Simulated Biogas Research Articles

Effects of different gas energy shares on combustion and emission characteristics of compression ignition engine fueled with dual-fossil fuel and dual-biofuel

This study systematically investigates the energetic and environmental performance of a four-cylinder compression ignition (CI) engine fueled by gaseous and liquid dual-fuel (D-F), utilising various combinations of fossil fuels and biofuels. Fossil diesel or pure hydrotreated vegetable oil (HVO) – new generation biodiesel was used as the pilot fuel to initiate ignition of the gaseous fuel. The gaseous fuels used were natural gas (NG) and simulated biogas (BG) composed of 60 % NG and 40 % CO2 by volume, injected into the intake manifold at varying gas energy shares (GES) of 40 %, 60 %, and 80 %. Reference values were provided from conventional combustion of diesel fuel and HVO. This study used numerical simulations to examine indicators of combustion, such as ignition delay, premixed combustion phase, diffusion combustion phase, and subsequent combustion phases, across diverse fuel combinations. Within lean dual-fuel mixtures, when the gaseous fuel remained below the flammability threshold, the peak pressure was diminished, the rate of pressure rise was lowered, and the combustion process decelerated, facilitating a faster transition to the diffusion phase. As the engine load and GES increased, the excess air ratio decreased, bringing the air-fuel mixture closer to the flammability limit, which in turn altered the combustion characteristics and engine performance trends. Combustion with increasing BG content showed partial similarities to that of NG, though the high CO2 content in biogas was found to suppress combustion, functioning similarly to an exhaust gas recirculation. The study also compared brake thermal efficiency (BTE), as well as specific emissions of CO, HC, NOX, CO2, and smoke for the D-F engine operation against pure diesel and HVO at different loads and GES levels. Additionally, an overlimit function was used to assess the emission levels of D-F engines with reference to emission limits.

Pilot-Scale CO2 Separation from Simulated Biogas in a Loop Reactor Based on Hydrate Technology

Pilot-Scale CO₂ Separation from Simulated Biogas in a Loop Reactor Based on Hydrate Technology

Conversion of dry biogas in a chemical looping reforming unit: Performance of Fe and FeMn-based oxygen carriers

Biogas conversion is a renewable alternative for producing hydrogen. In this work, dry reforming of simulated biogas was performed in a 1 kWth continuous chemical looping reforming (CLR) unit in which the oxygen required for the partial oxidation of biogas to CO and H2 is supplied by an oxygen carrier. The performance of two different oxygen carriers (an iron oxide-based residue and a synthetic material based on an iron-manganese mixed oxide) was evaluated. The residue was capable of performing the dry reforming of biogas to a larger extent than the synthetic oxygen carrier. To enhance hydrogen yield, NiO addition was also considered with both materials. The presence of NiO increased methane conversion and H2 selectivity for both oxygen carriers. A value of approximately 2.6 mol H2/mol CH4 was achieved with both materials with the presence of only 2.7 wt% NiO in the bed.

Decarbonization of simulated biogas with microchannel mixer by pressurized water scrubbing

Pressurized water scrubbing is an environmentally friendly technology for the decarbonization of biogas. However, the key bottlenecks such as low efficiency, high cost of water consumption and secondary CO2 emission by water absorption and desorption in the process of decarbonization are still necessary to be solved. This study focused on improve the mass transfer effect by introduce finger-crossed microchannel in the process of simulated biogas decarbonization using pressurized water scrubbing. The simulated biogas was mixed with pressurized water in the finger-crossed microchannel, and the gas-water mixture was continuously separated in the gas-water separation tank. The effects of pressure (26–30 bar), temperature (5–30 °C), gas-water ratio (5:1–12:1), liquid volumetric flowrate (5–10 mL/min), and other factors on the decarbonization were investigated. The overall mass transfer coefficient based on the liquid phase and the CO2 flux were also calculated and analyzed. The decarbonization parameters were optimized using the response surface methodology as follows: temperature 20 °C, pressure 29/27 bar, gas-water ratio 10:1, liquid volumetric flowrate 5 mL/min. The process remained stable, achieving 98 % removal of CO2 under optimal conditions. Furthermore, the CO2 concentration in the purified gas was maintained below 3 %. Additionally, a significant number of micro-nano bubbles were observed in the absorption water obtained through this mixer, and the releasing of CO2 from the water lasted 5 days. These results indicated the excellent decarbonization performance of the finger-crossed microchannel in pressurized water scrubbing and potential application value of new ways of CO2 absorption water without desorption.

