1,720,969 research outputs found
Factor-based assessment of continuous bio-H2 production from cheese whey
Full text linkDespite having been widely investigated, dark fermentative H2 production from organic residues is still limited by process-related issues which may hamper the perspectives of full-scale process implementation. Such constraints are mainly due to the process complexity, which is largely affected by multiple and often mutually interacting factors. In the present work, the results of continuous fermentative H2 production experiments using synthetic cheese whey as the input substrate were used to gain detailed knowledge of the process features and identify suitable and critical operating conditions. Specifically, innovative process interpretation involved a combination of analytical characterization of the fermentation broth, mass balance calculations and statistical methods (correlation and principal component analyses) to derive systematic considerations for process characterization and scale-up. The metabolic products mainly included acetate and butyrate, which however were likely to derive (in different proportions depending on the operating conditions) from both hydrogenogenic and competing pathways. For some tests, lactate and succinate were also found to have been formed. It was observed that the main features of the process (H2 yield and rate, stability condition) were correlated with the operational and analytical parameters. The first three principal components identified by the statistical analysis were able to account for: 1) the effect of retention time and total metabolites produced; 2) biogas (H2 and CO2) generation, butyrate production and stability condition; and 3) organic loading rate and propionate production. The results suggested that the main features of hydrogenogenic fermentation can be described by a reduced set of factors that may be usefully adopted for both process monitoring and prediction purposes
A dual-chamber Microbial Electrolysis Cell for electromethanosynthesis from the effluent of cheese whey dark fermentation
No full textDark fermentation of cheese whey (CW) for the production of biohydrogen generates an acidic effluent, containing high concentrations of volatile fatty acids, which needs to be further treated before disposal and possibly further valorised. This study develops a dual-chamber Microbial Electrolysis Cell (MEC) that achieves simultaneously the reduction of the organic content of this effluent to environmentally acceptable levels, along with bio-electrochemical reduction of CO2 to CH4. The MEC was operated for 140 days and the effect of the following conditions on the MEC performance was examined: (a) the feed concentration of the acidic fermentate (in the range 6–81 gCOD/L), (b) the conductivity of the feed modified via KCl addition (range 2–22 mS/cm), (c) the MEC operation mode (with or without catholyte renewal) and (d) the solids content (modified via CW filtration prior to its use). The results showed that high COD removal (>95 %) was achieved in all cases, along with a CH4 production of up to 1.1 mmol/gCODconsumed. The best performance of the cell was obtained for a feed COD concentration of ∼30 gCOD/L and a feed conductivity of ∼15 mS/cm; these conditions resulted in a COD removal exceeding 99 %, a CH4 production of 1.1 mmolCH4/gCODconsumed and a net energy production of 15.8 % compared to the energy demand of the system. The electrochemical study of the system revealed that higher and lower feed COD concentrations were characterized by higher internal resistances. The results indicate that the MEC can be exploited for further treatment and valorization of a high-strength effluent along with the production of CH4 with an energy surplus, as an efficient waste-to-energy technology
Insight into the integration of dark fermentation with electrochemical methods for H2 and electricity production
No full textDark fermentation (DF) is one of the most promising biochemical processes for sustainable management of organic waste through bio-H2 production. DF offers several advantages compared to other bio-H2 production processes, including higher production rate, flexibility of operation under different temperature and pressure conditions, and lower net energy input. It may also be applied to a wide range of organic substrates such as waste and wastewater. Nevertheless, there are still issues that need further investigation in order to improve the efficiency of the process. These include the intrinsic limitations related to biochemical constraints, which lead to notably lower H2 yields compared to those expected on a theoretical basis
Alternative end-of-life options for disposable bioplastic products: Degradation and ecotoxicity assessment in compost and soil
