Field Emissions Research Articles

Environmental and Management Drivers of Carbon Dioxide and Methane Emissions From Actively‐Extracted Peatlands in Alberta, Canada

AbstractThe installation of drainage ditches and removal of vegetation in preparation for vacuum harvesting alters the carbon dynamics of peatlands. However, we lack the measurements to understand the spatial distribution and environmental and substrate quality controls of carbon dioxide (CO2) and methane (CH4) emissions, as well as how these factors change over the 20–30 year extraction period. For three summers, we measured CO2 and CH4 emissions using the closed chamber method at three actively extracted peatlands near Drayton Valley, Alberta, ranging from 2 to 28 years since the start of extraction. Measurements were made in the ditches, and on segments of peat (fields) between adjacent ditches. Field emissions did not change with distance from ditches, likely due to the observed homogeneity of volumetric water content (VWC) and temperature across the fields. Understanding carbon dynamics in the ditches will be important, as they emitted on average two and 10 times, respectively, the amount of CO2 and CH4 per square meter of the fields. We found moderate to weak relationships between carbon emissions and soil temperature, VWC and ditch water level, though ditch emissions were significantly reduced when there was standing water present. Altering conventional site management, such as increasing ditch spacing, could substantially reduce CH4 emissions from the managed area. Emissions did not decrease with time since start of extraction. We suggest that Canadian emission factor calculations for land‐based emissions consider both peat quality variations among sites, and a site's extraction duration, which has been important in other studies.

Reduction of Electric and Magnetic Field Emissions caused by Overhead Power Lines

Calculations and measurements of magnetic and electric fields of overhead power lines existing in Slovenia show that electromagnetic field emissions on the border of overhead power line right of way could be too high. The allowed electromagnetic field emissions defined by Slovenian government in 1996 are very strict especially for newly constructed overhead lines. For that reason some modification should be applied for newly constructed overhead lines. This paper proposed a few solution of aforementioned problem regarding arrangements of overhead power line conductor.

Life cycle assessment of hemp-based milk alternative production in Lower Saxony, Germany, based on a material flow analysis of a pilot scale

PurposeRecently, demand for plant-based milk products (PBMP) has increased for multiple reasons, such as the rapid population growth expected to reach 9.7 billion by 2050, health concerns such as lactose intolerance, nutritional aspects, ethical reasons, and environmental concerns. This leads to increased demand for food and competition for natural resources. Hemp-based milk is an emerging dairy alternative, and stakeholders in the supply chain are becoming increasingly interested in learning about the environmental effects of its production. This article aims for a comparative life cycle assessment of hemp-based and bovine milk with fat and protein correction to account for the differences in macronutrient content.MethodsThe cradle-to-factory gate LCA relied on experimental cultivation and milk production in Lower Saxony, Germany. Inventory was based on primary data from fields and the pilot plant of DIL e. V. and on literature and ecoinvent database to develop a life cycle assessment (LCA) model. The LCA was performed using Simapro 9.3 software and IMPACT 2002+ impact assessment method. The life cycle stages include cultivation, harvesting, and milk production. The study compared hemp-based milk to bovine milk based on 1 kg fat and protein-corrected milk (FPCM) as a functional unit (FU). Co-products are taken into consideration using mass-economic allocation.ResultsThe results showed that hemp cultivation accounted for the highest impact (99%) in the production chain of hemp milk production. The GWP of 1 kg of FPCM hemp-based milk is 0.42 kg CO2 eq. The energy consumption for 1 kg of FPCM hemp-based milk is 4.73 MJ (12.26% lower than bovine milk). The other main factors impacting hemp-based milk production were terrestrial ecotoxicity (6.444E2 kg TEG soil) and aquatic ecotoxicity (2.458E2 kg TEG water). Hemp fiber was the co-product with 40% of the allocated impacts. The results are sensitive to the changes in fat-protein contents, functional unit, and system boundaries. The results demonstrated that the impacts of hemp milk production were within the range indicated for other PBMP production and 51.7% lower than bovine milk production in terms of GWP. This range primarily stems from field emissions, fertilizer application, and machinery usage during cultivation and harvest.ConclusionThe results of the comparisons of bovine milk and hemp-based milk were dependable on the FU. The hemp-based milk has the potential to be a more sustainable alternative to bovine milk due to considerably lower impacts in impact categories—land occupation (99% lower than bovine milk), global warming (52% lower than bovine milk), and ionizing radiation (23% lower than bovine milk). It is primarily due to less use of agricultural machinery, less land requirement, and lower NH3 emissions than bovine milk in various stages of milk production.

