Search

13 figures, 5 tables., The expected increase of hydrogen fuel cell vehicles has motivated the emergence of a significant number of studies on Hydrogen Refuelling Stations (HRS). Some of the main HRS topics are sizing, location, design optimization, and optimal operation. On-site green HRS, where hydrogen is produced locally from green renewable energy sources, have received special attention due to their contribution to decarbonization. This kind of HRS are complex systems whose hydraulic and electric linked topologies include renewable energy sources, electrolyzers, buffer hydrogen tanks, compressors and batteries, among other components. This paper develops a linear model of a real on-site green HRS that is set to be built in Zaragoza, Spain. This plant can produce hydrogen either from solar energy or from the utility grid and is designed for three different types of services: light-duty and heavy-duty fuel cell vehicles and gas containers. In the literature, there is a lack of online control solutions developed for HRS, even more in the form of optimal online control. Hence, for the HRS operation, a Model Predictive Controller (MPC) is designed to solve a weighted multi-objective online optimization problem taking into account the plant dynamics and constraints as well as the disturbances prediction. Performance is analysed throughout 210 individual month-long simulations and the effect of the multi-objective weighting, prediction horizon, and hydrogen selling price is discussed. With the simulation results, this work shows the suitability of MPC for HRS control and its significant economic advantage compared to the rule-based control solution. In all simulations, the MPC operation fulfils all required services. Moreover, results show that a seven-day prediction horizon can improve profits by 57% relative to a one-day prediction horizon; that the battery is under-sized; or that the MPC operation strategy is more resolutive for low hydrogen selling prices., This research has been developed within the CSIC Interdisciplinary Thematic Platform (PTI+) Transición Energética Sostenible+ (PTI-TRANSENER+)[TRE2103000] as part of the CSIC program for the Spanish Recovery, Transformation and Resilience Plan funded by the Recovery and Resilience Facility of the European Union, established by the Regulation (EU) 2020/2094; project MASHED [TED2021-129927B–I00] funded by MCIN/AEI/10.13039/501100011033 and by the ”European Union NextGenerationEU/PRTR”; and the project MAFALDA [PID2021-126001OB-C31] funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”.

The geological survey has been carried out in El Hierro with the aim to produce a new Geological Map at 1:12,500 scale for the Southern Rift. Almost 70 km2 have been mapped providing a detailed stratigraphic and volcano-tectonic reconstruction of its evolution. Our work focused on the last Rift Volcanism phase, where hundreds of cinder cones, associated with thin lava flows, cover most of the island’s surface. Lava flows fields (40), monogenetic volcanic edifices (>90), and volcano–tectonic structures (69), such as dykes, eruptive fissures, and faults have been surveyed and stored in the Geological Map. The map poses fundamental constraints on the Southern Rift geological evolution, mainly concerning its recent activity and allowing the definition of 4 main stages during the last 40 ka. Moreover, this 1:12,500 scale detailed map represents a primary tool for the volcanic hazard assessment of the Island, volcanic monitoring, urban planning, and further stratigraphic data-based investigations., The authors thank E. De Beni, B. Marston, and J. Szepesi for their useful revisions and suggestions, and the associated editor M. Pondrelli for managing the manuscript

New data-independent acquisition (DIA) modes coupled to chromatographic separations are opening new perspectives in the processing of massive mass spectrometric (MS) data using chemometric methods. In this work, the application of the regions of interest multivariate curve resolution (ROIMCR) method is shown for the simultaneous analysis of MS1 and MS2 DIA raw data obtained by liquid chromatography coupled to quadrupole-time-of-flight MS analysis. The ROIMCR method proposed in this work relies on the intrinsic bilinear structure of the MS1 and MS2 experimental data which allows us for the fast direct resolution of the elution and spectral profiles of all sample constituents giving measurable MS signals, without needing any further data pretreatment such as peak matching, alignment, or modeling. Compound annotation and identification can be achieved directly by the comparison of the ROIMCR-resolved MS1 and MS2 spectra with those from standards or from mass spectral libraries. ROIMCR elution profiles of the resolved components can be used to build calibration curves for the prediction of their concentrations in complex unknown samples. The application of the proposed procedure is shown for the analysis of mixtures of per- and polyfluoroalkyl substances in standard mixtures, spiked hen eggs, and gull egg samples, where these compounds tend to accumulate., Research grant from the Spanish Ministry of Economy, Industry, and Competitiveness (MINECO) for project PID2019-105732GB-C21 is acknowledged by the authors as financial support. IDAEA-CSIC is a Center of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S).

5 figures.-- Supporting information available., The sluggish kinetics of the oxygen evolution reaction (OER) is one of the most limiting factors for the development of many “green” electrochemical devices. Expensive ruthenium and iridium oxide electrodes are often used as advanced electrocatalysts to overcome this limitation. However, these materials are rare in nature, which further limit the implementation of this kind of electrochemical device on a global scale. Compounds based on transition metals and boron have proven to be promising alternatives to commercial electrocatalysts due to their high catalytic properties and robust stability under working conditions. However, such compounds are often obtained through expensive synthetic routes that often involve the use of supports, which increases the cost of electrocatalysts. Here, we present an easy and support-free synthesis of bimetallic borates based on the introduction of transition metals into cobalt borates. Depending on the metal, different morphologies, structural order, surface chemistry, and, most importantly, electrocatalytic properties toward the OER have been obtained. Among all the transition metals, nickel is the one that most improves the catalytic activity of cobalt borate for the OER in an alkaline electrolyte. An overpotential of 230 mV, similar to that of commercial and state-of-the-art electrocatalysts, was obtained by using a support-free synthesis route for the preparation of this catalyst., This study was partly supported by the French PIA project “Lorraine Université d’Excellence”, reference ANR-15-IDEX-04-LUE, and the TALiSMAN project funded by ERDF (2019-000214). SGD thanks the Ministerio de Universidades, the European Union, and the University of Oviedo for the financial support (MU-21-UP2021-030 30267158). JQB thanks the Ministerio de Universidades, the European Union, and the University of Alicante for the financial support (MARSALAS21-21).

Brackish springs have been extensively reported in Mediterranean coastal carbonate formations. The phenomenon is puzzling because these springs may discharge high flow rates with significant salinities at elevations of several meters above sea level. Although these springs have been studied for millennia (since the ancient Greeks), controversy persists. In essence, they are typically assumed to consist of a karstic conduit bringing fresh groundwater that meets a saltwater conduit at a branching point, where the brackish mixture flows up to the spring mouth. Here, we analyze the hydraulics of the system for two simple cases, depending on whether seawater flow occurs through an open conduit or a porous aquifer. To this end, we derive the equations governing variable-density turbulent flow through the conduits. These turn out to be similar to the traditional ones, except that (1) Bernouilli’s head (energy per unit weight) is substituted by the energy per unit volume, and (2) this energy is not a potential, as a flow path dependent term needs to be added. We solve these equations to obtain the characteristic functions relating fresh to seawater discharge depending on spring concentration. These functions are specific to every brackish spring and representative of the karst system and salinization mechanism. They allow us to show that the spring salinity is mostly controlled by the weight of the water column flowing towards the spring mouth (for low flow rates) and by energy dissipation (for high flow rates). When concentration and flow rate data are available, it is possible to characterize: (1) the resistance of the upwards conduit from the response at high flow rate; (2) the depth of the branching point from the concentration at low discharges; and (3) the hydraulic resistance of the seawater conduit from the slope of concentration vs. flow rate at low spring discharges. These patterns are compared to field data from three different springs, which yields insights on the conceptual model governing every particular spring., Comments by two anonymous reviewers and especially John M. (Jack) Sharp are gratefully acknowledged. Most of this work was funded by the European Union (SALTRANS project, contract no. EVK1-CT-2000-00062) and the Spanish Government (project Medistraes3. grant no. PID2019-110311RB-C21), and IDAEA-CSIC Center of Excellence Severo Ochoa (Grant CEX2018-000794-S). ES is also grateful to a FI doctoral scholarship from the Catalan Government. The authors wish to acknowledge Dr. Guangjing Chen for his help and useful comments on the formulation and code design. Data and documentation related to S’Almadrava spring was gently provided by the Junta d’Aigües de Balears.

