Search Results (29)

The use of CH₄ and CO₂ as fuels in direct internal reforming solid oxide fuel cells (DIR-SOFCs) is a promising strategy for efficient power generation with reduced greenhouse gas emissions. In this study, Ni catalysts supported on Ce–Pr mixed oxides with varying Pr contents (0–80 mol%) were synthesized, calcined at 1200 °C, and tested for dry reforming of methane (DRM), aiming at their application as catalytic layers in SOFC anodes. Physicochemical characterization (XRD, TPR, TEM) showed that increasing Pr loading enhances catalyst reducibility and promotes the formation of the Pr₂NiO₄ phase, which contributes to the generation of smaller Ni⁰ particles after reduction. Catalytic tests revealed that all samples exhibited low-carbon deposition, attributed to the large Ni crystallites. The catalyst with 80 mol% Pr showed the best performance, achieving the highest CH₄ conversion (72%), a H₂/CO molar ratio of 0.89, and improved stability. These findings suggest that Ni/Ce_0.2Pr_0.8 could be a promising candidate for use as a catalyst layer of anodes in DIR-SOFC anodes. Although electrochemical data are not yet available, future work will evaluate the catalyst’s performance and durability under SOFC-relevant conditions. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

A new high-temperature allothermal gasification technology is used to process three types of oil waste: ground oil sludge (GOS), tank oil sludge (TOS), and petcoke. The gasifying agent (GA), mainly composed of H₂O and CO₂ at a temperature above 2300 K and atmospheric pressure, is produced by pulsed detonations of a near-stochiometric methane-oxygen mixture. The gasification experiments show that the dry off-gas contains 80–90 vol.% combustible gas composed of 40–45 vol.% CO, 28–33 vol.% H₂, 5–10 vol.% CH₄, and 4–7 vol.% noncondensable C₂–C₃ hydrocarbons. The gasification process is accompanied by the removal of mass from a flow gasifier in the form of fine solid ash particles with a size of about 1 μm. The ash particles have a mesoporous structure with a specific surface area ranging from 3.3 to 15.2 m²/g and pore sizes ranging from 3 to 50 nm. The measured wall temperatures of the gasifier are in reasonable agreement with the calculated value of the thermodynamic equilibrium temperature of the off-gas. The measured CO content in the off-gas is in good agreement with the thermodynamic calculations. The reduced H₂ content and elevated contents of CH₄, CO₂, and C_xH_y are apparently associated with the nonuniform distribution of the waste/GA mass ratio in the gasifier. To increase the H₂ yield, it is necessary to improve the mixing of waste with the GA. It is proposed to mix crushed petcoke with oil sludge to form a paste and feed the combined waste into the gasifier using a specially designed feeder. Full article

Freeze–thaw events are predicted to be more frequent in temperate forest ecosystems. Whether and how freeze–thaw cycles change soil greenhouse gas fluxes remains elusive. Here, we compared the fluxes of three soil greenhouse gases (CO₂, CH₄, and N₂O) across the spring freeze–thaw (SFT) period, the growing season (GS), and the annual (ALL) period in a temperate broad-leaved Korean pine mixed forest in the Changbai Mountains in Jilin Province, Northeastern China from 2019 to 2020. To assess the mechanisms driving the temporal variation of soil fluxes, we measured eleven soil physicochemical factors, including temperature, volumetric water content, electrical conductivity, gravimetric water content, pH, total carbon, total nitrogen, total-carbon-to-total-nitrogen ratio, nitrate (NO₃⁻), ammonium (NH₄⁺), and dissolved organic carbon, all of which play crucial roles in soil carbon (C) and nitrogen (N) cycling. Our findings indicate that the soil in this forest functioned as a source of CO₂ and N₂O and as a sink for CH₄, with significant differences in greenhouse gas (GHG) fluxes among the SFT, GS, and ALL periods. Our results suggest freeze–thaw events significantly but distinctly impact soil C and N cycling processes compared to normal growing seasons in temperate forests. The soil N₂O flux during the SFT (0.65 nmol m⁻² s⁻¹) was 4.6 times greater than during the GS (0.14 nmol m⁻² s⁻¹), likely due to the decreased NO₃⁻ concentrations that affect nitrification and denitrification processes throughout the ALL period, especially at a 5 cm depth. In contrast, soil CO₂ and CH₄ fluxes during the SFT (0.69 μmol m⁻² s⁻¹; −0.61 nmol m⁻² s⁻¹) were significantly lower than those during the GS (5.06 μmol m⁻² s⁻¹; −2.34 nmol m⁻² s⁻¹), which were positively influenced by soil temperature at both 5 cm and 10 cm depths. Soil CO₂ fluxes increased with substrate availability, suggesting that the total nitrogen content at 10 cm depth and NH₄⁺ concentration at both depths were significant positive factors. NO₃⁻ and NH₄⁺ at both depths exhibited opposing effects on soil CH₄ fluxes. Furthermore, the soil volumetric water content suppressed N₂O emissions and CH₄ oxidation, while the soil gravimetric water content, mainly at a 5 cm depth, was identified as a negative predictor of CO₂ fluxes. The soil pH influenced CO₂ and N₂O emissions by regulating nutrient availability, particularly during the SFT period. These findings collectively contribute to a more comprehensive understanding of the factors driving GHG fluxes in temperate forest ecosystems and provide valuable insights for developing strategies to mitigate climate change impacts. Full article

