Producing renewable hydrogen from biomass is essential for the transition to low-carbon energy systems and sustainable fuel production. Biomass-derived syngas streams from biorefineries are a promising hydrogen source, but their compositional variability and high fractions of CO2 and H2 significantly affect hydrogen production performance. Sorption-enhanced steam reforming (SESR) combines steam reforming with in situ CO2 capture using CaO-based sorbents, enhancing hydrogen production through process intensification. This work investigates autothermal SESR enabled by CO2-rich feed compositions and heat integration to improve energy efficiency. An Aspen Plus equilibrium model was used to evaluate the effects of syngas composition and operating conditions (steam-to-carbon = 2.5-6.5, CaO/C = 1.5-2.5) on hydrogen production and energy performance at 600 °C and 10 bar. CO-rich feeds improve H2 purity, CH4 conversion, CO2 capture efficiency, and cold gas efficiency (CGE) by promoting the water-gas shift reaction and methane reforming through reduced CO2 partial pressure. In contrast, CH4- and H2-rich feeds decrease H2 purity and methane conversion due to lower effective steam-to-methane ratios and equilibrium limitations. However, these compositions improve overall energy efficiency by reducing the external fuel required for sorbent regeneration. Increasing steam availability enhances performance up to a threshold beyond which Ca-(OH)2 formation becomes significant, which strongly penalizes efficiency due to additional regeneration energy demand. Under optimal conditions, hydrogen purities up to 99.2 vol %, CO2 capture efficiency of 98.8%, and a CGE of 81% are achieved. These results help define operating windows for autothermal SESR and support the design of flexible and energy-efficient hydrogen production systems.

Meeting global climate goals requires significant deployment of carbon capture technologies, particularly in bioenergy systems. Bio-CHP (Combined Heat and Power) systems, when combined with carbon capture and storage (CCS), have the potential to achieve negative emissions by permanently removing CO2 from the atmosphere. The BioNETzero project aims to advance next-generation oxy-combustion technologies for bio-CHP, addressing key challenges such as biomass feedstock variability, combustion efficiency, and CO2 capture. Through experimental testing, computational modeling, and regional showcase studies, the project will optimize bio-CHP systems to deliver low-emission, cost-effective, and scalable solutions. This paper outlines the BioNETzero project's approach to advancing decarbonized bio-CHP technologies, with a focus on the environmental, technical, and economic benefits of deploying these systems across Europe.

Traditional methods to develop biomass-based carbon adsorbents generally involve carbonization followed by chemical or physical activation. However, routes involving the hydrothermal treatment of biomass are receiving growing interest. In this work, two different strategies for the synthesis of sustainable CO2 adsorbents are compared, i.e., in situ ionic activation and hydrothermal treatment followed by activation with CO2. The latter is a green and simple procedure that does not require the addition of chemicals or acid-washing stages, and which leads to carbon adsorbents with relatively high CO2 adsorption capacity at low pressures, up to 0.64 mmol g−1 at 15 kPa and 50 °C, conditions relevant for postcombustion CO2 capture applications. On the other hand, in situ ionic activation can lead to carbon adsorbents with superior CO2 adsorption capacity in the aforementioned conditions, 0.78 mmol g−1, and with reduced cost and environmental impact compared to conventional chemical activation.

Pine cone leaves (PCL) and pine kernel shells (PKS), abundant by-products of the Spanish food industry, were selected as precursors for activated carbons (ACs) to adsorb CO2 selectively at industrial post-combustion capture conditions. The goal was to maximize the development of narrow microporosity in the final carbons to boost the CO2 adsorption capacity. We have designed kinetics and equilibrium of adsorption experiments with CO2/H2O/ N2 on a selected AC derived from PCL in a thermogravimetric analyzer (TGA) at 50 degrees C and three partial pressures of CO2 to prove the suitability to capture CO2 from industrial off-gases. When humid flue gas streams were tested, competitive adsorption of CO2 and H2O occurred; however, the difference in the uptake rates favored CO2 adsorption in the early stages. The joint CO2 + H2O uptake was around 2 mmol g-1 at 50 degrees C in humid conditions, where CO2 reached the equilibrium uptake at the corresponding partial pressure for 15 and 32 vol% CO2 in the feed stream. Moreover, the dynamic performance was addressed by cyclic adsorption-desorption experiments representing different industrial post-combustion capture scenarios in a lab-scale fixed-bed rig. The selected AC showed a stable performance in adsorption-regeneration cycles and very remarkable CO2 capture capacity under dry conditions (up to 1.08 mmol g-1 at 50 C for 30 vol% CO2). Kinetics analysis also supported the faster adsorption of CO2 under cement flue gas conditions.

