Food Waste Ash Supported Nickel Catalyst to Steam Gasification of Food Waste for Enhanced Tar Reduction and Hydrogen Production

Abstract

In this study, a novel catalyst was developed by loading 5-10wt% Ni on food waste ash. The food waste ash worked as a support and promoter for the Ni catalyst. Thereafter, the catalyst was tested for enhanced tar reduction and higher H₂ production during steam gasification of food waste. The performance of this catalyst was evaluated using four different steam gasification processes; (i) conventional overlapping process (COP), (ii) COP in the presence of a catalyst (COP + catalyst), (iii) integrated two-stage process (ITP) and (iv) ITP in the presence of a catalyst (ITP + catalyst). All the experiments were performed at the constant temperature of 850 °C with a steam flow rate of 2.92 mL/min in a downdraft gasifier. Results showed that 33.3% catalyst content in the feed to the conventional gasification process of (COP + catalyst) enhanced the tar reduction by almost 90% and increased the syngas yield. The process of COP + catalyst yielded the highest syngas production at 91.90%. However, the use of the same catalyst did not enhance the tar reduction and syngas yield from the integrated process (ITP + catalyst) Additionally, the syngas composition showed that the hydrogen fraction in syngas from the processes with catalysts (COP + catalyst and ITP + catalyst) was higher (71.74% and 65.76%, respectively) than that from COP (66.27%) and ITP (59.75%) respectively. Therefore, the hydrogen yield was found to be highest (1.3 m³/kg) for COP + catalyst, as syngas and hydrogen fraction in syngas were highest for COP + catalyst. The tar composition indicated that tar from COP and ITP contained the highest fraction of anhydrous sugars (~ 23% & ~ 27%, respectively), whereas tar from COP + catalyst contained the highest fraction of oxygenated cyclic compounds (~ 17%) and tar from ITP + catalyst contained the highest fraction of aliphatic hydrocarbons (~ 18%). Moreover, cyclic hydrocarbons, aromatic hydrocarbons, esters, and aliphatic alcohols were present in a lesser fraction in tar from COP + catalyst and ITP + catalyst than from COP and ITP.