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[en] Hydrogen-producing granules formation was studied in a Continuos Stirred Tank Reactor (CSTR). The aim of this process is to later transfer the mixed liquor to a Up-flow Anaerobic Sludge Blanket (UASB) reactor to reduce its start-up period. Vinasses from a national bioethanol-producing industry (from sugar cane) were used as substrate and their anaerobic fermentation was carried out under mesophilic conditions. The seed sludge was collected from an UASB reactor operated in an industrial wastewater treatment plant and it was heat treated to inactivate methanogenic bacteria. Total viable and non-viable material growth curves were generated and it was determined that the exponential growth phase of the thermally pretreated mixed culture was between 20 and 120 h. Finally, the anaerobic fermentation of the vinasses in batch mode for 70 hours, and then in continuous CSTR mode for 7 days, showed to be an effective method for accelerating the formation of hydrogen-producing granules. Using this method, granules with an average size of 1.24 mm were achieved. The good efficiency of the process is attributed to high mass transfer in the CSTR reactor (author)
[es]Se estudio la formacion de granulos productores de hidrogeno en un Reactor de Tanque Agitado Continuo (CSTR), por sus siglas en ingles), con el fin de transferirlos luego a un reactor Up-flow Anaerobic Sludge Blanket (UASB, por sus siglas en ingles) y asi acortar el tiempo de arranque del mismo. El sustrato utilizado fueron vinazas provenientes de una agroindustria nacional productora de etanol a partir de melazas de cana de azucar y su fermentacion anaerobia se llevo a cabo bajo condiciones mesofilicas. Los lodos para realizar la inoculacion del sistema se tomaron de un reactor UASB de una planta de tratamiento de agua industrial, a los cuales se les realizo un tratamiento termico con el objetivo de inhibir el crecimiento de bacterias metanogenicas. Se generaron curvas de crecimiento de materia viable y no viable total, con las cuales se determino que la fase de crecimiento exponencial de las bacterias en cultivo mixto pretratadas termicamente se encontraba entre las 20 y las 120 h. Finalmente, la fermentacion anaerobica de las vinazas durante 70 horas en modo 'batch' (por lotes) y posteriormente durante 7 dias en modo continuo tipo CSTR, demostro ser un procedimiento efectivo para acelerar la formacion de los granulos productores de hidrogeno, lograndose obtener granulos con un tamano promedio de 1,24 mm. La alta eficiencia del proceso se le atribuye a la elevada transferencia de masa que se obtiene en el reactor CSTR (autor)
[en] Phragmites karka (Retz.) Trin. ex Steud. is a halophytic grass found in inland saline marshes potentially useful for biofuel industry. Growth, polyphenol content and antioxidant activity in different plant parts were investigated after 45 days NaCl (0,100, 200 and 400 mM) treatments. An increased in polyphenolic content (5.06 to 12.81 mg GAE g-1 DW) and antioxidant activity (0.64-3.21 IC50 mg ml-1 for DPPH and 9.09-17.91 mM Fe+2 g-1 DW for FRAP) was observed with the increasing salt concentrations among different plant parts. Increase in plant biomass, phenolic content and antioxidant activity with lower MDA at 100 mM NaCl indicates a strong protection against oxidative damage. Leaves exhibited highest polyphenol and antioxidant activity, followed by stem and root. Coefficient of regression shows the high predictability of antioxidant activity (0.705) and phenolic contents (0.763) with an increase in salinity. Our data indicates a link between production of polyphenolic antioxidants and salt stress in P. karka which indicates salinity as an effective tool to produce antioxidant rich biomass for industrial purposes. (author)
[en] Graphical abstract: Display Omitted - Highlights: • Anodic stripping voltammetry of Zn at gold electrode for fuel bioethanol analysis. • Portable batch injection analysis coupled to anodic stripping voltammetry. • Efficient gold electrode cleaning between measurements of Zn in fuel bioethanol. • Adequate sensitivity, recovery values and no sample treatment required. • On-site determination of metals on fuel bioethanol using mercury-free electrode. - Abstract: This article reports for the first time the anodic stripping voltammetric (ASV) detection of Zn at a gold disk macroelectrode for the analysis of fuel bioethanol. The accurate determination of Zn at gold macroelectrodes was only possible with the aid of batch injection analysis (BIA) associated with ASV; this statement was