DC6: Development of high-performance biogas systems for increased bioplastics degradation

Project title: Development of high-performance biogas systems for increased bioplastics degradation (WP2)

Host Institution: SLU

Country: Sweden

Supervisor: Maria Westerholm (PhD promoter); Co-supervisors: Julie Jimenez (INRAE)

Objectives: to investigate the potential of a novel anaerobic digester system to improve bioplastics degradation in sludge and contribute to a more fundamental understanding of the involved microbial mechanisms, to build on process strategies that minimize the risk of BP spreading upon land application of sludge.

DC6 will investigate the impact of a novel anaerobic digester set-up, i.e., 2-step mesophilic (37°C) process with an intermediate thermal treatment (70°C), on enhanced biodegradable plastics (BP) degradation. For this purpose, an in-house developed novel macro-fluidic bioreactor system combined with a motorized microscopy system for cultivation and analyses of anaerobic microorganisms will be employed. DC6 will continuously monitor the process performance (methane yield, presence of intermediate degradation compounds) of the digester. DC6 will carry out physico-chemical monitoring (particle size, consistency, discolouring, presence of additives, degradation products) to follow-up effective degradation. DC6 will employ molecular analyses, including illumina 16S rRNA gene illumina, whole-genome and RNA sequencing targeting selected genes and data analyses will be performed. DC6 will carry out pot trials simulating soil application of the obtained digestate. DC6 will identify key microorganisms for BP degradation and determine link with substrate and operating conditions.

Expected Results: Novel anaerobic digester set-up (two-step mesophilic process with inclusion of a mid-step thermal treatment) and impact on BP degradation and formation of microplastics. List with identified key microorganisms for BP degradation in various biogas plants. Recommendations for optimal substrate and operating conditions.

Enrolment in Doctoral degree(s):Dept. of Molecular Sciences, Swedish University of Agricultural Sciences (SE)

Planned secondments:

• Tekniska verken (Sup.: J. Moestedt): M10-13 (4 months): Training in system scale-up: design principles and building lab-scale fermenters; assessment of economic feasibility.
• INRAE (Sup.: J. Jimenez): M20-23 (4 months): Insights in microbial enrichment and enzyme activity measurements of hydrolytic bacteria responsible for BP degradation