Synergistic control of tar and particulate matter in steam gasification of six typical biowastes using a catalyst-integrated SiC membrane reactor

Clean syngas is valuable for fuel cells and high-value fuels/chemical synthesis; however, tar and particulate matter (PM) in syngas hinder its utilization. This study systematically investigated the steam gasification of six typical biowastes (covering agricultural, forestry, and aquatic categories) in an activated biochar catalyst-integrated SiC membrane reactor at 800 °C, focusing on the tar and PM formation and control mechanism. In control tests (without membrane, catalyst or steam), microalgae (MA) had the highest syngas tar content (395.6 g/m³), while herb residue (HR) showed the lowest (82.9 g/m³). MA also had the highest PM content (9.1 g/m³), followed by walnut shell (WS, 7.0 g/m³), whereas corncob (CC) and poplar wood (PW) had the lowest (1.2–1.4 g/m³), with PM content dependent more on coke from volatile polymerization than feedstock ash. In the catalyst-integrated membrane reactor, steam gasification of biowastes achieved tar conversion efficiencies of 88 %–96 % and PM removal efficiencies of 94 %–99 % across all biowastes, with excellent stability over 400 min. This performance should be attributed to the synergies among the three core components: the SiC membrane retained coarse PM to protect catalyst active sites; steam suppressed carbon deposition on both membrane and catalyst via coke reforming; and the biochar catalyst promoted tar cracking/reforming, followed by steam and then the membrane. These findings highlight the unique complementary roles of the integrated system, emphasizing the need to tailor gasification processes to biowaste characteristics for efficient clean syngas production.