8 figures.-- Supplementary information available., Physicochemical properties, kinetic pyrolysis and thermodynamic study of spent green tea, pure spent coffee grounds, spent coffee grounds blended with 50% torrefied barley and coffee husk were experimentally investigated using thermogravimetric analysis under an inert atmosphere to evaluate their thermochemical application. Five isoconversional methods were applied to determine effective activation energy (Ea) of the pyrolysis processes. All methods showed good agreement by determining fluctuating Ea values (150–500 kJ mol−1). Complex Ea profiles with conversion were divided into four stages corresponding to thermal degradation of main biomass constituents (extractives, hemicellulose, cellulose and lignin), indicating that extractives decomposition was the least demanding reaction while lignin decomposition was the most demanding. The kinetic process was verified by reconstruction according to the Friedman parameters. The thermodynamic parameters were evaluated to determine the energy demand and efficiency throughout the process. The values obtained for physicochemical properties such as volatile matter (> 68%) and higher heating value (> 17 MJ kg−1), average Ea (223–319 kJ mol−1) and significant energy efficiency implied that these types of biomass waste have significant reactivity and consequently the highest potential for the production of bioenergy and a range of high-value chemicals and materials., This work was supported and funded by the Ministry of Higher Education and Scientific Research (MESRST) in Tunisia through the Project “Thermochemical and biochemical conversion of solid waste” under a Contract between the MESRST and the Research and Technology Centre of Energy (Program contract 2019-2022). The financial support for this work also was given by the Spanish Ministry of Science and Innovation, the State Research Agency and the European Funds for Regional Development (No. RTI2018-095575-B-I00, MCI/AEI/FEDER, UE), as well as the Regional Government of Aragon (DGA) under the research groups support programme. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

The main aim of the current work is to find an experimental connection to the interatomic exchange-correlation energy as defined by the energy decomposition method Interacting Quantum Atoms (IQA). A suitable candidate as (essentially) experimental quantity is the nuclear magnetic resonance (NMR) J-coupling constant denoted 3J(H,H′), which a number of previous studies showed to correlate well with QTAIM’s delocalization index (DI), which is essentially a bond order. Inspired by Karplus equations, here, we investigate correlations between 3J(H,H′) and a relevant dihedral angle in six simple initial compounds of the shape H3C-YHn (Y = C, N, O, Si, P, and S), N- methylacetamide (as prototype of the peptide bond), and five peptide-capped amino acids (Gly, Ala, Val, Ile, and Leu) because of the protein direction of the force field FFLUX. In conclusion, except for methanol, the inter-hydrogen exchange-correlation energy Vxc(H,H′) makes the best contact with experiment, through 3J(H,H′), when multiplied with the internuclear distance RHH′., This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (PID2021- 125207NB-C32) and Comunidad de Madrid (P2018/EMT- 4329 AIRTEC-CM). Gratitude is due to the CTI (CSIC) for their continued computational support. P.L.A.P. acknowledges the EPSRC for funding through the award of an Established Career Fellowship (grant EP/K005472).

Synchrotron radiation based techniques are powerful tools for battery research and allow probing a wide range of length scales, with different depth sensitivities and spatial/temporal resolutions. Operando experiments enable characterization during functioning of the cell and are thus a precious tool to elucidate the reaction mechanisms taking place. In this perspective, the current state of the art for the most relevant techniques (scattering, spectroscopy, and imaging) is discussed together with the bottlenecks to address, either specific for application in the battery field or more generic. The former includes the improvement of cell designs, multi-modal characterization and development of protocols for automated or at least semi-automated data analysis to quickly process the huge amount of data resulting from operando experiments. Given the recent evolution in these areas, accelerated progress is expected in the years to come, which should in turn foster battery performance improvements., The authors are grateful for funding through PTI+ TRANS-ENER+: “Alta Tecnología clave en la transición en el ciclo energético”, part of the CSIC program for the Spanish Recovery, Transformation and Resilience Plan funded by the Recovery and Resilience Facility of the European Union, established by the Regulation (EU) 2020/2094. ICMAB-CSIC members thank the Spanish Agencia Estatal de Investigación Severo Ochoa Programme for Centres of Excellence in R&D (CEX2019-000917-S)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

The Aran Valley in Catalonia (Spain) was the site of large-scale Zn, Pb, Cu, Fe, and Ag mining from the late 19th century until approximately 1950. Although mining activities ceased over 70 years ago, some of the abandoned mining relics (e.g. tunnels, processing facilities, and tailings dumps) exhibit elevated concentrations of metals in the associated water systems, thus posing a health risk in the neighboring ecosystem. In this study, the largest underground zinc mine in the Aran Valley (the Victoria Mine) was chosen as a field site to showcase the processes affecting metal mobility in the environment. Three sampling campaigns to the mine (2019, 2020 and 2021) provide a spaciotemporal dataset showing the evolution of solute concentrations through the system along a flow path. Rainwater from the upper catchment flows into the host rock above the mine, dissolving ore materials (primarily Zn (sphalerite) and Fe (pyrite) sulfides with Ni and Cd impurities) that cause elevated Zn, Ni, and Cd concentrations in the water that enters the mine. Precipitation of hydrozincite (Zn5(CO3)2(OH)6) along the gallery where water flows serves as a metal-removal mechanism resulting in significantly diminished metal concentrations (e.g. Zn from 155 to 10 ppm, Ni from 377 to 32 ppb, and Cd from 105 to 22 ppb). Characterization of the solid samples taken from the mine reveals several different morphologies, Zn zonations in hydrozincite (i.e. purity changes), and small amounts of smithsonite (ZnCO3) and calcite (CaCO3). In general, all solids show layering, which is a result of intermittent precipitation of distinct solid products. These precipitation patterns are likely a result of changing solute concentrations and precipitation rates. Variations in rain events change the water residence time in both the host rock and in the gallery, thereby altering the water composition. Solubility experiments and speciation calculations demonstrate that hydrozincite here does not have a constant Keq value, but rather a range of values (30.0 < log[Keq] < 37.68 at 7 °C). This behavior is presumed to be a result of precursor effects as amorphous solids with higher solubilities may form before the structured hydrozincite. Notably, all analyzed solids from the collected mine samples show significant amounts of amorphous material, demonstrated by broad XRD peaks along with significant impurities in the analyzed solids, leading to the hypothesis that there exists a variability in the solubility of hydrozincite beyond a pure end-member value., We would like to thank Jordi Bellés, Natàlia Moreno, Rafael Bartrolí and Mercè Cabanas (IDAEA), David Artiga, Maite Romero and Xavier LLovet (SCT-Barcelona University) for analytical assistance and Jordi Gavaldà (Conselh Generau d'Aran) for field assistance. This work has been financed by the CGL2017-82331-R project (Spanish Ministry of Economy and Competitiveness), with contribution of FEDER funds, and 2021 SGR 00308 project (Catalan Government). IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S funded by MCIN/AEI/10.13039/501100011033). We are grateful to an anonymous reviewer and Editor, Stefano Albanese, for their insightful comments.

Editorial on the Research Topic: Chemical reactions and catalysis for a sustainable future, Developing catalytic chemical processes for a sustainable future is a constant challenge involving different knowledge áreas (Sakakura et al., 2007; Yang et al., 2013; Götz et al., 2016; Tian et al., 2023; Yu et al., 2023). It requires multidisciplinary actions that include economic sectors, industry, society, and the environment (Lee et al., 2006; Corma et al., 2007; Naik et al., 2010; Ferreira Mota et al., 2022; Tafete and Habtu, 2023). Furthermore, catalytic chemical processes require constant evaluation to achieve greater sustainability, mainly when applied in industries or on a domestic scale (Chheda et al., 2007; Khodakov et al., 2007; Oh et al., 2016; Deng et al., 2023). Indeed, chemical catalysis is inherent in developing a sustainable future (Kondratenko et al., 2013; Deng et al., 2023). Chemical reactions are inseparable from our subject since they are applied in different processes, such as the preparation of fuels, food, drugs, and energy (Arcadi, 2008; Lima et al., 2022; Moreira et al., 2022; Sales et al., 2022; de Sousa et al., 2023; Faizan and Song, 2023; Nogueira et al., 2023). In this context, we include scientific research to help make these processes more sustainable. Moreover, consequently, it reduce the negative impact on the environment (Wang et al., 2023a; Zhu et al., 2023). Regarding chemical catalysis, reducing the amount of energy involved in the processes is fundamental (Roy et al., 2010; Yang et al., 2023a; Nogueira et al., 2023). This has a positive impact on reducing the use of polluting energy sources so that these systems can happen, such as the use of petroleum-derived fuels (Torborg and Beller, 2009; Catumba et al., 2023; Jafarian et al., 2023; Park and Kim, 2023). Furthermore, the greater need to use high temperature and pressure conditions increases energy consumption and, consequently, the production of waste that pollutes the environment (Singh et al., 2018; Djandja et al., 2023). Thus, chemical catalysis must seek to reduce the energy required for these processes, for example, in the design of robust catalysts (Yang et al., 2023b); The design of robust catalysts for industrial applications can be presented in different physical states, such as solid, liquid, or gaseous (Mariscal et al., 2016; Ferreira Mota et al., 2022; Issaka et al., 2023). The principle of sustainable functioning of these catalysts must include the formation of desired products (Centi et al., 2013). Be highly efficient in guiding molecules of reagents to the formation of desired products and eliminating the generation of unwanted waste (Li et al., 2023a; Li et al., 2023b). Another crucial factor for the design of sustainable catalysts must include their stabilization power, that is, whether the catalyst can be used repeatedly in the same reused process, minimizing the formation of polluting species and being economically viable (Centi et al., 2013; Wang et al., 2023b). In this way, the formation of sustainable reaction processes is the realization of catalytic systems on a large scale (Abbas-Abadi et al., 2023; Abuzeyad et al., 2023). This strategy makes it possible to reduce energy and polluting waste generated in the environment (Zhao et al., 2023). This fact also implies a decrease in energy use from oil and contributes to green chemistry practices (Goyal et al., 2008; Akram et al., 2023). Therefore, catalysis is different in advancing clean, renewable, and consequently sustainable technologies (Waseem et al., 2023; Zhang et al., 2023). In this context, catalysis is fundamental in producing fuel cells, which convert chemical energy into electrical energy in an environmentally sustainable way (Zhao et al., 2015; Gong et al., 2023). Likewise, catalysis is fundamental in producing biofuels from renewable sources such as biomass (Li et al., 2023c; Jiang et al., 2023; Yu et al., 2023).

