Biomass resources have the potential to become a viable renewable technology and play a key role within the future renewable energy paradigm. Since CO2 generated in bio-energy production is equal to ...the CO2 absorbed during the growth of the biomass, this renewable energy is a net zero emissions resource. Biomass gasification is a versatile method for transforming waste into energy in which biomass material is thermochemically converted within a reactor. Gasification's superior flexibility, including both in terms of biomass type and heat generation or energy production alternatives, is what stimulates biomass gasification scientific and industrial potential. Downdraft gasifiers seem to be well-suited for small-scale generation of heat along with energy, whereas fluidised bed and entrained flow gasifiers currently attain significant economies of scale for fuel production. The operation of gasifiers is influenced by several factors, including operational parameters, feedstock types, and reactor design. Modelling is a valuable tool for building a unit based on the results of model predictions with different operational parameters and feedstock in such scenarios. Once verified, a suitable model may be used to assess the sensitivity of a gasifier's performance to changes in various operational and design factors. Effective models may help designers to theorise and predict the impacts of a variety of characteristics without the need for further empirical observations, which can help in the design and implementation of this technology. This work provides an overview of gasification technologies and a succinct guidance to the modelling decisions and modelling strategies for biomass gasification to enable a successful biomass to fuel conversion. A technical description and critical analysis of thermodynamic, kinetic, computational fluid dynamic and data-driven approaches is provided, including crucial modelling considerations that have not been explored in earlier studies. The review aims to aid researchers in the field to select the appropriate approach and guide future work.
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•Different modelling approaches to biomass gasification are critically reviewed.•Different gasifier technologies are technically described.•Models are categorised into four main approaches.•Accurate gasification modelling remains a key technical challenge to enable optimisation and design of bio-derived syngas.
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•Development of highly efficient Ni-based catalysts supported on CeO2-Al2O3 for the reverse water-gas shift reaction (RWGS).•Understanding the opposite role of CrOx and FeOx as ...promoters in the reverse water-gas shift reaction.•FeOx remarkably boosted the performance of the Ni-based catalysts in the RWGS, including in extreme conditions.
In the context of Carbon Capture and Utilisation (CCU), the catalytic reduction of CO2 to CO via reverse water-gas shift (RWGS) reaction is a desirable route for CO2 valorisation. Herein, we have developed highly effective Ni-based catalysts for this reaction. Our study reveals that CeO2-Al2O3 is an excellent support for this process helping to achieve high degrees of CO2 conversions. Interestingly, FeOx and CrOx, which are well-known active components for the forward shift reaction, have opposite effects when used as promoters in the RWGS reaction. The use of iron remarkably boosts the activity, selectivity and stability of the Ni-based catalysts, while adding chromium results detrimental to the overall catalytic performance. In fact, the iron-doped material was tested under extreme conditions (in terms of space velocity) displaying fairly good activity/stability results. This indicates that this sort of catalysts could be potentially used to design compact RWGS reactors for flexible CO2 utilisation units.
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•Highly efficient Mo2C catalysts for CO2 conversion via RWGS•Cu as a promoter boost the CO2 conversion due to higher active sites concentration.•Cs is an excellent dopant to enhance ...CO selectivity, especially at low temperatures.•Electronic interactions and re-carburisation accounting for Cs positive effect•Robust catalysts for long term operations.
Mo2C is an effective catalyst for chemical CO2 upgrading via reverse water-gas shift (RWGS). In this work, we demonstrate that the activity and selectivity of this system can be boosted by the addition of promoters such as Cu and Cs. The addition of Cu incorporates extra active sites such as Cu+ and Cu° which are essential for the reaction. Cs is an underexplored dopant whose marked electropositive character generates electronic perturbations on the catalyst’s surface leading to enhanced catalytic performance. Also, the Cs-doped catalyst seems to be in-situ activated due to a re-carburization phenomenon which results in fairly stable catalysts for continuous operations. Overall, this work showcases a strategy to design highly efficient catalysts based on promoted β-Mo2C for CO2 recycling via RWGS.