The conventional synthesis of the Metal–Organic Framework (MOF) MIL-101(Cr)-SO3H employs hydrofluoric acid as the modulator, posing handling challenges due to its irritating, corrosive, and toxic nature, as well as its reactivity with glass and metals. This study aims to find a new hydrofluoric acid-free synthesis route for MIL-101(Cr)-SO3H, proposing acetic acid and nitric acid as modulator alternatives. Four MIL-101(Cr)-SO3H samples were prepared: one without any modulator and the other three using a similar volume of either hydrofluoric acid, acetic acid, or nitric acid as the modulator. The so-obtained mass yield ranked as follows: without any modulator (32.6%) > acetic acid (29.6%) > nitric acid (25.2%) >> hydrofluoric acid (2.2%), whereas the total pore volume and BET surface area followed the order: hydrofluoric acid (0.87 cm3 g−1, 1862 m2 g−1) > nitric acid (0.81 cm3 g−1, 1554 m2 g−1) > acetic acid (0.72 cm3 g−1, 1374 m2 g−1) > without any modulator (0.69 cm3 g−1, 1342 m2 g−1). Despite the superior texture parameters obtained using hydrofluoric acid, the low synthesis yield and associated risks make this route non-viable. Acetic or nitric acid-based synthesis offers a promising alternative with a drastically higher yield, safer handling, and reduced environmental impact. In an attempt to improve the textural properties of the hydrofluoric acid-free MOFs, a series of samples were produced with increasing amounts of acetic acid, achieving BET surface areas of up to 1504 m2 g−1 and pore volumes of up to 0.81 cm3 g−1.

Renewable clean H2 has a very promising potential for the decarbonization of energy systems. Sorption enhanced steam reforming (SESR) is a novel process that combines the steam reforming reaction and the simultaneous CO2 removal by a solid sorbent, such as CaO, which significantly enhances hydrogen generation, enabling high-purity H2 production. The CO2 sorption reaction (carbonation) is exothermic, but the sorbent regeneration by calcination is highly endothermic, which requires extra energy. Biogas is one of the available carbon-neutral renewable H2 production sources. It can be especially relevant for the energy integration of the SESR process since, due to the exothermic sorption reaction, the CO2 contained in the biogas provides extra heat to the system, which can help to balance the energy requirements of the process. This work studies different process configurations for the energy integration of the SESR process of biogas for high-purity renewable H2 production: (1) SESR with sorbent regeneration using a portion of the produced H2 (SESR +REG_H2), (2) SESR with sorbent regeneration using biogas (SESR+REG_BG), and (3) SESR with sorbent regeneration using biogas and adding a pressure swing adsorption (PSA) unit for hydrogen purification (SESR+REG_BG+PSA). When using biogas as fuel (Cases 2 and 3), these configurations were studied using air and oxy-fuel combustion atmospheres in the sorbent regeneration step, resulting in five case studies. A thermodynamic approach for process modeling can provide the optimal process operating conditions and configurations that maximize the energy efficiency of the process, which are the basis for subsequent optimization of the process at the practical level needed to scale up this technology. For this purpose, process simulations were performed using a steady-state plant model developed in Aspen Plus, incorporating a complex heat exchanger network (HEN) to optimize heat integration. A comprehensive parametric study assessed the effects of biogas composition, temperature, pressure, and steam to methane (S/CH4) ratio on the process performance represented by the selected key performance indicators, i.e., H2 purity, H2 yield, CH4 conversion, cold gas efficiency (CGE), net efficiency (NE), fuel consumption for the sorbent regeneration step, and CO2 capture efficiency. H2 with a purity of 98.5 vol % and a CGE of 75.7% with zero carbon emissions can be achieved. When adding a PSA unit, nearly 100% H2 purity and CO2 capture efficiency were achieved with a CGE of 77.3%. The use of oxy-fuel combustion during regeneration lowered the net efficiency of the process by 2.3% points (since it requires an air separation unit) but allowed the process to achieve negative carbon emissions.