5 figures, 7 tables.-- Supplementary information available., The acid-free hydrothermal microwave–assisted selective scissoring (Hymass concept) of cellulosic substrates is gaining keen interest in the field of materials science. Besides, implementing catalytic methodologies to upgrade side streams produced during this process could contribute to better, holistic utilisation of the starting feedstock. This work depicts a zero-waste biorefinery concept based on cellulose defibrillation from almond hulls using various hydrotreatment technologies (hydrogenation and hydrodeoxygenation) for downstream processing on a ruthenium catalyst. Therein, the hemicellulose separated from the biomass preconditioning step was converted into sugar alcohols and/or marketable polyols with a relatively high yield (47.4%) by hydrolytic hydrogenation (437 K, 3h, 5.0 MPa H2). Meanwhile, a family of bioactive compounds (3-hydroxypyridines) could be directly extracted from the hydrolysate stream derived from microwave digestion, along with an energy carrier that was chemically stabilised (503 K, 60 min, 4.0 MPa H2) to obtain fuel additives (diethyl succinic acid, DES) and/or fuel intermediates., The authors are grateful for the financial support from the Spanish Ministry of Economy and Competitiveness (MINECO, Project ENE2017-83854-R) and the I+D+i project PID2020-115053RB-I00, funded by MCIN/AEI/10.13039/501100011033. J.R. is grateful to the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva Incorporación (JdC-I) fellowship (Grant Number: IJC2018-037110-I) awarded.

7 figures, 1 table.-- Supplementary information available. © 2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, In this study, efficient electrodes for the hydrogen evolution reaction (HER) based on low-cost and metal-free carbon catalysts are presented. Phytic acid, a biosourced molecule containing carbon (C) and phosphorus (P), was found to be an excellent precursor for producing carbon materials with high P content, depending on the carbonization temperature, from 27.9 wt% at 700 °C to 7.3 wt% at 1000 °C. A green and easy route to produce P-doped carbon materials by heat treatment of this biosourced precursor without the need for additional reagents is thus proposed. We show that the conversion of P-O-type groups into P-C-type species is of paramount importance for improving the catalytic activity in HER of P-doped carbon materials. P-C-type groups appear to be the key factor in the electrocatalytic activity, reaching an onset potential of - 0.27 V. This study sheds light on the origin of the catalytic activity of P-doped carbons, in which P is expected to modify the homogenous distribution of the electron density of undoped carbons and increase their catalytic performance., This study was partially supported by the French PIA project “Lorraine Université d’Excellence”, reference ANR-15-IDEX-04-LUE, and the TALiSMAN and TALisMAN2 projects funded by ERDF. SGD thanks the Ministerio de Universidades, the European Union, and the University of Oviedo for the financial support (MU-21-UP2021-030 30267158). JQB thanks the Ministerio de Universidades, the European Union, and the University of Alicante for the financial support (MARSALAS21-21).

16 figures, 2 tables.-- Supporting information available., The iron and titanium oxide ilmenite is a benchmark oxygen carrier for chemical looping combustion (CLC) and oxygen carrier-aided combustion (OCAC). Both of them are combustion technologies for biomass and waste fuels with lower emissions and low costs for carbon capture. Here, the interaction between the ash component zinc and oxygen carrier ilmenite is studied in a two-staged vertical tube reactor. Three types of ilmenites─Norwegian rock ilmenite, synthesized ilmenite, and ilmenite extracted after 200 h of OCAC in a full-scale fluidized bed unit─were exposed to gas-phase Zn and ZnCl2. Following the exposure, samples were analyzed concerning morphology, chemical distribution, composition, and crystalline phases. The observations were complemented with thermodynamic equilibrium calculations. It is observed that the iron-rich layer formed on the external surface of rock ilmenite after activation promotes the reaction with both gaseous zinc compounds, with zinc ferrite formed in the external Fe-rich layer. In contrast, ilmenite with no segregation of Fe and Ti showed to interact less with zinc species. Metallic Zn penetrated the particles, while the interaction depth was shallow with ZnCl2 for all investigated ilmenite oxygen carriers. The gaseous conditions, particle ash layer composition, and iron availability are shown to play an important role in the interaction between zinc compounds and ilmenite particles. Based on these results, interaction mechanisms for Zn and ZnCl2 are proposed. This interaction could have environmental implications for the toxicity of ash streams from waste combustion in addition to possibilities for Zn recycling., This work was financed by the Swedish Research Council (2016-06023 and 2020-03487), Technical University of Denmark, Sino-Danish Center for Education and Research, and by Nordic Energy Research (project: NEST─Nordic Network in Solid Fuels towards Future Energy Systems, 120626). I. Adánez-Rubio acknowledges “Juan de la Cierva” Program (Grant IJC2019-038987-I funded by MCIN/AEI/10.13039/501100011033).

Special issue from COP 26 to COP 27: Contributions of Systems Approaches to Address the Challenges Ahead.-- 35 pages, 2 figures, 12 tables.-- Data Availability Statement: Not applicable, It is often claimed that marine renewable energy alone could meet the electricity demand of current and future human societies. However, such claims are based on highly uncertain estimations of the global potentials of marine renewable energy sources (including tidal, ocean currents, wave, offshore wind and salinity and thermal gradients), and do not take into account the embedded energy of current technologies. To better understand the effective potential of marine energy, we conducted a literature review of its gross, technical, economic and sustainable potentials, as well as the energy return on investment (EROI), and estimated the net energy potential. We found that all marine technologies could provide a maximum energy surplus of 57,000 TWh /yr. This figure goes down to ∼5000TWh/yr when excluding offshore wind. The previous figures do not include the contribution from ocean currents, for which no reliable estimates of global potentials and EROIs could be obtained. Due to its high upfront costs and environmental impacts and low social acceptance, no additional tidal range capacity expansion is envisioned. Similarly, the combination of a low sustainable potential and the low EROI makes the large-scale exploitation of salinity gradients unlikely with current technologies. Including all technologies, the average EROI of marine energy is ∼20, but excluding offshore wind reduces the average EROI to ∼8. While we did consider sustainability constraints for some marine energy sources, our estimation of marine net energy potential primarily relied on technical factors and did not account for economic and legal constraints. Therefore, the results presented here should be interpreted as an upper bound for the actual net energy contribution of marine energy sources to the global energy mix, This work was supported by the European Union through the funding of the MEDEAS and LOCOMOTION projects under the Horizon 2020 research and innovation programme (grant agreements No 691287 and 821105, respectively), With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Widespread deployment of Geologic Carbon Storage (GCS) at the gigatonne scale is projected to play a vital role in reaching carbon neutrality and mitigating the climate crisis. One major concern with GCS scale-up is the ability of geologic formations to retain CO2 deep underground, at least over several thousand years. Of particular importance to this issue is the sealing capacity of the ideally low-permeability, high-gas-entry pressure caprock(s). Existing simulation studies to address the long-term fate of the injected CO2 could barely exceed multi-century time scales due to high computational costs. This work aims to provide an improved understanding of the extent to which the potentially leaked CO2 from basin-wide GCS may rise through a multi-layered system of laterally uniform aquifers and shale caprocks over geological time scales (million years). To this end, we develop a one-dimensional CO2 flow and transport model, which is arguably capable of capturing the dynamics of basin-scale upward CO2 migration. We consider two sets of caprock properties: (1) low intrinsic permeability (10-20 m2) and high capillary entry pressure (2.5 MPa), obtained from laboratory measurements on intact clay-rich shales, and (2) high permeability (10-16 m2) and low entry pressure (0.1 MPa), representative of pervasively fractured shales at regional scales. On the one hand, we find that the free-phase CO2 can hardly penetrate more than a few centimeters into the intact caprock directly overlying the storage reservoir. CO2 leakage in this scenario is exclusively governed by molecular diffusion with an estimated migration rate of 1 meter over thousands of years. On the other hand, the high permeability and low entry pressure of fractured caprocks enable CO2 to break through the whole primary caprock during the injection and through the secondary one(s) in the post-injection period. However, following the gradual CO2 pressure decline, brine imbibition back into caprocks suppresses CO2 leakage and the percolating path is cut by an overlying caprock. Once the pore fluid of upper aquifers becomes CO2-saturated, secondary CO2 accumulations form and may host a significant portion of the injected CO2. The extreme leakage scenario, which allows for further CO2 rise of nearly one hundred meters becomes eventually diffusion-dominated and hence relatively safe. Our model results suggest that the presence of multiple shaly caprock layers, even if pervasively fractured, provides secure CO2 containment in the subsurface over millions of years. ReferenceKivi, I. R., Makhnenko, R. Y., Oldenburg, C. M., Rutqvist, J., & Vilarrasa, V. (2022). Multi-layered systems for permanent geologic storage of CO2 at the gigatonne scale. Geophysical Research Letters, 49, e2022GL100443. https://doi.org/10.1029/2022GL100443

