1,720,972 research outputs found
Analysis of the influence of activated biochar properties on methane production from anaerobic digestion of waste activated sludge
Full text linkThis work describes the impacts of biochar (BC) addition to the anaerobic digestion (AD) of waste activated sludge (WAS). Three BCs, produced by pyrolysis at 550 °C of different waste biomasses (soft wood, sewage sludge and rice husk), then physically activated at 900 °C with CO2, were investigated as additives. AD tests were performed in batch mode at 37 °C, feeding 2% total solids and 10 g L−1 BC. While none of the considered BCs increased biogas yield compared to control digesters, the activated BCs with higher surface area, porosity and hydrophobicity (RH550a from rice husk and SS550a from sewage sludge) boosted methane yield (up to 105% for RH550a). The experimental methane production were: 0.037 Nm3 kgVS−1 for SWP550a, 0.081 Nm3 kgVS−1 for SS550a, 0.142 Nm3 kgVS−1 for RH550a and 0.069 Nm3 kgVS−1 for control reactors. CO2 adsorption (3.14 mmol g−1 for RH550a, 0.97 mmol g−1 SS550a) calculated from experimental data was consistent with literature (0.4–2.3 mmol g−1 BC). The fitting of experimental methane productions through the modified Gompertz equation showed an acceleration of methane production for all BCs, with a reduction of the lag phase compared to control reactors (0.5 days vs 2.6 days). This work, although confirming literature data about CO2 adsorption, brings new insights on the influence of specific physico-chemical properties of BC as additive in AD of WAS. Surface area, porosity, hydrophobicity and alkali and alkaline metals content in ashes were the most important BC properties affecting AD of activated sewage sludge
Addition of different biochars as catalysts during the mesophilic anaerobic digestion of mixed wastewater sludge
Full text linkBiochar (BC) recently gained attention as an additive for anaerobic digestion (AD). This work aims at a critical analysis of the effect of six BCs, with different physical and chemical properties, on the AD of mixed wastewater sludge at 37 °C, comparing their influence on methane production and AD kinetics. AD batch tests were performed at the laboratory scale operating 48 reactors (0.25 L working volume) for 28 days with the addition of 10 g L−1 of BC. Most reactors supplemented with BCs exhibited higher (up to 22%) methane yields than the control reactors (0.15 Nm3 kgVS−1). The modified Gompertz model provided maximum methane production rate values, and in all reactors the lag-phase was equal to zero days, indicating a good adaptation of the inoculum to the substrate. The potential correlations between BCs’ properties and AD performance were assessed using principal component analysis (PCA). The PCA results showed a reasonable correlation between methane production and the BCs’ O–C and H–C molar ratios, and volatile matter, and between biogas production and BCs’ pore volume, specific surface area, and fixed and total carbon. In conclusion, the physic-chemical properties of BC (specifically, hydrophobicity and morphology) showed a key role in improving the AD of mixed wastewater sludge
Semi-continuous anaerobic digestion of mixed wastewater sludge with biochar addition
Full text linkThis work analysed the effects of Biochar (BC) addition to the Anaerobic digestion (AD) of wastewater Mixed sludge (MS) in semi-continuous mode. A 3 L digester was operated at 37 °C for 100 days, feeding MS collected every three weeks in the same wastewater treatment plant, and 10 g L−1 of BC. The average performance of MS digestion (biogas 188 NmL d−1, 68% methane) improved in presence of BC (biogas 244 NmL d−1, 69% methane). According to the results of the multiple linear regression analysis performed on the experimental data, the 79% variation of the soluble COD in the MS was the driving factor for the 38% increase of biogas and methane yields. In conclusion, in the considered experimental conditions, the variability of the substrate's composition was the key factor driving the performances of the AD of MS, independently of the addition of BC
Superior activity of metal oxide biochar composite in hydrogen evolution under artificial solar irradiation: A promising alternative to conventional metal-based photocatalysts