Paper‐structured catalyst with a dispersion of ceria‐based oxide support for improving the performance of an SOFC fed with simulated biogas

AbstractSolid oxide fuel cells (SOFCs) can accept a direct feed of biogas for power generation; however, carbon deposition is a major obstacle to their practical application. When a paper‐structured catalyst (PSC) with a dispersion of Ni‐loaded flowerlike Ce0.5Zr0.5O2 (Ni/CZ(F)) was applied to the anode of an electrolyte‐supported cell (ESC), the open‐circuit voltage of the cell directly fed simulated biogas was increased from 0.87 to 0.98 V at 750°C. The rates of cell‐voltage degradation and coke formation of the ESC with the Ni/CZ(F)‐PSC during 100 h of operation were 4.3% kh−1 and 0.43 mg‐C g‐PSC−1 h−1, respectively, which were lower than those of an ESC with a Ni‐loaded PSC without the CZ(F) dispersion (10.4% kh−1 and 8.1 mg‐C g‐PSC−1 h−1, respectively). This performance improvement is attributed to the unique porous morphology and high oxygen storage capacity of CZ(F), which can contribute to the prevention of Ni agglomeration and the removal of coke from the catalyst surface, respectively. Thus, the Ni/CZ(F)‐PSC can function as a practically applicable reforming domain for an internal‐reforming biogas‐fueled SOFC.

Efficiency and mechanism of phosphate adsorption and desorption of a novel Mg-loaded biochar material.

Phosphate removal is complicated by the need for resource recovery. Biochar shows promise for efficient phosphate adsorption, but it must be modified to enhance its adsorption capacity. In this work, magnesium (Mg)-loaded biochar was synthesized through a two-step dipping and calcination process, and the MgBC600 product was used to adsorb phosphate from simulated water and biogas slurry wastewater. The phosphate adsorption capacity of Mg-loaded biochar was 109.35mg/g, which was 12 times higher than that of unmodified biochar. The R2 of the Langmuir and pseudo-second-order kinetic models were 0.988 and 0.990, respectively, which fitted the phosphate adsorption process of MgBC600. Phosphate adsorption by MgBC600 was a spontaneous and endothermic process. The adsorption mechanism study showed that phosphate adsorption was controlled by the formation and electrostatic attraction of MgHPO4. In addition, 98% of chemically adsorbed phosphate was released after regeneration. Using phosphate-adsorbed MgBC600 as a soil amendment, Arabidopsis thaliana was 1.47 times higher than that in the biochar-only group, demonstrating that this is a promising strategy for enhancing phosphate adsorption efficiency and adsorbent recycling.

Study on combustion characteristics of fully premixed water-cooled biogas burner

Biogas is a renewable gas produced by the fermentation of biomass and is an environmentally friendly alternative to traditional fossil fuels. To overcome the problems of traditional biogas burner, such as unstable combustion, easy flameout and backfire, and low thermal intensity, a new water-cooled biogas burner based on fully premixed combustion technology was designed and developed. Then, numerical simulations and experimental investigations were conducted to explore the effects of CO2 content, excess air coefficient, heat load, and cooling water temperature on the combustion characteristics of the burner. The results revealed that the designed burner exhibited good adaptability to simulated biogas with methane concentrations ranging from 55 % to 80 %. Increasing CO2 content resulted in decreased combustion temperatures and reduced NOx and CO emissions concentration at the burner outlet. In addition, reducing the excess air coefficient enhanced the combustion heat intensity and reduced combustion heat loss. Nevertheless, excessively low excess air coefficients yielded elevated levels of NOx and CO in the flue gas. The results showed that the designed burner demonstrated stable operation at a minimum heat load of 35 %, exhibited a favorable load regulation ratio, and had low emissions. It is a promising solution for utilizing biogas as a clean and sustainable energy source.