11 páginas, 3 tablas, 9 figuras, Biofuel potential of a widely grown perennial grass, Pennisetum polystachion, was analyzed using triethylammonium hydrogen sulfate ([TEA][HSO4]) pretreatment. The optimum pretreatment condition was selected based on the delignification efficiency. 80% [TEA][HSO4] at 140 °C for 45 min at 10% sample load, yielding high delignification rate (65.8%) was selected as the optimum pretreatment condition. Recycling of [TEA][HSO4] showed up to 90% IL recovery and significant delignification rates. Glucan yield in the biomass increased to 67.8%, whereas digestibility of biomass enhanced from 16.7% to 84.1%. Extensive deferuloylation (88%) and decoumarylation (86.4%) were observed in the sample following pretreatment. Diferulic acids were not detected in pretreated samples indicating their complete removal. HMF (0.1 mg/mL) and furfural (0.001 mg/mL) produced during pretreatment were very low compared to conventional methods. FTIR and XRD confirmed pronounced delignification and hemicellulose dissolution, and FESEM showed a marked difference in the surface morphology, including defibrillation and enhanced porosity. An ethanol yield of 275 mg/g biomass (84.7% of theoretical maxima) was achieved using Saccharomyces cerevisiae MTCC 36 after 15 h of fermentation. The results obtained from the current study can shed light on utilizing P. polystachion as a potential biofuel feedstock using a low-cost ionic liquid [TEA][HSO4]., The present study did not receive any specific grants from public, commercial or not-for-profit agencies.

Hydrogen is attracting global attention as a key future low-carbon energy carrier which could replace hydrocarbon usage in transport and fuel-intensive industry. However, to supply energy in the TWh-range necessary for Net Zero it requires storage at much larger volumes than the currently deployed surface tanks or salt caverns storage. A potential solution for large-scale hydrogen storage are porous saline aquifers and depleted hydrocarbon fields. This perspective is promising but remains technically challenging given the lack of active hydrogen storage knowledge and experience. Here we present the SHINE (Safe underground Hydrogen storage IN porous subsurface rEservoirs) project, recently funded under the Horizon 2020 MSCA Doctoral Networks scheme, which is a consortium of five Universities/Research Institutes and six energy companies with the aim of exploring the feasibility of hydrogen storage in porous reservoirs, addressing the technical, geological, biological, hydrogeological and geomechanical challenges related to hydrogen storage in subsurface porous reservoirs. For this purpose, 10 new doctoral students will be trained to tackle this scientific challenge. We will introduce the main concepts behind SHINE, the research package structure which aims at integrating analytical, monitoring and computational techniques to analyse how hydrogen may react with the subsurface minerals, fluids and microbial community potentially affecting the storage operations. SHINE will also model the stress field changes across hydrogen reservoir/caprocks and monitor their geomechanical response during repeated injection/production cycles. The expertly trained cohort of young research scientists resulting from the SHINE consortium will significantly enhance and improve our understanding of this underground storage strategy. This will support the implementation and de-risking of potential porous rock hydrogen storage projects by providing the necessary insights into this large scale storage technology for decision makers in government and industry. Our newly trained research scientists will actively contribute to the EU energy transition goals.

Fluid injection-induced earthquakes involve a series of complex physical processes. Evaluating these processes at the basin scale requires an amount of input data and a super computational ability to solve in near-real time risk analysis, which remains the most critical challenge in geo-energy related applications. Although the current computational tools can achieve a good simulation for the field scale problems, they are far away from the requirements of the basin scale analysis. Alternatively, we can apply verified analytical solutions of certain processes to speed the whole calculations when moving from the field to the basin scale. With this in mind, we adopt the analytical solutions for pore pressure diffusion and stress variations due to fluid injection into the reservoir. With the superposition principle, the analytical solutions can address the coupling problem of multi-injection wells at the basin scale. We then assess faults stability and the associated induced seismicity potential using the hydro-mechanical perturbations throughout the basin computed analytically. To handle the uncertainty of geological properties, including the fault and reservoir geometries, hydraulic and mechanical properties, we perform Monte Carlo simulations to analyze their effects on induced seismicity potential. Such comprehensive parametric space analysis currently represents an insurmountable obstacle to be solved numerically, even calculating the problem in parallel. We propose a feasible methodology to mitigate the magnitude of induced seismicity, and even to avoid large earthquakes for subsurface energy-related projects, based on the results obtained both at the field and basin scales. This development will represent a great tool for risk evaluation of induced earthquakes not only in the period of site selection, but also in the whole lifetime of geo-energy projects.

Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace element thorium (Th) can provide a signature of bedrock fracture processes spanning neighboring watersheds in Colorado. River Th concentrations show abrupt (subdaily) excursions and biexponential decay with approximately 1-day and 1-week time constants, concentration patterns that are distinct from all other solutes except beryllium and arsenic. The patterns are uncorrelated with daily precipitation records or seasonal trends in atmospheric deposition. Groundwater Th analyses are consistent with bedrock release and dilution upon mixing with river water. Most Th excursions have no seismic signatures that are detectable 50 km from the site, suggesting the Th concentrations can reveal aseismic fracture or fault events. We find, however, a weak statistical correlation between Th and seismic motion caused by distant earthquakes, possibly the first chemical signature of dynamic earthquake triggering, a phenomenon previously identified only through geophysical methods., This work was conducted as part of the Watershed Function Scientific Focus Area at Lawrence Berkeley National Laboratory and was supported by the US Department of Energy (DOE) Subsurface Biogeochemical Research Program, DOE Office of Science, Office of Biological and Environmental Research, under contract no. DE-AC02 − 05CH11231. The authors thank Jiamin Wan, Tetsu Tokunaga, Caitlin Bernier and the Rocky Mountain Biological Laboratory (RMBL).

While multi-junction geometries have the potential to boost the efficiency of organic solar cells, the experimental gains yet obtained are still very modest. This work proposes an alternative spectral splitting device concept in which various individual semiconducting junctions with cascading band gaps are laid side by side, thus the name RAINBOW. Each lateral sub-cell receives a fraction of the spectrum that closely matches the main absorption band of the given semiconductor. Here, simulations are used to identify the important material and device properties of each RAINBOW sub-cell. Using the resulting design rules, three systems are selected, namely PBDB-T-2F:IO-4Cl, PBDB-T-2F:Y6 and PTB7-Th:COTIC-4F, and their potential as sub-cells in this geometry is experimentally investigated. With the aid of a custom built setup that generates spectrally spread sunlight on demand, the simulations are experimentally validated, showing that this geometry can lead to a reduction in thermalization losses and an improvement in light harvesting, which results in a relative improvement in efficiency of 46.6% with respect to the best sub-cell. Finally, a working proof of concept monolithic device consisting of two sub-cells deposited from solution on the same substrate is fabricated, thus demonstrating the feasibility and the potential of the RAINBOW solar cell concept. This article is protected by copyright. All rights reserved., The Spanish "Ministerio de Ciencia e Innovación (MICINN)" is gratefully acknowledged for its supportthrough grant No. CEX2019-000917-S (FUNFUTURE) in the framework of the Spanish Severo OchoaCentre of Excellence program and the AEI/FEDER(UE) grants PGC2018-095411-B-I00(RAINBOW),TED2021-131911B-I00and PID2021-128924OB-I00(ISOSCELLES). The authors also thank the Cata-lan agency AGAUR for grant2021-SGR-00444. MCV acknowledges a FPI fellowship (PRE2019-089855)from MICINN co-financed by the European Social Fund and MGR acknowledges the scholarship FPU16/02631 from the Spanish "Ministerio de Educación". MCV and MGR also thank the PhD programme in Materi-als Science from Universitat Autònoma de Barcelona in which both were enrolled. KV and QL acknowl-edge funding by the European Research Council (ERC, grant agreement864625)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Correction to: Scientific Reports https://doi.org/10.1038/s41598-023-29701-x, published online 14 February 2023 The Supplementary Information published with this Article contained an error. In “Appendix C”, Figures C1 and C2, the label of the Y-axis “Concentration (ng/L)” was incorrectly given as “Concentration mg/l”.

