Preliminary Techno-economic Analysis Research Articles

Membrane-Free Electrocatalytic Co-Conversions of PBS Waste Plastics and Maleic Acid into High-PuritySuccinic Acid Solid.

Plastic pollution, an increasingly serious global problem, can be addressed through the full lifecycle management of plastics, including plastics recycling as one of the most promising approaches. System design, catalyst development, and product separation are the keys in improving the economics of electrocatalytic plastics recycling. Here, a membrane-free co-production system was devised to produce succinic acid (SA) at both anode and cathode respectively by the co-electrolysis of polybutylene succinate (PBS) waste plastics and biomass-derived maleic acid (MA) for the first time. To this end, Cr3+-Ni(OH)2 electrocatalyst featuring much enhanced 1,4-butanediol (BDO) oxidation reaction (BOR) activity has been synthesized and the role of doped Cr has been revealed as an "electron puller" to accelerate the rate-determining step (RDS) in the Ni2+/Ni3+ cycling. Impressively, an extra-high SA production rate of 3.02 g h-1 and ultra-high apparent Faraday efficiency towards SA (FEapparent=181.5%) have been obtained. A carbon dioxide-assisted sequential precipitation approach has been developed to produce high-purity SA and byproduct NaHCO3 solids. Preliminary techno-economic analysis demonstrates that the reported system is economically profitable and promising for future industrial applications.

Part-load analysis and preliminary annual simulation of a constant inventory supercritical CO2 power plant for waste heat recovery in cement industry

The present work investigates the part-load performance of a MW-scale sCO2 power plant designed as waste heat recovery unit for an existing cement plant located in Czech Republic, in the framework of the H2020 funded project CO2OLHEAT. The study first presents the selected power plant configuration and then focuses on the evaluation of its part-load operation due to variation of flue gas mass flow rate and temperature. The range of flue gas conditions at the outlet of the upstream process is retrieved from a preliminary statistical analysis of historical trends obtained through the cement plant monitoring. The numerical model developed for this study aims at providing realistic results thanks to the adoption of turbomachinery performance maps provided by the turbomachinery manufacturer of the project. Moreover, heat exchangers have been modelled through a discretized approach which has been validated against manufacturer data, while piping inventory and pressure losses have been assessed through a preliminary sizing that considers the actual distances to be covered in the cement plant. Performance decay is estimated for the whole range of flue gas conditions, reporting the most significant power cycle parameters, and identifying the main causes of efficiency loss. The part-load analysis is carried out considering a constant CO2 inventory, in order to reduce the system complexity and capital cost and simplify plant operation. Results show that the operation entails minor variation of the compressors operative points in the whole range of operating conditions of the cement plant, avoiding the risk of anti-surge bypass activation. Moreover, the plant is able to work close to the nominal thermodynamic cycle efficiency (20.5 %–23.0 %) for most of the year and benefits from part-load operation in terms of overall performance. In the last part of the work, a preliminary techno-economic analysis of the plant is also presented to highlight the potential advantages of sCO2 technology for waste heat recovery applications. The results of the part-load performance of the plant are combined with the flue gases data obtained from the preliminary statistical analysis and the cement plant historical monitoring. An annual electricity production equal to 13′909.7 MWh is obtained, corresponding to 6560 equivalent hours and a system capacity factor of 74.9 %. The investment cost of each CO2OLHEAT plant component is estimated by means of cost correlations obtained from literature and the non-discounted payback time is computed as a function of the electricity selling price. The results show that, even considering electricity prices before 2022, the payback time of the CO2OLHEAT plant is estimated to be lower than 8 years, justifying the industrial interest in the proposed technology.