proved by comparison with a conventional three-electrode system. The BIA system consisted of injections of bioethanol sample plugs (up to 1 mL) at 28.3 μL s"−"1 directly onto a working (gold disc) electrode immersed in 0.04 mol L"−"1 Britton-Robinson buffer (pH 7) solution through an electronic micropipette and the Zn deposition occurs simultaneously. The highest analytical response for Zn was obtained for a deposition time of 90 s, which indicated that Zn deposition also occurred from diffusion after the injection ended. The proposed method presented a low detection limit (5 μg L"−"1), a linear range between 25 and 250 μg L"−"1, and adequate recovery values (88–104%) for spiked samples, but no sample treatment was required. Such remarkable analytical features associated with the portability characteristics of BIA demonstrated the promising application of the proposed method for routine and on-site determination of metals in fuel bioethanol
[en] The sustainability of biofuels, including the greenhouse gas (GHG) reduction that they achieve, is getting increased attention. Life cycle analyses (LCAs) of biofuels production routes show that the GHG savings may vary significantly for different biofuels. An increasing number of governments are therefore looking for options to differentiate between biofuels according to their actual GHG savings. Accurate calculations of GHG savings thus become increasingly important. This paper deals with an omission of current LCAs for ethanol and ETBE blends, which leads to an underestimation of their calculated GHG savings. Current studies do not take into account that refiners will adjust their refinery operation when bioethanol or ETBE is added, because of the different characteristics of these products. The analysis indicates that the net effect of these refinery modifications on the GHG savings is positive, i.e. GHG-emissions reduce in both cases. The emission reduction is highest in the case of ETBE. We recommend to include this effect in future LCA calculations for ethanol and ETBE. As the calculation model used for this study is only a simplified representation of the EU refinery sector, we also advise to perform a more detailed analysis of these effects using more elaborate refinery models.
[en] Ethanol produced from cellulosic feedstocks has garnered significant interest for greenhouse gas abatement and energy security promotion. One outstanding question in the development of a mature cellulosic ethanol industry is the optimal scale of biorefining activities. This question is important for companies and entrepreneurs seeking to construct and operate cellulosic ethanol biorefineries as it determines the size of investment needed and the amount of feedstock for which they must contract. The question also has important implications for the nature and location of lifecycle environmental impacts from cellulosic ethanol. We use an optimization framework similar to previous studies, but add richer details by treating many of these critical parameters as random variables and incorporating a stochastic sub-model for land conversion. We then use Monte Carlo simulation to obtain a probability distribution for the optimal scale of a biorefinery using a fermentation process and miscanthus feedstock. We find a bimodal distribution with a high peak at around 10–30 MMgal yr"−"1 (representing circumstances where a relatively low percentage of farmers elect to participate in miscanthus cultivation) and a lower and flatter peak between 150 and 250 MMgal yr"−"1 (representing more typically assumed land-conversion conditions). This distribution leads to useful insights; in particular, the asymmetry of the distribution—with significantly more mass on the low side—indicates that developers of cellulosic ethanol biorefineries may wish to exercise caution in scale-up. (letters)
[en] Against the background of an increased use of residual and waste materials in this paper the specific GHG emissions and production costs of different lignocellulosic based bioethanol concepts are assessed and compared to a conventional wheat based bioethanol concept and to the fossil reference. In order to find the best concept regarding both the environment and the economics the GHG emissions and production costs are compared and the GHG mitigation costs are calculated. Concept 5 (reference concept with C5 sugar to bioethanol and a natural gas-/biogasboiler) could be a good compromise between the both targets. Furthermore this concept has lower GHG emissions and lower production costs compared to the conventional wheat based bioethanol concept.
