Assessing energy benefits of operating anaerobic digesters at low temperature with solids pre-ozonation

Zeinab Bakhshi, Shameem Jauffur and Dominic Frigon

Renewable Energy, 2018, vol. 115, issue C, 1303-1311

Abstract: Anaerobic digestion of sludge is one of the most widely used processes for biogas and energy production. Conventionally, anaerobic digesters are operated at 35 °C to overcome the hydrolysis rate-limiting step. However, the energy expenditure for heating anaerobic digesters may be significant. The feasibility of operating anaerobic digesters at low mesophilic temperature (20 °C) by combining sludge ozonation was studied. Operation of three anaerobic reactors for 350 days showed that integrating solids ozonation and anaerobic digestion at 20 °C led to a higher volatile suspended solids (VSS) destruction of 60% than anaerobic digestion at 35 °C with raw sludge. Methane production in the reactor at 20 °C with sludge ozonation was enhanced from 62.6 mL CH4/g VSSin to 71.3 mL CH4/g VSSin for the 35 °C digester without sludge ozonation. Energy analysis showed that the 20 °C-ozonated digester produced 35% more energy than the 35 °C digester, with a net energy balance of +174 GJ/d and +129 GJ/d, respectively. The 20 °C-ozonated digester had a higher Energy Sustainability Index (ESI) (2.88) than the 35 °C digester (2.33) suggesting a more energetically sustainable option.

Keywords: Anaerobic digestion; Ozonation; Low temperature; Biogas; Energy sustainability; Biosolids (search for similar items in EconPapers)
Date: 2018
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:115:y:2018:i:c:p:1303-1311

DOI: 10.1016/j.renene.2017.08.080

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