Grobler, J.J.Schabort, C.J.2020-02-272020-02-272018Grobler, J.J. & Schabort, C.J. 2018. The effect of aqueous phase recirculation during hydrothermal liquefaction of spent coffee grounds. 10th International Conference on Advances in Science, Engineering, Technology & Healthcare (ASETH-18), 19-20 Nov 2018, Cape Town, South Africa: 254-258. [https://doi.org/10.17758/EARES4.EAP1118260]978-81-938365-2-1http://hdl.handle.net/10394/34213https://www.eares.org/siteadmin/upload/3919EAP1118260.pdfhttps://doi.org/10.17758/EARES4.EAP1118260Batch hydrothermal liquefaction of spent coffee grounds was done in this study. The effect of subsequent diluted aqueous phase recirculation was studied at a constant temperature of 275 °C and residence time of 10 minutes. Four recirculation reactions were completed following a control reaction and the results were compared. It was found that the recirculation of the aqueous phase had increased the bio-oil mass yield by 51 %. An increase in the organics and nitrogen concentration was observed in the aqueous phase, while the total organic carbon decreased due to migration of carbon species to the bio-oil product phase. The bio-oil retained its high energy content following the recirculation reactions with a higher heating value of 32.61 MJ/kg. The main component of the bio-oil was identified as C16- C18 aliphatic acids with long carbon chain hydrocarbonsenAqueous phase recirculationBatch hydrothermal liquefactionSpent coffee groundsPresentation