1,720,993 research outputs found
A BIOREFINERY PLATFORM FOR BIOFUELS AND BIOPOLYMERS FROM ORGANIC WASTE
Full text linkThis 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
Hydrogen and Methane production from OFMSW and sewage sludge by two phases anaerobic codigestion.
No full textIn this paper a two-phase anaerobic codigestion of organic fraction of municipal solid waste and sewage sludge has been investigated experimentally. The aim of this work is to verify the feasibility and the performance of the process for the hydrogen and methane production. The experimental was carried out at pilot scale using two stirred reactors both maintained at thermophilic temperature (55°C) and fed semicontinuously with separate collected biowaste and sewage sludge. Nor chemicals neither recirculation were used to control the pH in first phase. The study lasted 50 days in which there were no evidences of any instability in the process.It was confirmed the possibility to obtain a stable hydrogen production with a specific average hydrogen production of 40 l per kg of total volatile solid (TVS) fed and a specific biogas production in the second phase of 0.32 m3per kgTVS fed.The biogas produced has a composition characterized by a stable presence of hydrogen over 5%. Therefore, the biogas produced meets the composition characteristic of biohythane
Mesophilic and thermophilic anaerobic digestion of the liquid fraction of pressed biowaste for high energy yields recovery
Full text linkDeep separate collection of the organic fraction of municipal solid waste generates streams with relatively low content of inert material and high biodegradability. This material can be conveniently treated to recovery both energy and material by means of simplified technologies like screw-press and extruder: in this study, the liquid fraction generated from pressed biowaste from kerbside and door-to-door collection was anaerobically digested in both mesophilic and thermophilic conditions while for the solid fraction "composting is suggested. Continuous operation results obtained both in mesophilic and thermophilic conditions indicated that the anaerobic digestion of pressed biowaste was viable at all operating conditions tested, with the greatest specific gas production of 0.92 m(3)/kgVS(fed) at an organic loading rate of 4.7 kgVS/m(3) d in thermophilic conditions. Based on calculations the authors found that the expected energy recovery is highly positive.
The contents of heavy metals and pathogens of fed substrate and effluent digestates were analyzed, and results showed low levels (below End-of-Waste 2014 criteria limits) for both the parameters thus indicating the good quality of digestate and its possible use for agronomic purposes. Therefore, both energy and material were effectively recovered. (C) 2015 Elsevier Ltd. All rights reserved
Ammonia concentration and pH control in pilot scale two-phase anaerobic digestion of food waste for hydrogen production: Focus on start-up
No full textThis paper deals with the start-up strategy of a two-phases thermophilic anaerobic digestion process treating food waste, optimized for the production of hydrogen and methane. In order to keep the pH of the dark fermentation reactor in the optimal H2 production range (5-6), recirculation of anaerobic digested sludge was used. A drawback of such approach is the accumulation of ammonia into the system with the risk of hydrogenogenic and methanogenic processes inhibition. Therefore this study was focused on the investigation of the recirculation ratio that allows to carry out the start-up phase control approach at pilot scale. Two pilot scale stirred reactors were used; the experiment was set-up considering two recirculation ratio of 0.4 and 1, maintaining the organic loading rate in the first and second phase of 18-20 kgtotal volatile solids/m3d and 4.5 kgtotal volatile solids/m3d respectively. The hydraulic retention time applied was of 3.3 days in the first and of 12.7 days in the second phase. A promising start-up strategy was obtained applying a recirculation ratio of 1; the partial alkalinity content in the second reactor of about 2,800 mgCaCO3/L allowed to reach a pH value in the first reactor of 5.5 after 10 days
Biohythane Production From Food Wastes
No full textBiohythane is the gaseous product from the organic matter degradation in two-stage anaerobic digestion (AD) process. It is composed of a mixture of hydrogen and methane, where the hydrogen concentration can be in the range from 10% to 30% v/v. This chapter illustrates the advantages of biohythane use compared to the use of hydrogen and methane, as separate biofuels. The two-stage AD process and the relative operative parameters have been discussed. The attention has been focused on the biohythane production from food wastes, the most abundant organic substrates treated by AD, reporting the main milestones and the future trends. In particular, it has been demonstrated that the possibility to codigest food wastes and sewage sludge is very performing from both the process and economic points of view. Because of its capability of improving the methane engines combustion and to reduce the contaminants release in the atmosphere, the developments of biohythane application on automotive sector have been deeply discussed
Valuable Routes for Sewage Sludge Utilization: Effect of Temperature and Hydraulic Retention Time in the Acidogenic Fermentation Process
