Solids Loading Rate Research Articles

(Invited) Streamlined Production of Protonic Ceramic Electrochemical Cells Via Ultrasonic Spray Coating

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. This presentation introduces ultrasonic spray coating technique (USC) for producing <10 µm thin electrolyte films, as well as uniform 4×4 cm2 oxygen electrode films, with a systematic process optimization considering solid loading rates, spray passes, and annealing temperature etc. Notably, the integrated approach highlights the versatility of USC in addressing both oxygen electrode and electrolyte fabrication challenges. The resulting protonic ceramic electrochemical cells, fabricated with these optimized parameters, exhibit remarkable electrochemical performance, structural integrity, and stability in both fuel cell and electrolysis modes. This presentation provides a holistic perspective on scalable production techniques, showcasing the potential of ultrasonic spray coating for advancing large-sized solid oxide electrochemical cells.

Biogas Production Potential of Mixed Banana and Pineapple Waste as Assessed by Long-Term Laboratory-Scale Anaerobic Digestion

Biogas is a renewable energy source generated through the anaerobic digestion (AD) of organic feedstocks. This study aims to quantify the biogas production potential (BPP) of fruit wastes via semi-continuous lab-scale mesophilic AD over a total of 100 days. The feed was composed of 80% banana peelings and 20% pineapple residues, mimicking the waste composition of a Costa Rican fruit processing facility used as a test case. The average loading rate of volatile suspended solids (VSS) corresponded to 3.6 kg VSS·m−3·d−1. Biogas yield and composition were monitored, along with the concentration of ammonium, volatile fatty acids, and pH. Discounting the start-up phase, the BPP averaged to 526 LN (kg VSS)−1 with a methane concentration of around 54%, suggesting suitability of the substrate for AD. We calculated that if upscaled to the Costa Rican test case facility, these values translate into a gross average heat and electricity production via AD of around 5100 MWhel·a−1 and 5100 MWhth·a−1, respectively. Deducting self-consumption of the AD treatment, this is equivalent to 73% of the facility’s electricity demand, and could save about 450,000 L of heavy oil per year for heat generation. To circumvent nitrogen shortage, the addition of a co-substrate such as dry manure seems advisable.

Microbiome assembly and stability during start-up of a full-scale, two-phase anaerobic digester fed cow manure and mixed organic feedstocks

Carbon transformations during anaerobic digestion are mediated by complex microbiomes, but their assembly is poorly understood, especially in full-scale digesters. Gene-centric metagenomics combining functional and taxonomic classification was performed for an on-farm digester during start-up. Cow manure and organic waste pre-treated in a hydrolysis tank were fed to the methane-producing digester and the volatile solids loading rate was slowly increased from 0 to 3.5 kg volatile solids m−3 d−1 over one year. The microbial community in the anaerobic digester exhibited a high ratio of archaea, which were dominated by hydrogenotrophic methanogens. Bacteria in the anaerobic digester had a high abundance of genes for ferredoxin cycling, H2 generation, and more metabolically complex fermentations than in the hydrolysis tank. In total, the results show that a functionally stable microbiome was achieved quickly during start-up and that the microbiome created in the low-pH hydrolysis tank did not persist in the downstream anaerobic digester.

Optimized yield of fermentable sugar from chemical hydrolysis of rice straw for application in ethanol fermentation

Lignocellulosic biomass is a rich source of carbohydrate polymers with cellulose and hemicellulose being the two primary carbohydrates made up of glucose and xylose monomers. These monomeric sugar molecules act as precursor molecules for ethanol production by the microbial fermentation process. Rice straw is a potent lignocellulosic feedstock for ethanol production, but its utilization on an industrial scale still faces significant challenges. The main obstacle lies in the chemical pretreatment process which needs to be designed optimally to enable a smooth supply of biomass-based fermentable sugar for ethanol businesses in a sustainable and cost-effective manner. The application of response surface curve analysis was made utilizing the Minitab software-based design of experiments which have demonstrated promising results in obtaining an optimized yield of fermentable sugar from the chemical hydrolysis of rice straw. The present study aimed to increase the fermentable sugar yield from chemical pretreatment of rice straw using Minitab computer software-based design of experiments. The optimal level of pretreatment variables was determined using Minitab 17 software-based analysis of the response surface curve to achieve a maximized release of fermentable sugar at 348.20 milligrams/gram of solid pretreated biomass. This study identified the corresponding optimum operating levels for each variable as (a) biomass solid loading rate (15% w/v), (b) H2SO4 concentration (12% v/v), (c) pretreatment reaction time (30 minutes) and (d) temperature (100°C).

