REDUCING GREENHOUSE GAS EMISSIONS IN RUSSIA: STATE OF THE PROBLEM AND COMPENSATING MEASURES FOR RESTORATION OF FORESTS AS A NET CO2 SENSOR

The article provides an overview and analysis of the state of the problem of reducing greenhouse gas (GHG) emissions in Russia, considers the measures developed at the level of the country and individual corporations that issue GHG to combat climate change. Particular attention is paid to methods of carbon dioxide (CO2) compensation, including taking into account the absorbing capacity of forests. The experience of the largest Russian oil company "Tatneft" is described in the implementation of a project for the breeding and scaling of triploid aspen with an increased absorptive capacity for planting seedlings in forests in order to reduce and compensate for the carbon footprint.

Fabrication of ZnO/CNTs for Application in CO2 Sensor at Room Temperature

Thin films of ZnO and ZnO/carbon nanotubes (CNTs) are prepared and used as CO2 gas sensors. The spray pyrolysis method was used to prepare both ZnO and ZnO/CNTs films, with CNTs first prepared using the chemical vapor deposition method (CVD). The chemical structure and optical analyses for all the prepared nanomaterials were performed using X-ray diffraction (XRD), Fourier transformer infrared spectroscopy (FTIR), and UV/Vis spectrophotometer devices, respectively. According to the XRD analysis, the crystal sizes of ZnO and ZnO/CNTs were approximately 50.4 and 65.2 nm, respectively. CNTs have average inner and outer diameters of about 3 and 13 nm respectively, according to the transmitted electron microscope (TEM), and a wall thickness of about 5 nm. The detection of CO2 is accomplished by passing varying rates of the gas from 30 to 150 sccm over the prepared thin-film electrodes. At 150 sccm, the sensitivities of ZnO and ZnO/CNTs sensors are 6.8% and 22.4%, respectively. The ZnO/CNTs sensor has a very stable sensitivity to CO2 gas for 21 days. Moreover, this sensor has a high selectivity to CO2 in comparison with other gases, in which the ZnO/CNTs sensor has a higher sensitivity to CO2 compared to H2 and C2H2.

Use of Multiple Low Cost Carbon Dioxide Sensors to Measure Exhaled Breath Distribution with Face Mask Type and Wearing Behaviour

The use of cloth face coverings and face masks has become widespread in light of the COVID-19 pandemic. This paper presents a method of using low cost wirelessly connected carbon dioxide (CO2) sensors to measure the effects of properly and improperly worn face masks on the concentration distribution of exhaled breath around the face. Four types of face masks are used in two indoor environment scenarios. CO2 as a proxy for exhaled breath is being measured with the Sensirion SCD30 CO2 sensor, and data are being transferred wirelessly to a base station. The exhaled CO2 is measured in four directions at various distances from the head of the subject, and interpolated to create spatial heat maps of CO2 concentration. Statistical analysis using the Friedman’s analysis of variance (ANOVA) test is carried out to determine the validity of the null hypotheses (i.e., distribution of the CO2 is same) between different experiment conditions. Results suggest CO2 concentrations vary little with the type of mask used; however, improper use of the face mask results in statistically different CO2 spatial distribution of concentration. The use of low cost sensors with a visual interpolation tool could provide an effective method of demonstrating the importance of proper mask wearing to the public.

PEDOT:PSS/GO NANOCOMPOSITE FOR INDOOR CO2 SENSOR

Carbon dioxide (CO2) which is a colourless and odourless gas, requires an efficient detection, as excessive amount in the environment would possibly leads to global warming. This work discusses on an environmentally friendly and non-toxic CO2 sensor for indoor air monitoring. The fabricated sensor is developed by using poly(3,4ethylenedioxythiophene):poly(4styrenesulfonate)/ graphene oxide (PEDOT:PSS/GO) nanocomposite. Nanocomposite characterisations are performed by using field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) to confirm excellent properties of PEDOT:PSS and GO as suitable materials for CO2 sensor development. Fabrication of one layer PEDOT:PSS/GO nanocomposite on environmentally friendly kaolin-coated paper substrate via dip coating method shows good electrical conductivity of 0.25 S. At room temperature, at fixed CO2 flow rate of 0.05 l/min, the fabricated sensor response time is 32 s, with sensor response and sensitivity of 0.8 and 16/l/min respectively. With fast chemiresistive response towards CO2 molecules, the fabricated sensor provides promising results for indoor CO2 monitoring.

A Miniaturised, Fully Integrated NDIR CO2 Sensor On-Chip

In this paper, we present a fully integrated Non-dispersive Infrared (NDIR) CO2 sensor implemented on a silicon chip. The sensor is based on an integrating cylinder with access waveguides. A mid-IR LED is used as the optical source, and two mid-IR photodiodes are used as detectors. The fully integrated sensor is formed by wafer bonding of two silicon substrates. The fabricated sensor was evaluated by performing a CO2 concentration measurement, showing a limit of detection of ∼750 ppm. The cross-sensitivity of the sensor to water vapor was studied both experimentally and numerically. No notable water interference was observed in the experimental characterizations. Numerical simulations showed that the transmission change induced by water vapor absorption is much smaller than the detection limit of the sensor. A qualitative analysis on the long term stability of the sensor revealed that the long term stability of the sensor is subject to the temperature fluctuations in the laboratory. The use of relatively cheap LED and photodiodes bare chips, together with the wafer-level fabrication process of the sensor provides the potential for a low cost, highly miniaturized NDIR CO2 sensor.

Development of Neutral Red as a pH/pCO2 Luminescent Sensor for Biological Systems

Neutral Red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO2 sensor, because of NR’s unique optical properties, which change with dissolved carbon dioxide (dCO2) concentrations. In the present study, optical sensitivity of NR was quantified as a function of changes in absorption and emission spectra to dCO2 in a pH 7.3 buffer medium at eight dCO2 concentrations. NR exhibited a response time of two minutes for equilibration in pure N2 to 100% CO2 with an ~200% percent change (%∆) in emission intensity and >400%∆ in absorbance, with full reversibility. Important to its application to biological systems, NR exhibited zero sensitivity to dissolved oxygen, which has routinely caused interference for CO2 measurements. NR exhibited pH sensitive emission and excitation energies with dual excitation wavelengths at 455 nm and 540 nm, and a single emission at 640 nm. The CO2 sensing properties of NR were benchmarked by a comparison to pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt) (HPTS). Future studies will evaluate the feasibility of NR as an intracellular in vivo pCO2 sensor in aquatic organisms critically impacted by increasing global CO2 levels.