Encapsulation of Methanotrophs within a Polymeric Matrix Containing Copper- and Iron-Based Nanoparticles to Enhance Methanol Production from a Simulated Biogas.

The production of renewable energy or biochemicals is gaining more attention to minimize the emissions of greenhouse gases such as methane (CH4) and carbon dioxide for sustainable development. In the present study, the influence of copper (Cu)- and iron (Fe)-based nanoparticles (NPs), such as Cu, Fe3O4, and CuFe2O4, was evaluated during the growth of methanotrophs for inoculum preparation and on the development of a polymeric-matrix-based encapsulation system to enhance methanol production from simulated biogas (CH4 and CO2). The use of simulated biogas feed and the presence of NP-derived inoculums produce a remarkable enhancement in methanol production up to 149% and 167% for Methyloferula stellata and Methylocystis bryophila free-cells-based bioconversion, respectively, compared with the use of pure CH4 as a control feed during the growth stage. Furthermore, these methanotrophs encapsulated within a polymeric matrix and NPs-based systems exhibited high methanol production of up to 156%, with a maximum methanol accumulation of 12.8 mmol/L over free cells. Furthermore, after encapsulation, the methanotrophs improved the stability of residual methanol production and retained up to 62.5-fold higher production potential than free cells under repeated batch reusability of 10 cycles. In the presence of CH4 vectors, methanol production by M. bryophila improved up to 16.4 mmol/L and retained 20% higher recycling stability for methanol production in paraffin oil. These findings suggest that Cu and Fe NPs can be beneficially employed with a polymeric matrix to encapsulate methanotrophs and improve methanol production.

La1.5Sr1.5Mn1.5Ni0.5O7 ±δ Vs La1.5Sr1.5Co1.5Ni0.5O7 ±δ: Exsolved Materials as Anodic Layers for Direct Biogas-Fueled SOFC

Currently, one of the main problems in commercial SOFC systems fueled directly with hydrocarbon compounds, such as biogas, is the high risk of blocking the active phase on the anode side (e.g. Ni-YSZ) due to carbon formation/deposition during the conversion of fuel into power energy. This issue causes a lowering in the overall performance and durability of the cell. Therefore, to overcome this deactivation mechanism, it was successfully demonstrated that an additional anodic active layer in commercial SOFC using materials based on exsoluted perovskites could be an interesting and viable alternative. This asseveration is based on the fact that using this kind of material is possible to get heterogeneous surface systems with highly stable and electrocatalytically active embedded nanoparticles uniformly distributed on the surface with a high carbon coking tolerance in a hydrocarbon fuel atmosphere.This study aimed to evaluate and compare the electrocatalytic behaviour of two new catalytic materials with Ni exsolution for direct dry biogas-fueled SOFC. The starting materials were Ruddlesden-Popper-type based on a nickel manganite (La1.5Sr1.5Mn1.5Ni0.5O7±δ or LSMN) and nickel cobaltite (La1.5Sr1.5Co1.5Ni0.5O7±δ or LSCN). Both materials have been synthesized by the Pechini method using stoichiometric amounts of precursors as nitrates. Once the respective gels have been formed, they were treated in the air at two dwell temperatures, 300°C for 2 h and 500°C for 3 h, to ensure the total elimination of the organic compounds. Finally, the resulting powders were treated in air at 1300°C for 12h and then, physicochemically characterized. For the electrochemical characterization, the as-treated powders were mixed individually with Gd0.1Ce0.9O2 (CGO) in a weight ratio of 70:30 using a ball milling for 6h. Finally, to get the slurry for the coating layer, each mixture (LSMN+CGO and LSCN+CGO) was ground for an additional 2h in the presence of 8 wt % of triethanolamine, 2 wt % polyvinyl butyral resin (BUTVAR B-98) and 2-propanol. Commercial button SOFC cells by InDEC® (anode-supported cell Ni-YSZ/YSZ/LSM) were painted on the anode side getting an active area of 2 cm2. The experiments were carried out at 800°C with pre-conditioning using diluted H2 and then, with simulated dry biogas. A Biologic tool was used as a device for the electrochemical measurements.The purpose of this communication is to present the results of experiments with two button cells derived from the same large area commercial cell (anode supporting cell) coated with the two electrocatalysts developed in this work. The electrochemical test carried out for more than 200 h demonstrated that this external functional layer on the anode side contributes to getting a stable potential within the whole working time at the selected galvanostatic conditions (500 mA cm−2). By comparing the results of these two tests, the exsolved LSCN layer showed better perfomances, because of the the B-site doped with Co instead of Mn which is responsible for an enhanced O2- transport within the crystal structures. Finally, post-reaction characterization revealed minimum/null carbonous species in both cases which suggests that the classical risks caused by the direct use of hydrocarbon fuels in commercial SOFC can be suppressed with this kind of approach which would lead us to think about the use of this type of materials in a next level or further electrochemical applications. Acknowledgements The authors acknowledge the project entitled "Direct utilisation of bio-fuels in solid oxide fuel cells for sustainable and decentralised electric power production and heat (DIRECTBIOPOWER)" Grant Agreement number: 2017FCFYHK.The authors acknowledge the Ministry of Ecological Transition of Italy (MiTE) for funding this research through the AdP "Piano Operativo di Ricerca (POR) sull'idrogeno verde Figure 1

