Enhancing physicochemical, rheological properties, and in vitro rumen fermentation of starch with Melastoma candidum D. Don fruit extract.

The utilization of polyphenol-modified starch in ruminants has not undergone extensive exploration. This study aimed to investigate the impact of the complex formed between starch and Melastoma candidum D. Don fruit extract on physicochemical properties, phenol release kinetics in various buffers simulating the gastrointestinal tract, methane production, and post-rumen digestibility. The interaction between starch and M. candidum D. Don fruit extract significantly (p < 0.001) increased resistant starch and particle size diameter. The maximum phenolic release from complex between starch and M. candidum D. Don fruit extract, due to gastrointestinal tract-simulated buffers, ranged from 22.96 to 34.60 mg/100 mg tannic acid equivalent. However, rumen and abomasum-simulated buffers released more phenolic content, whereas the intestine-simulated buffer showed higher antioxidant activity (ferric ion-reducing antioxidant power). Furthermore, complex between starch and M. candidum D. Don fruit extract significantly decreased dry matter rumen digestibility (p < 0.001) and maximum methane gas production (p < 0.001).

Distribution of mercury in modern bottom sediments of the Beaufort Sea in relation to the processes of early diagenesis: Microbiological aspect.

This study investigated the contents of total mercury (THg), trace metals, and CH4 and determined the signature microbes involved in various biogeochemical processes in the sediment of the Canadian Beaufort Sea. The THg ranged between 32 and 63 µg/kg and the trace metals such as Fe, Al, Mn, and Zn were significant in distributions. The pH, SO42-, Fe2+, and redox proxy metals were crucial factors in the spatial and vertical heterogeneity of geochemical distributions. CH4 was detected only at the mud volcano site. Microbial analyses identified Clostridium, Desulfosporosinus, Desulfofustis, and Desulftiglans as the predominant Hg methylators and sulfate reducers; Nitrosopumilus and Hyphomicrobium as the major nitrifiers and denitrifiers; Methanosarcina and Methanosaeta as keystone methanogens; and Methyloceanibacter and Methyloprofundus as signature methanotrophs. Altogether, this study expands the current understanding of the microbiological and geochemical features and could be helpful in predicting ecosystem functions in the Canadian Beaufort Sea.

Research on High Performance Methane Gas Concentration Sensor Based on Pyramid Beam Splitter Matrix.

Methane gas concentration detection faces the challenges of increasing accuracy and sensitivity, as well as high reliability in harsh environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve methane gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point-signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the four-channel methane gas concentration detection algorithm based on spectral refinement. Through the experiment, it was found that the sensor enables the full-range measurement of CH4; at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the limit of detection is 0.5 ppm. The sensor is still capable of achieving PPM-level detections under extreme conditions in which the sensor's optical window is covered by two-thirds and humidity is 85% or dust concentration is 100 mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Application of Semiconductor Metal Oxide in Chemiresistive Methane Gas Sensor: Recent Developments and Future Perspectives.

The application of semiconductor metal oxides in chemiresistive methane gas sensors has seen significant progress in recent years, driven by their promising sensitivity, miniaturization potential, and cost-effectiveness. This paper presents a comprehensive review of recent developments and future perspectives in this field. The main findings highlight the advancements in material science, sensor fabrication techniques, and integration methods that have led to enhanced methane-sensing capabilities. Notably, the incorporation of noble metal dopants, nanostructuring, and hybrid materials has significantly improved sensitivity and selectivity. Furthermore, innovative sensor fabrication techniques, such as thin-film deposition and screen printing, have enabled cost-effective and scalable production. The challenges and limitations facing metal oxide-based methane sensors were identified, including issues with sensitivity, selectivity, operating temperature, long-term stability, and response times. To address these challenges, advanced material science techniques were explored, leading to novel metal oxide materials with unique properties. Design improvements, such as integrated heating elements for precise temperature control, were investigated to enhance sensor stability. Additionally, data processing algorithms and machine learning methods were employed to improve selectivity and mitigate baseline drift. The recent developments in semiconductor metal oxide-based chemiresistive methane gas sensors show promising potential for practical applications. The improvements in sensitivity, selectivity, and stability achieved through material innovations and design modifications pave the way for real-world deployment. The integration of machine learning and data processing techniques further enhances the reliability and accuracy of methane detection. However, challenges remain, and future research should focus on overcoming the limitations to fully unlock the capabilities of these sensors. Green manufacturing practices should also be explored to align with increasing environmental consciousness. Overall, the advances in this field open up new opportunities for efficient methane monitoring, leak prevention, and environmental protection.

