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Upgrading anaerobic digestion by cascade fermentation coupled with biogas-based biopolymer production

Periodic Reporting for period 1 - UP-GRAD (Upgrading anaerobic digestion by cascade fermentation coupled with biogas-based biopolymer production)

Período documentado: 2020-12-01 hasta 2022-11-30

Nowadays,the inadequate management of food waste and plastics is a global concern due to its negative social impacts, economic losses and environmental damage. The latest statistical report stated that around 1.3 billion tonnes of food are wasted per year. In the European Union, 127 kg of food waste per inhabitant were generated in 2020. The global plastic production was estimated at 367 million tonnes in 2021, of which 22% is mismanaged and only 9% is appropriately recycled. The overuse of conventional fossil-based plastics along with their low recycling share severely damage both food chain and ecosystem health. Anaerobic digestion, which converts food waste matter into biogas, offers a sustainable route to valorising the enormous untapped potential of food waste. However, the use of food waste as feedstock in biorefineries is still at an early stage of development. UP-GRAD, which is an European project supported by the European Commission, H2020-MSCA-IF-2019 (with grant number 894515), is committed to support European efforts towards the development of a circular bioeconomy. UP-GRAD aims to improve the performance and stability of anaerobic digestion by developing a two-stage lactate-based process. The innovative and cost-competitive valorization routes for biogas foster the economic sustainability of anaerobic digestion and mitigate new potential methane emissions.
UP-GRAD performed the selection and enrichment of a mixed microbial consortium able to perform lactate type fermentation. This mixed culture is able no only to transform the organic matter of food waste, mainly carbohydrates, into lactate but also to produce biohydrogen from lactate. The production of biohydrogen from lactate opened a door for the production of renewable hydrogen. UP-GRAD also conducted the assessment of fermentation tests at lab scale using food waste as substrate and the enriched mixed culture as inoculum, which allowed to a better understanding of key process parameters. Another aim achieved was the comparison of single- and two-stage anaerobic digestion of food waste (in batch and continuous mode) using a steering hydrolysis-acidogenesis stage diverted to lactate-type fermentation. By applying that novel approach proposed, the rate of methanization was enhanced by up to 100% in batch processes, while the efficiency of methane production in continuous mode was improved by up to 20%. UP-GRAD also made research on the continuous biogas-based polyhydroxyalkanoates production by a mixed methanotrophic culture grown under constant biogas supply, cyclic nitrogen starvation and Taylor flow regime. This constitutes the first proof-of-concept study showing the feasibility of producing biopolymers from biogas in an engineered Taylor flow bioreactor, which is a reactor configuration characterized for sustaining relatively high mass transfer rates at a relative low energy consumption. Also, UP-GRAD obtained and microbiologically characterized a heterotrophic-methanotrophic consortium, needed for efficient biopolymer production from biogas.
UP-GRAD went beyond the current state-of-the-art of anaerobic digestion of food waste and the conversion of biogas into biodegradable bioplastics, which helps turning an environmental problem of food waste and plastic waste into a business opportunity for European industry. UP-GRAD upgraded a two-stage lactate-based anaerobic digestion process for an enhanced methanization of food waste and optimised the design and operation of high methane mass transfer bioreactors for selective production of bioplastics. UP-GRAD participated in several outreach and communication activities reaching the adult and youth public, increasing their awareness on food waste valorisation, bioplastic production, circular bioeconomy, sustainability, global warming mitigation, and biorefineries. The UP-GRAD project also disseminated results through scientific publications and oral presentations in international conferences.
17 th IWA World Conference