Automatic Identification and Statistical Analysis of Data Steps in Electric Field Measurements from CSES-01 Satellite

The spaceborne Electric Field Detector (EFD) is one of the payloads of the China Seismo-Electromagnetic Satellite (CSES-01), which can measure electric field data at near-Earth orbit for investigating fundamental scientific topics such as the dynamics of the top-side ionosphere, lithosphere–atmosphere–ionosphere coupling, and electromagnetic field emissions possibly associated with earthquake occurrence. The Extremely Low-Frequency (ELF) waveform shows anomalous step variations, and this work proposes an automatic detection algorithm to identify steps and analyze their characteristics using a convolutional neural network. The experimental results show that the developed detection method is effective, and the identification performance reaches over 90% in terms of both accuracy and area under the curve index. We also analyze the rate of the occurrence of steps in the three components of the electric field. Finally, we discuss the stability of the statistical results on steps and their relevance to the probe’s function. The research results provide a guideline for improving the quality of EFD data, and further applications in monitoring the low-Earth electromagnetic environment.

Effect of vane angle on turbulence-chemistry interactions, temperature, flow field, burnout, and NOx emissions in swirling flames fueled by semicoke mixtures.

To enhance the combustion efficiency and reduce NOx emissions in large-scale semicoke and bituminous coal blends, an extensive numerical study was conducted. The focus of this study was to optimize the quaternary air vane angle (αv) through detailed analysis of the temperature and flow fields, turbulence-chemistry interactions, char burnout, and NOx formation in a carefully scaled 1:5 dual-swirl burner. The results showed that with increasing αv, the high-temperature flame region was narrowed and the peak temperature was reduced along with the broadened inner recirculation zone and the shrunken external recirculation zone due to better pulverized fuel-oxidant blending and reinforced convective heat transfer. The peak turbulent Damköhler number Dat evidently increased from 197.5 to 496 with increasing αv, which implied a strengthened homogeneous combustion. Additionally, the corresponding mixing time scales increased while the chemical kinetics time scales decreased, which denoted that an intense diffusing flame was generated with a strong turbulent intensity. The peak heterogeneous Damköhler number Das-O2 showed a reduction from 2.54 to 2.27, while the peak values of Das-CO2 and Das-H2O decreased from 0.1 to 0.077 and from 0.02 to 0.015, respectively. The char-O2 reaction was controlled by diffusion/kinetics; both char-CO2 and char-H2O reactions were determined by kinetics, and all gas‒solid reactions showed a kinetically controlled regime. With increasing αv, the enlarged inner recirculation region increased the residence time, and a higher dilution level lessened the peak temperature, which led to reductions in fuel-NOx and the thermal-NOx. The αv range of 30-45° (or swirl number Sn = 0.55-0.95) was suggested by taking the high burnout and low-NOx formation into account.

