Study on the effect of different additives on the anaerobic digestion of hybrid Pennisetum: Comparison of nano-ZnO, nano-Fe2O3 and nano-Al2O3

The effects of three nanomaterials (ZnO, Al2O3, and Fe2O3) on the wet and dry anaerobic digestion (AD) processes of hybrid Pennisetum were assessed over 33 days, and the microbial communities of dry AD systems were studied. The results demonstrated that biogas production improved by 72.2% and 33.6% when nanoporous Al2O3 (nano-Al2O3) and nano-Fe2O3 were added during dry AD, respectively. However, biogas production decreased by 39.4% with nanoZnO. Kinetic analysis showed that the three nanomaterials could shorten the lag phase of the AD sludge, while the 16S rRNA gene amplicon sequencing results demonstrated that microbes such as Longilinea and Methanosarcina were enriched in the nano-Al2O3 reactors and methanogenic communities community such as Methanobacterium sp., Methanobrevibacter sp., and Methanothrix sp., which were enriched in the nano-Al2O3 and nano-Fe2O3 reactors. However, the microbial community and some methanogenic communities diversity and richness were inhibited by the addition of nano-ZnO.