Circular economy applied to the Wastewater Treatment Plant: sewage sludge conversion into Biodiesel from lipids accumulation by oleaginous microorganisms

Abstract

Biomass has been used worldwide as a renewable energy source (RES) to produce biofuels to mitigate the primary energy resources depletion and to fight against global warming (GW). This RES can be originated from agricultural crops as main products to produce bio-energy (first-generation biofuels), or from agricultural crops and industrial processes as by-products or waste (second-generation biofuels), or from oleaginous microorganisms (OMO), which are able to accumulate lipids that can be converted into biofuels, for instance, from municipal sewage sludge (MSS), as a third-generation of biofuels. The MSS can be considered as a potential feedstock for biofuel production due to its lipids content and abundant availability. On this way, by applying Circular economy (CE) concepts in Wastewater Treatment Plants (WWTP), raw materials from sewage sludge, such as lipids can be converted, for instance, via transesterification into valuable products, like biodiesel. Besides economic benefits, it contributes to the reduction of pollution due to sewage sludge generation, and also leads to the reduction of consumption of the natural resource “fossil diesel” by using biodiesel. In this work, a Lipids accumulation pilot plant was, for the very first-time, implemented and tested for biodiesel production from lipids accumulated by OMO, with focus on Microtrix parvicella, one of the most known filamentous bacteria in MSS. The preliminary results demonstrated that the Lipids-pilot plant is an interesting alternative to accumulate lipids from sewage sludge, once the results of extracted lipids from the bio-reactors were higher than those from the inlet wastewater and, consequently, with higher biodiesel production.