Periodic Reporting for period 1 - BioMAX (Friends or foes? The role of Biofilm microbiomes in industrial anaerobic membrane bioreactors to MAXimise bioenergy production)
Reporting period: 2022-04-01 to 2024-03-31
The industrialization, urbanization and centralization of modern societies have led to rising demands of energy and resources, accompanied by the production of large and persistent amounts of biodegradable waste and wastewater streams. These waste streams need to be managed, treated, reused, or disposed adequately to decrease the detrimental effects on the surrounding environment and human health. European Union (EU) directives, United Nations sustainable development goals, and an increasing number of individual citizens are advocating for a systematic change towards resource recovery schemes. Transforming waste and wastewater into renewable energy, clean water and add-value products achieves these goals with a threefold benefit by reducing environmental impact, offsetting raw materials demands and promoting circular bioeconomy markets. As part of this mission, the EU Best Available Techniques reference documents on Industrial Emissions (Directive 2010/75/EU) recommends energy-producing anaerobic biotechnologies for the treatment of biodegradable waste streams. Anaerobic biotechnologies are a mixed-culture microbial-mediated process that transforms biodegradable organic compounds into renewable energy in the form of methane-rich biogas or add-value compounds such as volatile fatty acids that can be used to produce bioplastics. To promote the widespread adoption of anaerobic biotechnologies for the valorization of biodegradable waste streams, the objective of this action was to quantify the distinctive role of beneficial microbes to improve the performance, robustness, and economic feasibility of anaerobic biotechnologies. To this aim, the action identified process-critical microorganisms to produce add-value compounds from anaerobic fermentation from food waste and sewage sludge, and their relationship towards process optimization laying the foundations to develop and improve microbial management strategies.
This work was carried out in two main settings, bench-scale laboratory bioreactors and municipal wastewater treatment facilities. In the laboratory set-up, anaerobic fermentation was optimized to produce volatile fatty acids from a mixture of food waste and sewage sludge. Volatile fatty acids are small molecules that can be precursors of bioplastics or biotextiles. The conversion of organic waste into volatile fatty acids is never complete, however the remaining waste can be further converted into methane rich gas. In the context of food waste, it contains high amounts of ammonia, which is an inhibitor compound for methanogens, process-critical microbes responsible for methane production. However, the integration of membrane technologies allowed us to remove the ammonia from the residual waste stream. This not only mitigated methanogens inhibition but also allowed for the capture of ammonia as a useful fertilizer and optimizing the methane production in the final step. These results show how future biorefineries treating waste can be set up to recover as many products as possible. In a municipal wastewater treatment facility, the concept of microbial management was put to work. The wastewater treatment facility used to suffer from bulking episodes, causing economic losses due to the reduced treatment capacity and the need to use strong anti-foaming chemicals to treat the bulking. In this action, we revealed that the different bulking episodes were caused by different filamentous bacteria. Once identified, this allowed us to choose the most effective control strategy minimizing the process disturbance and costs. All these results are still proof-of-concepts and further research is needed for the implementation in day-to-day society, therefore they have been disseminated in several open access scientific journals, as well as presented in international conferences.
The technological readiness of anaerobic fermentation for the recovery of volatile fatty acids is at its infancy, and its integration in a biorefinery scheme is at a proof-of-concept stage. Despite these early stages, this action has demonstrated the feasibility of the long-conceived waste treatment biorefineries. Such advancements have the potential to partially offset the reliance on raw materials derived from oil. The research foundations that this action has achieved has attracted the funding from national Spanish projects to keep developing and optimizing anaerobic biotechnologies through interdisciplinary research, combining engineering and microbiological methods for the future implementation of sustainable waste biorefineries.