Kraft lignin recovery from de-oiled Jatropha curcas seed by potassium hydroxide pretreatment and optimization using response surface methodology

The present study explores resource recovery from the de-oiled Jatropha curcas seed (DJS) using alkaline pretreatment. Potassium hydroxide (KOH) was utilized for the alkaline hydrolysis at a solid loading rate of 10 % w/v for the kraft lignin (KL) recovery. The process variables optimized were reaction time (6.36–73.63 min), temperature (85.68–156.3 °C), and KOH concentration (0.61–12.38 % w/w). Response surface methodology was used to optimize the process parameters. The maximum amount of KL recovered under optimal conditions was observed to be 89.6 %. The functional group changes in treated and untreated DJS were explored through Fourier transform infrared spectroscopy (FTIR) analysis. 1H NMR and FTIR techniques were employed to characterize recovered lignin. Nitrobenzene oxidation of the lignin was performed to understand the lignin monomer profile. The recovered lignin has an S/G ratio of 0.36. The pretreated DJS biomass can be subjected to enzymatic hydrolysis for enhanced sugar yield.

Optimization of liquid hot water pretreatment for extraction of nanocellulose crystal from South African waste corncobs

This study extracted nanocellulose crystals from South African waste corncobs via liquid hot water pretreatment and alkali treatment. The pretreatment process was designed and optimized using Central Composite Design (CCD) and Response Surface Methodology (RSM), respectively setting temperature (150–200 °C), time (10–60 min), and solid loading rate (3–10% w/w) as input variables. After pretreatment, the residue was treated with sodium hydroxide (2%wt) at 90 °C for 90 min. The extracted nanocellulose crystal was filtered, washed with deionized water, and dried in an oven. The characterization of the nanocellulose crystal was carried out based on standard procedures. The positive correlations between the input variables were observed, whereby a rise in the pretreatment conditions improved the nanocellulose crystal yield. Hence, the study obtained an optimum yield of 55.5% at 200 °C, 10% w/w, and 60 min. The surface morphology showed a more porous and rougher surface, and the crystallinity analysis indicated that run 7 had the most crystalline nanocellulose crystal with a crystallinity index of 57.3%. The study revealed that nanocellulose crystals could be extracted from corncobs via liquid hot water pretreatment and alkali treatment.

An Experimental Study on the Dilute Phase Pneumatic Conveying of Fat-Filled Milk Powders: Particle Breakage

Powder breakage during pneumatic conveying negatively affects the properties of dairy products and causes increased dusting, reduced wettability, and decreased product performance. In particular, particle breakage is a serious issue for fat-filled milk powder (FFMP) which, if it breaks, releases fat that causes odours and leads to sticky blocked pipes. In this work, a conveying rig (dilute phase, positive pressure) with 50 mm diameter food grade stainless steel pipes (1.5 m high and 5 m conveying distance with three 90° bends, two in the vertical plane and one in the horizontal plane) was built as the test system. The effects of operating conditions (conveying air velocity and solid loading rate) on the attrition of FFMP in a dilute phase conveying system were experimentally studied. Four quality characteristics were measured before and after conveying: bulk density, particle size distribution, wettability, and solubility, to access the influence of particle breakage. Conveying air speed shows a significant impact on powder breakage. As air speed increased, more breakage occurred, and the volume mean diameter D[4,3] decreased by around 50%, using the largest conveying air speed of 38 m/s. Bulk density increased accordingly whereas wettability decreased with an increase in air speed, resulting from the higher breakage rate. On other hand, improving the solid loading rate can further reduce the breakage level, but the positive effect is not as good as decreasing air speed.

