APPLICATION OF MICROBIAL ELECTROCHEMICAL SYSTEMS FOR VALORISATION OF CHEESE WHEY IN BIOREFINERY FRAMEWORK

In the last decades, the current unsustainable fossil-based economic model has been worldwide disputed by policies and public opinion. As consequence, the exploitation of biomasses has arisen as pivotal towards a green and circular economy. In this context, waste biorefineries would represent the optimal technical solution. Firstly, the integration of feasible bioprocess can generate a mix of biofuels and bioproducts, according to the cascade principle, thus making possible to hit the market with products characterised by either significant market size or high market value, guaranteeing economic sustainability. In addition, the use of organic wastes as alternative to dedicated biomasses would significantly tackle costs of waste management and related environmental impacts. Due to their qualitative homogeneity and volumes of production, agro-industrial residues are currently pointed out as suitable for multi-step valorisation in biorefinery. However, their valorisation is currently aimed to few products, like biogas and compost, characterised by low market value. Therefore, the full achievement of waste biorefineries potential has to be achieved yet, since it would greatly impact the economic and environmental resilience of the whole agro-industrial sector, in particular for smaller supply chains. Sheep milk supply chain is a notable example in this respect: even though it represents a small portion of European milk market, it is a fundamental source of income in few southern regions like Sardinia, and it cyclically experiences economic difficulties. This research aims to evaluate the integration of Microbial Electrochemical Systems (MESs) in a biorefinery framework for the valorisation of cheese whey, as the main by-product of dairy industry. It started by assessing the state of art of available bioprocesses for feedstock valorisation. The literature review highlighted the current weakness of MESs treating this substrate, but also found how their integration as downstream process of Dark Fermentation (DF) can significantly enhance the power output generation in comparison to standalone processes. Consequently, a general overview on DF and MESs was provided, to also stress out how MESs can also expand material outputs generated during DF. The experimental work focused then on the application of Electro fermentation of lactate rich effluents from DF to propionate and acetate, which are seldom reported as main metabolites in DF broths. Then, a novel Microbial Fuel Cell for electricity generation is presented and characterised by mathematical modelling, aiming to a deeper understanding of reactor design to favour future systems scale up. Last experimental work gives a proof of concept of hydrogen production by Microbial Electrochemical Cells, underlining the further energy recovery and carbon removal achievable by their implementation. Finally, two biorefinery schemes are presented and analysed, pointing out their novelty and potential benefits to cheese making plants