The Kuqa Depression is rich in oil and gas resources and serves as a key production area in the Tarim Basin. However, controversy persists over the genesis of oil and gas in the various structural zones of the Kuqa Depression. This study employs natural gas composition analysis, gas carbon isotope analysis and gold pipe thermal simulation experiments, to comprehensively analyze the differences in the genesis and sources of hydrocarbon gas fluid from the eastern and western Kuqa Depression. The results show that the Kuqa Depression is dominated by alkane gas, with an average gas drying coefficient of 95.6, with nitrogen and carbon dioxide as the primary non-hydrocarbon gases. The average of δ¹³C₁, δ¹³C₂ and δ¹³C₃ values in natural gas are −27.70‰, −20.43‰ and −21.75‰, respectively. Based on comprehensive natural gas geochemical maps, the CO₂ in the natural gas from the Tudong and Dabei areas, as well as the KT-1 well of the Kuqa Depression, is thought to be of organic origin. Additionally, natural gas formation in the Tudong area is relatively simple, consisting entirely of thermally generated coal gas derived from the initial cracking of kerogen. The natural gas in the KT-1 well and the Dabei area are mixed gasses, formed by the initial cracking of kerogen from highly evolved lacustrine and coal-bearing source rocks, exhibiting characteristics resembling those of crude oil cracking gas. The methane (CH₄) content of natural gas in the Dabei area is high and the carbon isotopes are unusually heavy. Considering the regional geological background, potential source rock characteristics and geochemical features may be related to the large-scale invasion of dry gas contributed by CH₄ from highly evolved, underlying coal-bearing source rocks. Consequently, the CH₄ content in the mixed gas is generally high (Ln (C₁/C₂) can reach up to 5.38), while the relative content of heavy components is low, though remains relatively unchanged. Thus, the map of the relative content of heavy components still reflects the characteristics of the original gas genesis (initial cracking of kerogen). Mixed-source gas was analyzed using thermal simulation experiments and natural gas composition ratio diagrams. The contributions of natural gas from deep, highly evolved coal-bearing source rocks in the KT-1 well and the Dabei area accounted for more than 90% and approximately 60%, respectively. This analysis provides theoretical guidance for natural gas exploration in the research area. Full article

Mechanism analysis and technical scheme optimization on CO₂ displacement and CO₂ storage are based on the high-pressure physical properties of CO₂-added formation oil. Oil and natural gas samples from the BZ25-1 block in the Bohai oilfield were used to conduct high-pressure physical property experiments to explore the impacts of CO₂-CH₄ mixed gas on the properties of formation oil. After injecting different amounts of mixed gas, the saturated pressure was measured by constant mass expansion test, the viscosity was measured by falling ball method, the expansion coefficient was measured by gas injection expansion test, and the gas–oil ratio and volume coefficient were obtained by single degassing test. The results show that with gas injection, the saturation pressure and dissolved gas–oil ratio of formation oil increase, the volume coefficient and expansion factor go up, while the oil viscosity reduces. With the increase in gas addition, the properties of formation oil continue to improve, but the increase in improvement becomes flat. With the increase in pressure, the amount of dissolved gas in the formation oil will also increase. High-purity CO₂ is more helpful to change the properties of formation oil, while the gas mixed with CH₄ is more beneficial to elevate the formation energy. For the BZ 25-1 block, the gas injection amount of about 80 mol% is appropriate and the CO₂ purity of 60% can well balance the oil properties improvement and the formation pressure elevation. Full article

