1,720,976 research outputs found
BIOGAS PRODUCTION FROM BIODEGRADABLE BIOPLASTICS
No full textIn this study, the potential for biogas production from biodegradable bioplastics was evaluated. Mater-Bi® (a family of maizestarch
based flexible films) and PLA (PolyLactic Acid; a rigid, polylactide-based, polymer) bioplastics were digested in laboratory
batch reactors, alone or in co-digestion with pig slurry or scotta (partially deproteinized cheese whey), at 35°C or 55°C. Methane
(CH4) and hydrogen (H2) production were monitored during the incubation period. Maximum CH4 (Mmax) or H2 (Hmax)
production per reactor, potential CH4 (BMP) or H2 (BHP) production g-1 volatile solids (VS), and residual VS in the digestates
were determined. Methane was produced when bioplastics were digested alone or with pig slurry, whereas H2 was produced only
in co-digestion with scotta. Mmax, BMP, Hmax and BHP were on average higher at 55°C than at 35°C (+69%, +158%, +51% and
+45%, respectively). At 35°C, in monodigestion, small amounts of CH4 (33 mL g-1 VS) were produced with Mater-Bi® only. At
55°C, the BMP for Mater-Bi® and for PLA were equal to 113 mL and 282 mL CH4 g-1 VS, respectively. Monodigestion of Mater-
Bi® and PLA at 55°C reduced the initial VS content by 51%. When PLA was in co-digestion with pig slurry, Mmax was 12%
higher than the theoretical one, with a synergistic effect. In co-digestion with scotta, a nearly significant 12% increase in H2
production was observed for Mater-Bi® incubated at 35°C. The exploitation of bioplastic waste in anaerobic digestion for biogas
production, together with or in alternative to conventional composting, appears a promising possibility for a successful waste
management
Biophysical factors affecting the anaerobic digestion of waste cooking oil in model systems
No full textThe anaerobic digestion (AD) of fat-containing waste is often prolonged in time and problematic. Differences in AD performances could rely in a different probability for microorganisms to access the substrate. The aim of this study was to study the AD of waste cooking oil (WCO) with a biophysical approach. Two laboratory experiments were carried out using model systems consisting of WCO + hydration medium (HM) in 100 mL, static, in-batch reactors. In the first experiment, we assumed the WCO to HM (OtoW) ratio as an indicator of the accessibility of substrate to microorganisms: the higher the ratio, the greater the probability of feeding for the microbial cells. AD performances were evaluated in relation to 5 decreasing OtoW ratios. In the second experiment, we favored the formation of emulsions through alkalinisation, by adding to our model system 5 increasing amounts of KOH 1M (pH range from 6.7 to 10.1). High OtoW ratios (that is, relatively low volumes of aqueous phase) increased the CH4production rate while allowing CH4yields close to the theoretical. However, the highest OtoW ratio resulted in AD failure. A proper amount of alkali halved the time to join the maximum CH4production. Reasoning in terms of biophysical factors, more than in terms of oil concentration or inoculum-to-substrate ratio, could be helpful for the improvement of AD of fat-containing substrates
Initial pH influences in-batch hydrogen production from scotta permeate
No full textWe studied the influence of initial pH on hydrogen (H2) production using permeate from scotta (a partially deproteinized cheese whey from ricotta production) as substrate (51 g Lâ1lactose). Dark fermentation was carried out at 35 °C in laboratory batch reactors, in an unbuffered system. Hydrogen production and metabolite (volatile fatty acids, ethanol, and lactic acid) evolution during a 96-h period were monitored in reactors with initial pH varying in the range 4â10. In all reactors, H2production started only when pH fell below 6. However, it was much higher (+31%) in the reactors with initial alkaline pH. We conclude that H2production occurs only at acidic pH values, but initial alkaline pH values increase the overall H2production in dark fermentation of lactose-rich substrates
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
Biogas production from wheat straw pre-treated with hydrolytic enzymes or sodium hydroxide
No full textLignocellulosic residues are relatively recalcitrant to bioconversion during anaerobic digestion (AD) for biogas production. Pretreatments with cellulolytic enzymes or diluted alkali can facilitate biomass hydrolysis and enhance the process. Both pretreatments require low energy and chemical inputs, without accumulation of inhibitor. Milled wheat straw was pre-treated with hydrolytic enzymes or with diluted NaOH before AD. The pre-treatments were performed on sterilized, stabilized with formic acid or not sterilized wheat straw to evaluate the effect of straw indigenous microorganisms on the sugar concentration before AD. Anaerobic digestion was carried out in batch reactors, at 35 °C, for 3 months. The maximum cumulated methane production (Mmax) and the daily rate of methane accumulation (R) were estimated by a modified Gompertz equation. The NaOH pretreatment was the most effective, with average increases of 23 and 85 % for Mmax and R, respectively, in comparison with no pre-treatment. The enzymatic pre-treatment only increased Mmax by 14 %. However, the same increase was observed with heatinactivated enzymes, thus it was merely caused by the bioconversion into methane of the organic compounds contained in the enzymatic preparations. Moreover, all the pre-treatments determined a holocellulose conversion into reducing sugars lower than 4 %. In particular, the sugar concentration from not sterilized or stabilized with formic acid straw was lower than from sterilized straw, probably due to straw indigenous microorganisms activity. In conclusion, hydrolytic enzyme addition does not seem to provide a real advantage in terms of methane yield from wheat straw, differently from alkali pre-treatment
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
Biogas production from wheat straw pre-treated with ligninolytic fungi and co-digestion with pig slurry
No full textThis study carried out for the first time a comparison among ligninolytic (white-rot) and cellulosolytic or xylanolytic (Trichoderma) pre-treated wheat straw, for biogas production, potential, without or with pig slurry in co-digestion. Methane (CH4) production from wheat straw pre-treated for 4 and 10 weeks with seven different fungal isolates was preliminarily measured. Then, the effects on biogas yield of the co-digestion with pig slurry were checked on straw pre-treated with 3 selected fungal strains. The maximum production of CH4 from pre-treated straw with Ceriporiopsis subvermispora (SUB) for 4 and 10 weeks was higher than the control (16% and 37%, respectively). The accumulation daily rate was higher than control (42% and 81%, respectively). A positive correlation between CH4 accumulation daily rate and straw enzymatic digestibility was found. In co-digestion with pig slurry, SUB pre-treated straw for 10 weeks showed an accumulation daily rate of 17.4 mL d-1 g-1 VS, significantly higher (17%) than that of the control. The time to reach the maximum CH4 production was shortened on average from 34 to 21 days in co-digestion with pig slurry, in comparison with pre-treated mono-digested wheat straw. The biological pre-treatment with selected white-rot fungi appears a promising technology to increase methane production from wheat straw
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