Low-Temperature Wastewater Electrolysis for H2 and Clean Water Generation

Water electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (H2O → 2H+ + 2e- + ½O2, ∆H° = 275 kJ/mol H2, E° = −1.18 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$4/kg H2. Hence, we need to find alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.Wastewater electrolysis represents an alternative approach to generate H2 with renewable sources by electrochemically oxidizing organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, ∆H° = 53 kJ/mol, E° = −0.02 V,) which has up to 5 times lower energy requirement than water electrolysis. As opposed to water electrolysis that requires clean water streams, wastewater electrolysis uses readily available waste streams that need cleanup anyway to generate H2; hence, integrating a second application in addition to H2 generation.1-3 In this work, we compare the performance of heterogeneous electrocatalysts for the electrocatalytic oxidation (ECO) of organic molecules present in wastewater as well as electrocatalysts for the H2 evolution reaction (HER) at room temperature. ECO electrocatalysts were developed and tested using real wastewaters derived from several sources including the hydrothermal liquefaction (HTL) of food waste. We synthesized the ECO electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) with equimolar loadings and tested them as a function of half-cell potential. Our results show that both PGM- and BGM-based bimetallics improve the activity and stability compared to the baseline RuO2-based catalysts4-6. We performed a preliminary techno-economic analysis and showed that the levelized costs of using this technology to process the wastewater alone is equivalent to that of traditional wastewater processing. The sale of the produced H2 co-product will decrease the levelized processing cost below that of current wastewater processing. References Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Gutiérrez, O. Y.; Holladay, J. D., Performance of Base and Noble Metals for Electrocatalytic Hydrogenation of Bio-Oil-Derived Oxygenated Compounds. ACS Sustainable Chemistry & Engineering 2020, 8 (11), 4407-4418.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. Journal of Applied Electrochemistry 2021, 51 (1), 107-118.Lopez-Ruiz, J. A.; Andrews, E.; Akhade, S. A.; Lee, M.-S.; Koh, K.; Sanyal, U.; Yuk, S. F.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Glezakou, V.-A.; Rousseau, R.; Gutiérrez, O. Y.; Holladay, J. D., Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compounds. ACS Catalysis 2019, 9 (11), 9964-9972.Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Appl. Catal. B-Environ. 2022, 305, 121060.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Qiu, Y.; Lopez-Ruiz, J. A.; Sanyal, U.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt. Appl. Catal. B-Environ. 2020, 277, 119277. Figure 1

Cost-effective and modular CO2 capture to support decarbonisation for oil and gas, industrial and hard-to-abate sectors

Reducing emissions from the industrial and fossil fuel-based power sectors is crucial to achieving net zero emissions. These sectors contribute to ~60% of global carbon dioxide (CO2) emissions. However, there are several challenges that current CO2 capture technology faces. The use of coal in steel and cement industries produces flue gases with high CO2 content but also with nitrogen and sulfur oxides (NOx and SOx) as impurities. These impurities cause faster degradation of amine-based solvents in the current CO2 capture system. Additionally, capturing CO2 from flue gases from the hard-to-abate sector, such as steel plants, is complex as it is not easy to capture CO2 from multiple sources and different CO2 concentration flue gas streams. For cement and other kiln processes, limited availability of water/steam can add to the difficulty and cost of CO2 capture. CO2CRC’s HyCaps process, an efficient and compact hybrid of solvent absorption and membrane technology, overcomes some of these challenges. It takes advantage of the capture efficiency of the solvent system, controlled flow regime and high surface-to-volume ratio of membrane technology. The mode of interaction between gas and liquid in HyCaps limits solvent exposure to NOx and SOx, reducing solvent degradation. In HyCaps, as solvent is regenerated at a lower temperature, low-quality, low-cost waste heat can be effectively utilised to reduce operational expenditure. Successful trials at three different industrial setups and preliminary techno-economic analysis from test trial data show the HyCaps process has the potential to offer very competitive capture solutions for various industrial settings.

Renewable methyl acetate production from dimethyl ether carbonylation in a fluidized bed reactor

The carbonylation of bio-based dimethyl ether (DME) using ferrierite offers a renewable approach to methyl acetate (MA) production with a potential reduction in carbon emissions. This work showcases the feasibility of employing fluidized-bed reactors in this process, leveraging benefits such as effective solid mixing, uniform temperature distribution, and facile catalyst purge and makeup. Through parametric studies, the impact of operating conditions on the reaction kinetics and reactor hydrodynamics was elucidated. Both physical and chemical catalyst deactivation were found to be dependent on the fluidization regime. Numerical models based on experimental results enabled the prediction of reaction yield and selectivity in the process simulation and optimization. Preliminary techno-economic analysis (TEA) and life cycle assessment (LCA) showed the potential for a 40% reduction in production costs and an 8% reduction in the global warming potential compared to the fossil-based benchmark. Overall, this study highlights the operation simplicity, cost competitiveness, and environmental benefit of MA production from DME carbonylation in a fluidized-bed reactor, providing insights for process scale-up and feedstock sourcing.

