A Master of Science thesis in Chemical Engineering by Omar Mohamed Moussa entitled, “Experimental Investigation of Sewage Sludge Pyrolysis In An Auger Reactor”, submitted in November 2020. Thesis advisor is Dr. Yassir Makkawi. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Waste-to-energy technology is fast growing around the world in order to satisfy the growing demand for renewable energies and to avoid the negative impact of the current practice of waste disposal into landfills. This thesis aims at carrying out an experimental study of the thermochemical conversion of sewage sludge, to bio-oil, fuel gas and bio-char. As with many biomass-based materials, sewage sludge, when heated to a high temperature (> 300 ºC) in the absence of oxygen (i.e. pyrolysis), produces a gas and a solid phase. Upon rapid condensation, the effluent pyrolysis gas produces a liquid oil and a non-condensable gas. The gas and bio-oil can be used for energy generation, with the former being more attractive for application in the transportation sector. Generally, bio-char has great potential in soil amendment, especially in desert soil such as in the UAE. In this thesis, two different sewage sludge samples collected from water treatment plants in Abu Dhabi (post-anaerobic digestion) and Sharjah (pre-anaerobic digestion) were subjected to thermal conversion at 450 ˚C, 550 ˚C, and 600 ˚C to assess their suitability for biofuel and bio-char production and investigate the effect of temperature on the pyrolysis products. The maximum bio-oil yield from the two samples was 35.82 wt.% (Abu Dhabi sludge) and 44.22 wt.% (Sharjah sludge), both at the pyrolysis temperature of 550 ˚C. The high heating values of the bio-oils from the Abu Dhabi sample were found to be in the range of 32.70-32.96 MJ/kg, while the same from the Sharjah sewage sample were in the range of 25.5-29.8 MJ/kg. The difference in the bio-oil yield between the samples was attributed to the higher volatile matter content in the Sharjah sludge, and the higher ash in the Abu Dhabi sludge. These results are important to shed light on the effect of sludge treatment on the quality of the pyrolysis products. For the UAE, this study presents evidence that sewage sludge can be used to produce valuable products and counter the negative environmental impact caused by the current practice of dumping the sewage sludge into landfills.