Més enllà del biogàs com a energia renovable

Davant de la gran demanda anual d'energia i la seva consegüent emissió de grans quantitats de diòxid de carboni contribuint al canvi climàtic, cada vegada més és necessari l'ús d'energies renovables per solucionar aquests problemes. Per això, aquest nou projecte pretén utilitzar el biogàs per obtenir metanol, una font combustible neta renovable que conté una gran quantitat d'energia útil i amb grans avantatges de transport i manipulació.Ante la gran demanda anual de energía y su consiguiente emisión de grandes cantidades de dióxido de carbono contribuyendo al cambio climático, cada vez más es necesario el uso de energías renovables para solucionar estos problemas. Por ello, este nuevo proyecto pretende utilizar biogás para obtener metanol, una fuente combustible limpia renovable que contiene una gran cantidad de energía útil y con grandes ventajas de transporte y manipulación.Given the high annual demand for energy and its consequent emission of large amounts of carbon dioxide contributing to climate change, it is increasingly necessary to use renewable energy to solve these problems. That is why this new project aims to use biogas to obtain methanol, a renewable clean fuel source that contains a large amount of useful energy and great advantages of transport and handling

Cobalt Nanocomposites as Catalysts for Carbon Dioxide Conversion to Methanol †

Carbon capture and utilisation (CCU), has arisen as an alternative to the reduction of CO concentration in the atmosphere by converting it into value-added products. CO conversion to methanol presents certain drawbacks, such as high pressure and temperature conditions and, to solve these issues, new materials are being investigated. Among them, cobalt stands out due to its abundance and low price compared to noble metals. Cobalt and its oxides exhibit interesting electronic and magnetic properties and are being used as catalysts in a wide range of reactions. In this work, we present a systematic comparison of different cobalt and cobalt oxide nanocomposites in terms of their efficiency as catalysts for CO hydrogenation to methanol, and how porous and non-porous supports can enhance their catalytic capacity. For this purpose, a fixed bed reactor operating with continuous flow is used, under mild temperature (160-260 °C) and pressure (10-15 bar) conditions. Several parameters are measured to evaluate the efficiency of the catalysis: CO conversion; space-time yield (STY), which indicates the methanol production yield per mass unit of catalyst and reaction time, and methanol selectivity, which evaluates the production of reaction side products such as carbon monoxide. How the adsorption capacity provided by the porous supports can enhance the catalytic capacity of cobalt and cobalt oxide is confirmed, as well as how porous supports such as zeolite and graphene clearly improve this capacity compared with a non-porous support such as silicon dioxide

Enhanced anaerobic digestion of food waste using purified lactonic sophorolipids produced by solid-state fermentation of molasses and oil waste : A circular approach

Altres ajuts: acords transformatius de la UABIn the present work, the effect of pure lactonic sophorolipids (SL) on the anaerobic digestion of biowaste was investigated. For this purpose, crude SL were produced from organic waste (a mixture of molasses and winterization oil cake) through solid-state fermentation (SSF) in a 22L pilot-scale aerobic bioreactor using the yeast Starmerella bombicola as SL-producing microorganism. The crude material extracted from the SSF exhaust solid contained several forms of SL and it was purified using High-Performance Liquid Chromatography (HPLC) and characterized by means of Liquid Chromatography-Mass Spectrometry (LC-MS) yielding a high-purity C18 lactonic SL (>99%). This pure SL was used to enhance the batch anaerobic digestion of source-selected biowaste, mainly composed by kitchen waste. The best dosage of SL was in the range of 0.02-0.04 g SL/g TS, with an increment of methane yield of 41% in NmL/g VS. The presence of SL did not significantly alter the structure of the microbial community or general biodiversity. In summary, we propose a circular approach for waste valorisation in which different organic waste streams are combined in a biorefinery-like configuration, where the solid-state fermentation is used to produce SL and results in an enhanced bioenergy production

Enhancement of Anaerobic Digestion with Nanomaterials : A Mini Review

Altres ajuts: Fundación Ramón Areces: projecte META2NOL/CIVP19A5952In recent years, the number of articles reporting the addition of nanomaterials to enhance the process of anaerobic digestion has exponentially increased. The benefits of this addition can be observed from different aspects: an increase in biogas production, enrichment of methane in biogas, elimination of foaming problems, a more stable and robust operation, absence of inhibition problems, etc. In the literature, one of the current focuses of research on this topic is the mechanism responsible for this enhancement. In this sense, several hypotheses have been formulated, with the effect on the redox potential caused by nanoparticles probably being the most accepted, although supplementation with trace materials coming from nanomaterials and the changes in microbial populations have been also highlighted. The types of nanomaterials tested for the improvement of anaerobic digestion is today very diverse, although metallic and, especially, iron-based nanoparticles, are the most frequently used. In this paper, the abovementioned aspects are systematically reviewed. Another challenge that is treated is the lack of works reported in the continuous mode of operation, which hampers the commercial use of nanoparticles in full-scale anaerobic digesters

Adsorptive removal of siloxanes from biogas : recent advances in catalyst reusability and water content effect