Operational condition and furnace geometry for premixed C3H8/Air MILD combustion of high thermal-intensity and low emissions

MILD combustion is usually operated at relatively low thermal intensity to achieve uniform temperature field and low pollutant emissions, further understanding of its emission characteristics at high thermal intensity condition is required to widen its application. In the present numerical study of premixed C3H8/air MILD combustion, different operational conditions (equivalence ratio Φ and thermal input Pinput) and furnace geometries (side wall angle α and aspect ratio AR) are considered to reveal their correlations with pollutant emissions including CO, NOx and unburned hydrocarbon (UHC) at thermal intensities up to 1.06 MW/m3. By adopting reactor network calculation with detailed combustion chemistry, it is found that AR plays a notable role in controlling CO, NOx and UHC emissions, while NOx emission is insensitive to the variation of side wall angle. Both the CO and UHC emissions are related to the location of the internal recirculating vortex. Moreover, following the parametric study and NOx formation analysis, the optimized furnace geometry and operating condition of AR = 5, α = 0° and Φ = 0.6 are obtained to significantly reduce the pollutant emissions by 90 % for both C3H8 and CH4 fuels. The present investigation offers valuable insights into the high thermal intensity MILD combustion.

Tunable Tesla-Scale Magnetic Attosecond Pulses through Ring-Current Gating.

Coherent control over electron dynamics in atoms and molecules using high-intensity circularly polarized laser pulses gives rise to current loops, resulting in the emission of magnetic fields. We propose, and demonstrate with ab initio calculations, "current-gating" schemes to generate direct or alternating-current magnetic pulses in the infrared spectral region, with highly tunable waveform and frequency, and showing femtosecond-to-attosecond pulse duration. In optimal conditions, the magnetic pulse can be highly isolated from the driving laser and exhibits a high flux density (∼1 T at a few hundred nanometers from the source, with a pulse duration of 787 attoseconds) for application in forefront experiments of ultrafast spectroscopy. Our work paves the way toward the generation of attosecond magnetic fields to probe ultrafast magnetization, chiral responses, and spin dynamics.

Investigation of a Circularly Polarized Metasurface Antenna for Hybrid Wireless Applications.

The increasing prevalence of the Internet of Things (IoT) as the primary networking infrastructure in a future society, driven by a strong focus on sustainability and data, is noteworthy. A significant concern associated with the widespread use of Internet of Things (IoT) devices is the insufficient availability of viable strategies for effectively sustaining their power supply and ensuring their uninterrupted functionality. The ability of RF energy-harvesting systems to externally replenish batteries serves as a primary driver for the development of these technologies. To effectively mitigate concerns related to wireless technology, it is imperative to adhere strictly to the mandated limitations on electromagnetic field emissions. A TA broadband polarization-reconfigurable Y-shaped monopole antenna that is improved with a SADEA-tuned smart metasurface is one technique that has been proposed in order to accomplish this goal. A Y-shaped printed monopole antenna is first taken into consideration. To comprehend the process of polarization reconfigurability transitioning from linear to circular polarization (CP), a BAR 50-02 V RF PIN Diode is employed to shorten one of the parasitic conducting strips to the ground plane. A SADEA-driven metasurface, which utilizes the artificial intelligence-driven surrogate model-assisted differential evolution for antenna synthesis, is devised and positioned beneath the radiator to optimize performance trade-offs while increasing the antenna's gain and bandwidth. The ultimate prototype achieves the following: an impedance bandwidth of 2.58 GHz (3.27-5.85 GHz, 48.45%); an axial bandwidth of 1.25 GHz (4.19-5.44 GHz, 25.96%); a peak gain exceeding 8.45 dBic; and when a highly efficient rectifier is integrated, the maximum RF-DC conversion efficiency of 73.82% and DC output of 5.44 V are obtained. Based on the results mentioned earlier, it is considered appropriate to supply power to intelligent sensors and reduce reliance on batteries via RF energy-harvesting mechanisms implemented in hybrid wireless applications.