Quantifying and controlling fugitive methane emissions from oil and gas facilities remains essential for addressing climate goals, but the costs associated with monitoring millions of production sites remain prohibitively expensive. Current thinking, supported by measurement and simple dispersion modelling, assumes single-digit parts-per-million instrumentation is required. To investigate instrument response, the inlets of three trace-methane (sub-ppm) analyzers were collocated on a facility designed to release gas of known composition at known flow rates between 0.4 and 5.2 kg CH₄ h⁻¹ from simulated oil and gas infrastructure. Methane mixing ratios were measured by each instrument at 1 Hertz resolution over nine hours. While mixing ratios reported by a cavity ring-down spectrometer (CRDS)-based instrument were on average 10.0 ppm (range 1.8 to 83 ppm), a mid-infrared laser absorption spectroscopy (MIRA)-based instrument reported short-lived mixing ratios far larger than expected (range 1.8 to 779 ppm) with a similar nine-hour average to the CRDS (10.1 ppm). We suggest the peaks detected by the MIRA are likely caused by a micrometeorological phenomenon, where vortex shedding has resulted in heterogeneous methane plumes which only the MIRA can observe. Further analysis suggests an instrument like the MIRA (an optical-cavity-based instrument with cavity size ≤10 cm³ measuring at ≥2 Hz with air flow rates in the order of ≤0.3 slpm at distances of ≤20 m from the source) but with a higher detection limit (25 ppm) could detect enough of the high-concentration events to generate representative 20 min-average methane mixing ratios. Even though development of a lower-cost, high-precision, high-accuracy instrument with a 25 ppm detection threshold remains a significant problem, this has implications for the use of instrumentation with higher detection thresholds, resulting in the reduction in cost to measure methane emissions and providing a mechanism for the widespread deployment of effective leak detection and repair programs for all oil and gas infrastructure. Full article

The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H₂O/CO₂ mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H₂, CO, CH₄, CO₂, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H₂ and CO, or into energy gas with high contents of CH₄ and C₂-C₃ hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H₂ and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H₂/CO ratio in the produced syngas from 1.3 to 3.4. Full article

Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH₃)₂CO in a main gas flow of argon. We performed experiments at two ((CH₃)₂CO + Ar)/Ar) ratios and observed that two visually distinct types of layers were deposited after a one-hour deposition process. The first layer type, which appears more inhomogeneous, has areas of SiO₂ (about 5% of the surface area substrates) beside shiny bright and rough paths, and its Raman spectrum corresponds to diamond-like carbon, was deposited at a (CH₃)₂CO+Ar)/Ar = 1/5 ratio. The second layer type, deposited at (CH₃)₂CO + Ar)/Ar = a 1/0 ratio, appears homogeneous and is very dark brown or black in color and its Raman spectrum pointed to defect-rich multilayered graphene. The performed structural studies reveal the presence of diamond and diamond polytypes and seldom SiC nanocrystals, as well as some non-continuously mixed SiC and graphene-like films. The performed molecular dynamics simulations show that there is no possibility of deposition of sp³-hybridized on sp²-hybridized carbon, but there are completely realistic possibilities of deposition of sp²- on sp²- and sp³- on sp³-hybridized carbon under different scenarios. Full article

Composting is a biochemical as well as a heterogeneous process, and the turning operation is important to maintain aerobic conditions and improve the efficiency of the composting process. Therefore, the turning frequency is an important factor for the precise control of the composting reactor. It is necessary to determine the changes in the physical and chemical parameters of the composting process and to simulate them. Pretreated vinegar residue and wool washing sludge were mixed at a mass ratio of 6:4 for the composting process. The composting reactor’s temperature, CO₂, CH₄, and organic matter content were collected during the composting process. According to the principles of composting, a kinetic model of composting based on the change in CO₂ gas concentration and heat balance in the composting reactor is developed, which provides a theoretical basis for the subsequent control of the composting reactor. The comparison of the model predictions to the measured results of the composting reactor shows that the SSE, R², and RMSE for the organic matter content simulation are 8.122, 0.943, and 1.274 g/kg, respectively, and the SSE, R², and RMSE for the temperature simulation are 29.54, 0.959, and 2.71 °C, respectively. Based on the prediction of the temperature in the reactor based on the composting kinetics model, the process control for the turning operation is proposed to achieve precise control of the composting process. The results show that the duration of high temperature in a composting reactor is prolonged for 2 days, the degradation rate of organic matter occurs at a more rapid speed, and the operation efficiency of the production line can be improved by more than 10%. This indicates that the decision-making method based on the composting kinetics model can improve the composting efficiency. Full article

