A new approach for hydrogen generation from sewage sludge

• H2 production by heating the mixture of sewage sludge with Ca and Ni hydroxides.
• The yield varies on the added ratios of two hydroxides.
• Ca carbonate and Ni metal in the reaction products confirm the synergistic effects.
• Both hydrous and dried samples may be used as raw materials.

A new process to produce hydrogen efficiently from sewage sludge (SWS) was developed with co-grinding operation of the dried SWS with calcium and nickel hydroxides (Ca(OH)2 and Ni(OH)2) and subsequent heating of the ground mixture at relatively low temperature below 600 °C. A set of analytical methods were used to characterize the ground samples before heating and the gaseous and solid products after heating. Thermo-mass spectroscopic (TG-MS) analysis showed hydrogen occurrence around 450 °C. Hydrogen yield over 70 g per kg SWS with concentration of 93.6% was obtained with the hydroxide additions of Ca to C from SWS at 1:1 and Ni to C at 1:6, respectively. X-ray diffraction (XRD) analysis of the solid residues after heating confirmed the existences of calcium carbonate and nickel metal. Based on the obtained results, possible reaction pathway was proposed.

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