Sustainable syngas production by oxy-steam reforming of simulated biogas over NiCe/MgAl hydrotalcite-derived catalysts: Role of support preparation methods on activity

Herein, a series of hydrotalcite-derived MgAl supports were prepared by co-precipitation and hydrothermal methods. NiCe/MgAl catalysts were prepared by loading Ni (10 wt%) and Ce (2.5 wt%) on supports using sequential incipient wetness impregnation and tested in oxy-steam reforming of simulated biogas to produce syngas. N2-physisorption, XRD, XPS, SEM, TEM, ICP-OES, TGA, and Raman were used for catalyst characterization. Reactivity was evaluated at 600 °C, 700 °C, and 800 °C with a constant GHSV (45,000 ml gcat−1 h−1) and feed ratio (CH4/CO2/O2/H2O = 1/0.67/0.1/0.3). The results demonstrate that increasing the co-precipitation aging temperature and the hydrothermal reaction temperature affected the surface area, pore volume, and Ni crystallite size. However, no significant change in reactivity was observed. The NiCe/MgAl catalyst with co-precipitation aging temperature of 140 °C (NCMA140-Co) exhibited lower carbon deposition probably due to higher Ce4+ concentration. Therefore, NCMA140-Co provided high stability and conversions of CH4 (94%) and CO2 (82%) with H2/CO ratio (1.6) at 800 °C without carbon deposition.

Methane and Carbon Dioxide Separation Characteristics of Quaternary Ammonium Salt Hydrates for Biogas Upgrading under Static Conditions of Gas–Solid Contact

This report describes the methane and carbon dioxide separation characteristics of stoichiometric quaternary ammonium salt (QAS) hydrates for gas–solid contact with simulated biogas (CH4, 0.613 mol fraction; CO2, 0.387 mol fraction). Tests for elucidating the separation characteristics were conducted using tetra-n-butylammonium fluoride (TBAF), tetra-n-butylammonium chloride (TBAC), and tetra-n-butylammonium bromide (TBAB) hydrates as solid phases. To ascertain system temperature and pressure effects on their gas separation performance, the tests were conducted at 253–293 K under the initial fed pressures of 3.0 and 0.9 MPa. The gas–solid contact between the simulated biogas with 0.387 mol fraction of CO2 and the QAS hydrates reduced CO2 in the gas phase to 0.26–0.37 mol fraction and enriched CO2 in the hydrate phases to 0.54–0.89 mol fraction. All QAS hydrates showed selective incorporation of carbon dioxide into the hydrate phase. Under all comparable conditions, TBAC hydrate exhibited the highest separation factor (15.2 ± 3.0 under initial pressure of 3.0 MPa at 253 K and 13.9 ± 2.5 under initial pressure of 0.9 MPa at 253 K), indicating that TBAC hydrate had the highest CO2 separation performance for biogas upgrading among the QAS hydrates we examined. At the same initial pressure, high gas separation performance was shown for low-temperature ranges. The separation factors of the QAS hydrates were maintained or improved by lowering the initial pressure at the same contact temperature, suggesting that the separation performance of the QAS hydrates, even at lower pressures, was nearly equal to or better than that achieved at higher pressures. The results contrasted against those reported for tetrahydrofuran hydrate, for which the separation factor decreases with lower initial pressure. The use of the QAS hydrates is expected to lower a system’s operating pressure without compromising separation performance.

