Catalytic steam gasification of food waste with food waste ash supported Nickel catalyst: conventional vs in-situ two-stage approach.

In this study, first, a novel Ni catalyst was developed where 5% nickel was loaded on food waste ash and thereafter, it was used in steam gasification of food waste via two different processes: conventional overlapping process (COP) with simultaneous pyrolysis and gasification, and in-situ two-stage process (ITP) with consecutive pyrolysis and gasification. The temperature for the pyrolysis and gasification stage in ITP was maintained at around 850 °C. Both the processes (COP and ITP) were also conducted at the same temperature of 850°C with a steam flow rate of 0.73 mL/min for 100 g of the food waste sample. The processes were conducted in a downdraft gasifier with variations in catalyst content. The catalyst content in the feed-catalyst mixture was varied from 0 to 50 g, and results indicated that the use of a 50 g catalyst during COP increased the syngas yield quite significantly (∼70%). However, the results showed that the Ni catalyst did not have much effect on syngas yield from ITP, though it increased the hydrogen fraction in syngas (∼80%). The highest hydrogen fraction in syngas from COP and ITP was found to be 71.74% and 66.53% respectively. Consequently, the highest hydrogen yield of 1.3 m³/kg was obtained from COP for 50 g of catalyst in a feed-catalyst mixture. Furthermore, performance parameters such as high heating value (HHV), carbon conversion efficiency (CCE), and cold gas efficiency (CGE) were determined for performance analysis of the Ni-based catalyst in conventional and in-situ steam gasification.