11 figures, 5 tables.-- Supplementary information available., Biomass chemical looping gasification (BCLG) is a novel technology that enables the production of renewable syngas without the need for an external supply of energy or power while achieving negative carbon emissions. In this work, the behavior of a synthetic Cu-based (14 wt% CuO) oxygen carrier, Cu14Al_ICB, was tested for 45 h in a 1.5 kWth continuous unit using pine sawdust as fuel. The effect of the oxygen-to-fuel ratio (λ) and gasification temperature on syngas composition and gasification parameters, including fuel conversion, carbon capture, cold gas efficiency, and syngas yield, was studied. A decrease in the oxygen-to-fuel ratio increased molar flows of H2 and CO in the syngas, while an increase in gasification temperature mainly improved char gasification, also enhancing H2 and CO generation. High amounts of syngas with low CH4 molar flows (∼2.3 mol CH4/kg of dry biomass) were obtained under any conditions due to the catalytic effect of metallic copper on CH4 reforming reactions. Syngas yield values were achieved approximating those obtained with Ni-based solids. The oxygen carrier also had a very positive effect on tar removal, reaching tar concentration values similar to those obtained by operating under chemical looping combustion conditions. The attrition rate measured with this oxygen carrier was the lowest obtained to date for any oxygen carrier operating under BCLG conditions. In addition, the mechanical properties, reactivity, and oxygen transport capacity of the oxygen carrier were maintained throughout the campaign. Therefore, the Cu14Al_ICB oxygen carrier has proved to be an excellent material for the BCLG process., This work was supported by ENE2017-89473-R AEI/FEDER, UE, and the CO2SPLIT Project, Grant PID2020-113131RB-I00, funded by MICIN/AEI/10.13039/501100011033. I. Samprón thanks the Spanish Ministerio de Ciencia, Innovación y Universidades (MICIU) for the PRE2018-086217 predoctoral fellowship. A. Cabello is grateful for Grant IJC2019-038908-I funded by MICIN/AEI/10.13039/501100011033.

Induced seismicity is a limiting factor for the development of Enhanced Geothermal Systems (EGS). Its causal mechanisms are not fully understood, especially those of post-injection seismicity. To better understand the mechanisms that induced seismicity in the controversial case of the Basel EGS (Switzerland), we perform coupled hydro-mechanical simulation of the plastic response of a discrete pre-existing fault network built on the basis of the monitored seismicity. Simulation results show that the faults located in the vicinity of the injection well fail during injection mainly triggered by pore pressure buildup. Poroelastic stressing, which may be stabilizing or destabilizing depending on the fault orientation, reaches further than pressure diffusion, having a greater effect on distant faults. After injection stops, poroelastic stress relaxation leads to the immediate rupture of previously stabilized faults. Shear-slip stress transfer, which also contributes to post-injection reactivation of distant faults, is enhanced in faults with slip-induced friction weakening., A.B. and V.V. acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program through the Starting Grant GEoREST (www.georest.eu) under Grant agreement No. 801809. IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Grant CEX2018-000794-S funded by MCIN/AEI/ https://doi.org/10.13039/501100011033). This research has been carried out within the framework of the activities of the Spanish Government through the “Maria de Maeztu Centre of Excellence” accreditation to IMEDEA (CSIC-UIB) (CEX2021-001198).

Induced seismicity is a limiting factor in the widespread deployment of Enhanced Geothermal Systems (EGS). Induced seismicity occurs not only during injection, but also after the stop of injection, with the largest magnitude earthquakes usually occurring after the stop of injection at different scales of time (hours to months). The post-injection large magnitude seismicity is counterintuitive and is still not well understood. Multiple mechanisms have been identified as triggering induced seismicity in EGS systems. Pore pressure increase due to fluid injection is the most commonly accepted triggering mechanism to explain induced seismicity. Yet, coupled poromechanical effects and static stress transfer are also important mechanisms in the process of fault reactivation. We study the combination of these different mechanisms by simulating coupled hydromechanical processes of the Deep Heat Mining Project at Basel, Switzerland (2006), a well-known case of short-term post-injection large-magnitude seismicity. We apply the material characteristics and stress conditions of the site to a simplified 2-dimensional fault network that is based on the monitored seismic events. In our model, pore pressure has a dominant effect on the triggering of the seismicity in the vicinity of the injection well, but its effect decreases away from the well as static stress transfer and poroelastic stressing gain importance. Poroelastic stress can have a stabilizing effect when its direction is opposite to the fault slipping orientation; but an abrupt shut-in, and consequently a quick poroelastic relaxation, reactivates the fault soon after the shut-in. Later post-injection induced seismicity is partially due to the post-injection diffusion of the pore pressure, but is mainly induced by constant static stress redistribution from reactivations of the different faults of the domain. Understanding the processes inducing seismicity, and especially the post-injection large-magnitude seismicity, should enable developing better strategies of shut-in to mitigate the risks of post-injection large-magnitude seismic events.

Reservoir impoundment is usually accompanied by induced/triggered seismicity. The rise in the number of planned hydropower plants requires improving the understanding of the causes of this induced/triggered seismicity, which eventually could serve to propose mitigation measures to reduce the induced/triggered-seismicity risk. We investigate the case of reservoir-triggered seismicity at Nova Ponte, Brazil, where triggered seismicity started shortly after reservoir impoundment, with the maximum magnitude of M3.5 when reaching the highest water level on the dam, and followed by delayed seismicity, with the largest earthquake being a M4.0 about 4.5 years after impoundment. We have built a hydro-mechanical fully-coupled numerical model reproducing the T shape of the reservoir and including the three geological layers placed below the reservoir down to 10 km depth. Simulation results serve to identify the nodal plane, from the two nodal planes of the proposed focal mechanism, which nucleated the seismicity of the M3.5 earthquake: a vertical, E-W-oriented strike-slip fault with a reverse-displacement component. The initial seismicity was triggered by the undrained response of the subsurface to the loading of the reservoir. We also find that the delayed seismicity was triggered by pore pressure diffusion, bringing a critically oriented vertical fault to failure conditions. The vertical permeability to allow the pore pressure perturbation to reach the depth of the M4.0 earthquake, i.e., 3 km depth, in 4.5 years is 6.6·10-15 m2, two to three orders of magnitude higher than the expected permeability of the host rock, a low-permeability mica-schist. We contend that hydro-mechanical models are a useful tool to understand the triggering mechanisms of reservoir-triggered seismicity.

Coastal areas are more densely populated than inland areas and present faster rates of population increase and urbanization. This trend is expected to continue in the coming decades, and thus, the demand of natural resources in coastal areas, such as water and energy resources, increasing the pressure and impact on the environment, superposed to the effects of climate change. Currently, in Europe, the demand for heating in buildings and businesses outnumbers the demand for cooling. However, the latter is gradually catching up due to rising demand for air cooling or refrigeration for industry such as food, technological and medical supplies. The energy required to cool buildings in Europe is expected to increase by more than 70% by 2030, while energy used to heat buildings may decrease by 30% (UE, 2018). Low Temperature Geothermal Energy (LTGE) is most likely the green energy production method for heating and cooling with the highest potential to provide affordable and clean energy and meet the CO2-emissions reduction goals of the Green Deal. Despite advances on LTGE technologies, the efficiency of these systems remains inherently sensitive to changes in hydrodynamics and the media (e.g., changes in the groundwater thermal regime). Groundwater, on the other hand, is the world's largest freshwater resource, and it is especially important in coastal areas because interactions between aquifer systems and sea water may lead to salinization and resource loss. Because geothermal systems and coastal aquifers interact directly, specially at groundwater discharge areas, it is clear that a better understanding of the potential interactions of geothermal systems with current and prospective coastal aquifer processes is essential for their design and foreseeing potential environmental effects. To address these issues, we model variable-density groundwater coupled with heat transport to simulate the long-term evolution of groundwater salinity and aquifer thermal energy discharge. We find that the heating/cooling-induced water density variations affect the seawater intrusion. Understanding the behavior of the groundwater system is required to ensure sustainable water, energy, and coastal ecosystem management.

Nos encontramos en un estado de emergencia climática provocado por las actividades humanas. La emisión a la atmósfera de grandes cantidades de dióxido de carbono (CO₂) procedentes de la quema de combustibles fósiles (carbón, petróleo y gas) han producido un calentamiento de la superficie de la Tierra de unos 1,2 ℃ de media por encima del nivel preindustrial. Los impactos del calentamiento global ya se han manifestado en fenómenos meteorológicos extremos más intensos y frecuentes. Ante este panorama, las tecnologías de eliminación del carbono desempeñarán un papel indispensable en el camino a la descarbonización. La capacidad instalada actual de captura de CO₂ es de unas 40 megatoneladas (1 millón de toneladas) al año. Pero aún estamos peligrosamente lejos de cumplir los objetivos climáticos. La capacidad de captura y almacenamiento de CO₂ debe multiplicarse aproximadamente por 100 de aquí a 2050. Aunque las realidades económicas y políticas son determinantes, el temor a las fugas de CO₂ a la superficie ha provocado retrasos en la implementación generalizada de esta tecnología. Un miedo que, según nuestros estudios, no tiene por qué hacerse realidad., Iman Rahimzadeh Kivi recibe fondos del Ministerio de Ciencia e Innovación (Ref. PCI2021-122077-2B). Víctor Vilarrasa Riaño recibe fondos del Consejo de Investigación Europeo (ERC por sus siglas en inglés) (Ref. 801809) y del Ministerio de Ciencia e Innovación (Ref. PCI2021-122077-2B y Ref. CEX2021-001198).