Exploitation of indigenous bamboo macrophyte species and bamboo biochar for faecal sludge treatment with constructed wetland technology in the Sudano-Sahelian ecological zone

Treatment of faecal sludge (FS) has been a major challenge in most developing countries of Sub-Saharan Africa due to the difficulties in finding appropriate technology. Previous studies have however highlighted the potentials of the vertical flow constructed wetland for FS treatment, yet efforts in the identification of potential indigenous plant species as macrophyte for the Sudano-Sahelian ecological zone have been unsuccessful due to toxic levels of FS quality. This research studied the macrophyte potentials of indigenous bamboo species and bamboo biochar as a conditioner for FS treatment in a vertical flow constructed wetland (VFCW). Typical yard scale experiment consisting of filter media of sand supported at the base with gravels and planted with Bamboo shoots was used. Treatments were Bamboo Constructed Wetland (CW) and Faecal Sludge (FS) load only (CW-FS), Bamboo CW with a mixture of FS and Bamboo biochar (CW–BCH), unplanted drying bed with a mixture of FS and bamboo biochar (UDB-BCH) and an unplanted drying bed with FS (UDB-FS), and in triplicates. Control setup (CTR) consisted of Bamboo CW irrigated with wastewater. Morphological development (plant height, number of plants, number of leaves and culm diameter) of indigenous Bamboo species and reduction of faecal contaminants were monitored. Loading of FS was carried out in a single batch twice per week with a hydraulic loading rate of 56.47/mm/d with an annual Total Solid loading rate of 155.6 and 233.2 kg TS/m2/year for CW-FS and CW-BCH respectively. The bamboo species adapted to the complex wetland conditions, observed by a progressive increase in morphological development for all the treatments. Removal efficiencies of effluent quality parameters generally ranged from 70 to 99%, except for PO43−, TOC and TDS and indicator micro-organisms which were found below 50%. A strong positive linear relationship was determined among species growth parameter with coefficient (r) ranging between 0.83 – 0.99. Except for pH and TSS, all the effluent quality parameters exceeded the national allowable limits for safe discharge. Nonetheless, the study demonstrated positive potentials for adopting indigenous bamboo species as emergent macrophytes for FS treatment using VFCW. Further treatment to reduce contaminant levels in a second to a third series of a connected constructed is recommended wetland prior to reuse for agriculture.

The Impact of Preservation Techniques on Methane-Arrested Anaerobic Digestion of Nutrient-Rich Feedstocks.

The carboxylate platform is a promising biomass-to-energy pathway that uses methane-arrested anaerobic digestion (MAAD) to convert biomass to carboxylic acids, which can be chemically converted to industrial chemicals and liquid fuels. Lignocellulose is an energy-rich carbon source, but lacks nutrients necessary for microbial growth. Chicken manure (rural waste) and sewage sludge (urban waste) are rich in nitrogen and useful macronutrients; therefore, co-digesting these wastes with lignocellulose improves MAAD performance. However, waste nutrients must be digested immediately, or preserved. This study investigated the effects of various preservation techniques - frozen (fresh), air-dried, and baked - on chicken manure and sewage sludge. Batch experiments were performed with office paper (carbon source) and chicken manure or sewage sludge (nutrient source) with different methods of preservation. Fresh substrates produced higher acid yields and biomass conversion (the amount of biomass consumed during digestion) than dried substrates. Baked chicken manure showed reduced conversion and total acid production, which suggests that oven-drying reduces digestibility. From the batch data, the Continuum Particle Distribution Model (CPDM) predicted results of a four-stage countercurrent digestion. The data are displayed on maps showing the impact of liquid residence time (LRT) and volatile solids loading rate (VSLR) on conversion and product concentration. Co-digesting office paper and wet chicken manure at a non-acid volatile solid (NAVS) concentration of 300g/Lliq, the model predicted a high total acid concentration of 52.8g/L and conversion of 0.89g NAVSdigested/NAVSfed at a volatile solid loading rate of 4g/(Lliq·day) and liquid retention time of 35days.