Effect of Biochar on N2O Emission in a Vegetable Field

Effect of Biochar on N₂O Emission in a Vegetable Field

Spatially-explicit environmental assessment of bioethanol from miscanthus and switchgrass in France

Bioethanol is promoted as a means of tackling climate change, diversifying energy sources and securing energy supply. However, there also concerns that their wider deployment could lead to unintended environmental consequences. Life cycle assessment (LCA) is a widely used methodology to assess the environmental performance of biofuels. However, its outcomes strongly depend on the inventory data and modeling assumptions. Agronomic variables such as crop yields, nitrogen fertilizer rates or field emissions of nitrous oxide are very sensitive inputs, as are soil carbon dynamics in response to land use changes (LUC) entailed by the deployment of energy crops. Models simulating agroecosystem processes and the economics of agricultural farms are promising tools to predict such variables and improve the reliability of LCA.Here, we combined the agro-ecosystem model CERES-EGC, the farm economic model AROPAj and the LCA approach to investigate the effect of local drivers on the environmental impacts of bioethanol from miscanthus and switchgrass over France.Overall, lignocellulosic bioethanol achieved GHG abatement targets in the 74 %–94 % range compared to gasoline, and complied with the 50 % minimum imposed by European regulations. Miscanthus-based ethanol achieved up to twice lower environmental impacts than switchgrass due to 50 % higher biomass yields overall. Low fertilizer N input rates (in the 0-30 kg N ha-1 yr-1 range) proved the most efficient strategy to optimize energy return. Significant inter-regional variability occurred, especially in terms of soil C sequestration rates, which weighed in substantially on GHG budgets. Some regions were more efficient than others as a result, which advocates a site-specific approach and a potential prioritization when planning biorefineries, taking into account local production and environmental performance potentials. Compared to previous studies, ours provided high-resolution data in terms of crop yields, nitrous oxide emissions and soil C dynamics, factoring in LUC effects at local to regional scales.

Greenhouse gas emissions along the value chain in palm oil producing systems: A case study of Cameroon

The agricultural sector is the second most emitting sector globally, contributing about 18% of total global greenhouse gas (GHG) emissions. Multipurpose high in-demand commodities like palm oil contribute significantly to these emissions. The Roundtable on Sustainable Palm Oil (RSPO) with an objective to make the palm oil sector sustainable, developed a new tool to quantify carbon emissions from palm oil mills. The PalmGHG tool has been used in Southeast Asia to measure carbon emissions from palm oil production and for palm oil certification. However, no studies have used the tool to evaluate GHG emissions from palm oil mills in sub-Saharan Africa, which contributes about 24% of global palm oil production and is home to one of the last remaining primary forests in the world. In this study, we quantify GHG emissions along the crude palm oil (CPO) life cycle in a growing palm oil producing region in Cameroon. We use the RSPO PalmGHG accounting tool, to identify sources of CO2 emissions and quantify them in tons of CO2 equivalent. Six mills across the South West and Center regions of Cameroon were sampled. We found that the sources of carbon emissions from our sampled mills in decreasing order of magnitude are land conversion (78%), palm oil mill effluent (21%), fertilizer use (0.9%), mill fuel combustion (0.1%) and grid electricity utilization (0.04%). The average GHG emissions per ton of crude palm oil produced were exceptionally high at 22.3 tCO2e compared to other palm oil producing regions in the world such as Indonesia with only 1.6 tCO2e/ton of CPO. In addition, we found that planting oil palm on previously logged land instead of primary forest conversion could prevent field emissions by up to about 89% and by up to about 69% for replanting old oil palm stands. Intensification measures like improving palm oil mill extraction rates and improving yields would drastically reduce emissions per ton of crude palm oil produced. Although land conversion associated with deforestation remains the major source of palm oil GHG emissions, farm and mill practices such as reduction in fertilizer use, biogas capture and use of clean energy could help reduce emissions in the long run.

PEAKS PREDICTION OF BUILDING CARBON EMISSION BASED ON BUILDING ENERGY CONSUMPTION MONITORING: A CASE STUDY OF NINGBO CITY

ABSTRACT The premise of implementing the total amount control plan of building carbon emission should be based on the prediction of the future change trend of building carbon emission. This paper investigates and analyzes peaks of building carbon emission in Ningbo city of China through the Ningbo’s building energy monitoring platform and uses the STIRPAT model to predict the medium and long-term carbon emissions in Ningbo. The peak time and peak value of carbon in the construction field at the city level under the dynamic scenario are simulated based on the Monte Carlo method. The results show that under the benchmark scenario, the carbon emission in the construction field of Ningbo will peak around 2037, with a peak of 22.68 million tons. Through the improvement of building energy-saving laws and regulations, the popularization of green energy-saving buildings, and the establishment of a building energy-saving system, the Ningbo construction department will achieve its carbon emission peak time in 2031 (±2), with a peak of about 15.45 (±1.07) million tons of CO2.