Effect of Hydraulic retention time on performance of anaerobic membrane bioreactor treating slaughterhouse wastewater.

Slaughterhouse wastewater is a major environmental concern in many Vietnamese cities due to its high organic content and unpleasant odor. This study aimed to evaluate performance of a submerged flat sheet Anaerobic membrane bioreactor (AnMBR) system at different hydraulic retention time (HRT, 8-48 h) treating wastewater from a slaughterhouse in Hanoi City (Vietnam) at ambient temperature. The wastewater characteristics were as follows: chemical oxygen demand (COD) of 910 ± 171 mg/L; suspended solids (SS) of 273 ± 139 mg/L; and total nitrogen (T-N) of 115 ± 31 mg/L. The AnMBR system achieved high removal efficiencies for SS (99%) and COD (>90%) at an optimum HRT of 24 h. The biomethane yield reached 0.29 NL CH4/g CODinf. Importantly, the system maintained stable operation without flux decay and membrane fouling. HRT longer than 24 h could offer the better effluent quality without an increase in transmembrane pressure (TMP); however, it led to a lower methane production rate. Shorter HRT of 8-12 h caused a high TMP over -10 kPa, posing a risk for membrane fouling and biomass loss during cleaning, thus resulting in a low methane production. Our results suggest that AnMBR can be a reliable technology for wastewater treatment, reuse and energy recover from slaughterhouse wastewater in Vietnam and other similar climate countries.

Methane migration and explosive fringe localisation in retreating longwall panel under varied ventilation scenarios: a numerical simulation approach.

Methane-based inflammable underground coal mine environment has led to catastrophic losses in the past. Migration of methane from the working seam and desorption region above and below the seam causes explosion hazard. In this study, the computational fluid dynamics (CFD)-based simulations of a longwall panel in a methane-rich inclined coal seam of the Moonidih mine in India established that the ventilation parameters greatly influence the methane flow in the longwall tailgate and porous medium of the goaf. The field survey and CFD analysis revealed that methane accumulation on the "rise side" wall of the tailgate is attributable to the geo-mining parameters. Further, the turbulent energy cascade was observed to impact the distinct dispersion pattern along the tailgate. The numerical code was used to investigate the changes in ventilation parameters made to dilute the methane concentration in the longwall tailgate. Methane concentration in the tailgate outlet decreased from 2.4 to 1.5% as the inlet air velocity increased from 2 to 4 m/s. The oxygen ingress into the goaf increased from 0.5 to 4.5 lps as the velocity was increased, causing the explosive zone in the goaf to expand from 5 to 100 m. Amongst all velocity variations, the lowest level of gas hazard was observed at an inlet air velocity of 2.5 m/s. This study, thus, demonstrated the ventilation-based numerical method to assess the coexistence of gas hazard in the goaf and longwall workings. Moreover, it provided impetus to the necessity of novel strategies to monitor and mitigate the methane hazard in U-type longwall mine ventilation.

Imbedding Pd Nanoparticles into Porous In2O3 Structure for Enhanced Low-Concentration Methane Sensing.

