We report a very low energy cost (EC) for nitric monoxide (NO) radical formation found in atmospheric spark discharge. For this purpose non-equilibrium air discharges working in spark and glow regimes were studied showing the optimum performance in the vicinity of the spark-to-glow transition. The minimum EC for NO production of about 80 eV/molecule (calculated based on the total direct current power applied to the discharge generator) is achieved in the spark regime before the transition, whereas the maximum NO yield (of about 10 ⁴ part per million) corresponds to the glow regime. Based on the estimated power absorbed in plasma the EC below 4 eV/molecule is achievable in the spark regime, which is close to the Zeldovich reaction enthalpy of NO formation (about 3 eV/molecule). The result implies that the energetic efficiency of a single spark likely exceeds that of the modern Haber–Bosch cycle (with EC of about 5 eV/molecule in the case of ammonia, according to Patil et al (2015 Catal. Today 256 49). The found low EC is associated with the discharge non-equilibrium caused by short spark duration.

In this work, we developed a portable device with low production and operation costs for generating ambient-air glow discharge (AAGD) that is transferred to the surface of flowing liquid and demonstrated its applicability to practical use in agriculture. An experiment procedure that ensured the stable treatment of various liquids was established. Additionally, it was found that humidity did not have a significant effect on the treatment process, which makes the use of the developed device possible in various locations. It was found that an _L-phenylalanine solution treated with AAGD allows simultaneous 40% hydroponic radish-sprout growth promotion with a bactericidal effect. Further, scalability and practical-application possibilities in hydroponic plant growth were discussed.

In this work, we developed a portable device with low production and operation costs for generating an ambient air low-current arc (AALCA) that is transferred to the surface of a treated liquid. It was possible to generate a stable discharge, irrespective of the conductivity of the treated liquid, as a sequence of corona, repeating spark, and low-current arc discharges. The estimated concentration of reactive oxygen and nitrogen species (RONS) in plasma-treated water (PTW) produced using AALCA treatment was two orders of magnitude higher than that of PTW produced using conventional He nonequilibrium atmospheric pressure plasma jets or dielectric barrier discharges. The strong bactericidal effect of the treatment using AALCA and the water treated using AALCA was confirmed by survival tests of Escherichia coli. Further, the possibility of treating a continuous flow of liquid using AALCA was demonstrated.

Background: Vanillin is the main byproduct of alkaline-pretreated lignocellulosic biomass during the process of fermentable-sugar production and a potent inhibitor of ethanol production by yeast. Yeast cells are usually exposed to vanillin during the industrial production of bioethanol from lignocellulosic biomass. Therefore, vanillin toxicity represents a major barrier to reducing the cost of bioethanol production.Results: In this study, we analysed the effects of oxygen-radical treatment on vanillin molecules. Our results showed that vanillin was converted to vanillic acid, protocatechuic aldehyde, protocatechuic acid, methoxyhydroquinone, 3,4-dihydroxy-5-methoxybenzaldehyde, trihydroxy-5-methoxybenzene, and their respective ring-cleaved products, which displayed decreased toxicity relative to vanillin and resulted in reduced vanillin-specific toxicity to yeast during ethanol fermentation. Additionally, after a 16-h incubation, the ethanol concentration in oxygen-radical-treated vanillin solution was 7.0-fold greater than that from non-treated solution, with similar results observed using alkaline-pretreated rice straw slurry with oxygen-radical treatment.Conclusions: This study analysed the effects of oxygen-radical treatment on vanillin molecules in the alkaline-pretreated rice straw slurry, thereby finding that this treatment converted vanillin to its derivatives, resulting in reduced vanillin toxicity to yeast during ethanol fermentation. These findings suggest that a combination of chemical and oxygen-radical treatment improved ethanol production using yeast cells, and that oxygen-radical treatment of plant biomass offers great promise for further improvements in bioethanol-production processes.