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COMBINATION OF COMMINUTION AND SONICATION AS PRE-TREATMENTS OF LIGNOCELLULOSIC SUBSTRATES AHEAD OF ANAEROBIC DIGESTION
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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
Influence of the pH control strategy and reactor volume on batch fermentative hydrogen production from the organic fraction of municipal solid waste
Full text linkThree different experimental sets of runs involving batch fermentation assays were performed to evaluate the influence of the experimental conditions on biological hydrogen production from the source-separated organic fraction of municipal solid waste collected through a door-to-door system. The fermentation process was operated with and without automatic pH control, at a pH of 5.5 and 6.5, food-to-microorganism ratios of 1/3 and 1/1 (wet weight basis) and with different working volumes (0.5 and 3 L). The experimental results showed that the pH control strategy and the reactor volume did not affect the final hydrogen production yield but played an important role in determining the time evolution of the process. Indeed, although the different experimental conditions tested yielded comparable hydrogen productions (with maximum average values ranging from 68.5 to 88.5 NLH2 (kgTVSOF)-1), the automatic pH control strategy improved the process from the kinetic viewpoint resulting in a t95 reduction from an average of 34.9 h without automatic pH control to an average of 19.5 h
Carbon footprint of anaerobic digestion combined with ultrasonic post-treatment of agro-industrial organic residues
No full textAnaerobic digestion (AD) of organic waste, although widely practiced, may require suitable accompanying treatments to enhance the degradability of complex materials. Since these may require significant efforts in terms of energy and chemical demand, careful assessment of their overall environmental sustainability is mandatory to evaluate their full-scale feasibility. The study aims to represent the environmental profile of ultrasonication (US) applied as a post-treatment of anaerobic digestion of agro-industrial organic residues. There is an interest in the US treatment for the processing of complex organic materials prior to AD in order to enhance the hydrolysis of complex organic substrates and increase the biogas yield of the biological process. An attributional, process-based life cycle assessment (LCA) study was applied to quantify and compare the potential environmental impacts of an AD plant, the biogas utilization options as well as the different digestate processing alternatives grouped into a set of 16 scenarios. Based on the results, upgrading of biogas and bio-methane use as vehicle fuel instead of energy generation from CHP or fuel cell was recommended due to the lower impact on GWP. Similarly, composting was a suitable option to reduce environmental impacts compared to belt drying. From the uncertainty analysis, AD without US as post-treatment proves to be more sustainable in terms of GWP compared to when US is used, showing net savings in GHG emissions especially when upgrading of biogas is applied. The analysis provides useful indications to policy makers to define sustainable management alternatives for organic residues as well as identify the environmental advantages associated with biogas utilization and digestate treatment and disposal alternatives
Analysis of parameter effects on fermentative H2 production from cheese whey
No full textCheese whey (CW) is one of the most abundant by-products of cheese manufacturing, with~9.0 kg of CW beinggenerated perkg of cheese produced. Among the different optionsfor CW management, anaerobic digestion can be regarded as one of the most promising, being able to reduce the organic load of CW while harversting its energy content. Recently, an increasing attention has specifically been paid to dark fermentation of CWaimedatbiological H2production. In the present study, the effect of pH conditions and inoculum addition on H2production from CW was investigated under continuously stirred batch conditions by designing the experiments according to the principles of a factorial design. According to this approach, the set-point of the pH values of the system and the amount of inoculum added to CW werevaried over fourvalues. As the inoculum, the aerobic sludge from a wastewater treatment plant was used, after heat-shocking at 110 °C for 30 minutes so as to harvest the hydrogenogenic biomass. Process performance was evaluated in terms of H2production and substrate conversion efficiency, by twoprocess indicators: 1) amount and composition of the produced biogas evolution of the metabolic pathways, 2) evolution of substrate degradation, expressed as the removal total organic carbonand carbohydrates
Agroindustrial residues utilization as a feedstock for biorefineries
No full textIn order to reduce the amount of landfilled waste and to attain the valorization of the material and energy content of organic wastes, the integrated approach based on the biorefinery concept appearsto be the most promising in terms of potential for resource recovery, technical feasibility as well as overall environmental and economic benefits. Biorefineries are aimed at converting biomass into biofuels and bio-based products, thus they can contribute to reducing the overall consumption of fossil fuels and minimizing the global carbon footprint of both energy and material production. Compared to conventional refineries, the bio-basedconfiguration allows to produce gaseous/liquid fuels, plastics and other valuable chemicalsstarting from organic biomass instead of hydrocarbons. Irrespectiveof the specific outputs, microbial fermentation, possibly controlled so as to increase the process yields and the products quality, represents the core process in the biorefinery concept. As for the biomass to be treated, an intense debate has grown over the utilization of food crops for biofuels and biomaterials production since the end of 1900, when the opponents stated that such a practice involve turning food for the poor into fuel for the rich, worsen soil erosion and may result into marginal replacement of fossil fuels. A strategy to overcome the food vs. fuel dilemma may involvethe utilization of residual biomass, such as the biodegradable fraction of municipal waste and agro-industrial residues, as a feedstock for biorefineries. The present paper presents an overview of the most interesting metabolic pathways for liquid and gaseous biofuels. Conceptual schemes for integrating different fermentation processes aimed at biofuels and bioplastics production will also be shown
Effect of ultrasonication on anaerobic degradability of solid waste digestate
No full textThis paper evaluates the effect of ultrasonication on anaerobic biodegradability of lignocellulosic residues. While ultrasonication has been commonly applied as a pre-treatment of the feed substrate, in the present study a non-conventional process configuration based on recirculation of sonicated digestate to the biological reactor was evaluated at the lab-scale. Sonication tests were carried out at different applied energies ranging between 500 and 50,000kJ/kg TS. Batch anaerobic digestion tests were performed on samples prepared by mixing sonicated and untreated substrate at two different ratios (25:75 and 75:25 w/w). The results showed that when applied as a post-treatment of digestate, ultrasonication can positively affect the yield of anaerobic digestion, mainly due to the dissolution effect of complex organic molecules that have not been hydrolyzed by biological degradation. A good correlation was found between the CH4 production yield and the amount of soluble organic matter at the start of digestion tests. The maximum gain in biogas production was 30% compared to that attained with the unsonicated substrate, which was tentatively related to the type and concentration of the metabolic products. © 2015 Elsevier Ltd
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