Experimental Investigation of Segregation in the Dilute Phase Transport of Nonspherical Particles through a Pneumatic Conveying System

The current study aims to investigate the segregation in the dilute phase transport through a pneumatic conveying system. Different types of nonspherical particles such as ellipsoids (prolate and oblate), cube, and elongated needles are mixed with spherical particles to study the influence of non-sphericity. Experiments are performed to examine the effects of particle and system parameters such as particle size, particle shape, gas velocity, and solid loading rate on segregation. A unique decreasing segregation trend is observed for the shape of large particles as oblate > prolate > elongated needle and for the small nonspherical shape as small prolate > small cube. The particle acceleration (drag force per unit mass) is calculated by empirically measuring the average velocity for different particle types. The data shows a correlation between the observed segregation trend and relative particle acceleration for the various particles flowing through the pneumatic conveying system.

Valorizing prickly pear cladodes via methane-arrested anaerobic digestion for carboxylic acid production.

To address climate change, liquid biofuels are an essential alternative to fossil fuels, especially for transportation. The carboxylate platform uses methane-arrested anaerobic digestion (MAAD) to ferment biomass to carboxylic acids, which can be chemically converted to liquid fuels via the carboxylate platform. Most biomass sources require expensive pretreatments to remove lignin; however, prickly pear (Opuntia ficus-indica) cladodes have low lignin content and therefore do not require pretreatment. Furthermore, this sugar-rich feedstock is readily digested to high concentrations of carboxylic acids. At various substrate concentrations, batch MAAD of prickly pear cladodes yielded primarily acetic, butyric, and caproic acids. From these batch data, continuum particle distribution modeling (CPDM) simulated four-stage countercurrent digestion. At a non-acid volatile solid (NAVS) concentration of 100 g/Lliq , CPDM predicts a high total acid concentration of 93 g/L and conversion of 0.93 g NAVSdigested /NAVSfed at a volatile solid loading rate of 6g/(Lliq ·d) and liquid retention time of 35 days. Without chemical pretreatment, co-digestion, or in situ product removal, prickly pear produced high yields, biomass conversion, product concentration, and selectivity compared to previously studied lignocellulosic feedstocks.

Review on solid-state anaerobic digestion of lignocellulosic biomass and organic solid waste.

Sustainable management of organic solid wastes especially the municipal solid waste (MSW) is essential for the realization of various sustainable development goals (SDGs). Resource recovery centric waste processing technologies generate valorizable products to meet the operations and maintenance (O&M) costs while reducing the GHG emissions. Solid-state anaerobic digestion (SSAD) of organic solid wastes is a biomethanation process performed at a relatively higher total solids (TS) loading in the range of 10-45%. SSAD overcomes various limitations posed by conventional anaerobic slurry digesters such as higher degradable matter per unit volume of the bioreactor resulting in a smaller footprint, low freshwater consumption, low wastewater generation, simple upstream and downstream processes, relatively lower operation, and maintenance costs. This review elucidates the recent developments and critical assessment of different aspects of SSAD, such as bioreactor design, operational strategy, process performances, mass balance, microbial ecology, applications, and mathematical models. A critical assessment revealed that the operating scale of SSAD varies between 1000 and 100,000 ts/year at organic loading rate (OLR) of 2-15g volatile solids (VS)/L·day. The SSAD experiences process failures due to the formation of volatile fatty acids (VFAs), biogas pockets and clogging of the digestate outlet. Acclimatization of microbes accelerates the startup phase, steady-state performances, and the enrichment of syntrophic microbes with 10-50 times greater population of cellulolytic and xylanolytic microbes in thermophilic SSAD over mesophilic SSAD. Experimental limitations in the accurate determination of rate constants and the oversimplification of biochemical reactions result in an inaccurate prediction by the models.