No full textA series of new hybrid photocatalysts based on Fe3O4 and standard biochar (biochar obtained by pyrolysis of Sewage Sludge (SS), Soft Wood Pellets (SWP), and Rice Husk (RH) at 700 °C) were successfully prepared using impregnation method. The biochar and resulting photocatalysts were characterized by wide range physicochemical techniques and investigated in hydrogen evolution under artificial solar irradiation. It can be noticed that when Fe3O4 is supported on SWP700 and RH700, presented a superior photocatalytic activity. Our best hybrid photocatalyst (Fe3O4-2.5%/RH700) achieved hydrogen production of 4162 μmol/g. Comprehensive electrochemical measurements reveal that the superior performance of Fe3O4- 2.5%/RH700 may be attributed to the lower band gap energy (2.27 eV), higher photocurrent density, and lower charge transport resistance. In addition, SS700 showed extraordinarily high activity (3845 μmol/g) in the conversion of deionized water to hydrogen, which is comparable to those of iron oxide photocatalysts supported on SWP700 and RH700. Based on the ultimate and proximate analyses, unique structure, high electric conductivity, dense aromatic structure, and exclusive mineral composition account for the enhanced activity exhibited by the SS700. These encouraging results showed that biochar derived from SS could be a low-cost, renewable, environmentally friendly and metal-free photocatalyst in hydrogen generation
Superior visible-light photocatalytic activity of biocarbon derived from sewage sludge in the absence of active phase for hydrogen production
No full textSewage sludge, a bioproduct generated in surplus amount from the domestic wastewater treatment has always been a chief environmental concern. Thermochemical and biological conversion of Sewage sludge into the valuable products can be an effective and efficient alternative strategy than conventional disposal method. Herein, Sewage sludge was pyrolyzed at highest treatment temperature of 700 °C in rotary kiln pilot-scale pyrolysis unit (Stage III) at the UKBRC, University of Edinburgh to obtain biochar, bio-oil and biogas. Basic utility properties of Sewage sludge biochar (SS700) such as CHNS, functional group, crystalline structure, electric conductivity, Polycyclic Aromatic Hydrocarbons, Dioxin/Furan and Polychlorinated Biphenyls were determined and then SS700 was utilized for photocatalytic hydrogen generation. Photocatalytic H2 production of SS700 was studied under visible-light irradiation. The H2 yield was 3331 μmol/g which is higher than its conventional carbon-based competitors (i.e. Graphene, CNTs and C3N4). In order to justification of superior activity of SS700, photocurrent measurements were carried out and ultraviolet-visible (UV-vis) diffuse reflectance spectra were recorded. The superior activity is attributed to its aromatic carbon structure, high surface area, inorganic materials, electron-conductive nature and hydrophilic surface functional group. This work introduces SS700 as a low-cost, stable, environmentally friendly, and sustainable method which can be a great leap forward toward the more sustainable energy development
Biochar is a long-lived form of carbon removal, making evidence-based CDR projects possible
Full text linkScience should drive policies and regulations to ensure a sustainable (environmentally, socially, and economically) green transition to a Net-Zero / Net-Negative circular economy. Since 2015, which saw COP21 in Paris, Net Zero has been a global target that must be rapidly accompanied by a Net Negative strategy to mitigate climate change. Accordingly, biochar's role as a durable carbon removal method is gaining attention and increasing. In this work, we discuss the durability of the carbon in biochar and the need for analytical techniques to support stakeholders on a project level. The different ecologically relevant groups of carbon forms contained in biochar are presented, and possible project-based methods to assess the quality and durability of the product versus the regulatory requirements for the permanence of carbon removals are summarized. Biochar is today one of the CDR technologies with the highest technology readiness level (TRL 8–9) that can ensure permanent removals for time frames relevant to climate change mitigation projects, combined with co-benefits that are gaining relevance in terms of mitigating climate impacts in agricultural soils. Graphical Abstract: (Figure presented.
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
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
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
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