Syngas Quality Improvement Through Co-Gasification of Calliandra calothyrsus and Municipal Solid Waste in a Downdraft Reactor: An Experimental Study

The co-gasification of biomass and municipal solid waste (MSW) has high potential for sustainable energy generation and waste-to-energy applications. Calliandra calothyrsus (CC) and MSW pellets have complementary thermochemical properties, although there are few experimental studies on their co-gasification in downdraft reactors. This study analyzed the effect of the feedstock composition on the temperature distribution inside the reactor, the syngas composition, and the quality of syngas energy in a 1–2.5 kg/h downdraft gasifier during co-gasification. Six feedstock blend compositions were experimentally evaluated: they were 100 CC, 70 CC–30 MSW, 60 CC–40 MSW, 40 CC–60 MSW, 30 CC–70 MSW, and 100 MSW. The criteria considered for measuring include reactor temperature distribution, syngas composition (CO, H2, CO2, and CnHm), and lower heating value (LHV). The results indicated that the 70 CC–30 MSW blend had the best syngas performance with a higher oxidation-zone temperature, greater CO concentration, reasonably steady H2 generation, lower CnHm concentration, and the highest syngas LHV compared to other feedstock compositions. In the gasification process, the increase in the proportion of CC was beneficial to char reactivity, oxidation–reduction reaction, and tar cracking. The increase in MSW fractions decreased syngas quality due to the increase in ash and moisture content. The results show that co-gasification of Calliandra calothyrsus and bio-dried MSW pellets can increase syngas quality and provide practical insight into the optimization of biomass–MSW blending for downdraft gasification systems.