A spectral splitting CPV/T hybrid system based on wave-selecting filter coated compound parabolic concentrator and linear Fresnel reflector concentrator

Efficient full-spectrum solar energy utilization shows great potential to improve solar energy conversion efficiency. In this paper, a spectral splitting concentrated photovoltaic/thermal hybrid system based on a wave-selecting filter-coated compound parabolic concentrator and linear Fresnel reflector mirror field is developed. Optical models to simulate the linear Fresnel reflector have been developed and validated. With the wave-selecting filter coated compound parabolic concentrator, the visible and near infrared spectra transmit onto the photovoltaic cells, while the rest are reflected to the receiver tube. Furthermore, a simplified receiver indoor test prototype is designed to investigate the characteristic of solar photovoltaic module with the spectral filter in the context of the compound parabolic concentrator. The measured I–V curves are compared with the modeled results. Additionally, the thermodynamic performance of the system is analyzed. Parametric studies are performed to investigate the effect of key design parameters including the mirror width, focal length and the radius of the receiver tube on the solar flux density and the exergy efficiency. An exergy efficiency of 35.51% and an optical efficiency of 94.78% are achieved. With a preliminary techno-economic analysis, the levelized cost of the electricity of the system is $0.209/kWh with a payback period of 10 years.

Techno-economic analysis and process optimization of a PET chemical recycling process based on Bayesian optimization

Chemical recycling has gained interest as a promising option to reduce the consumption of fossil feedstocks and relieve environmental issues concerning plastic waste. In this study, we present a preliminary techno-economic analysis of a process design for chemical recycling of polyethylene terephthalate (PET). A conceptual base case design was developed for a continuous catalytic PET depolymerization process. The process design was optimized to minimize total annualized cost (TAC) based on a simulation-based Bayesian optimization approach. A novel interface was utilized to manipulate the process variables, and to retrieve simulation and economic evaluation results. Through five trials of optimization, the process design was improved by about 4.2∼4.4 % in terms of TAC. Sensitivity analyses investigating the effect of process parameters and price variables on the minimum selling price of main product, p-xylene, are presented. The feedstock PET flake price was identified as the most critical factor affecting the economic viability of the process.

Hybrid osmotically assisted reverse osmosis and reverse osmosis (OARO-RO) process for minimal liquid discharge of high strength nitrogenous wastewater and enrichment of ammoniacal nitrogen

Ammoniacal nitrogen (NH4N) is a ubiquitous nitrogen pollutant found in wastewater, which could cause eutrophication and severe environmental stress. It is therefore necessary to manage NH4N by enrichment and recovery for potential reuse, as well as to regulate the amount of environmental discharge. Hybridization of membrane-based processes is an attractive option for further enhancing water and nutrient reclamation from waste streams; thus, in this present work, a hybrid osmotically assisted reverse osmosis (OARO) and reverse osmosis (RO) process was demonstrated for subsequent ammoniacal nitrogen enrichment and wastewater discharge management. Using a commercially-available cellulose triacetate membrane module, model and real wastewater containing approximately 4,000ppm NH4N were effectively dewatered and enriched to a final NH4N content of 40,300ppm. This corresponds to enrichment of around 10 times and approximately 90% pure water recovery. The effective combination of both processes resulted in high efficiency, as well as economical and energy-saving benefits, as shown by the process performance and our preliminary techno-economic analysis. The specific energy consumption of the hybrid process projected to operate at a capacity of 2,000 m3h−1 was determined to be 8.8kWh m−3, or 0.56kWh kg−1 NH4Cl removed/recovered for an initial feed solution containing around 15,300ppm NH4Cl. Hybrid OARO and RO operation was able to achieve satisfactory enrichment by the OARO process and obtaining clean water by the RO process. The hybrid OARO-RO process has shown great potential as a suitable end-stage membrane-based process for wastewater dewatering and NH4N enrichment and recovery toward a circular economy and environmental management, as well as clean water recovery.