Polyhydroxybutyrate Production from Methane and Carbon Dioxide by a Syntrophic Consortium of Methanotrophs with Oxygenic Photogranules without an External Oxygen Supply.

Here, a syntrophic process was developed to produce polyhydroxy-β-butyrate (PHB) from a gas stream containing CH4 and CO2 without an external oxygen supply using a combination of methanotrophs with the community of oxygenic photogranules (OPGs). The co-culture features of Methylomonas sp. DH-1 and Methylosinus trichosporium OB3b were evaluated under carbon-rich and carbon-lean conditions. The critical role of O2 in the syntrophy was confirmed through the sequencing of 16S rRNA gene fragments. Based on their carbon consumption rates and the adaptation to a poor environment, M. trichosporium OB3b with OPGs was selected for methane conversion and PHB production. Nitrogen limitation stimulated PHB accumulation in the methanotroph but hindered the growth of the syntrophic consortium. At 2.9 mM of the nitrogen source, 1.13 g/L of biomass and 83.0 mg/L of PHB could be obtained from simulated biogas. These results demonstrate that syntrophy has the potential to convert greenhouse gases into valuable products efficiently.

Longevity Demonstration of Methane to C2 via a Nonthermal Plasma Microreactor.

Hydrocarbon processing using plasmas has tremendous potential, yet there still exist many uncertainties pertaining to practical operation over long durations. Previously, it has been demonstrated that a nonthermal plasma operating in a DC glow regime can transform methane into C2 species (acetylene, ethylene, ethane) in a microreactor. Using a DC glow regime in a microchannel reactor allows for lower power consumption, at the expense of greater consequence of fouling. Since biogas can be a source of methane, a longevity study was undertaken to understand how the microreactor system would change over time with a feed mixture of simulated biogas (CO2, CH4) and air. Two different biogas mixtures were used, one of which contained 300 ppm H2S, while the other had no H2S. Potential difficulties observed from previous experiments included carbon deposition on the electrodes, which could interfere with the electrical characteristics of the plasma discharge as well as material deposition in the microchannel, which could affect gas flow. It was found that raising the temperature of the system to 120 °C helped prevent hydrocarbon deposition in the reactor. Purging the reactor periodically with dry air was also found to have positive effects as it removed carbon buildup on the electrodes themselves. Successful operation over a 50 h time period without any significant deterioration was demonstrated.

A Comprehensive Study of the Effects of Various Operating Parameters on a Biogas-Diesel Dual Fuel Engine

Alternative fuels are found to be the most promising solution to the problem of conventional IC engine pollution because their use curtails its huge emissions without exerting a negative impact on its performance. In this research, a conventional compression ignition engine is investigated by operating it with the combination of simulated biogas and neat diesel under a dual fuel mode of operations. The simulated biogas in the current work comprises different proportions of methane and carbon dioxide in the mixture. The full factorial approach in this work involved studying the effects of parameters such as biogas flow rate, composition, intake temperature, torque, and methane enrichment (complete removal of CO2 from biogas) on the engine performance, emissions, and combustion indices with an extensive number of experiments. It is witnessed from the research that biogas is capable of providing a maximum of 90% of the overall energy input, while the CI engine operates under dual fuel mode. Under the dual fuel mode of operation involving biogas, a significant amount of reductions are witnessed in secondary fuel consumption (67%), smoke (75%), and NOx (55%) emissions. At low flow rates, biogas is found to improve brake thermal efficiency (BTE), whereas it reduces hydrocarbon and carbon monoxide emissions. Methane enrichment resulted in more diesel substitution by 5.5% and diminishes CO and HC emissions by 5% and 16%, respectively. Increasing the intake temperature caused an increase in thermal efficiency (2%) and a reduction in diesel consumption (~35%), and it curtailed all emission elements except NOx.