[en] Bioconversion of hemicellulose sugars is essential for increasing fuel ethanol yields from lignocellulosic biomass. We report for the first time with rape straw, bioethanol production from hemicellulose sugars. Rape straw was pretreated at mild conditions with sulfuric acid to solubilize the hemicellulose fraction. This pretreatment allows obtaining a prehydrolysate, consisting basically in a solution of monomeric hemicellulosic sugars, with low inhibitor concentrations. The remaining water insoluble solid constitutes a cellulose-enriched, free of extractives material. The influence of temperature (120ºC and 130ºC), acid concentration (2-4% w/v) and pretreatment time (30-180 min) on hemicellulose-derived sugars solubilisation was evaluated. The highest hemicellulosic sugars recovery, 72.3%, was achieved at 130ºC with 2% sulfuric acid and 60 min. At these conditions, a concentrated sugars solution, 52.4 g/L, was obtained after three acid consecutive contacts, with 67% xylose and acetic acid concentration above 4.5 g/L. After a detoxification step by activated charcoal or ion-exchange resin, prehydrolysate was fermented by ethanologenic Escherichia coli. An alcoholic solution of 25 g/L and 86% of theoretical ethanol yield was attained after 144 h when the prehydrolysate was detoxified by ion-exchange resin. The results obtained in the present work show sulfuric acid pretreatment under mild conditions and E. coli as an interesting process to exploit hemicellulosic sugars in rape straw. (Author)
[en] This study aims at the screening of four cultivars of sorghums as a feedstock for bioethanol production. The straw of these varieties were subjected to pretreatment (dilute sulfuric acid) followed by enzyme hydrolysis to evaluate their potential to produce sugars. Four factor full factorial experimental design (2*2*2*4=32) was used to investigate the effects of experimental factors; sorghum varieties (84-Y-01, 85-G-86, Mr. Buster and RARI S-3), acid concentration (1 and 2%), temperature (121 and 140 degree C) and pretreatment time (30 and 60 min). The tested sorghum varieties follow the order 85-G-86 (47 g/100g) > Mr. Buster (44.6 g/100g) > 84-Y-01 (42 g/100g) > RARI S-3 (36 g/100g) for their sugar yield. The factors followed given order of significance; variety > temperature > acid concentration > pretreatment time. Sorghum variety (85-G-86) was selected as an appropriate feedstock for bioethanol production due to its higher sugar yield and lower concentration of by-products and furans. (author)
[en] Stability of cell growth was achieved continuously at a steady state in a packed-bed bioreactor. The highest productivity of ethanol was achieved (0.02 g/ L/ h) when 0.003 vvm was employed. The productivity of bio ethanol increases when dilution rate increases. The highest production of 0.037 g/ L/ h was recorded when the dilution rate (D) was at 0.05 per hour. The production of bio ethanol was successfully maintained in a non 100 b % anaerobic condition. The best aeration for the continuous production of bio ethanol in a condition of steady state growth was at an aeration rate of 0.003 vvm. (author)
[en] Biofuels policies and projects may lead to environmental, economic and social impacts. A number of studies point out the need to deliver comprehensive sustainability assessments regarding biofuels, with some presenting analytical frameworks that claim to be exhaustive. However, what is often found in the literature is an overexploitation of environmental and economic concerns, by contrast to a limited appraisal of the social aspects of biofuels. Building on a systematic review of the peer-reviewed literature, this paper discusses the social constraints and strengths of ethanol, with regard to the product's lifecycle stages and the actors involved. Its objective is to contribute to the development of social frameworks to be used in assessing the impact of ethanol. Main findings indicate that ethanol developments can increase the levels of social vulnerability, although there is little evidence in the literature regarding the positive and negative social impacts of 1st-generation ethanol and potential impacts of cellulosic ethanol. Further work is needed on the formulation of social criteria and indicators for a comprehensive sustainability assessment of this biofuel. Policy makers need to internalise the social dimension of ethanol in decision-making to prevent public opposition and irreversible social costs in the future. - Highlights: ► The literature lacks evidence on the social impacts of ethanol. ► Further work is needed on social criteria and indicators for assessment. ► Ethanol developments can increase the levels of social vulnerability. ► Decision-making should internalise the social dimension of biofuels sustainability