Full text linkThe disposal of sewage sludge potentially reaches the 50-60% of WWTP’s total operation cost. Such stream
can be considered a renewable carbon source to produce added-value products. Different pre-treatment
methods have been applied on thickened sewage sludge (SS) coming from the domestic wastewater treatment
plant (WWTP) of Treviso (northeast Italy) to favour its acidogenic fermentability. Alkaline (pH 9-11) and thermal
(50-70°C) hydrolysis were applied separately and in combination The following fermentation process was
addressed to the recovery of volatile fatty acids (VFA) as valuable building blocks substances. Batch
fermentation tests were conducted at lab-scale under controlled temperature (T): 20, 37, 55 and 70°C by using
an available mixed fermentative consortium as inoculum. Thermophilic T (55°C) was chosen in the following
semi-continuous fermentation process (fill and draw), carried out with three different hydraulic retention time
(HRT; 4-5-6 days). In terms of organic matter solubilisation, the thermal hydrolysis (70°C) allowed to obtain a
soluble chemical oxygen demand (CODSOL) concentration around 10.0 g/L, with no additional benefits from the
combined alkaline treatment. The batch acidogenic fermentation tests highlighted the T effect on acidification
performances; thermophilic trials (55°C) showed the highest CODVFA/CODSOL ratio (0.81). The three semicontinuous
tests (HRT 4-5-6 days) were followed for 45 days (roughly), under the chosen thermophilic condition
(55°C). The highest fermentation rate was obtained at 4.0 d as HRT (22 mgCODVFA/gVS d); on the contrary, the
highest fermentation yield (0.30 gCODVFA/gVS) and CODVFA/CODSOL ratio (0.73) were obtained at 6.0 d as HRT.
In practice, low HRT selected for a mixed consortium with high fermentation rate, but less efficient in the
conversion of the organic matter into VFA. No HRT’s effect was instead observed in the VFA composition,
always rich in acetic (29-31% COD basis) and butyric acid (31-32%), and poorer in propionic (14-15%), valeric
(12-13%) and caproic acid (11-12%)
Two phase anaerobic codigestion of organic waste and activated sludge: energy and rbCOD recovery.
No full textThe following study dealt with the application of the anaerobic co-digestion process for production of biohythane and volatile fatty acids (VFA)
First- and second-generation valorisation of wastes and residues occurring in the food supply chain
No full textDespite the high potential to increase sustainability of food systems, wastes and by-products occurring in the food supply chain are currently only partially valorised at different value-added levels. First-generation valorisation strategies that aim at utilisation of complete material streams for production of animal feed, energy, compost and/or specific consumer applications are already widely implemented and experience further dissemination and/or development (e.g. biohydrogen/biohythane production) – either in the form of single processes or as part of cascade utilisations. Second-generation valorisation strategies comprise various forms of fractionised utilisation of material streams. They rely on integration of adapted recovery and conversion procedures for specific components in order to obtain sequentially different classes of products, e.g. fine chemicals, commodity products and biofuels. Such advanced strategies are particularly suitable for wastes and by-products occurring during industrial food processing. Valorisation of food by-products for functional food is an emerging trend
INFLUENZA DEL RAPPORTO DI RICIRCOLO A CARICO DELLA FASE METANOGENICA IN UN PROCESSO DI DIGESTIONE ANAEROBICA A FASI SEPARATE DELLA FRAZIONE ORGANICA DEL RIFIUTO SOLIDO URBANO OTTIMIZZATA PER LA PRODUZIONE DI IDROGENO E METANO
No full textThermophilic two-phase anaerobic digestion of source-sorted organic fraction of municipal solid waste for bio-hythane production: effect of recirculation sludge on process stability and microbiology over a long-term pilot-scale experience
No full textA two-stage thermophilic anaerobic digestion process for the concurrent production of hydrogen and
methane through the treatment of the source-sorted organic fraction of municipal solid waste was
carried out over a long-term pilot scale experience. Two continuously stirred tank reactors were
operated for about 1 year. The results showed that stable production of bio-hythane without
inoculum treatment could be obtained. The pH of the dark fermentation reactor was maintained in
the optimal range for hydrogen-producing bacteria activity through sludge recirculation from a
methanogenic reactor. An average specific bio-hythane production of 0.65 m3 per kg of volatile solids
fed was achieved when the recirculation flow was controlled through an evaporation unit in order to
avoid inhibition problems for both microbial communities. Microbial analysis indicated that dominant
bacterial species in the dark fermentation reactor are related to the Lactobacillus family, while the
population of the methanogenic reactor was mainly composed of Defluviitoga tunisiensis. The
archaeal community of the methanogenic reactor shifted, moving from Methanothermobacter-like to
Methanobacteriales and Methanosarcinales, the latter found also in the dark fermentation reactor
when a considerable methane production was detected
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