Validation of MODIS Temperature and Emissivity Products Based on Ground-Based Mid-Wave Hyperspectral Imaging Measurement in the Northwestern Plateau Region of Qinghai, China

The climatic fluctuations in northern China exhibit remarkable variability, making it imperative to harness the power of MODIS data for conducting comprehensive investigations into the influences of desertification, desert expansion, and snow and ice melting phenomena. Consequently, the rigorous evaluation of MODIS land surface temperature (LST) and land surface emissivity (LSE) products takes on a momentous role, as this provides an essential means to ensure data accuracy, thereby instilling confidence in the robustness of scientific analyses. In this study, a high-resolution hyperspectral imaging instrument was utilized to measure mid-wave hyperspectral images of grasslands and deserts in the northwest plateau region of Qinghai, China. The measured data were processed in order to remove the effects of sensor noise, atmospheric radiation, transmission attenuation, and scattering caused by sunlight and atmospheric radiation. Inversion of the temperature field and spectral emissivity was performed on the measured data. The inverted data were compared and validated against MODIS land surface temperature and emissivity products. The validation results showed that the absolute errors of emissivity of grassland backgrounds provided by MCD11C1 in the three mid-wave infrared bands (3.66–3.840 μm, 3.929–3.989 μm, and 4.010–4.080 μm) were 0.0376, 0.0191, and 0.0429, with relative errors of 3.9%, 2.1%, and 4.8%, respectively. For desert backgrounds, the absolute errors of emissivity were 0.0057, 0.0458, and 0.0412, with relative errors of 0.4%, 4.9%, and 3.9%, respectively. The relative errors for each channel were all within 5%. Regarding the temperature data products, compared to the inverted temperatures of the deserts and grasslands, the remote sensing temperatures provided by MOD11L2 had absolute errors of ±2.3 K and ±4.1 K, with relative errors of 1.4% and 0.7%, respectively. The relative errors for the temperature products were all within 2%.

Effects of intake parameters and compression ratio on ammonia combustion and emissions in SI engines

Ammonia is an attractive hydrogen carrier and zero-carbon fuel for achieving de-carbonization targets. However, realistic engines with pure ammonia often suffer from serious issues like ignition instabilities, combustion variations, and heavy emissions. It has shown that ammonia combustion is highly sensitive to combustion boundary conditions. However, comprehensive parametric studies on combustion and emissions of ammonia engines are still lacking currently. In this work, ammonia combustion and emissions were numerically investigated in a spark-ignition engine under various operating conditions, emphasis on pressure characteristics, combustion flow field, and NOx and unburned NH3 emissions. The results show that ammonia combustion can be promoted significantly at elevated intake temperatures and pressures and compression ratios, manifesting increased peak pressure, accelerated flame propagation, and shortened combustion duration. Indicated power increases at elevated compression ratios and intake pressures while decreasing at elevated intake temperatures. Equivalence ratios affect ammonia combustion nonmonotonically, and the highest peak pressure and thermal efficiency are achieved at Φ = 1.2 and 1.1, respectively. Besides, equivalence ratios have large impacts on the shortening of late-stage combustion duration (i.e., CA50-CA90). Regarding emission characteristics, it shows that fuel-NO is dominant while thermal-NO is minimal. Equivalence ratios can result in pronounced NO emissions under lean-burning conditions. Unburned NH3 decreases while NO2 and N2O remain low levels at an elevated compression ratio, intake temperature and pressure and equivalence ratio of around 1.1. This work demonstrates the significance of active thermo-atmosphere in the optimization of ammonia engine performance.