Methane (CH4), as the main component of natural gas and coal mine gas, is widely used in daily life and industrial processes and its leakage always causes undesirable misadventures. Thus, the rapid detection of low concentration methane is quite necessary. However, due to its robust chemical stability resulting from the strong tetrahedral-symmetry structure, the methane molecules are usually chemically inert to the sensing layers in detectors, making the rapid and efficient alert a big challenge. In this work, palladium nanoparticles (Pd NPs) embedded indium oxide porous hollow tubes (In2O3 PHTs) were successfully synthesized using Pd@MIL-68 (In) MOFs as precursors. All In2O3-based samples derived from Pd@MIL-68 (In) MOFs inherited the morphology of the precursors and exhibited the feature of hexagonal hollow tubes with porous architecture. The gas-sensing performances to 5000 ppm CH4 were evaluated and it was found that Pd@In2O3-2 gave the best response (Ra/Rg = 23.2) at 370 °C, which was 15.5 times higher than that of pristine-In2O3 sensors. In addition, the sensing materials also showed superior selectivity against interfering gases and a rather short response/recovery time of 7 s/5 s. The enhancement in sensing performances of Pd@In2O3-2 could be attributed to the large surface area, rich porosity, abundant oxygen vacancies and the catalytic function of Pd NPs.

Caracterización de un Consorcio Microbiano Metanogénico de una Mina de Carbón en la Cuenca de Bogotá / Characterization of a Methanogenic Microbial Consortium from a Coal Mine in Bogotá Basin

RESUMEN En el trabajo se estudió un consorcio microbiano metanogénico de una mina de carbón de la cuenca de Bogotá en Colombia. Se establecieron cultivos de enriquecimiento de carbón ex situ para el crecimiento y la producción de gas de novo. El gas biogénico producido por los cultivos se analizó mediante cromatografía de gases con detectores de ionización de llama y conductividad térmica. Los cultivos se utilizaron para aislar estirpes microbianas y para generar bibliotecas del gene 16S rARN empleando de cebadores de bacteria y de arquea. El análisis de cromatografía de gases mostró producción de metano a 37 oC, pero no a 60 oC, donde el CO2 fue el componente principal del gas biogénico. El análisis de la secuencia del gen 16S rARN de estirpes microbianos y de las bibliotecas de clones, estableció que el consorcio microbiano metanogénico estuvo formado por especies de bacterias de los géneros Bacillus y Gracilibacter más la arquea del género Methanothermobacter. El consorcio microbiano metanogénico identificado es potencialmente responsable de la generación de gas biogénico en la mina de carbón La Ciscuda. Los resultados sugirieron que los metanógenos de este consorcio producían metano por vía hidrogenotrófica o de reducción de CO2.

ABSTRACT The work studied the methanogenic microbial consortium in a coal mine from the Bogotá basin in Colombia. Ex situ coal-enrichment cultures were established for in vitro growth and de novo gas production. Biogenic gas produced by cultures was analyzed by gas chromatography using thermal conductivity and flame ionization detectors. Cultures were used to isolate microbial specimens and to generate 16S rRNA gene libraries employing bacterial and archaeal primer sets. The gas chromatographic analysis showed methane production at 37 oC, but not at 60 oC, where CO2 was the major component of the biogenic gas. 16S rRNA gene sequence analysis of microbial isolates and clone libraries established that the methanogenic microbial consortium was formed by bacteria species from Bacillus and Gracilibacter genera plus archaea from the Methanothermobacter genus. This meth-anogenic microbial consortium was potentially responsible for biogenic gas generation in La Ciscuda coal mine. The results suggested that these methanogens produced methane by hydrogenotrophic or CO2 reduction pathways.

Graphene Film Growth on Silicon Carbide by Hot Filament Chemical Vapor Deposition.