Techno-economic analysis of an integrated bio- and hydrometallurgical process for base and precious metal recovery from waste printed circuit boards

Electronic waste (e-waste) is one of the fastest-growing waste streams and is often referred to as an urban mine due to its high base and precious metal content. Printed circuit boards (PCBs) have been the focus of numerous studies investigating bio- and hydrometallurgical pathways to extract and recover metals of value. This study evaluated the economic feasibility of an integrated bio- and hydrometallurgical process for extracting and recovering base and precious metals from PCBs. The process consisted of collecting and processing PCBs, extracting and recovering base metals using biogenic sulfuric acid and ferric iron, and extracting and recovering precious metals using hydrometallurgical pathways. A preliminary techno-economic analysis (TEA) was conducted to examine the potential costs of a plant that can process 1,000 tons per year of PCBs in Australia. The key factors that influence the economic feasibility were identified, and the effects of various factors, such as process efficiencies and market conditions, on the plant's profitability were evaluated. This assessment provided insight into the economic aspects of the process and assisted in identifying critical research pathways. Based on this analysis, the proposed process is profitable under optimised conditions and can address many challenges associated with e-waste processing in Australia.

Efficient solar hydrocarbon fuel production by integrating Fischer-Tropsch synthesis with high-temperature solid oxide co-electrolysis and electrolysis

Solar production of syngas from water and carbon dioxide followed by solar-driven Fischer-Tropsch synthesis is promising technology to produce syngas with zero carbon emission. A solar-driven integrated system by coupling solid oxide electrolysis cells with Fischer-Tropsch process is proposed for green hydrocarbons production. The proposed system is numerically modeled, developed and verified in this study. The effect of the solid oxide electrolysis cell temperature and current density on the system performance, especially the solar-to-fuels efficiency, is investigated parametrically. The results show that the solar-to-fuels efficiency increases with rise in the solid oxide electrolysis cell temperature. In addition, there is an optimum solar-to-fuels efficiency by varying current density. A maximum solar-to-fuels efficiency of 12.8% is obtained, which is more than 2.82% higher than the benchmark efficiency of solar hydrocarbons production system utilizing high-temperature co-electrolysis only. Moreover, a preliminary techno-economic analysis is performed to investigate the techno-economic feasibility of the proposed system. Based on the analysis, the levelized cost of the fuel for the proposed system is 1.944 Euro/kg. This study does not only verify the thermodynamic feasibility of the system but also provides a baseline for further optimization.

Low-Temperature Wastewater Electrolysis for H2 and Clean Water Generation

Water electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (H2O → 2H+ + 2e- + ½O2, ∆H° = 275 kJ/mol H2, E° = −1.18 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$5/kWh. Hence, we need to find alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.Wastewater electrolysis represents an alternative approach to generate H2 with renewable sources by electrochemically oxidizing organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, ∆H° = 53 kJ/mol, E° = −0.02 V,) which has up to 5 times lower energy requirement than water electrolysis. As opposed to water electrolysis that requires clean water streams, wastewater electrolysis uses readily available waste streams that need cleanup anyway to generate H2; hence, integrating a second application in addition to H2 generation.1-3 In this work, we compare the performance of heterogeneous electrocatalysts for the electrocatalytic oxidation (ECO) of organic molecules present in wastewater as well as electrocatalysts for the H2 evolution reaction (HER) at room temperature. ECO and HER electrocatalysts were developed and tested using real wastewaters derived from the hydrothermal liquefaction (HTL) of food waste. We synthesized the electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) with equimolar loadings and tested them as a function of potential. Our results show that while PGM-based electrocatalysts were required to perform ECO of HTL-derived wastewater4-6, BGM-based electrocatalysts were able to perform HER similarly to PGM electrocatalysts in HTL-derived wastewater. We performed a preliminary techno-economic analysis to outline a path towards $1/kg H2 via wastewater electrolysis and identified the next research and development areas. References Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Gutiérrez, O. Y.; Holladay, J. D., Performance of Base and Noble Metals for Electrocatalytic Hydrogenation of Bio-Oil-Derived Oxygenated Compounds. ACS Sustainable Chem. Eng. 2020, 8 (11), 4407-4418.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Lopez-Ruiz, J. A.; Andrews, E.; Akhade, S. A.; Lee, M.-S.; Koh, K.; Sanyal, U.; Yuk, S. F.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Glezakou, V.-A.; Rousseau, R.; Gutiérrez, O. Y.; Holladay, J. D., Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compounds. ACS Catalysis 2019, 9 (11), 9964-9972.Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Appl. Catal. B-Environ. 2022, 305, 121060.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Qiu, Y.; Lopez-Ruiz, J. A.; Sanyal, U.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt. Appl. Catal. B-Environ. 2020, 277, 119277. Figure 1