Mainstream partial denitrification‐anammox in sand and expanded clay deep‐bed polishing filters under practical loading rates and backwashing conditions

AbstractThis study focused on evaluating the feasibility of expanded clay and sand as media types for mainstream partial denitrification‐anammox (PdNA) in deep‐bed single‐media polishing filters under nitrogen and solids loading rates as well as backwash conditions similar to conventional denitrification filters. The surface roughness and iron content of the expanded clay were hypothesized to allow for enhanced anammox retention, nitrogen removal rates, and runtimes. However, under the tested loading rates and backwash conditions, no clear benefit of expanded clay was observed compared with conventional sand. This study showed the feasibility of PdNA in filters with both sand and expanded clay with PdN efficiencies of 76% and 77%, PdNA rates of 840 and 843 g N/m3/d and TIN removal rates of 960 and 964 g N/m3/d, respectively. Glycerol demands were 1.5–1.6 g COD added per g TIN removed, thus indicating potential carbon savings up to 75% compared with conventional denitrification. Overall, this study showed for the first time PdNA filters performing at nitrogen removal rates double that of previous PdNA studies under realistic conditions while providing insights into the media choice and backwashing conditions. Future research on expanded clay backwash conditions is needed to provide its full potential in PdNA filters.Practitioner Points Hydraulic and TSS loading rates similar to conventional denitrification can be applied in PdNA filters. Conventional sand can be used when retrofitting conventional denitrification filters into PdNA filters. Carbon savings up to 75% can be achieved with glycerol when retrofitting conventional filters into PdNA filters

An evaluation of temporal changes in physicochemical properties of gully pot sediments

Diffuse pollution is recognised as a major challenge in achieving EU Water Framework Directive compliance, with urban runoff being a key pathway connecting various sources to receiving waters. Gully pots, as one of the ubiquitous urban drainage infrastructures, are placed at the inlets of piped drainage pipe network and actively drain runoff from urban catchment with suspended solids proportionally retained. The physiochemical properties of these retained solids reflect the activities within the catchment during the accumulation period. In this work, seven gully pots in two catchment types (highway and housing) in Luleå, Sweden were fully emptied and sediments analysed for total mass, particle size distribution and selected metal concentrations by six size fractions. The results of this sampling campaign are compared with the results of a 2005 study of the same gully pots to identify changes in the physicochemical properties of sediments over time and examine whether changes identified can be linked to changes in wider catchment management practices. The results highlight the potential impacts of winter road maintenance operations (e.g. up to a 15-fold higher solids loading rate in road catchment gully pots), reaching a normalised solids accumulation rate of 0.176–0.819 kg m2 year−1. An increase in tyre and road wear associated with winter road maintenance operations is also understood to contribute to the temporal increase of several metals including Cu, Zn, Co, Cr and V in the < 63-µm solids fraction in the road catchment gully pots. The concentrations of As and Pb decrease in all size fractions in both catchments, with the implementation of unleaded fuels (for Pb in housing catchment only), End-of-Life Vehicle Directive (Directive 2000/53/EC) (for Pb in both catchments), and strengthened industrial emission reduction measures suggested as possible drivers. The high contamination load for Zn, Cu, Cd and Pb in < 63-µm sediments from low-traffic housing catchment also emphasised the necessity of tracing and restricting non-traffic-related metal sources. Further seasonal monitoring of gully pot sediments is recommended to fully follow up the development of metals loading in both catchments.

Assessment of corn stover pretreated with shock and alkali using methane-arrested anaerobic digestion.