In natural ventilation system-enabled dairy buildings (NVDB), achieving accurate gas emission values is highly complicated. The external weather affects measurements of the gas concentration of pollutants ($c_P$) and volume flow rate (Q) due to the open-sided design. Previous research shows that increasing the number of sensors at the side opening is not cost-effective. However, accurate measurements can be achieved with fewer sensors if an optimal sampling position is identified. Therefore, this study attempted to calibrate the outlet of an NVDB for the direct emission measurement method. Our objective was to investigate the $c_P$ gradients, in particular, for ammonia ($c_{N{H}_3}$), carbon dioxide ($c_{C{O}_2}$), and methane ($c_{C{H}_4}$) considering the wind speed (v) and their mixing ratios ([$\overline{{\mathrm{c}}_{{\mathrm{CH}}_4}/{\mathrm{c}}_{{\mathrm{NH}}_3}}$]) at the outlet, and assess the effect of sampling height (H). The deviations in each $c_P$ at six vertical sampling points were recorded using a Fourier-transform infrared (FTIR) spectrometer. Additionally, wind direction and speed were recorded at the gable height (10 m) by an ultrasonic anemometer. The results indicated that, at varied heights, the average $c_{N{H}_3}$ (p < 0.001), $c_{C{O}_2}$ (p < 0.001), and (p < 0.001) were significantly different and mostly concentrated at the top (H = 2.7). Wind flow speed information revealed drastic deviations in $c_P$, for example up to $+105.1\%$ higher $c_{N{H}_3}$ at the top (H = 2.7) compared to the baseline (H = 0.6), especially during low wind speed (v < 3 m s${}^{-1}$) events. Furthermore, [$\overline{{\mathrm{c}}_{{\mathrm{CH}}_4}/{\mathrm{c}}_{{\mathrm{NH}}_3}}$] exhibited significant variation with height, demonstrating instability below 1.5 m, which aligns with the average height of a cow. In conclusion, the average $c_{C{O}_2}$, $c_{C{H}_4}$, and $c_{N{H}_3}$ measured at the barn’s outlet are spatially dispersed vertically which indicates a possibility of systematic error due to the sensor positioning effect. The outcomes of this study will be advantageous to locate a representative gas sampling position when measurements are limited to one constant height, for example using open-path lasers or low-cost devices. Full article

We report on the use of quartz-enhanced photoacoustic spectroscopy (QEPAS) for multi-gas detection. Photoacoustic (PA) spectra of mixtures of water (H${}_2$O), ammonia (NH${}_3$), and methane (CH${}_4$) were measured in the mid-infrared (MIR) wavelength range using a mid-infrared (MIR) optical parametric oscillator (OPO) light source. Highly overlapping absorption spectra are a common challenge for gas spectroscopy. To mitigate this, we used a partial least-squares regression (PLS) method to estimate the mixing ratio and concentrations of the individual gasses. The concentration range explored in the analysis varies from a few parts per million (ppm) to thousands of ppm. Spectra obtained from HITRAN and experimental single-molecule reference spectra of each of the molecular species were acquired and used as training data sets. These spectra were used to generate simulated spectra of the gas mixtures (linear combinations of the reference spectra). Here, in this proof-of-concept experiment, we demonstrate that after an absolute calibration of the QEPAS cell, the PLS analyses could be used to determine concentrations of single molecular species with a relative accuracy within a few % for mixtures of H${}_2$O, NH${}_3$, and CH${}_4$ and with an absolute sensitivity of approximately 300 (±50) ppm/V, 50 (±5) ppm/V, and 5 (±2) ppm/V for water, ammonia, and methane, respectively. This demonstrates that QEPAS assisted by PLS is a powerful approach to estimate concentrations of individual gas components with considerable spectral overlap, which is a typical scenario for real-life adoptions and applications. Full article

In the deposition of polymer-like carbon (PLC) films on Si substrates via radio-frequency plasma CVD (RF-PCVD), the effect of the Ar/CH₄ gas mixture ratio on the bio-interface of the PLC films remains unclear and the effectiveness of introducing Ar gas must be proven. In this study, five types of PLC films are prepared on Si substrates via RF-PCVD with an Ar/CH₄ gas mixture. The effects of the Ar/CH₄ gas ratio on the structure, surface properties, and osteoblast proliferation of the PLC films are investigated. The PLC film structure is graphitized as the hydrogen content in the PLC film decreases with the increasing Ar gas ratio. Based on in vitro cell culture tests, a PLC film with a higher Ar gas ratio promotes the osteoblast proliferative potential after 72 h compared with a PLC film with a relatively low Ar gas ratio. Moreover, the surface roughness and hydrophilicity of the PLC film increase with the Ar gas ratio. Accordingly, we demonstrate the effectiveness of Ar gas incorporation into the RF-PCVD process to promote the biological responsiveness of PLC films. PLC coatings are expected to be widely applied for surface modification to improve the mechanical characteristics and biological responses of orthopedic implant devices. Full article