The electrical properties of graphene on dielectric substrates, such as silicon carbide (SiC), have received much attention due to their interesting applications. This work presents a method to grow graphene on a 6H-SiC substrate at a pressure of 35 Torr by using the hot filament chemical vapor deposition (HFCVD) technique. The graphene deposition was conducted in an atmosphere of methane and hydrogen at a temperature of 950 °C. The graphene films were analyzed using Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy. Raman mapping and AFM measurements indicated that few-layer and multilayer graphene were deposited from the external carbon source depending on the growth parameter conditions. The compositional analysis confirmed the presence of graphene deposition on SiC substrates and the absence of any metal involved in the growth process.

Adsorption and photocatalytic conversion of ethyl mercaptan to diethyl disulfide on Fe2O3-loaded HNbMoO6 nanosheet.

Ethyl mercaptans which commonly exist in natural gas need to be removed due to their toxic, odorous, and corrosive properties. Herein, a novel Fe2O3-modified HNbMoO6 nanosheet catalyst (Fe2O3@e-HNbMoO6) was prepared by an exfoliation-impregnation method for the ethyl mercaptans removal. In the heterojunction catalyst, e-HNbMoO6 can be excited by visible light to generate the photogenic charge and has certain adsorption property for ethyl mercaptan with hydrogen bonding (Nb-OH or Mo-OH as the hydrogen bonding donor); Fe2O3 plays the role of accelerating photogenerated electrons and holes, and enhancing the adsorption of ethyl mercaptan with another hydrogen bonding (Fe-OH as the hydrogen bonding donor and receptor). Results showed that the adsorption capacity of Fe2O3@e-HNbMoO6 is 69.9 µmol/g for ethyl mercaptan. In addition, the photocatalytic conversion efficiency of ethyl mercaptan to diethyl disulfide is nearly 100% and it is higher than that of the other Nb-Mo based photocatalysts, such as LiNbMoO6, Fe1/3NbMoO6, Ce1/3NbMoO6, TiO2-HNbMoO6, e-HNbMoO6, CeO2@e-HNbMoO6, and Ag2O@e-HNbMoO6. Under the experimental conditions, the photocatalytic conversion efficiency is greater than the adsorption efficiency over Fe2O3@e-HNbMoO6, and there is no ethyl mercaptan output in the process of adsorption and photocatalytic conversion. Fe2O3@e-HNbMoO6 heterojunction catalyst has practical value and reference significance for purifying methane gas and enhancing photocatalytic conversion of ethyl mercaptan.

Influence of salinity on biofilm formation and COD removal efficiency in anaerobic moving bed biofilm reactors.

Anaerobic digestion is widely used for wastewater treatment, but this approach often relies on microbial communities that are adversely affected by high-salinity conditions. This study investigated the applicability of an anaerobic moving bed biofilm reactor (AMBBR) to treating high-salinity wastewater. The removal performance and microbial community were examined under salinity conditions of 1000-3000 mg/L, and a soluble chemical oxygen demand (sCOD) removal efficiency of up to 8% ± 2.74% was achieved at high-salinity. Scanning electron microscopy showed that microorganisms successfully attached onto the polyvinyl alcohol gel carrier, and the extracellular polymeric substances on the biofilm increased at higher salt concentrations. The AMBBR also maintained traditionally accepted levels of total alkalinity and volatile fatty acids for stable wastewater processing under these operating conditions. High-throughput sequencing indicated that Desulfomicrobium and three methanogenic groups were the dominant contributors to sCOD removal. Overall, the results showed that the AMBBR can successfully treat fish factory wastewater under varying salinity conditions.

An updated look at petroleum well leaks, ineffective policies and the social cost of methane in Canada's largest oil-producing province.