Enhancing Supercapacitive Swing Adsorption of CO2 with Advanced Activated Carbon Electrodes

AbstractGlobal warming due to anthropogenic CO2 emissions argues for the rapid development of efficient carbon capture technologies. Supercapacitive swing adsorption (SSA) is a gas separation technology that relies on the reversible charge and discharge of supercapacitor electrodes to absorb and desorb CO2 highly selectively and reversibly. However, thus far SSA only showed low sorption capacity, and slow sorption kinetics. Herein, it is shown that the sorption capacity can be substantially increased via the use of carbons with a higher specific capacitance. The highest gravimetric sorption capacity is measured with electrodes made from garlic‐roots derived activated carbon valuing 273 mmol kg−1 having a specific capacitance of 257 F g−1. In addition, the overall adsorption rate and productivity are improved. Cycling the electrodes for over 100 h showed highly reproducible, reversible CO2 adsorption and desorption behavior. A preliminary technoeconomic and sensitivity analysis is provided to demonstrate the potential of SSA for commercial applications.

Trash to treasure: electrocatalytic upcycling of polyethylene terephthalate (PET) microplastic to value-added products by Mn0.1Ni0.9Co2O4-δ RSFs spinel

Microplastic pollution has emerged as a pressing environmental issue of global concern due to its detrimental effects on the environment and ecology. Restricted to their characters of complex composition, it is a great challenge to propose a more cost-effective approach to achieve highly selective conversion of microplastic into add-value products. Here we demonstrate an upcycling strategy for converting PET microplastics into added-value chemicals (formate, terephthalic acid and K2SO4). PET is initially hydrolyzed in KOH solution to produce terephthalic acid and ethylene glycol, which is subsequently used as an electrolyte to produce formate at the anode. Meanwhile, the cathode undergoes hydrogen evolution reaction to produce H2. Preliminary techno-economic analysis suggests that this strategy has certain economic feasibility and a novel Mn0.1Ni0.9Co2O4-δ rod-shaped fiber (RSFs) catalyst we synthesized can achieve high Faradaic efficiency (> 95%) at 1.42 V vs. RHE with optimistic formate productivity. The high catalytic performance can be attributed to the doping of Mn changing the electronic structure and reducing the metal-oxygen covalency of NiCo2O4, reducing the lattice oxygen oxidation in spinel oxide OER electrocatalysts. This work not only put forward an electrocatalytic strategy for PET microplastic upcycling but also guides the design of electrocatalysts with excellent performance.

Scale-up and techno-economic analysis of microbial electrolysis cells for hydrogen production from wastewater

Microbial electrolysis cells (MECs) have demonstrated high-rate H2 production while concurrently treating wastewater, but the transition in scale from laboratory research to systems that can be practically applied has encountered challenges. It has been more than a decade since the first pilot-scale MEC was reported, and in recent years, many attempts have been made to overcome the barriers and move the technology to the market. This study provided a detailed analysis of MEC scale-up efforts and summarized the key factors that should be considered to further develop the technology. We compared the major scale-up configurations and systematically evaluated their performance from both technical and economic perspectives. We characterized how system scale-up impacts the key performance metrics such as volumetric current density and H2 production rate, and we proposed methods to evaluate and optimize system design and fabrication. In addition, preliminary techno-economic analysis indicates that MECs can be profitable in many different market scenarios with or without subsidies. We also provide perspectives on future development needed to transition MEC technology to the marketplace.