A comparative environmental analysis of conventional and organic rice farming in Thailand in a life cycle perspective using a stochastic modeling approach

System stochasticity is an inherent characteristic of agricultural systems. Many studies have been conducted in Thailand to analyze the rice production systems. However, most of the prior work just focused on deterministic approach to investigate the rice production systems while disregarding the system variability. In this study, the conventional and organic rice farming systems in Thailand were compared considering the uncertainties associated with parameters. The system variability was taken into account by employing a stochastic modeling approach. The considered impact categories include global warming, ozone formation (human health), freshwater ecotoxicity, terrestrial acidification, fine particulate matter formation, freshwater eutrophication, and fossil resource scarcity. The results showed that yield had considerable influence on the environmental profiles of the two systems; organic and conventional farming showed similar results in terms of global warming on a per hectare basis, but the considerable difference was observed on a per tonne basis. The field emissions due to farm inputs were the most significant contributor to most of the impact categories. The fuel used for irrigation, land preparation, and harvesting also contributed significantly to several impact categories. On the other hand, the impacts of inputs production and material transportation were modest. Uncertainty analysis outcomes indicated that there was a noticeable deviation from the deterministic results in terms of global warming and freshwater ecotoxicity. However, when considering the associated uncertainties, no significant difference was observed between the environmental profiles of the two systems.

Sustainability of bio-mediated and bio-inspired ground improvement techniques for geologic hazard mitigation: a systematic literature review

This is a systematic literature review of quantitative sustainability assessments, focusing on life cycle sustainability assessment (LCSA), of bio-mediated and bio-inspired ground improvement technologies applied to geologic hazard mitigation. The aims of the systematic review are to 1) compare the sustainability of various ground improvement techniques and, 2) to evaluate the rigor and consistency of sustainability assessment methods applied to these techniques. The literature review considers studies identified through keyword searches of bibliographic databases. After selection criteria were applied to ensure identified articles were within scope, a total of 8 articles were found which assessed bio-mediated and bio-inspired ground improvement technologies. The technologies represented in the literature include enzyme induced carbonate precipitation (EICP), microbially induced carbonate precipitation (MICP), and microbially induced desaturation and carbonate precipitation (MIDP). While sustainability is typically conceived to include environmental, economic and social impacts, most studies examined only life cycle environmental impacts, three included life cycle cost accounting, and none included social impacts. Analysis of the studies’ system boundaries show inconsistencies across studies, making comparison of results inaccurate. The most common environmental impact categories included in the identified studies are global warming and eutrophication. Raw materials production and field emissions from the biogeochemical reactions that drive the technologies are the largest contributors to these impacts. Based on the review, it is clear that a set of LCSA guidelines is needed to produce high-quality LCSAs that can be used in comparative assessments and to confidently identify processes where the impacts of bio-mediated and bioinspired technologies can be reduced.

Observation of tunable persistent luminescence in XAl2O4: Eu2+ (X=Ca, Sr) doped borate glass for efficient optical information storage

Eu2+ doped XAl2O4 (X = Ca, Sr) phosphor is usually prepared to study the monochromatic afterglow emission in a single crystal field, but the tunable afterglow emission with multiple emission bands in polycrystal fields has hardly been explored. In this paper, by fine-tuning the ratio of calcium carbonate to strontium carbonate in the borate matrix, Eu2+ ions are introduced into CaAl2O4 and SrAl2O4 crystals in different concentrations. Results review that reduction-induced oxygen vacancy defects distribute shallow or deep near Eu2+ 5d state to obtain the tunable polychromatic long afterglow emission from green to indigo to dark blue. Also, the additional red emission from Eu3+ in the borate glass matrix further enriches the luminescent characteristics by equipping the samples with tunable photoluminescence from yellow-green, yellow to purple. Such material is proved to have good optical information storage ability, which is expected to promote the development of long persistent luminescence materials.