Temporarily plugged or "suspended" wells pose environmental and economic risks due to the large volume of methane gas leaked. In the Canadian Province of Alberta, which, by far, has the largest number of petroleum wells in Canada, there are no regulations stipulating the maximum length of time a well can be left suspended. In recent years, an increasing number of wells have been put into the suspended state by owners. We show using a large data set obtained from the Alberta Energy Regulator that leak spells have increased between 1971 and 2019. For the same time period, the probability of an unresolved leak has also increased, and the amount of methane emitted per leak has substantially gone up. Lastly, we provide simple social-cost-of methane computations indicating that responsible policies can incentivize well owners towards remediation and reclamation and support efforts to fight climate change and improve upon economic expedience. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10584-021-03044-w.

Small Intestinal Bacterial Overgrowth Syndrome: A Guide for the Appropriate Use of Breath Testing.

The increased availability of noninvasive breath tests, each with limitations, has led to widespread testing for small intestinal bacterial overgrowth (SIBO) in patients with non-specific gastrointestinal complaints. The lactulose breath test (LBT) is based upon an incorrect premise and therefore incorrect interpretations which has resulted in the over-diagnosis of SIBO and the excessive use of antibiotics in clinical practice. Despite limitations, the glucose breath test (GBT) should be exclusively employed when considering SIBO in appropriately chosen patients. This review suggests guidelines for the optimal use and appropriate interpretation of the GBT for suspected SIBO. The LBT should be discarded from future use, and the literature based upon the LBT should be discounted accordingly.

Continuous and real-time indoor and outdoor methane sensing with portable optical sensor using rapidly pulsed IR LEDs.

We designed a simple, portable, low-cost and low-weight nondispersive infrared (NDIR) spectroscopy-based system for continuous remote sensing of atmospheric methane (CH4) with rapidly pulsed near-infrared light emitting diodes (NIR LED) at 1.65 µm. The use of a microcontroller with a field programmable gate array (µC-FPGA) enables on-the-fly and wireless streaming and processing of large data streams (~2 Gbit/s). The investigated NIR LED detection system offers favourable limits of detection (LOD) of 300 ppm (±5%) CH4,. All the generated raw data were processed automatically on-the-fly in the µC-FPGA and transferred wirelessly via a network connection. The sensing device was deployed for the portable sensing of atmospheric CH4 at a local landfill, resulting in quantified concentrations within the sampling area (ca 400 m2) in the range of 0.5%-3.35% CH4. This NIR LED-based sensor system offers a simple low-cost solution for continuous real-time, quantitative, and direct measurement of CH4 concentrations in indoor and outdoor environments, yet with the flexibility provided by the custom programmable software. It possesses future potential for remote monitoring of gases directly from mobile platforms such as smartphones and unmanned aerial vehicles (UAV).

Combined simultaneous enzymatic saccharification and comminution (SESC) and anaerobic digestion for sustainable biomethane generation from wood lignocellulose and the biochemical characterization of residual sludge solid.

Simultaneous enzymatic saccharification and comminution (SESC) was used for large-scale anaerobic digestion of wood lignocellulose to generate methane and unmodified lignin. During SESC, 10% aqueous mixture of powdered debarked wood from various species was subjected to bead milling with hydrolytic enzymes to generate particles below 1 µm. This slurry was directly used as a cosubstrate for anaerobic digestion in a 500 L stirred-tank reactor. Temperature and hydraulic retention time (HRT) were maintained at 50 °C and 30 days, respectively. At stable operation periods, an average yield of 224 L of methane per kg of cedar was attained. Comparable yields were achieved with red pine, elm, oak, and cedar bark. High-throughput microbial analysis established the presence of a relevant community to support the elevated level of methane production. The stability of the unmodified lignin in anaerobic digestion was also confirmed, allowing for its recovery as an important by-product.

Co-Evaporated CuO-Doped In2O3 1D-Nanostructure for Reversible CH4 Detection at Low Temperatures: Structural Phase Change and Properties.