This work showcases cost-effective elemental mercury capture strategy enabled by bamboo saw dust and bromine flame retardant (BFR) derived sorbent prepared by a novel hydrothermal-pyrolysis method. ...The hydrothermal treatment of bamboo and BFR blend was conducted in subcritical water resulting in a hydrothermal char. Subsequently, the hydrothermal char was pyrolyzed in nitrogen atmosphere leading to an improved pore architecture. The resulting biomaterials were proven highly effective for Hg removal. A thorough analysis of the physicochemical properties of the samples was conducted by means of BET, SEM, XRD, XPS and FT-IR. Key parameters such as bamboo/BFR ratio, hydrothermal temperatures and pyrolysis temperatures influence Hg0 removal capacity of our bio-sorbents. Overall, the optimal bamboo/BFR ratio, hydrothermal temperature and pyrolysis temperature are 2:1, 320 °C and 800 °C, respectively. Under these optimized conditions, a very promising elemental mercury removal efficiency of 99% is attained. The kinetics and mechanism of Hg0 removal are also proposed. The experimental data fit well with a pseudo-second-order model, indicating that Hg0 adsorption over sorbents was dominated by chemisorption. Our results indicate that the C–Br groups in sorbents provide active sites for oxidizing Hg0 into HgBr2.
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•Bamboo and BFR were used to prepare sorbents for Hg0 removal.•A novel hydrothermal-pyrolysis method was proposed.•The optimal preparation parameters were determined.•Hg0 adsorption over sorbents was dominated by chemisorption.•C-Br groups were dominated active sites for oxidizing Hg0 into HgBr2.
Understanding the viability of the RWGS from a thermodynamic and techno-economic angle opens new horizons within CO2 conversion technologies. Unfortunately, profitability studies of this technology ...are scarce in literature and mainly focused on overall conversion and selectivity trends with tangential remarks on energy demands and process costs. To address this research gap, herein we present a comprehensive techno-economic study of the RWGS reaction when coupling with Fischer-Tropsch synthesis is envisaged to produced fuels and chemicals using CO2 as building block. We showcase a remarkable impact of operating conditions in the final syngas product and both CAPEX and OPEX. From a capital investment perspective, optimal situations involve RWGS unit running at low temperatures and high pressures as evidenced by our results. However, from the running cost angle, operating at 4 bar is the most favorable alternative within the studied scenarios. Our findings showcase that, no matter the selected temperature the RWGS unit should be preferentially run at intermediate pressures. Ultimately, our work maps out multiple operating scenarios in terms of energy demand and process cost serving as guideline to set optimal reaction conditions to unlock the potential of the RWGS for chemical CO2 recycling.
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•Techno-economic study of the RWGS as CO2 conversion process.•Impact of methanation as competitive route to RWGS.•Analysis of multiples scenarios including energy demands and auxiliary equipment.•Technology comparison in terms of energy requirement, CAPEX and OPEX.
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•Economically viable catalysts for gas phase CO2 upgrading.•Ni promoted active phases supported on saponite clay as nature inspired catalysts.•Advantageous bimetallic Ni-Cu ...formulation to suppress methanation.•Remarkable selectivity for low temperature RWGS using Ni-Cu/Saponite.
Chemical CO2 upgrading via reverse water gas shift (RWGS) represents an interesting route for gas phase CO2 conversion. Herein, nature inspired clay-based catalysts are used to design highly effective materials, which could make this route viable for practical applications. Ni and transition metal promoted Ni saponite clays has been developed as highly effective catalysts for the RWGS. Saponite supported NiCu catalyst displayed a remarkable preference for the formation of CO over CH4 across the entire temperature range compared to the saponite supported NiCo and Ni catalysts. The NiCu sample is also highly stable maintaining ∼ 55% CO2 conversion and ∼ 80% selectivity for CO for long terms runs. Very importantly, when compared with reference catalysts our materials display significantly higher levels of CO2 conversion and CO selectivity. This confirmed the suitability of these catalysts to upgrade CO2-rich streams under continuous operation conditions.
•Profitability of novel route for biomethane – urea co-production from biogas.•The idea emerges to boost the profitability of biogas upgrading plants.•Four biogas plant sizes (100, 250, 500, and ...1000 m3/h) are analysed.•The results are compared for Spain, Italy, United Kingdom and Germany.•Our results reveal the importance of supporting policies for biomethane production.
In this paper we present a techno-economic analysis of a novel route for biomethane – urea co-production from biogas. The idea emerges as an alternative path for improving the profitability of biogas upgrading plants. The profitability of four different biogas plant sizes (100, 250, 500, and 1000 m3/h) in four European countries (Spain, Italy, United Kingdom and Germany) is studied under the current policy schemes for biomethane production of each country. Our study evidences that with the present policy schemes for biomethane production, only medium and large scale plants (500 and 1000 m3/h) in Italy would be profitable. The reason is the current strong support for biomethane production in Italy through feed-in tariffs subsidies. In this sense, we analysed the potential benefits of governmental incentives through bio-methane subsidies (feed-in tariffs and investment percentage). Feed-in tariffs proved to be a worthwhile solution for large plants. Indeed, profitability is reached under subsidies of 30–48 €/MWh. Overall, plants located in southern EU countries are more likely to reach profitability with lower subsidies. The potential of costs reduction (i.e. ammonia price) was also analysed, showing that cutting-down production costs is essential to reduce the amount of subsidies received. In summary, our study shows the challenge that European policies face in the path towards a bio-based economy using biogas upgrading as reference case.