Greenhouse Gases: Science and TechnologyVolume 13, Issue 2 p. 123-124 Editorial From the Spanish CO2 technology platform Covadonga Pevida, Covadonga Pevida [email protected] Instituto de Ciencia y Tecnología del Carbono (INCAR), CSIC, Oviedo, SpainSearch for more papers by this authorFernando Rubiera, Fernando Rubiera Instituto de Ciencia y Tecnología del Carbono (INCAR), CSIC, Oviedo, SpainSearch for more papers by this author Covadonga Pevida, Covadonga Pevida [email protected] Instituto de Ciencia y Tecnología del Carbono (INCAR), CSIC, Oviedo, SpainSearch for more papers by this authorFernando Rubiera, Fernando Rubiera Instituto de Ciencia y Tecnología del Carbono (INCAR), CSIC, Oviedo, SpainSearch for more papers by this author First published: 10 March 2023 https://doi.org/10.1002/ghg.2211Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume13, Issue2Special Issue: CCUS contributions from the Spanish CO2 Technology Platform Association (PTECO2)April 2023Pages 123-124 RelatedInformation

Anaerobic digestion plays a starring role in the development of a bioeconomy due to the practical advantages that gaseous fuels have over solid fuels (i [...]

Adsorption using bio-based adsorbents has been pointed out as an economical and environmentally benign technology for CO2 gas separation and storage. A bio-based adsorbent can be fabricated from low-cost worldwide available biomass feedstock and bio-wastes from different industries (e.g., dairy manure, forestry, agriculture). As a result, it is a carbon rich material of hydrophobic nature, activated to gain high porosity development, and requires mild regeneration conditions. However, large-scale deployment of bio-based adsorption processes remains challenging. Our group has been intensively developing biomass-based adsorbents in conjunction with the design of tailored CO2 adsorption-based cyclic processes for the envisioned application. Herein, key concepts on adsorption technology, biomass waste management, and different activation techniques for biomass-based adsorbent precursors are discussed. This review addresses the most relevant studies in the literature, from lab experimentation on a milligram scale (volumetric and gravimetric tests) to dynamic tests in bench or large-scale cyclic adsorption processes (i.e., pressure swing adsorption, temperature swing adsorption, vacuum swing adsorption). Therefore, the main target is to give a holistic view of the industrial applications where CO2 separations with these materials are more suitable. Finally, concluding remarks and future perspectives of bio-based adsorbents in carbon capture are presented. (c) 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

To achieve net zero carbon emissions from energy systems, biogas has become an attractive renewable resource for hydrogen production. The sorption enhanced steam reforming (SESR) process is proposed to produce high-purity hydrogen from biogas, enabled by combining the catalytic reforming reaction with the simultaneous CO2 removal by sorption in a single reactor. One of the most critical challenges in using biogas in conventional reforming processes is the presence of H2S since it may deactivate the reforming catalyst. Here we experimentally study the effect of the biogas H2S concentration on the H2 production by SESR, i.e., accounting for the presence of a CaO-based solid sorbent. This work was performed in a fixed-bed reactor using a Pd/Ni-Co hydrotalcite-like material (HT) catalyst and dolomite as CO2 sorbent. Biogas (60CH4/40CO2 vol.%) with different concentrations of H2S (150, 350, 500 and 1000 ppm) was evaluated. The catalyst did not deactivate for biogas H2S concentrations of 150 and 350 ppm during five cycles of the SESR process. However, a slight decrease in the catalyst activity was detected under higher sulfur concentrations after the third SESR cycle. Sulfur was detected in the spent catalyst and sorbent materials, with a higher proportion in the sorbent for the highest H2S concentration tested (1000 ppm). H2 yield decreased by 10.8 % and 4.5 % points for biogas H2S concentrations of 500 and 1000 ppm after five cycles, respectively, while H2 purity decreased by only 3 vol% and 2 vol% points, respectively.

The use of bio-waste for the production of bio-based adsorbents not only has intrinsic benefits to the environment but is also a route for its valorization. Based on the concept of a circular economy, this book chapter aims to provide an overview of present trends and future potential in the conversion of bio-waste into bio-based adsorbents with particular emphasis on its application to carbon dioxide capture. Bio-based adsorbents have recently gained considerable attention as benign and cost-effective materials for CO2 capture applications. These adsorbents can be produced from cheap and widely available biomass feedstocks and bio-wastes from different industries (e.g., dairy manure, forestry, and agricultural). As a result, a carbon-rich material of hydrophobic nature is obtained, which is activated to gain high porosity development, and it requires mild regeneration conditions. However, large-scale deployment of bio-based adsorption processes remains challenging.