A simple approach to make the commercial solid, oxide fuel cells flexible in the use of fuels – CK-3L05

In this paper, we propose a simple approach consisting in the use of a coating layer on a commercial SOFC in order to increase its fuel flexibility. Using the same CO2-laser-cut cell, we compared the I–V curves and impedance spectra (EIS) of four experiments. Three different ceramics (NiCu-CGO, NiFe-CGO, and NiCo-CGO) were evaluated as protective layers for cells fed with dry biogas or bioethanol, with the goal of determining which layer would be most promising. Electrochemical experiments revealed that an additional layer adds resistance to the cell, which negatively affects its performance. A slight decrease in maximum performance was observed when the coated cells were fed H2. However, power density was not significantly different from the bare cell at potentials between 0.7 and 0.8 V, which provide a trade-off between performance and voltage efficiency. Additionally, such an approach improved the effectiveness of cells in using simulated biogas and ethanol as demonstrated by I–V curves and EIS analysis. As shown in the test results, NiCo-CGO provided the highest power density of 0.56 W cm−2 at 0.6 V. However, all the cells with protective layers performed significantly better than the bare cell in the dry biofuel tests.

The influencing mechanism of O2, H2O, and CO2 on the H2S removal of food waste digestate-derived biochar with abundant minerals

Hydrogen sulfide (H2S) removal has been a significant concern in various industries. In this study, food waste digestate-derived biochar (DFW-BC), a by-product of food waste treatment with abundant minerals, was assessed for removing H2S from different simulated biogas containing oxygen (O2) and carbon dioxide (CO2) and under different moisture (H2O) contents (0% and 20%) of biochar. The influencing mechanisms of the gas conditions combined with the moisture contents were also investigated. The results showed an H2S removal of 1.75 mg g−1 for dry biochar under pure H2S, 4.29 mg g−1 for dry biochar under H2S + O2, 5.29 mg g−1 for humid biochar under H2S, and 12.50 mg g−1 for humid biochar under H2S + O2. For dry DFW-BC, the high Fe content was responsible for the O2 enhancement. In contrast, O2 + H2O activated the catalytic H2S oxidation of the less reactive minerals (mainly Ca). The inhibition of CO2 on H2S adsorption was not obvious for dry DFW-BC; the specific pore structure may have provided a buffer against the physisorption competition of CO2. However, when H2O was present on DFW-BC, the changes in critical biochar properties and sulfur speciation as opposed to that without H2O implied an evident occurrence of CO2 chemisorption. This CO2 chemisorption partially hindered O2 + H2O enhancement, decreasing the H2S removal capacity from 12.50 to 8.88 mg g−1. The negative effect was ascribed to mineral carbonation of CO2, neutralizing the alkaline surface and immobilizing metal oxides, which thus reduced the acceleration in H2S dissociation and activation in catalytic H2S oxidation by O2 + H2O.Graphical

Outstanding performance of a Cu-based oxygen carrier impregnated on alumina in chemical looping combustion

Chemical looping combustion (CLC) allows the combustion of a fuel with inherent CO2 capture by using an oxygen carrier to transfer the oxygen from the air to the fuel. Previously to the CLC scale-up, tests should be done in lab-scale CLC units to determine the combustion performance of promising oxygen carriers and, at the same time, to evaluate the durability of these materials. For that, the effect of operating conditions on the oxygen carrier ageing should be considered, which is often disregarded. In this work, tests were done burning a simulated biogas stream in a continuous 500 Wth CLC unit with a promising Cu-based oxygen carrier (Cu14Al_ICB). Operating conditions were carefully selected to maximize the durability of this oxygen carrier while complete CH4 combustion was achieved. These operating conditions were based on limiting both the variation of solids conversion by choosing suitable solids circulation rates and the oxidation degree of the particles in the air reactor by minimizing the air excess. Thus, the Cu14Al_ICB material exhibited an excellent mechanical resistance, estimating a particle lifetime of 20,000 h at 900 °C. In addition, copper migration to the surface of the particles and loss of copper were not relevant. This is the first time that under certain operating conditions, a Cu-based oxygen carrier can exhibit outstanding mechanical properties during continuous CLC operation at 900 °C.