12 figures, 3 tables.-- Supplementary information available., The use of bio-ethanol in chemical looping combustion (CLC) and reforming (CLR) has the potential to produce energy and/or hydrogen and, as a negative-emissions technology (NET), to remove CO2 from the atmosphere at low cost following the principles of bio-energy with CO2 capture and storage (BECCS). The determination of the rate of the chemical processes involving the fuel conversion with the oxygen carrier is required for the modelling and design of a chemical looping unit. In this work, a kinetic study of ethanol conversion is performed considering a NiO-based material as the oxygen carrier. Combined experiments in TGA and fixed bed were conducted. TGA tests confirmed that the oxygen carrier was reduced by a ethanol-containing gaseous stream at temperatures higher than 773 K. An apparent reaction kinetics for the NiO reduction with ethanol was determined, which might be used in simplified fuel reactor models. However, tests performed in a fixed bed revealed that products derived of the ethanol decomposition, such as CH4, CO, H2 were responsible for NiO reduction, instead of the direct reduction with ethanol. High temperature kinetics of processes involved in ethanol conversion, namely dehydration, dehydrogenation and decomposition, were determined. Both, non-catalytic and Ni-catalytic reactions were of relevance under chemical looping conditions. A reaction pathway was described to be used in detailed fuel reactor models of chemical looping units., This work was supported by Serviço Nacional de Aprendizagem Industrial, SENAI-DR/RN (Ref. 20194247).

7 figures, 6 tables., Biogas is a renewable fuel generated in the anaerobic digestion of organic material. The expansion of biogas as a bioenergy source in the next decades leads to find new ways for its energy exploitation such as the Chemical Looping technologies. In this work, a low-cost Fe-based residue was used as oxygen carrier in two processes with biogas, namely Chemical Looping Combustion (CLC) and Chemical Looping Reforming (CLR). CLC process is focused on the energy production with CO2 capture. CLC experiments showed higher methane combustion efficiency (∼86%) than those referred in literature with other low-cost Fe-based materials. CLR process is dedicated to the production of syngas or hydrogen without CO2 emissions. Ni- or Cu-based oxygen carrier had been successfully used in order to catalyse the methane reforming. Here, the Fe-based material was also used for CLR. The biogas composition facilitated dry reforming of biogas to obtain syngas. In the dry-CLR of biogas, it was possible to reach about 55% methane conversion with a yield to syngas of 1.3 mol (CO + H2)/mol CH4. A suitable management of the effluent gas is proposed to maximize CH4 conversion and syngas yield, which includes CO2 separation, H2 purification and CH4 recirculation. Both results confirm the potential of the energy use of biogas under these technologies and the promising results with the new oxygen carrier developed., This work was supported by Grant PID2020-113131RB-I00 funded by MICIN/AEI/10.13039/501100011033CO2SPLIT (CO2SPLIT project). [...]. A. Cabello also thanks the Grant IJC2019-038908_I funded by MCIN/AEI/10.13039/501100011033.

La transición energética es una necesidad urgente. Debemos acordar lugares de encuentro para poder discutir nuestras diferencias y trabajar juntos para construir un futuro sostenible

Geo-energies, such as geothermal energy, geologic carbon storage, and subsurface energy storage, will play a relevant role in reaching carbon neutrality and allowing net-carbon removal towards the midcentury. Geo-energies imply fluid injection into and/or production from the subsurface, which alter the initial effective stress state and may destabilize fractures and faults, thereby inducing seismicity. Understanding the processes that control induced seismicity is paramount to develop reliable forecasting tools to manage induced earthquakes and keep them below undesired levels. Accurately modeling the processes that occur during fracture/fault slip leading to induced seismicity is challenging because coupled thermo-hydro-mechanical-chemical (THMC) processes interact with each other: (1) fluid injection causes pore pressure buildup that changes total stress and deforms the rock, (2) deformation leads to permeability changes that affect pore pressure diffusion, (3) fluids reach the injection formation at a colder temperature than that of the rock, which cools down the vicinity of the well, causing changes in the fluid properties (density, viscosity, enthalpy, heat capacity) and cooling-induced stress reduction, (4) the injected fluids are not in chemical equilibrium with the host rock, leading to geochemical reactions of mineral dissolution/precipitation that may alter rock properties, in particular, the shear strength. In the framework of GEoREST (www.georest.eu), a Starting Grant from the European Research Council (ERC), we aim at developing forecasting tools for injection-induced seismicity by developing methodologies to efficiently simulate the coupled THMC processes that occur as a result of fluid injection, which allows us to improve the understanding of the mechanisms that trigger induced seismicity. To this end, we use the fully coupled finite element method software CODE_BRIGHT, which includes capabilities like friction following the Mohr-Coulomb failure criterion with strain weakening and dilatancy, enabling simulations of fracture/fault reactivation. Our investigations have already contributed to the understanding of the processes that induced the seismicity at the Enhanced Geothermal System (EGS) at Basel, Switzerland, at the Castor Underground Gas Storage, Spain, and the reservoir-induced seismicity at Nova Ponte, Brazil. To achieve scalability and speed up the calculations to eventually manage induced seismicity in real time, we intend to incorporate efficient state-of-the-art linear solvers, like HYPRE and PETSc, in CODE_BRIGHT.

Fluid injection in subsurface reservoirs often induces seismicity, which is a limiting factor in the deployment of geo-energies, as it is the case for Enhanced Geothermal Systems (EGS). EGS are commonly deep granitic reservoirs subject to hydraulic stimulation in order to enhance the fracture permeability and consequently the heat production. Injection-induced seismicity occurs also after the stop of injection, and in many cases the largest earthquakes occur after the shut-in. The counterintuitive post-injection large magnitude seismicity is still not well understood and its modelling is necessary to improve the understanding of the processes triggering the seismicity. Pressure-driven processes, as pore pressure increase and poroelastic stress/strain variations, have been identified as triggers of seismicity, together with stress interactions, thermal disparities and geomechanical interactions. We design a coupled hydro-mechanical 2D model of the well-known case of post-injection induced seismicity of Basel EGS (Deep Heat Mining Project at Basel, Switzerland, 2006). We use CODE_BRIGHT, a finite element method software able to perform monolithic coupled thermo-hydro-mechanical analysis in geological media. The faults respond to a Mohr-Coulomb failure criterion with strain weakening and dilatancy, which allow to simulate fault reactivation and its aperture variation. The model is able to reproduce the pressure and stress variations, and the consequent fault reactivations through the simulations. The Basel EGS has been well documented and its characteristics are available. We are able to reproduce the spatio-temporal induced seismicity. Yet, our current numerical method takes long computational time. To speed up simulations, we simplify the model geometry by grouping faults that yield similar static stress transfer, computed with the code Coulomb3, which solves an analytical solution to compute stress changes caused by fault slip. The combination of numerical with analytical solutions is an effective way of obtaining faster computing models. By simultaneously assimilating monitoring data in real-time with an efficient computing model would enable a better understanding of the fluid-injection effects on the stability of the reservoir, and potentially the mitigation of the induced seismicity.

Los autores del artículo apuestan por la celebración de la primera asamblea ciudadana sobre energía en España

10 figures, 6 tables.-- Supplementary information available., Alkaline metal-air batteries are unique systems for energy storage. These devices require a bifunctional catalyst in the positive electrode that must perform both the oxygen evolution and reduction reactions (OER and ORR, respectively). Generally, cobalt-based oxides are employed as air electrodes; however, cobalt is a critical raw material. Future battery devices will mandatorily need non-critical raw materials based on highly abundant metals. Here we investigate the feasibility of iron-doped manganese oxide in the form of nanowires (Fe-MONW) combined with carbon nanofibers. MnO2 is known for being active for the ORR, however its activity towards the OER is not yet fully understood. Carbon nanofibers (CNF) on the other hand, provide the necessary electrical conductivity to the catalytic system. Simple methods and economic materials are employed to synthesize the Fe-MONW/CNF composites. Our results show that there is a synergistic effect between CNF and MONW, especially for the ORR, which manifests in an increase in the number of exchanged electrons– from 2.9 to 3.5 – and a shift in the onset potential of 70 mV. Doping MONW with iron further enhances the catalytic activity, for both the ORR and OER. Fe ions generate defects in the manganese oxide structure, favoring the adsorption of oxygen and eventually enhancing the catalytic activity. Fe-doped-MONW shows onset potentials for OER comparable to the benchmark catalyst, IrO2. The improvement on the catalytic activity is particularly evident in terms of the reversibility gap, ΔE. ΔE is the difference between the potential when the current density is 10 mA cm−2 in OER and the half-wave potential for the ORR, being a fundamental parameter to assess the performance of metal-air batteries. The reversibility gap for the best catalyst, 5Fe-MONW/CNF, is ΔE = 922 mV (140 mV lower than non-doped MONW/CNF and between 160 and 320 mV lower than the individual components, MONW and CNF). Endurance tests show remarkable stability of the iron-doped MONW/CNF, with a stable potential and an even lower ΔE of 800 mV for ca. 20 h of operation (charge-discharge cycles at ± 10 mA cm−2)., The authors wish to acknowledge the grant PID2020-115848RB-C21 funded by MCIN/AEI/10.13039/501100011033. Authors also acknowledge Gobierno de Aragón (DGA) for the financial support to Grupo de Conversión de Combustibles (T06_20R). N. Villanueva-Martínez also acknowledges DGA for his pre-doctoral contract.