In order to improve the sensitivity and to reduce the working temperature of the CH4 gas sensor, a novel 1D nanostructure of CuO-doped In2O3 was synthesized by the co-evaporation of Cu and In granules. The samples were prepared with changing the weight ratio between Cu and In. Morphology, structure, and gas sensing properties of the prepared films were characterized. The planned operating temperatures for the fabricated sensors are 50-200 °C, where the ability to detect CH4 at low temperatures is rarely reported. For low Cu content, the fabricated sensors based on CuO-doped In2O3 showed very good sensing performance at low operating temperatures. The detection of CH4 at these low temperatures exhibits the potential of the present sensors compared to the reported in the literature. The fabricated sensors showed also good reversibility toward the CH4 gas. However, the sensor fabricated of CuO-mixed In2O3 with a ratio of 1:1 did not show any response toward CH4. In other words, the mixed-phase of p- and n-type of CuO and In2O3 materials with a ratio of 1:1 is not recommended for fabricating sensors for reducing gas, such as CH4. The gas sensing mechanism was described in terms of the incorporation of Cu in the In2O3 matrix and the formation of CuO and In2O3 phases.

Methane Gas Photonic Sensor Based on Resonant Coupled Cavities.

In this paper we report methane gas photonic sensors exploiting the principle of absorption-induced redirection of light propagation in coupled resonant cavities. In particular, an example of implemented architecture consists of a Fabry-Pérot (FP) resonator coupled to a fibre ring resonator, operating in the near IR. By changing the concentration of the methane gas in the FP region, the absorption coefficient of the FP changes. In turn, the variation of the methane gas concentration allows the redirection of the light propagation in the fibre ring resonator. Then, the methane gas concentration can be evaluated by analysing the ratio between the powers of two resonant modes, counter-propagating in the fibre ring resonator. In this way, a self-referenced read-out scheme, immune to the power fluctuations of the source, has been conceived. Moreover, a sensitivity of 0.37 ± 0.04 [dB/%], defined as the ratio between resonant modes at different outputs, in a range of methane concentration included between the 0% and 5%, has been achieved. These results allow a detection limit below the lower explosive limit (LEL) to be reached with a cost-effective sensor system.

Understanding the effect of methane gas sensitivity using ultrasonic sensors and multi-matching layers inside a natural gas vehicle tank.

This research paper is the experimental study to investigate the effect of ultrasound sensitivity in the pure methane gas space as the pressure and sensor distance increases. We offer the solution to overcome the low sensitivity characteristics of ultrasonic sensors in the methane gas space. This proposal shows the physical characteristics analyzed with self-induced vibration, beam pattern, amplitude, attenuation, and Gaussian distribution validation in CH4 gas space. An ultrasonic sensor is designed with PbTio3 material of an MS-50 PTZ. The signal processing analysis system (APAS) is composed of the mechanical and controlling sections including three mass flow controllers, an air cylinder, safety valves, three pressure regulators, a CVC, ultrasound sensors, and two gas tanks (air and CH4). The experiment is performed in a wide range of the initial conditions, i.e., supplying voltage of 25 V, current of 0.2 A, pulse rate of 7 Hz, measuring distance of 0.32 to 1.02 m, resonance frequency of 57.3 Hz, ambient temperature of 296 K, and pressure increases of 1, 2, 3 and 4 bar. The ultrasonic sensitivity of a sensor (T: EVA and R: EVA) significantly enhanced the acoustic impedance in a methane gas space as pressure increases. It is verified that the sensitivity effect of an ultrasonic sensor used with ethylene vinyl acetate (EVA) matching layer is higher in the methane gas space than a chemical wood (CW) matching layer. Consequently, the effect of gas sensitivity computed by a GDA including the width (W), area (A), and height (H) is enhanced by an EVA sensor in comparison to other Models.