Effect of Sn loading variation on the electrochemical performance of dry internal reforming of biogas in solid oxide fuel cells

Solid Oxide Fuel Cells (SOFC) operations at 750 °C by using direct-biogas fuel without pre-reforming or steam addition on undoped Ni/YSZ and tin-doped Ni/YSZ (Sn-Ni/YSZ) anodes with varied Sn loadings were tested. High CH4/CO2 ratio (2:1) was used as simulated biogas with the absence of steam. The average current density of the undoped Ni/YSZ cells at 0.7 V and 750 °C was approximately 150 mA/cm2, while that of Sn-Ni/YSZ cells produced 300–420 mA/cm2 depending on Sn/Ni dopant concentration. Repeated cell tests revealed that the SOFC electrochemical performance is very sensitive to the quantity of Sn doped into the Ni/YSZ anode even with dopant amount as low as 0.10 wt% Sn/Ni. The highest electrochemical performance in H2 and biogas was obtained from Sn-Ni/YSZ with 0.38 wt% Sn/Ni loading in the anode. The SEM micrographs of the tested anode surface showed no apparent sign of carbon deposition on the anode while small amount of carbon quantified on the SOFC tested cells with Temperature Programmed Oxidation (TPO). The successful operation of SOFC using biogas as fuel broadens the application of SOFC to directly produce electricity at places where biogas produced from anaerobic digestion of waste is available. However, due to the gradual degradation in the long durability test (150 h) shown in biogas there are further studies need to be carried out.

Solid oxide fuel cells (SOFCs) fed with biogas containing hydrogen chloride traces: Impact on direct internal reforming and electrochemical performance

This study is particularly aimed at investigating the influence of hydrogen chloride traces in biogas on direct internal reforming in solid oxide fuel cells (SOFCs). The experiments are performed with simulated biogas containing methane to carbon dioxide ratio of 3:2, the usual average proportion in biogas. To the best of our knowledge, there are no reported studies that investigated the effect of hydrogen chloride on direct internal reforming by clearly establishing the effect of reforming with outlet gas composition measurements. The experiments at SOFC operating temperature of 850 °C reveals no negative effect on reforming or cell performance, with 4, 8, and 12 ppm(v) of hydrogen chloride in biogas. At 800 °C, there is no visible performance degradation, but a negligible amount of methane (∼ 1%) is detected in the anode off gas. Both the reforming and electrochemical performance are marginally affected at 750 °C. Further, post-test analyses (FESEM-EDS, XRD) of the used SOFC reveals no damage to the cell at microstructure level or chlorine poisoning. All the experiments are performed in the context of utilizing the biogas generated from sewage treatment plants in an SOFC system. The reported level of chlorine traces in biogas generated from sewage sludge is < 10 ppm(v) and hence the limit set for experiments is at par with this value.

Dissolved CO2 profile in bio-succinic acid production from sugars-rich industrial waste

The inorganic carbon source (CO2) availability to the microorganisms has a key role in the succinic acid (SA) fermentation process. This study aims to investigate the behavior of the inorganic carbon source for SA production and underline the importance of CO2 in the fermentation process. The effect of pressure was investigated for CO2 availability and its overall impact on the fermentation process. Results obtained demonstrated a significant effect of pressure on yield, productivity and CO2 fixation rate. Industrial waste, rich in maltose, glucose, and sucrose, was used as feedstock combined with a gas mixture of CH4 and CO2, which simulated biogas composition. A final titer for succinic acid of 25.5 ± 2.4 g/L was detected at a headspace gas pressure of 1.4 atm. The yield raised from 0.48 g/g sugars to 0.64 and 0.65 g/g sugars when 1.4 and 1.6 atm pressure was applied, respectively. Overall, this study represents one of the first attempts to explore CO2 availability during succinic acid production, using biogas as a CO2 source and sugars-rich industrial waste as feedstock.