H2 production by sorption enhanced steam reforming (SESR) of bio-oil/biogas blends was demonstrated in a fluidized bed reactor. It combines steam reforming (SR) with simultaneous CO2 capture by a solid sorbent. SESR was performed on a Pd/Ni-Co catalyst derived from a hydrotalcite-like material (HT) using dolomite as CO2 sorbent. Bio-oil from fast pyrolysis of biomass is a carbon-neutral and renewable energy source with great po-tential for clean H2 production by steam reforming processes. Biogas is also a promising renewable bio-based resource for hydrogen generation that can be used to increase the H2 production of a biomass-based plant. In turn, it could improve the energy efficiency of the process due to the exothermic reaction of the CO2 contained in biogas with the sorbent. Bio-oil composed of acetic acid and acetone (1/1 mol/mol) and biogas composed of CH4 and CO2 (60/40 vol%) were used as fuels. They were blended (50 wt% bio-oil + 50 wt% CH4) to study the SESR process. Effects of temperature, steam/C molar ratio, and pressure on the process performance were evaluated. SESR results showed an effective reforming of bio-oil/biogas blends and an enhancement in the H2 production and fuel conversion compared to conventional SR. Higher temperature and steam/C ratio, but lower pressure, favored H2 yield and purity. High H2 yield (87.1%) and H2 purity (98.6 vol%) were obtained at 625 degrees C and 2.5 bar (steam/C molar ratio three times higher than the stoichiometric value). The thermodynamic energy analysis of the SESR of bio-oil/biogas blends rendered 1.34% higher cold gas efficiency (CGE) than bio-oil SESR.

The main challenge of adsorption consists in the production of materials that can be used in real situations. This study comprehensively describes the CO2 and H2O adsorption behavior of honeycomb-shaped sorbents commonly used in rapid pressure swing adsorption cycles (RPSA). With this purpose, the kinetics and equilibrium of adsorption of CO2/H2O/N2 mixtures on three honeycomb carbon monoliths (793, 932, and AM03) were assessed in a thermogravimetric analyzer (TGA) under different postcombustion capture scenarios (temperature of 50 °C and several concentrations of CO2). The kinetics study exhibited that the single adsorption of CO2 and H2O can be adequately described by the Avrami and exponential decay-2 models, respectively. As expected, the three carbon monoliths presented fast adsorption of CO2 from a CO2/H2O mixture. Furthermore, when humid flue gas was considered, overall adsorption kinetics were governed by CO2. Besides, the experimental data fitting to the intraparticle diffusion model showed that gradual CO2 and H2O diffusion toward the micropores was the rate-limiting stage. The obtained results give a better insight into the selective adsorption of CO2 and the potential of honeycomb carbon monoliths to separate CO2 from humid flue gas in the context of the cement industry. Carbon monolith 793 is the best carbon monolith candidate to capture CO2 under the evaluated conditions: a capacity of adsorption of 1 mmol of CO2 g-1 and favorable kinetics in 32 vol % CO2 and 4 vol % H2O(v), at 50 °C and 101.3 kPa.

Pressure Swing Adsorption (PSA) is one of the implemented technologies for removing carbon dioxide in biogas streams. Different adsorbents, mostly zeolite-based, and process configurations have been patented and commercially demonstrated. In this study, we have developed a numerical model to successfully describe the dynamic performance of biomass-derived activated carbon in biogas purification. It is the first step in designing a biomass-based carbon capture unit within the bioenergy and circular economy context. Microporous activated carbon pellets prepared from pine sawdust by physical activation with CO2 was the adsorbent material choice. The model was built with the fittings of single-component adsorption isotherms of CO2 and CH4 at different temperatures to the Langmuir-Freundlich model and the Ideal Adsorbed Solution Theory (IAST) to account for multicomponent adsorption. The kinetics of mass transfer in the solid phase was described by the Linear Driving Force model (LDF). The dynamic simulations were performed with the aid of the commercial software Aspen Adsorption and experimental data previously obtained in the laboratory used for the model validation [1]. The model was applied to address the separation performance of a biogas upgrading biomass-based PSA process by running a parametric study to determine the influence of key performance parameters. The sensitivity analysis concluded that a single stage 4-step PSA can produce methane with a purity above 95% and a recovery of around 60% in a configuration with P/F ratios (quotients of molar flows of CH4 in the purge and the feed streams) between 0.67 and 1 for an adsorption pressure of 3 bar.