Electrocatalytic nitrate reduction to ammonia coupled with organic oxidation

Electrocatalytic nitrate reduction using renewable energy is a potential approach to environmental remediation and ammonia production, yet it is hindered by sluggish kinetics and poor efficiency. Herein, a well-defined carbon nanosheet array-supported cobalt phosphide (CoP; [email protected]) electrocatalyst is synthesized, achieving remarkable performance for nitrate reduction to ammonia with a Faraday efficiency of 95.1% at −0.30 V vs. reversible hydrogen electrode (RHE) and a yield rate of 43.9 mg h−1 cm−2 at −1.0 V vs. RHE. Moreover, an electrocatalytic nitrate reduction coupled with glycerol oxidation system is constructed, which delivers dramatically enhanced ammonia production (15.2 mg h−1 cm−2) and gains high value-added formate (111.4 mg h−1 cm−2) at 1.8 V cell voltage. Preliminary technoeconomic analysis confirms the economic feasibility of the coupled system. We also design a new CO2 capture strategy by using as-prepared ammonia as absorbent, which is promising for sustainable ammonia synthesis and its application.

A preliminary techno-economic analysis of photofermentative hydrogen production

Photofermentative hydrogen production promises sustainable energy using cheap feedstock and sunlight. While successful laboratory and pilot-scale photofermentative production studies are widespread, overall economic feasibility remains to be demonstrated. In this study, a preliminary techno-economic analysis of photofermentative production based on current technology was carried out, and the results were compared to alternatives such as photovoltaic electrolysis.Specific photofermentative hydrogen cost was estimated based on an existing outdoor, pilot-scale (20 L) photobioreactor system. The annual capital cost was calculated as 124 USD/year including equipment and land. Operating cost was calculated as 42 USD/year including maintenance, energy consumption and feedstock. The specific hydrogen production cost was found as 2.7 USD/mol (1362 USD/kg H2), and 395 USD/kg H2 when equipment cost is subsidized. Further analysis shows that utilization of wastewater as feedstock and a boost in hydrogen productivity could reduce specific cost of hydrogen to levels competitive with alternative technologies.

Single-stage waste oil conversion into biodiesel via sonication over bio-based bifunctional catalyst: Optimization, preliminary techno-economic and environmental analysis

To intensify biodiesel production, sonication and heterogeneous catalysis has received widespread focus from the research community. In this study, sonication was used for the single-stage biodiesel generation from waste oil catalyzed by KOH/corncob activated carbon. The results from response surface-based optimization showed 3 wt% catalyst loading, 5 min reaction time, and 18:1 methanol-to-oil molar ratio to be the optimal reaction conditions. The biodiesel yield was 88 % without the generation of soap, and it conforms to the standard ASTM criteria. The ultrasound-assisted heterogeneously catalyzed procedure was found to be favorable since it decreased the reaction time and eliminates saponification. Consequently, this combination enhances the overall biodiesel productivity, its economic viability, and environmental performance. Besides, the production cost, return on investment (ROI), and total emissions were $0.776 per liter of biodiesel, 334 %, and 0.08 kg CO2/kg of biodiesel, respectively.

Continuous recovery of phosphoric acid and Rare-Earths containing particles from phosphoric acid sludge using a decanter centrifuge