©2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, This study presents a vanadium redox flow battery model that considers the most important variables that have a crucial role in the performance of the system. A complete model divided in an electrochemical, thermal, hydraulic and voltage submodels is presented. The analytic analysis of the model is carried out to reduce the system order according to some conservation laws. Based on this analysis, a subsequent calibration of the model parameters is developed using real experimental data. The validation is performed comparing the real measured voltage and the one estimated with the model. To calibrate the model an algorithm based on the implementation of a particle swarm optimizer is used. Results obtained in both short and long-term operation are presented, in order to compare and validate if the model can be used for both state of charge and state of health estimation., This research has been developed within the CSIC Interdisciplinary Thematic Platform (PTI+) Transición Energética Sostenible+ (PTI- TRANSENER+) as part of the CSIC program for the Spanish Recovery, Transformation and Resilience Plan funded by the Recovery and Re- silience Facility of the European Union, established by the Regulation (EU) 2020/2094, the Spanish Ministry of Science and Innovation under projects MAFALDA (PID2021-126001OB-C31 and C32 funded by MCIN/AEI/10.13039/501100011033/ERDF, EU), and MASHED, Spain (TED2021-129927B-I00), and by the Spanish Ministry of Universities funded by the European Union - NextGenerationEU (2022UPC-MSC- 93823).

In recent years there has been vigorous debate whether asymptotic transverse macrodispersion exists in steady three-dimensional (3D) groundwater flows in the purely advective limit. This question is tied to the topology of 3D flow paths (termed the Lagrangian kinematics), specifically whether streamlines can undergo braiding motions or can wander freely in the transverse direction. In this study we determine which Darcy flows do admit asymptotic transverse macrodispersion for purely advective transport on the basis of the conductivity structure. We prove that porous media with smooth, locally isotropic hydraulic conductivity exhibit zero transverse macrodispersion under pure advection due to constraints on the Lagrangian kinematics of these flows, whereas either non-smooth or locally anisotropic conductivity fields can generate transverse macrodispersion. This has implications for upscaling locally isotropic porous media to the block scale as this can result in a locally anisotropic conductivity, leading to non-zero macrodispersion at the block scale that is spurious in that it does not arise for the fully resolved Darcy scale flow. We also show that conventional numerical methods for computation of particle trajectories do not explicitly preserve the kinematic constraints associated with locally isotropic Darcy flow, and propose a novel psuedo-symplectic method that preserves these constraints. These results provide insights into the mechanisms that govern transverse macrodispersion in groundwater flow, and unify seemingly contradictory results in the literature in a consistent framework. These insights call into question the ability of smooth, locally isotropic conductivity fields to represent flow and transport in real heterogeneous porous media., The authors thank the reviewers for their constructive feedback which has improved the manuscript. M.D. acknowledges the support of the Spanish Research Agency (https://doi.org/10.13039/501100011033), Spanish Ministry of Science and Innovation and European Regional Development Fund “A way of making Europe” through Grants CEX2018-000794-S and HydroPore PID2019-106887GB-C31. Open access publishing facilitated by RMIT University, as part of the Wiley - RMIT University agreement via the Council of Australian University Librarians.

4 figures, 2 tables., [EN] The use of concentrated solar energy to provide heat in the hydrothermal liquefaction is an attractive method to transform biomass into valuable products reducing the environmental impact. However, the coupling of both technologies requires further research. This work analyses the effect of solar fluctuations on the yields, and main characteristics of products obtained in a solar reactor with direct heating method. Results indicate that by direct heating in a solar furnace, at sustained reaction temperatures of 250 ºC, produced a bio-oil and char yield up 24 and 33%, respectively. The results are consistent with conventional heating systems, however direct heating results in higher temperature gradients between the frontal and nonirradiated walls (above 200 ºC), which results in an unstable system, especially at high heating rates and temperatures above 300 ºC, therefore, at the end of this work a modified solar reactor was proposed., [ES] El uso de energía solar concentrada para suministrar calor en el procesamiento hidrotermal de biomasa representa una alternativa atractiva para la transformación de biomasa en productos valiosos con menor impacto ambiental. Sin embargo, el acoplamiento de ambas tecnologías requiere más investigación en el tema. Este trabajo analiza el efecto de las variaciones en la irradiancia solar en los rendimientos y composición de los productos. Los principales resultados muestran rendimientos en el bioaceite y carbón de hasta 24 y 33%, respectivamente. Adicionalmente, se encontró que el tiempo de residencia entre 30-60 min favorece la formación superficial de una estructura porosa en el carbón. Los resultados obtenidos son consistentes con los sistemas de calentamiento convencional, sin embargo, el calentamiento directo del reactor solar genera grandes gradientes térmicos entre la pared frontal y la pared no irradiada (arriba de 200 ºC), lo que resulta en un sistema inestable, especialmente con rampas de calentamiento rápidas y temperaturas arriba de 300 ºC, por lo tanto, al final de este trabajo se propone un reactor mejorado., Authors would like to acknowledge J.J. Quiñones- Aguilar for the design of the modified solar reactor, and the financial support received from Fondo Sectorial CONACYT-SENER-Sustentabilidad Energética through Grant 207450, “Centro Mexicano de Innovación en Energía Solar (CeMIE-Sol)”, within strategic project No. 120 “Tecnología solar para obtención de productos con valor agregado mediante procesamiento hidrotermal” and DGAPA-PAPIITUNAM Project number IN107923: Licuefacción hidrotérmica solar de biomasa residual.

9 figures, 5 tables. Supplementary material available., Platinum group metal-free catalysts have been intensively investigated in the last decades as an alternative to platinum with the aim of lowering the cost of polymer electrolyte fuel cells. In particular, iron-nitrogen-carbon (Fe-N-C) has proved to be the most active towards the oxygen reduction reaction. For practical application, a hierarchical pore structure is required, with micropores favouring the creation of active sites and larger pores (meso- and macropores) facilitating the mass transport. In this work, carbon xerogels are investigated to hosting iron and nitrogen species obtained by a template-free method. The introduction of nitrogen in a one-step polymerization of urea with resorcinol and formaldehyde is investigated for the first time in this field by varying the relative content of reactants. The urea/resorcinol ratio greatly influences the pore structure of the Fe-N-C catalyst and the ORR electrocatalytic activity thereof. The ORR activity is favored for a balanced urea/resorcinol ratio where porosity is well developed and relatively high iron and nitrogen contents are incorporated to the carbon xerogel. In acid (0.5 M H2SO4), the onset potential is 0.82 V vs. RHE, with a number of exchanged electrons very close to 4 (i.e. full conversion to water) and low Tafel slope of 71 mV dec−1, for the most active catalyst of the series, possessing the best compromise of iron and nitrogen active sites. Fuel cell tests corroborate that the catalyst with the most developed porous structure shows the best performance., The authors wish to acknowledge the grant PID2020-115848RB-C21 funded by MCIN/AEI/10.13039/501100011033. Authors also acknowledge Gobierno de Aragón (DGA) for the financial support to Grupo de Conversión de Combustibles (T06_20R). L. Álvarez acknowledges also DGA for her pre-doctoral contract.

8 figures, 6 tables., This paper provides a simple methodology for the design of the air reactor of a chemical looping combustor to optimize its characteristics when it is employed connected to a turbo expander to produce power. The design process, given a certain objective (e.g., electric power) defines the reactor specifics, namely height and diameter, taking into account the following aspects: solids inventory of the air reactor; gas velocity; air reactor transport disengaging height (TDH); solids concentration profile along the reactor height, dense bed height; freeboard height; pressure drop depending on air reactor injectors design and configuration. The total air reactor height was about 9.5 m, while the diameter was about 1.8 m. The total inventory was about 10,880 kg; while the circulation rate in the air reactor was about 110 kg/s. The operating pressure and temperature were, respectively, 12 bar and 1200 °C. The average velocity of the gases inside the reactor was about 4 m/s. The fluidization regime resulted to be comprised between turbulent and fast fluidization. Further work must be directed into the estimate of the pressure drop of the reactor, which will affect the plant efficiency in a considerable way., This work has been funded by the GTCLC-NEG project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 101018756.

5 figures.-- Supplementary information available., Single atoms and nanoclusters of Fe, Ni, Co, Cu, and Mn are systematically designed and embedded in a well-defined C1N1-type material that has internal cavities of ≈0.6 nm based on four N atoms. These N atoms serve as perfect anchoring points for the nucleation of small nanoclusters of different metal natures through the creation of metal-nitrogen (TM-N4) bonds. After pyrolysis at 800 °C, TM@CNx-type structures are obtained, where TM is the transition metal and x < 1. Fe@CNx and Co@CNx are the most promising for oxygen reduction reaction and hydrogen evolution reaction, respectively, with a Pt-like performance, and Ni@CNx is the most active for oxygen evolution reaction (OER) with an EOER of 1.59 V versus RHE, far outperforming the commercial IrO2 (EOER = 1.72 V). This systematic and benchmarking study can serve as a basis for the future design of advanced multi-functional electrocatalysts by modulating and combining the metallic nature of nanoclusters and single atoms., ANR-15-IDEX-04-LUE and the TALiSMAN and TALiSMAN2 projects, financed by the European Regional Development Fund (ERDF), are gratefully acknowledged. J.Q.B. thanks the Ministerio de Universidades, the European Union, and the University of Alicante for the financial support (MARSALAS21-21). S.G.D. thanks the Ministerio de Universidades, the European Union, and the University of Oviedo for the financial support (MU-21-UP2021-030 30267158).