The increase in the global population has caused an increment in energy demand, and therefore, energy production has to be maximized through various means including the burning of natural gas. However, the purification of natural gas has caused CO₂ levels to increase. Hollow fiber membranes offer advantages over other carbon capture technologies mainly due to their large surface-to-volume ratio, smaller footprint, and higher energy efficiency. In this work, hollow fiber mixed matrix membranes (HFMMMs) were fabricated by utilizing cellulose triacetate (CTA) as the polymer and amine-functionalized metal-organic framework (NH₂-MIL-125(Ti)) as the filler for CO₂ and CH₄ gas permeation. CTA and NH₂-MIL-125(Ti) are known for exhibiting a high affinity towards CO₂. In addition, the utilization of these components as membrane materials for CO₂ and CH₄ gas permeation is hardly found in the literature. In this work, NH₂-MIL-125(Ti)/CTA HFMMMs were spun by varying the air gap ranging from 1 cm to 7 cm. The filler dispersion, crystallinity, and functional groups of the fabricated HFMMMs were examined using EDX mapping, SEM, XRD, and FTIR. From the gas permeation testing, it was found that the NH₂-MIL-125(Ti)/CTA HFMMM spun at an air gap of 1 cm demonstrated a CO₂/CH₄ ideal gas selectivity of 6.87 and a CO₂ permeability of 26.46 GPU. Full article

Volatiles transported from the Earth’s interior to the surface through permeable faults provide insights on the gas composition of deep reservoirs, mixing and migration processes, and can also be applied as gas-geothermometer. Here, we present carbon (δ¹³C), hydrogen (δ²H) and nitrogen (δ¹⁵N) isotopic data of CO₂, CH₄, and N₂ from gas samples collected from the Kızıldere and Tekke Hamam geothermal fields, located along the eastern segment of the Büyük Menderes Graben, Turkey. The stable isotopic composition of carbon (δ¹³C) ranges from +0.30 to +0.99‰ (PDB) for CO₂ from Kızıldere and is slightly more variable (−0.95 to +1.3‰) in samples from Tekke Hamam. Carbon isotope data in combination with CO₂/³He data reveal that ~97% (Tekke Hamam) to ~99% (Kızıldere) of CO₂ derives from limestone sources, with the residual CO₂ being magmatic in origin with no evidence for CO₂ from organic sources. The slightly higher contribution of limestone-derived CO₂ in Kızıldere, compared to Tekke Hamam can be attributed to the higher temperatures of the Kızıldere reservoir and resulting amplified fluid–limestone interaction, as well as helium depletion during phase separation for Kızıldere samples. In contrast to the carbon isotopic composition of CO₂, the δ¹³C values of methane from Kızıldere and Tekke Hamam are clearly distinct and vary between −23.6 and −20.8‰ for Kızıldere and −34.4 and −31.7‰ for Tekke Hamam, respectively. The δ²H-CH₄ composition is also distinct, measured as −126.7‰ for Kızıldere and −143.3‰ for Tekke Hamam. CO₂-CH₄ carbon isotope geothermometry calculations based on the isotopic fractionation of δ¹³C between the dominant component CO₂ and the minor component CH₄ reveals temperatures 20–40 °C and 100–160 °C higher than the bottom–hole temperatures measured for Tekke Hamam and Kızıldere, respectively. Based on the CO₂-CH₄ carbon isotope disequilibrium, unusual high methane concentrations of ~0.3 to 0.4 vol.-% and CH₄/³He-δ¹³C-CH₄ relationships we suggest thermal decomposition of late (Tekke Hamam) to over-mature (Kızıldere) organic matter and, to some extent, also abiogenic processes as principal source of methane. The N₂/³⁶Ar ratios of most samples reveal the existence of a non–atmospheric nitrogen component within the gas mixture issuing from both fields, in addition to a constant contribution of atmospheric derived nitrogen accompanied into the system via the meteoric recharge of the geothermal system. Based on the δ¹⁵N isotopic ratios (varying between −4.44‰ and 4.54‰), the non–atmospheric component seems to be a mixture of both sedimentary (crustal organic) and mantle nitrogen. The thick Pliocene sedimentary sequence covering the metamorphic basement is the likely major source for the thermogenic content of CH₄ and crustal N₂ gas content in the samples. Full article