Altres ajuts: acords transformatius de la UABThe valorization of biogas as a renewable energy source faces a major obstacle regarding its purification. Siloxane is one of the impurities that cause problems such as damages to equipment of combustion engines, turbines, and boilers used for biogas conversion to heat and electricity. In this review, adsorption for siloxane removal is widely discussed, with two specific approaches: adsorbents sensitivity to water and regeneration, two essential points for industrial application. Thus, determining factors in adsorbents capacity, reusability, and water tolerance including textural properties, surface functional groups, and hydrophobicity are deeply analyzed. Studies oriented to the optimization of traditional adsorbents such as activated carbon, silica gel, and aluminosilicates as well as newly emerging adsorbents such as metal organic frameworks, graphene oxides, and waste-derived materials are studied in detail in terms of reusability and water tolerance. Although activated carbon is commercially used, its low selectivity, pore blockage due to siloxane polymerization, and unsuccessful regeneration make it disadvantageous. Silica gel, however, shows better reusability as a result of less adsorbent-adsorbate dissociation energy. In addition, aluminosilicates, despite its low adsorption capacity, proved to be more practical for real biogas due to their high hydrophobicity. Graphene oxide cost and energy efficiency in their synthesis make them more industrially appealing candidates despite their low adsorption capacity. Finally, metal organic frameworks demonstrated high selectivity, high adsorption capacity, and more efficient regeneration and therefore have more advantages and less drawbacks, although the number of published studies is still limited

Solid-State Fermentation from Organic Wastes : A New Generation of Bioproducts

This research was funded by the Spanish Ministerio de Ciencia e Investigación, grant number PID2020-114087RB-I00.Solid-state fermentation (SSF) is part of the pathway to consolidate waste as a relevant alternative for the valorization of organic waste. The objective of SSF is to produce one or several bioproducts of added value from solid substrates. Solid-state fermentation can use a wide variety of organic waste as substrates thus, it is an excellent candidate in the framework of the circular bioeconomy to change the status of waste from feedstock. The development of SSF was boosted in the previous decade by scientific efforts devoted to the production of hydrolytic enzymes. Nowadays, SSF has expanded to other valuable products: biosurfactants, biopesticides, aromas, pigments, and bio-flocculants, among others. This review explores the conditions to obtain the main emerging SSF products and highlight and discuss the challenges related to the scale-up of these processes and the bioproducts downstream, which hamper their further commercialization

Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge : Evolution of nanoparticles and microbial community dynamics

Altres ajuts: Acord transformatiu CRUE-CSICThe effects of adding zero-valent iron nanoparticles (nZVI) on the physicochemical, biological and biochemical responses of a semi-continuous anaerobic digestion of sewage sludge have been assessed. Two sets of consecutive experiments of 103 and 116 days, respectively, were carried out in triplicate. nZVI were magnetically retained in the reactors, and the effect of punctual doses (from 0.27 to 4.33 g L) over time was studied. Among the different parameters monitored, only methane content in the biogas was significantly higher when nZVI was added. However, this effect was progressively lost after the addition, and in 5-7 days, the methane content returned to initial values. The increase in the oxidation state of nanoparticles seems to be related to the loss of effect over time. Higher dose (4.33 g L) sustained positive effects for a longer time along with higher methane content, but this fact seems to be related to microbiome acclimation. Changes in microbial community structure could also play a role in the mechanisms involved in methane enhancement. In this sense, the microbial consortium analysis reported a shift in the balance among acetogenic eubacterial communities, and a marked increase in the relative abundance of members assigned to Methanothrix genus, recognized as acetoclastic species showing high affinity for acetate, which explain the rise in methane content in the biogas. This research demonstrates that biogas methane enrichment in semicontinuous anaerobic digesters can be achieved by using nZVI nanoparticles, thus increasing energy production or reducing costs of a later biogas upgrading process

The use of magnetic iron oxide based nanoparticles to improve microalgae harvesting in real wastewater

A novel approach for harvesting Scenedesmus sp. microalgae from real wastewater by using adsorbents of magnetite-based nanoparticles (Fe3O4 NPs) was tested in this study for the first time for this microalgae. Using these NPs, the harvesting efficiency was even higher than 95%. The optimal conditions (0.14 gNPs/L, a short magnetic separation time of only 8 min and 27 min of contact time) were found using the response surface methodology. The best fitting of the adsorption equilibrium results was achieved by the Langmuir isotherm model, and the maximum adsorption capacity for Scenedesmus sp. reached 3.49 g dry cell weight (DCW)/g Fe3O4 NPs. Zeta potential measurements and the Dubinin-Radushkevich isotherm model analysis pointed out that the main adsorption mechanism between Scenedesmus sp. cells and Fe3O4 NPs was electrostatic interaction. Finally, Fe3O4 NPs were six times successfully reused by combining an alkaline treatment with an ultrasonication process, which implies microalgae lysis. The results herein obtained highlight the potential for magnetic separation of microalgae from wastewater, which is capable of reaching a high harvesting efficiency in a very short time.Peer ReviewedPostprint (author's final draft

In-situ methane enrichment in continuous anaerobic digestion of pig slurry by zero-valent iron nanoparticles addition under mesophilic and thermophilic conditions

The effect of zero-valent iron nanoparticles (nZVI) addition on methane production during anaerobic digestion of pig slurry was assessed. Experiments were conducted using two experimental set-ups: batch and long-term continuous operation at a fixed nZVI dosage. Two different temperature operation ranges (mesophilic and thermophilic) were assessed. Biogas production and methane content were monitored, and the specific methanogenic activity of the biomass and nZVI oxidation state were evaluated at different timesThis research was funded by the Spanish Ministry of Economy and Competitiveness (INIA project RTA2015-00079-C02-01). The support of the CERCA Program and of the Consolidated Research Group TERRA (ref. 2017 SGR 1290), both from the Generalitat de Catalunya, is also acknowledged.Peer ReviewedPostprint (updated version