No full textFour different end-of-life options for disposable bioplastic cups were investigated and compared based on their environmental implications. Two products with distinct polymeric composition were tested simulating the following scenarios at laboratory scale: i) industrial composting (180 days at 58 °C); ii) anaerobic digestion followed by industrial composting (45 days at 55 °C and 180 days at 58 °C); iii) anaerobic digestion followed by direct digestate use on soil for agricultural purposes (45 days at 55 °C and 180 days at 25 °C); iv) uncontrolled release into a soil environment (180 days at 25 °C). Ecotoxicity tests were run at the end of each experiment to investigate the effects of the materials on three main groups of terrestrial model organisms: plants, earthworms and nitrifying bacteria. Complete biodegradation of the cups was observed in 180 days in the scenarios involving composting environment. A low degree of biodegradation (22.9 ± 4.5%) of the digestates in soil was observed, warning for a potential micro-bioplastics discharge into the environment. No degradation was observed for the cups in soil during the same testing period. Ecotoxicity tests revealed a negative effect on plants biomass growth across all samples, which was 17–30% lower compared to the blank sample. The experimental campaign highlighted the need for a systematic assessment of controlled treatment of bioplastics, as well as the need for a harmonized legislative framework
Continuous fermentative hydrogen production from cheese whey – new insights into process stability
No full textContinuous dark fermentation experiments for hydrogen production from synthetic cheese whey were conducted at different HRTs and OLRs. The study mainly aimed at developing a novel criterion to quantitatively assess stability and relating it to the evolution of microbial pathways and associated metabolic products. For HRTs = 6–8 h and OLRs = 65–97.5 g TOC/(L·d), the best hydrogen generation performance was attained, yielding 42–50 L H2/kg TOC. Instead of using a stability index for the entire test length, accounting for the fluctuations of hydrogen production over 1-HRT periods (dynamic stability index) provided a more accurate assessment of process stability showing a clear correlation with the hydrogen yield. The analysis of the metabolic reactions provided evidence of a competition among acidogenic, hydrogen-consuming and hydrogen-neutral microbial species. This explained the lower process performance in comparison to the theoretical yield expected, pointing out at the need for further investigation on suitable strategies to effectively inhibit undesired metabolic pathways
Preliminary Investigation of a New Integrated Bio-Electrochemical System for Bio-Hydrogen Production from Cheese Whey
No full textThe present study addresses the feasibility of enhancing the H2 production yield of dark fermentation of
organic waste through the integration with electrochemical methods in a new combined system. The
integrated bio-electrochemical system is based on the electrochemical conversion of the protons released
by the organic acids generated during the organic substrate degradation. The conversion of protons into
H2 simultaneously produces electricity and also has the positive outcome of contrasting system
acidification as a consequence of volatile fatty acids accumulation. In this work, different experimental
set-ups were compared to identify the optimal bio-electrochemical cell configuration and a preliminary
assessment of the integrated system was performed through cheese whey utilization. The early findings
were promising displaying a 3-times higher H2 yield compared to the conventional dark fermentation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bio-electrochemical production of hydrogen and electricity from organic waste: preliminary assessment
Full text linkThis study investigated the performance of a novel integrated bio-electrochemical system for synergistic hydrogen production from a process combining a dark fermentation reactor and a galvanic cell. The operating principle of the system is based on the electrochemical conversion of protons released upon dissociation of the acid metabolites of the biological process and is mediated by the electron flow from the galvanic cell, coupling biochemical and electrochemical hydrogen production. Accordingly, the galvanic compartment also generates electricity. Four different experimental setups were designed to provide a preliminary assessment of the integrated bio-electrochemical process and identify the optimal configuration for further tests. Subsequently, dark fermentation of cheese whey was implemented both in a stand-alone biochemical reactor and in the integrated bio-electrochemical process. The integrated system achieved a hydrogen yield in the range 75.5–78.8 N LH2/kg TOC, showing a 3 times improvement over the biochemical process. Graphical abstract: [Figure not available: see fulltext.
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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