Up-Grading Biofuel Production by Co-pyrolysis of Landfill Leachate Concentrate and Sewage Sludge Mixture

Abstract

The co-pyrolysis of landfill leachate concentrate (LC) generated by reverse osmosis leachate treatment units and sewage sludge (SS) mixture was performed at laboratory scale fixed-bed reactor under nitrogen atmosphere, in order to produce high-grade pyrolytic liquid. The results show that 550 °C as pyrolysis temperature, 10 °C min−1 as heating rate and − 5 °C as condensation temperature seem to be the optimum conditions considering maximum bio-oil yield and properties. LC and SS co-pyrolysis produced great amounts of liquid and gas but less bio-char than that of pyrolysis of SS solely. The addition of LC into SS not only increased the bio-oil yield (from 25 wt% of SS pyrolysis to 31 wt% for LC:SS-30:70 co-pyrolysis); but also improved its properties (with more aliphatic hydrocarbons content). The released gas from co-pyrolysis showed good H2 concentration and high light hydrocarbon (CH4 and CnHm) content, and thus gave a good heating value (from 8.48 MJ kg−1 for SS pyrolysis to 12.29 MJ kg−1 for LC:SS co-pyrolysis). The results also revealed that LC with SS co-pyrolysis had a positive synergistic effect on the liquid and gaseous yields and highlighted the robustness of this approach to handle such harmful and highly abundant wastes (SS and LC) and convert them into useful/sustainable products (chemicals and biofuels).