Corn stover, an underutilized agricultural residue, is a promising lignocellulosic feedstock for producing biofuels. To fully utilize it, pretreatment is needed. Typically, pretreatments are rapidly assessed using extracellular enzymes that release sugars from cellulose and hemicellulose. In contrast, this study uses methane-arrested anaerobic digestion (MAAD) to assess pretreatments. Although time consuming, MAAD is a more accurate assessment technique when lignocellulose is employed in the carboxylate platform, a promising approach that utilizes nearly all biomass components. Using recommended pretreatment conditions identified from a previous study, three corn stover pretreatments were compared using MAAD: (1) shock-only, (2) NaOH-only, and (3) shock + NaOH. Air-dried sewage sludge was used as nutrient source. At 100 g/L initial substrate concentration, compared to untreated corn stover, shock-only decreased conversion (amount of biomass digested) by 14%, NaOH-only increased conversion by 82%, and shock + NaOH increased conversion by 104%. Using batch MAAD data, the continuum particle distribution model simulated four-stage countercurrent fermentation. At an industrial non-acid volatile solids (NAVS) concentration of 300 g/Lliq , for both NaOH-only and shock + NaOH, the model predicts total carboxylic acid concentration of about 58 g/L and conversion of about 0.85 g NAVSdigested /g NAVSfed at liquid retention time of 35 days and volatile solid loading rate of 4g/(Lliq ⋅day). At this long solid residence time, shock is not necessary; however, with short solid residence times, shock acts synergistically to aid NaOH pretreatment. Shock treatment offers a way to reduce pretreatment costs without sacrificing pretreatment efficacy.

Combined effect of mild pretreatment and fungal fermentation on nutritional characteristics of canola meal and nutrient digestibility of processed canola meal in rainbow trout

The effects of mild pretreatment and fungal fermentation on the nutritional characteristics of hexane extracted canola meal (HECM) was examined. HECM is a by-product of canola oil extraction process and has restricted use in animal diets due to presence of high levels of antinutritional factors (ANFs) and limited digestibility resulting in low nutrient availability. In this study, HECM was washed with water at different solid loading rates (SLR) to remove soluble ANFs. The wash process removed significant amounts of soluble carbohydrate and glucosinolates from HECM, yielding a meal with higher levels of proteins and amino acids when compared to raw HECM. The digestibility test conducted on rainbow trout with the feed that had 30% of fish meal replaced with washed HECM showed slight improvement with no statistical significance in protein digestibility when compared to HECM. Fermentation of washed HECM and raw HECM with mono- and co-cultures of Aureobasidium pullulans, Neurospora crassa and Aspergillus niger resulted in higher protein and amino acid content when compared to the uninoculated controls. Additionally, different strains under mono- and co-culture fermentations exhibited varied reduction in the ANFs. Overall, these findings suggested that pretreatment with mild water washing and/or fermentation enhances the nutritional value of HECM.

Numerical simulation on the larger concentration difference characteristics of dense granular jet in a coaxial gas stream

AbstractThis work is devoted to the numerical study of particle dispersion prediction of gas–solid coaxial jet with a larger concentration difference. In pulverized coal gasifier, the pulverized coal is very dense at the nozzle outlet, and its volume fraction can reach 0.3. Then, it is dispersed rapidly under the action of high‐speed annular gas, and the particle volume fraction in the space is less than 0.002. In order to better predict the motion characteristics of a gas–solid jet with a high concentration gradient, the applicability of the three models is compared. The results show that the dense discrete phase model (DDPM) and Eulerian two‐fluid model (TFM) models considering particles collision can accurately predict the dense jet flow at low annular gas velocity. The DDPM and discrete phase model (DPM) show a good simulation for the dispersion characteristics of particles at high annular velocities where the particles' collision could be ignored. Therefore, DDPM has better adaptability for coaxial jet with large concentration gradient. The DDPM was used to predict the particle velocity and concentration for different annular gas velocities and different particle mass loads. It is found that particle flow is contracted first and then dispersed gradually under the action of airflow. The particle dispersion range increases with the increase of solid loading rate, and the corresponding radial distribution of particle velocity is greater.

Full-scale application of a down-flow hanging sponge reactor combined with a primary sedimentation basin for domestic sewage treatment.

