Enhanced performances of anaerobic digestion processes treating organic wastes: Role of iron and carbon based nanomaterials

Issues of climate change, energy demand and antibiotic resistance are calling for advanced methods to convert waste into fuels, value-added materials and safe byproducts. Anaerobic digestion (AD) is a major technology treating organic-rich wastes such as sewage sludge, kitchen waste, and animal manure. AD allows to convert waste into energy such as biogas and electricity, and resources such as fertilizers. Nevertheless, biogas production from organic waste is limited by the low biodegradability of resistant organic matter and the short retention time in AD bioreactors. As a consequence, recent researches have focused on the use of additives to improve the performance of AD. For example, nanomaterials are increasingly used as additives due to their properties in the promotion of direct inter-species electron transfer between microorganisms, and the improvement of the microbial community structure. In this study, we review firstly the contribution of nanomaterials to system stability, digestive performance and risk control of AD processes systematically. Then we sorted the enhanced performances by co-digestion of nano-magnetite with sewage sludge, kitchen waste, livestock and poultry manure thoroughly. Finally we discussed mechanisms on how nanomaterials such as iron- and carbon-based nanomaterials addition could enhance production of volatile fatty acids, and inhibit the production of hydrogen sulfide and the transmission of antibiotic resistance genes simultaneously.