Numerous distinct clades of lichen-forming fungi have independently specialized as foliicolous colonists of living leaves in the humid tropics and subtropics. Because of technical difficulties, the anatomy of their minute crustose thalli has not been compared in detail. In the present study, we applied SEM-BSE imaging to sectioned blocks of embedded thalli representing six lecanoralean taxa of foliicolous lichen-forming fungi with unicellular green algal partners. We compared our observations with those obtained in a previous study of foliicolous Gomphillaceae (Ostropales), which utilize a similar type of algal partner. The upper surface of the thalli was a mostly continuous layer of mycobiont hyphae of typical diameter, unlike the largely acellular epilayer found previously in the foliicolous Gomphillaceae. Byssoloma leucoblepharum was exceptional in lacking a covering layer altogether. Thalli were essentially unstratified, with algal symbionts not confined to any distinct layer. Whereas the prothallus of foliicolous Gomphillaceae was derived from the overlying epilayer, in the lecanoralean taxa examined here the prothallus was derived from hyphae continuous with either the upper surface of the thallus or the lower surface, or both. This finding suggests that the prothallus of lichen forming fungi may represent structures of developmentally different origins in different taxa.

11 figures, 3 tables.-- Supplementary information available., Carbon nanostructures provide a unique platform for the synthesis of novel catalysts for biomass conversion. In this work, a set of graphene oxide (GO)-based materials (nanofibers (GONF), sheets of few-layers (FLGO), and quantum dots (GOQD)), differing structurally in morphology and size, was prepared from fishbone-carbon nanofibers (CNF) and their catalytic behavior was compared on the hydrolysis of amorphous cellulose under microwave (MW) radiation. First, the influence of the reaction temperature (135–180 ºC), holding time (0–120 min), catalyst morphology and cellulose/water ratio (0.25–2.0 wt%) was thoroughly screened and compared with conventional heating mode. The use of GO morphologies in concert with MW energy showed the potential to achieve similar kinetic profiles than previously reported sulfonated carbons (110 kJ/mol) but using considerably less amount of catalyst (cellulose-to-catalyst ratio 12-fold lower). Overall, the reactivity of the GO-catalyst was related to their degree of oxidation/exfoliation, decreasing as follows: GOQD > FLGO > GONF. Compared with conventional heating, MW-technology enabled higher loadings of cellulose (2.0 vs. 0.25 wt%) to be processed in a shorter time (20 min instead of 24 h), which is a landmark achievement toward process intensification., The authors are grateful for the financial support from the Spanish Ministry of Economy and Competitiveness (MINECO, Project ENE2017–83854-R) and the I+D+i project PID2020–115053RB-I00, funded by MCIN/ AEI/10.13039/501100011033. E.F. also thanks Ibercaja bank entity for a grant-in-aid for foreign research stays (CB 7/19). J.R. is grateful to the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva Incorporación (JdC-I) fellowship (Grant Number: IJC2018–037110-I) awarded. DT is grateful for the Juan de la Cierva Incorporación (JdC-I) fellowship (Grant Number: IJC2020–045553-I) funded by MCIN/AEI/ 10.13039/501100011033 and by “European Union NextGenerationEU/PRTR”.

[EN] Very small-sized shoots of the Mediterranean seagrass Posidonia oceanica, defined as “bonsai” shoots, were found in areas with most intense CO2 emissions and low pH associated with four vents systems off Panarea island (Aeolian Archipelago, Sicily, Southern Tyrrhenian Sea). Bonsai shoots were sampled in September 2021 and October 2022: Bottaro crater (8 m depth), Camp 7 (16 m and 21 m), Black Point (20 m) and Hot/Cold Points (10 m). They had 2–6 leaves, and adult-intermediate leaves were 5–21 cm long and 3.5–7 mm wide, with leaf shoot surface ranging 4.8 and 44.5 cm2, and shoot leaf biomass between 16 and 89 mg (d.w.). These values were all significantly lower (t-test p < 0.006–0.0001) than those measured in normal-sized shoots collected within the vents and in control sites not affected by gas emissions. Bonsai shoots had 86–89% lower leaf surface, and 61–75% lower leaf biomass than all normal-sized shoots measured. The sheath thickness of the bonsai shoots was very low (0.1–0.8 mm), and the temporal trend of sheath thickness along the rhizome (lepidochronology) showed an irregular pattern, without the clear cyclical seasonal variation typical of normal-sized shoots. The reasons of size reduction and lack of temporal cycle in lepidochronology are discussed in the light of plant acclimatization and the constraints imposed by the continuous exposure to the stressful conditions of seawater acidification and presence of phytotoxic gases (e.g. hydrogen sulfide) in the vents., We wish to thank the staff of the 5th and 6th School of scientific diving at Panarea (2021–2022) and the 2nd stage on Posidonia oceanica ecology at Salina (2022; founded by the Blue Marine Foundation), as well as the diving Amphibia coordinated by Andrea Fogliuzzi, for the support at sea and in the laboratory. Thanks to the ECCSEL NatLab Italy infrastructure of the OGS for the logistic support at Panarea. We wish to thank the anonymous reviewers, and the Editor B. van Tussenbroek, for the useful and constructive comments.

The REPRO-TDE test was performed at a depth of about 400 m in the ONKALO underground research facility in Finland. Synthetic groundwater containing radionuclide tracers [tritiated water tracer (HTO), 36Cl, 22Na, 133Ba, and 134Cs] was circulated for about 4 years in a packed-off interval of the injection borehole. Tracer activities were additionally monitored in two observation boreholes. The test was the subject of a modeling exercise by the SKB GroundWater Flow and Transport of Solutes Task Force. Eleven teams participated in the exercise, using different model concepts and approaches. Predictive model calculations were based on laboratory-based information concerning porosities, diffusion coefficients, and sorption partition coefficients. After the experimental results were made available, the teams were able to revise their models to reproduce the observations. General conclusions from these back-analysis calculations include the need for reduced effective diffusion coefficients for 36Cl compared to those applicable to HTO (anion exclusion), the need to implement weaker sorption for 22Na compared to results from laboratory batch sorption experiments, and the observation of large differences between the theoretical initial concentrations for the strongly sorbing 133Ba and 134Cs, and the first measured values a few hours after tracer injection. Different teams applied different concepts, concerning mainly the implementation of isotropic versus anisotropic diffusion, or the possible existence of borehole disturbed zones around the different boreholes. The role of microstructure was also addressed in two of the models., Funding was provided through the Task Force partner organizations participating in this modeling exercise (POSIVA OY, Finland; SKB, Sweden; SÚRAO, Czech Republic; KAERI, Republic of Korea; NUMO, Japan). JAEA’s modeling study was performed as a part of “The project for validating near-field assessment methodology in geological disposal system” funded by the Ministry of Economy, Trade and Industry of Japan (grant no. JPJ007597). The modeling studies by TUL, UJV, CTU, and PROGEO were performed as part of the Radioactive Waste Repository Authority (SÚRAO, Czech Republic) project, “Research support for the safety assessment of a deep geological repository.” IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S). The helpful comments on an early version of the paper by Kersti Nilsson, Johan Byegård, and Lasse Koskinen, and the constructive comments by the editorial office and by two anonymous reviewers are gratefully acknowledged.

[EN] Shallow Geothermal energy is theoretically available anywhere on the Earth’s surface and has the potential to play a key role in minimizing polluting emissions, making a significant contribution to the new economic model referred to as the green economy.

8 figures, 8 tables.-- Supplementary information available.-- © 2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, Co-firing of coal and biomass is a feasible pathway for low- or even negative-carbon transformation of power sector in countries that rely on coal. There are two main kinds of coal and biomass co-firing pathways: biomass gasification co-firing with pulverized coal (BGCPC) and biomass direct co-firing with pulverized coal (BDCPC). However, few attentions have been paid to the comparative study of techno-environmental assessments for the above two main technologies with or without carbon capture and storage (CCS). Here we present a comparative system evaluation framework based on chemical simulation and life cycle assessment (LCA) to compare the energy performances and environmental impacts of different biomass co-firing and CCS technology combinations. A new metric, global warming potential of per unit exergy efficiency loss (GWPUEL) is proposed to reveal the trade-off between greenhouse gas (GHG) emission abatement and exergy efficiency loss. Results show that BGCPC-CCS units of all capacities can achieve negative life-cycle GHG emissions under 25% co-firing ratio scenario, but only 1000 MW BDCPC-CCS units can achieve near-zero life-cycle GHG emissions. Though 300 MW units show the minimum carbon reduction potential among all the selected capacities, they can achieve the most promising GWPUEL benefits for their mild exergy efficiency loss after CCS retrofit. This indicator provides a comprehensive viewpoint to weigh the compromise between energy performance and environmental burdens of different bio-based and CCS technology combinations, further facilitating various decarbonization schemes of global power sector under the carbon neutrality target., This work was supported by the National Natural Science Foundation of China [No. 52076099, 42201315, and 72293601] and the Fundamental Research Funds for the Central Universities [HUST: YCJJ 202203014].