Estimativa do potencial de recuperação energética de resíduos sólidos urbanos usando modelos matemáticos de biodigestão anaeróbia e incineração / Estimation of municipal solid waste energy recovery potential using mathematical models of anaerobic biodigestion and incineration

RESUMO Atualmente, um dos grandes problemas enfrentados pelos gestores de resíduos sólidos urbanos (RSU) é a disposição final dos resíduos gerados por sua população. As disposições de resíduos devem ser feitas em espaços e sob condições adequados de modo a minimizar os impactos socioeconômicos e ambientais. Nesse contexto, este artigo teve por objetivo estimar o potencial de recuperação energética de RSU usando modelos de simulação matemática para a biodigestão anaeróbia e a incineração. Como objeto de estudo, foram considerados os resíduos dispostos no aterro sanitário de Caieiras, localizado no município de Caieiras (SP). Para avaliação da biodigestão anaeróbia, foram analisados modelos matemáticos que permitem estimar a produção de metano em função dos diversos fatores que interferem no processo (concentração de acetato e de micro-organismos, variação do pH, entre outros). No caso da incineração, foram considerados modelos matemáticos empíricos (baseados nas análises imediata, gravimétrica e elementar) para estimar o poder calorífico inferior dos RSU. De acordo com os resultados obtidos, para a biodigestão anaeróbia seria possível obter potência média de 38,8 MW. Caso a incineração fosse adotada como método de tratamento dos RSU, seria possível obter potência elétrica média de 214 MW (considerando a incineração de 100% dos resíduos). Com base nas simulações realizadas para a biodigestão anaeróbia e a incineração como possíveis métodos de destinação dos RSU, conclui-se que o processo de incineração apresenta potencial de geração de eletricidade aproximadamente cinco vezes maior do que a conversão energética da biodigestão anaeróbia.

ABSTRACT Currently, one of the major problems faced by managers of solid urban waste is the final disposal of the waste generated by their population. Waste disposals should be done in spaces and/or under appropriate conditions, in order to minimize socioeconomic and environmental impacts. In this context, this article aims at estimating the energy recovery potential of urban solid waste using mathematical simulation models for anaerobic biodigestion and incineration. As object of study, the waste disposed in Caieiras landfill, located in the city of Caieiras/SP, was considered. To evaluate the anaerobic digestion, mathematical models were used to estimate methane production as function of the various factors that influence the process (acetate and microorganisms concentration, pH variation among others). In the case of incineration, empirical mathematical models (based on immediate, gravimetric and elementary analysis) were used to estimate the lower heating value of urban solid waste. According to the results obtained, it would be possible to obtain an average power of 38.8 MW for anaerobic digestion. If the incineration method was adopted, it would be possible to obtain an average electrical power of 214 MW (considering the total incineration of the waste). Based on the simulations carried out for anaerobic biodigestion and incineration as possible methods of municipal solid waste disposal, it is concluded that the incineration process of municipal solid waste presents a greater potential of electricity generation, approximately five times higher than the energy conversion potential of anaerobic digestion.

Enhanced Sensitivity of a Love Wave-Based Methane Gas Sensor Incorporating a Cryptophane-A Thin Film.

A Love wave-based sensing chip incorporating a supramolecular cryptophane A (CrypA) thin film was proposed for methane gas sensing in this work. The waveguide effect in the structure of SiO2/36° YX LiTaO3 will confine the acoustic wave energy in SiO2 thin-film, which contributes well to improvement of the mass loading sensitivity. The CrypA synthesized from vanillyl alcohol by a double trimerisation method was dropped onto the wave propagation path of the sensing device, and the adsorption to methane gas molecules by supramolecular interactions in CrypA modulates the acoustic wave propagation, and the corresponding frequency shifts were connected as the sensing signal. A theoretical analysis was performed to extract the coupling of modes for sensing devices simulation. Also, the temperature self-compensation of the Love wave devices was also achieved by using reverse polarity of the temperature coefficient in each media in the waveguide structure. The developed CrypA coated Love wave sensing device was connected into the differential oscillation loop, and the corresponding gas sensitive characterization was investigated. High sensitivity, fast response, and excellent temperature stability were successfully achieved.