The down-flow hanging sponge (DHS) reactor is advantageous for sewage treatment since it produces an effluent quality that complies with the standards for reuse and there is little excess sludge. A full-scale DHS module was efficiently employed for the treatment of domestic sewage (200 m3day-1) flowing from a primary sedimentation basin (PSB), which was used to reduce the suspended solids loading rate and enhance the oxidation of organics by heterotrophs. The combined PSB-DHS was successfully operated at a total hydraulic retention time of 3.4h (2.4h for PSB and 1.0h for DHS) for the relatively long period of 600days at sewage temperatures of 10°C to 32°C. The PSB-DHS consistently produced an effluent quality with minimum values of chemical oxygen demand, biochemical oxygen demand, and suspended solids of 59 ± 15, 12 ± 3.0, and 15 ± 7mg L-1, respectively. The proposed system performed exceptionally well at removing organics and particulate matter over a short hydraulic retention time.

Exploring the structural uniformity and integrity of protonic ceramic thin film electrolyte using wet powder spraying

Thin protonic ceramic electrolyte contributes to lower ohmic resistance and enhances electrochemical performance of protonic ceramic electrochemical cells. However, manufacturing of large-scale thin electrolyte remains a challenge. Wet powder spraying is an attractive technique to deposit <10 μm thin electrolyte when advanced atomizing techniques and optimized spraying process are integrated. Here ultrasonic atomization is integrated in the wet powder spray technique to reduce the thickness of electrolyte. Moreover, a parametric study is conducted to optimize the wet powder spray process to deposit uniform and crack-free electrolyte film. It is illustrated that tuning of solid loading rates and spray passes can affect the morphology of the as-sprayed electrolyte film, enabling the structural compactness of the sintered electrolyte layer. To maintain chemical stability of the electrolyte layer during sintering, effect of sintering temperature is further investigated to produce a physically thin, structurally dense, and chemically homogeneous electrolyte layer. The protonic ceramic electrochemical cells fabricated with optimized spraying and sintering parameters demonstrate excellent performance under both fuel cell and electrolysis modes. In addition, the cells exhibit remarkable structural integrity during redox and long-term stability tests. • A wet powder spraying technique was integrated into the manufacturing of protonic ceramic electrochemical cells. • Solid loading rates, spray passes, and sintering temperatures were explored and optimized. • PCECs with a 7-μm thick BZCYYb electrolyte were successfully fabricated and demonstrated good structural uniformity and electrochemcial performance.

Bioethanol from autoclaved municipal solid waste: Assessment of environmental and financial viability under policy contexts

Globally, 2.01 billion tonnes of municipal solid waste (MSW) were generated in 2016, about 37% of which was disposed of into landfills. This study evaluates the environmental and financial viability of producing ethanol from autoclaved MSW via fermentation. Experimental screening of four different microorganisms (i.e., S. cerevisiae, Z. mobilis, E. coli, and S. pombe) and process modelling indicate that MSW-derived ethanol can significantly reduce greenhouse gas emissions relative to gasoline (84% reduction following EU Renewable Energy Directive accounting methodology, and by 156–231% reduction following the US Energy Independence and Security Act methodology). Utilisation of wastes for biofuel production in the UK benefits from policy support and financial support for renewable fuels (Renewable Transport Fuel Certificates). Financial analysis highlights that microorganisms achieving higher ethanol yield and productivity (S. cerevisiae and Z. mobilis) can achieve financial viability with higher cumulative net present value than E. coli, S. pombe. However, the positive net present value can be achieved primarily due to the benefit of gate fees received by diverting wastes to autoclave and ethanol production (64% of total revenues), rather than from revenues from ethanol sales (7% of total revenues). Key process improvements must be achieved to improve the financial viability of ethanol production from MSW and deliver a clear advantage over waste incineration, specifically improving hydrolysis yield, reducing enzyme loading rate and, to a lesser extent, increasing solid loading rate. The results provide significant insights into the role of policy and technology development to achieve viable waste-to-biofuel systems.