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•Novel strategy for synergizing biogas upgrading & Power-to-Gas.•A profitability analysis of the alternative route is performed.•The profitability analysis evidences the need of ...subsidies.•The forecasted cost reduction for H2 production and CO2 methanation are examined.
This work presents a profitability analysis of a novel route to produce biomethane and synthetic natural gas through Power-to-Gas technology. Differently to traditional Power-to-Gas processes, the process configuration herein proposed allows to produce biomethane even if a source of hydrogen is not available. The novelties of this work are both the new process configuration and the comparison among results for several plant sizes (100, 250, 500, and 1000 m3/h) under two representative EU scenarios (Spain and Germany). The main finding of this work is that no profitable results can be obtained at the present natural gas prices, evidencing the need of incentives. Largest plant could reach profitability under reasonable subsidies (12–15 €/MWh). The forecasted cost reduction for H2 production and CO2 methanation are also analysed. The results show that subsidies are needed even in the most optimistic scenario. A corollary of this study is the current technological great challenge to develop low carbon routes which push forward the transition towards sustainable societies.
The conversion of biogas, mainly formed of CO2 and CH4, into high-value platform chemicals is increasing attention in a context of low-carbon societies. In this new paradigm, acetic acid (AA) is ...deemed as an interesting product for the chemical industry. Herein we present a fresh overview of the current manufacturing approaches, compared to potential low-carbon alternatives. The use of biogas as primary feedstock to produce acetic acid is an auspicious alternative, representing a step-ahead on carbon-neutral industrial processes. Within the spirit of a circular economy, we propose and analyse a new BIO-strategy with two noteworthy pathways to potentially lower the environmental impact. The generation of syngas via dry reforming (DRM) combined with CO2 utilisation offers a way to produce acetic acid in a two-step approach (BIO-Indirect route), replacing the conventional, petroleum-derived steam reforming process. The most recent advances on catalyst design and technology are discussed. On the other hand, the BIO-Direct route offers a ground-breaking, atom-efficient way to directly generate acetic acid from biogas. Nevertheless, due to thermodynamic restrictions, the use of plasma technology is needed to directly produce acetic acid. This very promising approach is still in an early stage. Particularly, progress in catalyst design is mandatory to enable low-carbon routes for acetic acid production.
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•Biogas conversion to acetic acid represents a circular economy route for chemicals manufacturing.•Two new BIO-strategies are proposed to obtain acetic acid from CO2 and CH4.•The implementation of plasma technology in dry reforming represents a step-ahead on carbon-neutral processes.•The state-of-the-art of lab-scale non-thermal plasma dry reforming to value-added products has been reviewed.
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•Advanced catalysts for Chemical CO2 recycling.•Opening the possibility to couple a RWGS unit with a syngas upgrading reactor.•Cu as an excellent promoter to improve the ...activity/selectivity of FeOx-based catalysts.•Remarkable RWGS activity at low medium-low temperatures with very high selectivity.
The RWGS reaction represents a direct approach for gas-phase CO2 upgrading. This work showcases the efficiency of Fe/CeO2-Al2O3 catalysts for this process, and the effect of selected transition metal promoters such as Cu, Ni and Mo. Our results demonstrated that both Ni and Cu remarkably improved the performance of the monometallic Fe-catalyst. The competition Reverse Water-Gas Shift (RWGS) reaction/CO2 methanation reaction was evident particularly for the Ni-catalyst, which displayed high selectivity to methane in the low-temperature range. Among the studied catalysts the Cu promoted sample represented the best choice, exhibiting the best activity/selectivity balance. In addition, the Cu-doped catalyst was very stable for long-term runs – an essential requisite for its implementation in flue gas upgrading units. This material can effectively catalyse the RWGS reaction at medium-low temperatures, providing the possibility to couple the RWGS reactor with a syngas conversion reaction. Such an integrated unit opens the horizons for a direct CO2 to fuels/chemicals approach.
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