Anaerobic Sludge Fermentation Samples Genome sequencing and assembly. Chloroflexia

Sewage sludge, as carbon-rich byproducts from wastewater treatment, holds significant untapped potential as renewable resource. Upcycling this troublesome waste stream represents great promise in addressing global escalating energy demands through its wide practice of biofuels recovery concurrently. Here, we develop a novel biotechnology to gain renewable high-value liquid bioenergy from sewage sludge in a self-sufficient platform, by directly transforming sludge into medium chain fatty acids (MCFAs). Our findings suggest that yeast, cheap and readily available commercial powder, would involve ethanol type fermentation in chain elongation to achieve abundant MCFAs production from sewage sludge using electron donors (i.e., ethanol) and acceptors (i.e., short-chain fatty acids) produced in-situ. The abundance and transcription of CE-related genes in this novel sludge fermentation paradigm confirm the efficient self-production capacity of MCFAs with the metabolic network formed by yeast and anaerobic microorganisms. Furthermore, life cycle assessment and techno-economic analysis evidence the sustainability and economic competitiveness of this biotechnology. Overall, this work provides insights into high-value energy recovery from sewage sludge independent of additional carbon input, which can be applied in existing anaerobic sludge fermentation infrastructure, as well as to develop new applications in a diverse range of industries.