Non-destructive mid-IR spectroscopy with quantum cascade laser can detect ethylene gas dynamics of apple cultivar ‘Fuji’ in real time

Many plants, including fruits and vegetables, release biogenic gases containing various volatile organic compounds such as ethylene (C2H4), which is a gaseous phytohormone. Non-destructive and in-situ gas sampling technology to detect trace C2H4 released from plants in real time would be attractive for visualising the ageing, ripening, and defence reactions of plants. In this study, we developed a C2H4 detection system with a detection limit of 0.8 ppb (3σ) using laser absorption spectroscopy. The C2H4 detection system consists of a mid-infrared quantum cascade laser oscillated at 10.5 µm, a multi-pass gas cell, a mid-IR photodetector, and a gas sampling system. Using non-destructive and in-situ gas sampling, while maintaining the internal pressure of the multi-pass gas cell at low pressure, the change in trace C2H4 concentration released from apples (Malus domestica Borkh.) can be observed in real time. We succeeded in observing C2H4 concentration changes with a time resolution of 1 s, while changing the atmospheric gas and surface temperature of apples from the ‘Fuji’ cultivar. This technique allows the visualisation of detailed C2H4 dynamics in plant environmental response, which may be promising for further progress in plant physiology, agriculture, and food science.

Assessment of the applicability of a low-cost sensor–based methane monitoring system for continuous multi-channel sampling

Systems that are made of several low-cost gas sensors with automatic gas sampling may have the potential to serve as reliable fast methane analyzers. However, there is a lack of reports about such types of systems evaluated under field conditions. Here, we developed a continuous methane monitoring system with automated gas sampling unit using low-cost gas sensors, TGS 2611 and MQ-4, that use a simple cloud-based data acquisition platform. We verified the consistency, repeatability, and reproducibility of the data obtained by TGS 2611 and MQ-4 low-cost gas sensors by measuring high- and low-concentration methane samples. The normalized root-mean-square errors (NRMSEs) of the samples with high methane concentrations, [CH4] of 3, 4, 6, and 7%, were 0.0788, 0.0696, 0.1198, and 0.0719 for the TGS 2611 sensor, respectively, and were confirmed using a gas chromatograph as a reference analyzer. The NRMSEs of the samples with low [CH4] of 0.096, 0.145, 0.193, and 0.241% measured by the TGS 2611 sensor were 0.0641, 0.1749, 0.0157, and 0.1613, whereas those NRMSEs of the same concentrations measured by the MQ-4 sensor were 0.3143, 0.5766, 0.6301, and 0.6859, respectively. Laboratory-scale anaerobic digesters were tested using the developed system. The anaerobic digesters were continuously operated for 2 months, demonstrating the potential use of sensors for detecting and monitoring methane in the field level application. This study utilized a unique way to combine the advantages of low-cost sensors and develop a reliable monitoring system by minimizing drawbacks of low-cost sensors.

Research and Assessment of Biogas Composition at the TKO Running and Recommendations for Its Use

The article deals with the main problems, namely the emission of biogas into the atmospheric air, during operation and after the closure of MSW landfills. Biogas, which contains methane, is considered not only as a strong greenhouse gas, but also as a valuable fuel that can be used as an energy resource. To assess the biogas potential at the operating landfill, field studies were carried out, which made it possible to determine the intensity and composition of gas emissions. The main points of landfill gas sampling at the landfill have been selected. Methods have been worked out and the equipment necessary for environmental monitoring at a real operating landfill has been selected. Using gas-geochemical surveys, environmental monitoring of biogas emissions from the MSW landfill was carried out at 49 sampling points. Coordinates in the WGS84 coordinate system, maps of the concentration distribution of the main components of biogas (methane, hydrogen sulfide, carbon dioxide, oxygen) were obtained at a depth of 50 cm from the surface of the landfill body. A zone recommended for drilling biogas wells was selected and recommendations were developed for installing a degassing station and using biogas as a source of electricity