Many countries have assigned an indispensable role for carbon capture and storage (CCS) in their national climate change mitigation pathways. However, CCS deployment has stalled in most countries with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. If the Paris Agreement is to be met, then this progress must be replicated widely, including hydrocarbon-limited countries. In this study, we present a novel source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment and attract renewed public and political interest in viable deployment pathways. Here, we apply this methodology to Spain, where fifteen emission hubs from both the power and the hard-to-abate industrial sectors are identified as potential CO2 sources. A priority storage structure and two reserves for each hub are selected based on screening and ranking processes using a multi-criteria decision-making method. The priority source-to-sink clusters are identified indicating four potential development regions, with the North-Western and North-Eastern Spain recognised as priority regions due to resilience provided by different types of CO2 sources and geological structures. Up to 68.7 Mt CO2 per year, comprising around 21% of Spanish emissions can be connected to clusters linked to feasible storage. CCS, especially in the hard-to-abate sector, and in combination with other low-carbon energies (e.g., blue hydrogen and bioenergy), remains a significant and unavoidable contributor to the Paris Agreement’s mid-century net-zero target. This study shows that the hubs and clusters approach can facilitate CCS deployment in Spain and other hydrocarbon-limited countries.

Woody biomass pellets' demand for primary energy production is increasing. To guarantee sustainable and cost-efficient pellet production the diversification of biomass feedstock is mandatory. In this work it is proposed to re-use the solid biochar obtained from pyrolysis of eucalyptus (PEc) at 700 degrees C as an additive to produce enhanced pine sawdust (PIN) pellets. The process required the addition of glycerol as a lubricant in a percentage of 1 and 2 wt% per 5 and 10 wt% of pyrolyzed eucalyptus in the blend, respectively. Small additions of PEc enhanced PIN pellets' grindability and water-resistance, providing products with remarkable values of durability (up to 99%), net calorific value (up to 20 MJ/kg), energy density (up to 13.3 GJ/m3), and particle density (up to 1.24 g/cm3). N, S, chlorine, and heavy metals contents were also analyzed. The proposed pellets fulfill the A1/A2 and the I1/I2 quality classes for domestic and industrial wood pellets, respectively. A preliminary economic evaluation indicated that pellets made up from a mixture of 90% PIN and 10% PEc are competitive compared to raw PIN pellets, with expected savings in the costs of production, energy, transport, and construction of a storage site of 4, 13,10 and 7%, respectively. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Energy generation from non-hazardous waste streams, which are unfeasible to be reused or recycled, can help overcome some of the problems related to fossil fuel depletion, global increase in energy demand and waste generation management under restricted landfilling. One of the main drawbacks of waste-to-energy strategies is the poor combustion properties of waste, which densification could help to circumvent. This work studies the copelletization of refused derived fuel (RDF) and pine sawdust (PIN) in a continuous pilot pellet mill that resembles industrial pelletization. The effect of RDF contents up to 90 wt% on a set of parameters has been assessed: pelletization energy consumption, physical properties (durability, particle and bulk densities), net calorific value and energy density of the obtained pellets. In addition, slagging, fouling and corrosion, phenomena associated with combustion, were estimated from the ash composition. Results showed that obtaining pellets with a low RDF loading (2-9 wt%) was feasible. They accomplished ISO 17225-2 solid biofuels standard for industrial use, and presented low deposition and corrosion risks. On the other hand, pellets with 30-90 wt% RDF were also manufactured and complied with the UNE-EN 15359:2012 solid recovered-fuel standard for energy recovery in incineration and co-incineration plants. All the produced pellets presented durability and net calorific value above 96.9% and 10.7 MJ/kg, respectively. Energy density higher than 10.6 GJ/m3 was obtained for pellet formulations with RDF content up to 50 wt%. It was demonstrated that the blends of RDF and PIN can provide high-quality pellets with a high load of waste material, under the same operational conditions required for PIN pelletization. It is a versatile process that can be tailored to different product requirements depending on the enduse. It promotes energy recovery and generates value out of a waste fraction with no relevant use, adding economic and environmental benefits.