A combination of organic fertilizers partially substitution with alternate wet and dry irrigation could further reduce greenhouse gases emission in rice field

Alternate wet and dry (AWD) irrigation and organic fertilizers substitution (OFS) have contrasting effects on CH4 and N2O emissions in rice cultivation. Combining these two practices may be feasible for simultaneous reduction of CH4 and N2O emission from paddy. Hence, we conducted a two-year field experiment to explore the reduction of greenhouse gases under the combination of AWD and OFS. The field experiment which was designed with two irrigation methods (continuous flooding (CF) irrigation and AWD irrigation), and five nitrogen regimes (N0, N135, and N180 represent 0, 135, and 180 kg N ha-1, respectively, ON25 and ON50 represent 25% and 50% OFS for inorganic fertilizer, respectively). The results showed a single-peak emission for CH4 fluxes during the whole rice growing season in all water and nitrogen treatments while the N2O fluxes peak only observed during tillering period with AWD irrigation. AWD irrigation and OFS showed a limited reduction in global warming potential (GWP). These were owing to that AWD irrigation reduced 38.3% CH4 emissions while increase 145.9% N2O emissions when compared to CF irrigation, and the low rate (25%) OFS only reduced CH4 emission by 29.4% while high rate (50%) only reduce N2O emission by 38.8% when compared to conventional inorganic nitrogen fertilizer (N180). Combined AWD and ON25 could maximize the reduction in GWP and yield-scaled GWP, which were reduce 58.0% and 52.5%, respectively, compare to the conventional water and nitrogen management (CF and N180). Furthermore, the structural equation modelling (SEM) indicated that the soil dissolved organic carbon (DOC) and rice aboveground biomass showed a significant positive effect on CH4 fluxes while soil NH4+ with a negative effect, and the soil NH4+, nitrification potential, denitrification potential significant affected N2O fluxes with a positive effect while DOC with a negative effect. These results investigated that 25% OFS rate for inorganic fertilizer could further reduce warming potential in AWD irrigation rice field.

Effects of nitrogen fertilization on soil CO2 emission and bacterial communities in maize field on the semiarid Loess Plateau

Effects of nitrogen fertilization on soil CO2 emission and bacterial communities in maize field on the semiarid Loess Plateau

On the Stability and Characteristics of Biogas/Methane/Air Flames Fired by a Double Swirl Burner

CO2-diluted methane fuel is relevant to biogas combustion applications. Despite its poor heating value and low reactivity, which limit its practical applicability, biogas gains popularity as a renewable fuel. However, implementing it in combustion systems requires either modifying or replacing the existing burners. This study investigates the stability, temperature field, and pollutant emissions of CH4/CO2/air-premixed flames fired by a double-swirl burner. A CH4/air mixture of equivalence ratio, Φout, was used in the outer stream, while a CH4/CO2/air mixture was supplied to the inner stream. The CO2 mole fraction, $${x}_{{\mathrm{CO}}_{2}}$$ , in the inner fuel blend varied from 0 to 0.4 for various inner stream equivalence ratios, Φin. The stability diagram of these flames was mapped in terms of Φin verses $${x}_{{\mathrm{CO}}_{2}}$$ for a fixed Φout. Based on the stability map, the inflame temperature field was investigated for six flames. Increasing the %CO2 in the biogas modifies the stability map by increasing the inner stream lean blow-off limits. However, increasing Φout sustains the flame stability, while reducing the CO2 decreases the overall flame blow-off equivalence ratio. Flame size growth with increasing $${x}_{{\mathrm{CO}}_{2}}$$ requires a longer residence time for efficient combustion. The addition of CO2 physically and chemically affects the thermal flame structure, and hence the pollutant emissions. In this burner, ultra-low NOX emission was reported, while an increase in the CO and unburned hydrocarbons (UHC), with increasing $${x}_{{\mathrm{CO}}_{2}}$$ was observed. However, the results show that, for a given $${x}_{{\mathrm{CO}}_{2}}$$ , controlling Φin and Φout could reduce CO and UHC emissions.