A BIOREFINERY PLATFORM FOR BIOFUELS AND BIOPOLYMERS FROM ORGANIC WASTE

This thesis aims a bio-refinery platform that derives from the union of different projects that have been concatenated together in order to develop an integrated approach for the treatment of wastes of organic origin. The novelty of this thesis is the proposal of a waste treatment plant where multi-feedstock will be managed and multi-bio-products will be produced. A further developing interpretation of the anaerobic digestion processes is proposed in order to consider the waste management as a real production process. Therefore, the production should be maximized and its quality standardised. Starting from organic waste of different origin (food waste and sewage sludge), a selection of different bio-based compounds and bio-fuels will be produced. First aim of the bio-refinery focused on the municipal organic waste pre-treatment; the application of a press systems for the separation of segregated biowaste into liquid and solid fraction. This pre-treatment implements initiatives to support and improve the quality of the biowaste treated, to enhance energy production by anaerobic digestion and reduce energy costs to manage this increasing urban waste stream. It's a new paradigm for biogas plant pre-treatment configuration. Moreover, there is a vast interest for orienting anaerobic digestion towards biohythane (10% H2, 60% CH4 and 30% CO2) or biomethane (>90% CH4) for their potential use both for automotive sector and grid injection; also following several governments and EU directives, a number of EU funded projects are now focusing on these themes, such as GasHighWay (IEE), Valorgas (FP7-Energy), and Alt-Hy-tude and MHyBUS (Life+). The second aim of the thesis is the production of hydrogen and methane by double-phase anaerobic digestion (fermentation coupled with methanogenesis) and the development of an automatic pilot scale process control. By controlled fermentation volatile fatty acids can be produced and other products with a larger added-value can be also obtained using VFAs as building blocks. Bio-products with added-value are liquid biofuels, platform chemicals and biopolymers. Polyhydroxyalkanoates (PHAs) have a good potential for the market, provided that a) their present cost decreases; b) their environmental impact is further reduced. Both objectives could be achieved by using the organic fraction of municipal solid waste (post controlled fermentation process) as the PHA feedstock, since it has no cost and no competition against the food-chain. Therefore, the third aim of the thesis is the production scenario of PHAs. Controlled fermentation will be developed in order to produce organic acids. Volatile fatty acids are of particular interest as they constitute a key group among the building-block chemicals that can be produced via fermentative pathways by mixed microbial cultures (MMC). This research project will develop a range of new industrial bio-based processes for processing and managing the food waste and sewage sludge from wastewater treatment plants. The ambition is to obtain valuable and sustainable products, along with reducing the volume of MSW requiring ultimate disposal by landfill. Some techniques are innovative applications to the waste sector (increased conversion into bio-fuels), as well a novelty approach is proposed (pilot-scale production of biopolymers from organic waste) and a further innovation is in the way they are combined together.