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The production of hydrogen from plastic and biomass waste via processes powered by renewable electricity can be a pivotal contributor to an effective waste management system in a circular economy. Copyrolysis of plastic and biomass waste mixtures can be economically appealing, not only by eliminating the need for waste stream separation but also by potentially synergizing hydrogen production. In this study, we present evidence of such hydrogen production synergy in plasma copyrolysis of mixtures of low-density polyethylene (LDPE) and cellulose (CE) as plastic and biomass waste models, respectively. We treated samples made of mixtures of LDPE and CE powders at five different mass ratios, ranging from 100% LDPE to 100% CE. We used non-thermal nitrogen plasma and argon plasma in a Streamer Dielectric-Barrier Discharge (SDBD) configuration under atmospheric pressure conditions. Synergistic hydrogen production was observed when nitrogen was used as the working gas, but not with argon, resulting in up to 37% greater hydrogen production compared to non-synergistic expectations. This outcome is attributed to the nitrogen-doped oxygenated carbonaceous residues from CE pyrolysis catalyzing the dehydrogenation and reforming of light alkanes resulting from the decomposition of LDPE. [Display omitted] • Plasma copyrolysis of LDPE and cellulose using nitrogen leads to increased hydrogen yield. • Synergy leads to up to 37% increased hydrogen production. • The lowest energy cost of 1.5 MWh/kg-H 2 is achieved for 1:2 LDPE:cellulose mass ratio. • Synergy attributed to nitrogen doping of cellulose-derived carbonaceous residues. [ABSTRACT FROM AUTHOR]

The valorization of waste, by creating economic value while limiting environmental impact, can have an essential role in sustainable development. Particularly, polymeric waste such as biomass and plastics can be used for the production of green hydrogen as a carbon-free energy carrier through the use of nonthermal plasma powered by renewable, potentially surplus, electricity. In this study, a Streamer Dielectric-Barrier Discharge (SDBD) reactor is designed and built to extract hydrogen and carbon co-products from cellulose and low-density polyethylene (LDPE) as model feedstocks for biomass and plastic waste, respectively. Spectroscopic and electrical diagnostics, together with modeling, are used to estimate representative plasma properties, namely electron and excitation temperatures, number density, and power consumption. Cellulose and LDPE are plasma-treated for different treatment times to characterize the evolution of the hydrogen production process. Gas products are analyzed using gas chromatography to determine the mean hydrogen production rate, production efficiency, hydrogen yield, selectivity, and energy cost. The results show that the maximum hydrogen production efficiency for cellulose is 0.8 mol/kWh, which is approximately double that for LDPE. Furthermore, the energy cost of hydrogen production from cellulose is 600 kWh/kg of H 2 , half that of LDPE. Solid products are examined via scanning electron microscopy, revealing the distinct morphological structure of the two feedstocks treated, as well as by elemental composition analysis. The results demonstrate that SDBD plasma is effective at producing hydrogen from cellulose and LDPE at near atmospheric pressure and relatively low-temperature conditions in rapid-response and compact processes. [Display omitted] • Streamer Dielectric Barrier Discharge (SDBD) reactor for hydrogen production from polymeric solids. • Treatment of cellulose and LDPE as biomass and plastic waste models for different treatment times. • Quantification and characterization of gas and solid products. • Minimum energy cost of 600 kWh/kg of H 2 for cellulose, half of that for LDPE. [ABSTRACT FROM AUTHOR]

Hydrogen is largely produced via natural gas reforming or electrochemical water-splitting, leaving organic solid feedstocks under-utilized. Plasma technology powered by renewable electricity can lead to the sustainable upcycling of plastic waste and production of green hydrogen. In this work, low-temperature atmospheric pressure plasma reactors based on transferred arc (transarc) and gliding arc (glidarc) discharges are designed, built, and characterized to produce hydrogen from low-density polyethylene (LDPE) as a model plastic waste. Experimental results show that hydrogen production rate and efficiency increase monotonically with increasing voltage level in both reactors, with the maximum hydrogen production of 0.33 and 0.42 mmol/g LDPE for transarc and glidarc reactors, respectively. For the transarc reactor, smaller electrode-feedstock spacing favors greater hydrogen production, whereas, for the glidarc reactor, greater hydrogen production is obtained at intermediate flow rates. The hydrogen production from LDPE is comparable despite the markedly different modes of operation between the two reactors. • Hydrogen production from polyethylene via atmospheric nonthermal plasma demonstrated. • Two plasma reactor designs with complementary characteristics experimentally evaluated. • Hydrogen production as function of operational parameters assessed. • Hydrogen production efficiency comparable despite different operation of the reactors. [ABSTRACT FROM AUTHOR]