC BY [], which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


  • Biodiesel
  • Combustion
  • Digestate
  • Emission
  • Engine
  • Pyrolysis


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