The conversion of waste to energy is an essential process in the Middle East, especially in Saudi Arabia, where it plays a crucial role in waste management. The annual analysis of the decomposition hazards of the landfills in the city of Makkah showed that they ranged from 168,000 Mg in 1994 to 297,000 Mg in 2022. The emission costs of pollution ranged from 4 million in 1994 to 7 million in 2022. The number of gas emissions of plastic waste accumulating in the analyzed landfill has increased from 128,000 Mg in 1994 to 227,000 Mg in 2022. The thermal plasmas used were produced by air plasma torches, which are an essential part of plasma reactors. The operational characteristics of air plasma torches were investigated at a flow rate of 10-30 g/s, including current-voltage characteristics, applied power, applied flow rate, average temperatures of the exiting plasma jet ranging from 15,000 to 19,000 K, average velocity of the exiting plasma jet (1677.3-2763.2) m/s, wavelength of the emitted radiation ranging from 153 to 193 nm, and the corresponding beam lengths ranging from 400 to 450 mm. The proposed plasma gasification is the greenest method for processing plastic waste in the light of ecological, economic, and strategic visions with an amount of recovered pyrolysis oil in the year 2022 of 3.17 × 10⁵ tons with an equivalent energy of 12.55 × 109 MJ, with an output efficiency value equal to 81%. A roadmap for the economic and environmental visions was introduced, where the economic return on investment (ROR%) was 80%, the payback period (PBP) was 1.2 years, and the gross profit reached 129%.

The acceleration of inactivating viable cells of Escherichia coli (E. coli), by using new direct and indirect innovative methods, is the targeted method of using an atmospheric pressure plasma jet (APPJ) operated by an AC high-voltage power source with variable frequency up to 60 kHz and voltage ranging from 2.5 to 25 kV. Discharges using dry argon (0% O₂) discharges and different wet argon discharges using admixtures with O₂/Ar ratios ranging from 0.25% to 1.5% were studied. The combined effects of dry and wet argon discharges, direct and indirect exposure using a mesh controller, and hollow magnets were studied to reach a complete bacterial inactivation in short application times. Survival curves showed that the inactivation rate increased as the wettability increased. The application of magnetized non-thermal plasma discharge with a 1.5% wetness ratio causes a fast inactivation rate of microbes on surfaces, and a dramatic decrease of the residual survival of the bacterial ratio due to an increase in the jet width and the enhanced ability of fast transport of the charges to viable cells, especially at the edge of the Petri dish. The membrane damage of E. coli mechanism factors in the activation process by APPJ is discussed.

Dry argon (Ar) discharge and wet oxygen/argon (O₂/Ar) admixture discharge for alternating current atmospheric pressure plasma jets (APPJs) were studied for Ar discharges with flow rates ranging from 0.2 to 4 slm and for O₂/Ar discharges with different O₂ ratios and flow rates ranging from 2.5 to 15 mslm. The voltage–current waveform signals of APPJ discharge, gas flow rate, photo-imaging of the plasma jet length and width, discharge plasma power, axial temperature distribution, optical emission spectra, and irradiance were investigated. Different behavior for varying oxygen content in the admixture discharge was observed. The temperature recognizably decreased, axially, far away from the nozzle of the jet as the flow rate of dry argon decreased. Similar behavior was observed for wet argon but with a lower temperature than for dry argon. The optical emission spectra and the dose rate of irradiance of a plasma jet discharge were investigated as a function of plasma jet length, for dry and wet Ar discharges, to determine the data compatible with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) data for irradiance exposure limits of the skin, which are suitable for the disinfection of microbes on the skin without harmful effects, equivalent to 30 μJ/mm².

Waste-to-energy (WTE) conversion is a vital process in the Middle East, especially in the Kingdom of Saudi Arabia (KSA), which is considered sustainable development for the environmental strategic project. Previous publications dealt with the environmentally friendly plasma treatment of wastes such as municipal waste, scrap tire waste, plastic waste, and grey water, using thermal plasmas produced by the cornerstone part of plasma reactors, namely the air plasma torch. In the present paper, with a view to energy recovery from medical waste, the thermodynamic properties of air plasma torches with a flow rate of air ranging from 10 mg/s to 30 mg/s and plasma jet temperatures ranging from 1500 °C to 5000 °C were investigated; these include power loss, enthalpy, plasma flux, and torch efficiency variation with plasma input power and air flow rate. The measured electrothermal efficiency of the plasma torch is in the range of 42% to 80% and increases with the increasing input power and gas flow rate. In Makkah, the number of beds in the hospitals is 10,500; the average annual weight of the medical waste in the hospitals is 2835 × 10³ t, with an extracted amount of pyrolysis oil equivalent to 2268 × 10³ t and an equivalent energy of 90 × 10⁹ M J. In the proposed plasma treatment project, the amount of diesel oil after the distillation process will reach up to 1928 × 10³ t, with an estimated sale profit of the electricity reaching up to 21 × 10⁶ MW·h. The sale profit of pyrolysis oil in 2022 reaches up to USD 34.44 million, and the sale profit of electricity extracted by using the diesel oil in 2022 reaches up to USD 1020 million for households and USD 1445 million for factories.

This study focuses on the development of Co–CuO thin film with hierarchical morphology to serve as a promising photoelectrode for efficient photoelectrochemical (PEC) water splitting, enabling environmentally friendly H₂ production.

Acceleration of antibacterial properties is the targeted fashion of the recent part of our project by studying different techniques, on the culture media of E. coli., including the non-thermal effect using atmospheric pressure plasma jet (APPJ) and the non-thermal effects combined with the photocatalytic effects using APPJ coupled with a titanium dioxide TiO₂ precursor. The electrical, non-thermal, and optical characteristics of the laminar and turbulent mode flow of a dry argon discharge afterglow using APPJ were vital in the study of the antibacterial properties, with the measured characteristics in the laminar mode flow as follows: frequency 25 kHz; applied voltage 11.2 kV; flow rate, 2.4 slm; power, 2.34 W; jet temperature, 340 K; jet length, 11.5 mm; jet width, 1.6 mm; energy, 96 mJ; and Reynolds number, 2819. Under all the measured characteristics of maximum laminar flow mode with the flow rate, 2.4 slm, the optical emission spectroscopy data of APPJ for dry Ar discharge and for wet argon (coupled with TiO₂ precursor with the emerging jet) were measured. Survival curves of live microbes confirmed that as TiO₂ precursor concentration increases in the range from 0 to 0.5 g l⁻¹, the deactivation rate of E. coli increases due to the photocatalytic disinfection performance, because of the TiO₂ precursor concentrations dosage enhances the effect of the incident plume of the non-thermal jet, leading to the generation of more active substances that can be absorbed by the cells causing acceleration of the sterilization efficiency.