Recovery of rare earth elements (REEs) from various industrial and natural streams currently draws significant attention in efforts to meet the demands of the manufacturing industry. Among many industrial byproducts and waste streams, phosphoric acid sludge could be one of the most economically feasible resources for the recovery of REEs because solid particles in the sludge contain relatively concentrated REEs, up to 3,000 ppm, while the liquid component of the sludge is valuable phosphoric acid (P2O5) that can be recovered and returned to the main product. Due to high viscosity and large solids content (e.g., 30–40 %), however, this byproduct stream requires multistep separation and purification processes. In this study, a single-step process involving a continuous-flow decanter centrifuge (CFDC) was employed to investigate its feasibility for continuous solid/liquid separation from real phosphoric acid sludge. High centrifugal forces generated from up to 1500 G gravity acceleration separate solid particles from the sludge, generating a liquid-rich stream and a solids-rich stream at the exit of the CFDC. A single pass of phosphoric-acid sludge through the CFDC yielded 95 % liquid recovery and 90 % recovery of REEs-containing solids from 20 to 34 wt% solids-containing sludge. A reduced order model developed for the CFDC operation showed good agreement with experimental data, and preliminary technoeconomic analysis revealed potential process feasibility.

Insights on the acetic acid pretreatment of wheat straw: Changes induced in the biomass properties and benefits for the bio-oil production by pyrolysis

This work discloses how the pretreatment of wheat straw with acetic acid (AA) solutions modifies the biomass composition, strongly affecting the pyrolysis product distribution. AA in diluted solutions is a renewable and eco-friendly reagent, being also one of the main components of the pyrolysis bio-oil* (water-free basis). In comparison with water and diluted ammonia treatments, AA washing leads to a higher removal degree of alkali and alkaline-earth elements (AAEMs) from the biomass ash. In addition, the AA pretreatment reduces the content of char and gas precursors, as is the case of soluble lignin and extractives. Consequently, the bio-oil* yield is drastically increased up to ∼53 wt% during the pyrolysis of the AA washed wheat straw, being much higher than the value obtained for the raw biomass (∼35 wt%). Likewise, the bio-oil* composition is highly improved by the pretreatment with AA, dramatically increasing the concentration and yield of levoglucosan, which is a valuable precursor to produce both advanced biofuels and bio-based chemicals. In contrast, the opposite occurs during the pyrolysis of the extracted matter samples, recovered from the washing solutions, since its high content of AAEMs, lignin and extractives promotes the formation of char and gases in the detriment of the bio-oil fraction. Based on a preliminary techno-economic analysis, it is concluded that pretreatment with AA solutions may improve significantly the economic performance of the wheat straw pyrolysis process. This is due to the increased incomes coming from the higher yield of both bio-oil* and levoglucosan that largely compensate the additional capital and fresh AA costs.

High-current density alkaline electrolyzers: The role of Nafion binder content in the catalyst coatings and techno-economic analysis.

We report high-current density operating alkaline (water) electrolyzers (AELs) based on platinum on Vulcan (Pt/C) cathodes and stainless-steel anodes. By optimizing the binder (Nafion ionomer) and Pt mass loading (mPt) content in the catalysts coating at the cathode side, the AEL can operate at the following (current density, voltage, energy efficiency -based on the hydrogen higher heating value-) conditions (1.0A cm-2, 1.68 V, 87.8%) (2.0A cm-2, 1.85 V, 79.9%) (7.0A cm-2, 2.38 V, 62.3%). The optimal amount of binder content (25wt%) also ensures stable AEL performances, as proved through dedicated intermittent (ON-OFF) accelerated stress tests and continuous operation at 1A cm-2, for which a nearly zero average voltage increase rate was measured over 335h. The designed AELs can therefore reach proton-exchange membrane electrolyzer-like performance, without relying on the use of scarce anode catalysts, namely, iridium. Contrary to common opinions, our preliminary techno-economic analysis shows that the Pt/C cathode-enabled high-current density operation of single cell AELs can also reduce substantially the impact of capital expenditures (CAPEX) on the overall cost of the green hydrogen, leading CAPEX to operating expenses (OPEX) cost ratio <10% for single cell current densities ≥0.8A cm-2. Thus, we estimate a hydrogen production cost as low as $2.06 kgH2 -1 for a 30 years-lifetime 1MW-scale AEL plant using Pt/C cathodes with mPt of 150μg cm-2 and operating at single cell current densities of 0.6-0.8A cm-2. Thus, Pt/C cathodes enable the realization of AELs that can efficiently operate at high current densities, leading to low OPEX while even benefiting the CAPEX due to their superior plant compactness compared to traditional AELs.