V článku jsou shrnuty výsledky hodnocení termicko-oxidační stability a studia procesů stárnutí pyrolýzních olejů získaných ze zpracování odpadních plastů a pneumatik. Vzhledem k vysokému podílu reaktivních nenasycených uhlovodíků podléhají pyrolýzní oleje při skladování sekundárním degradačním reakcím, které nepříznivě ovlivňují jejich vlastnosti. Hlavním cílem práce bylo vybrat vhodnou metodiku stanovení oxidační stability a optimalizovat její podmínky pro specifika pyrolýzních produktů. Dále byl porovnán vliv zrychleného teplotního stárnutí s dlouhodobým přirozeným skladováním. Výsledky ukázaly, že standardní podmínky testů oxidační stability používané pro ropné produkty jsou pro reaktivní pyrolýzní oleje příliš agresivní, a pro hodnocení pyrolyzátů byly zmírněny pro dosažení vyšší citlivosti testu. Při studiu podmínek stárnutí se překvapivě ukázalo, že složení atmosféry nad vzorkem má zanedbatelný vliv na rychlost degradace. Naopak aplikace příliš vysokých teplot při zrychleném stárnutí vede k nežádoucím sekundárním reakcím, které výslednou stabilitu zkreslují. Podmínky testů se projevují jinak na pyrolyzátech z různých surovin – zatímco u olejů z polyolefinů se degradační procesy projeví postupným poklesem oxidační stability, u olejů z pneumatik dochází k odlišnému chování vlivem tvorby nerozpustných úsad. Upravený postup stanovení oxidační stability vycházející z metody PetroOxy se ukázal jako vhodný a rychlý nástroj pro předpověď skladovatelnosti pyrolýzních olejů z odpadních plastů a pryží.
In the EU, renewable hydrogen may seem to be experiencing a hype. However, the situation in the Czech Republic is different. Despite the acceptance of several political strategies and legislation on renewable hydrogen, as well as policymakers speaking about hydrogen technologies, the public has shown little interest in the topic. As researchers have shown, one link between policymaking and public debate is the media. We addressed two research questions: 1) What attributes and themes link media messages to renewable hydrogen, and 2) Which actors are associated with renewable hydrogen in the media, and how are these actors portrayed? To find answers, we conducted a content analysis of 78 articles from selected Czech media outlets between 2021 and 2025. Regardless of the outlet, we found that business discourse dominates, presenting renewable hydrogen as a business or investment opportunity. Media framing has made renewable hydrogen a business topic that the public acknowledges but does not feel the need to engage with. Additionally, we found that the portfolio of actors mentioned in connection with renewable hydrogen corresponds with how it is framed. Economic actors were mentioned most frequently in the corpus. Other actors play relatively insignificant roles in the renewable hydrogen segment, including the state and the EU. While SMEs and their successful projects receive the most media coverage in the renewable hydrogen field, this positive image does not bring fundamental topics to public debate. Regarding renewable hydrogen, Czech media has not built bridges between policymakers and the public nor laid the groundwork to do so.
This study investigates the potential of castor stalk, an abundant agricultural residue in Gujarat, India, as a feedstock for sustainable bioenergy production through pelletization and pyrolysis. The castor stalk was processed and characterized to determine its proximate and ultimate composition, bulk density, and higher heating value. Pelletization significantly enhanced the energy density from 2665.66 MJ.m-3 to 7406.12 MJ.m-3. Pyrolysis experiments were conducted in a batch-scale pyrolyzer across a temperature range of 400 °C to 600 °C. The optimal temperature for maximum bio-oil yield (42.80 wt. %) was found at 450 °C, accompanied by bio-char (33.60 wt. %) and pyro-gas (23.60 wt. %) production. Gas chromatography analysis revealed the presence of energy-rich gases such as H2, CO, and CH4 in the pyro-gas, with a maximum higher heating value of 14.80 MJ m-3. The bio-char exhibited both favourable fuel properties and potential for use in agriculture and industrial applications. Overall, the study demonstrates the viability of castor stalk as a cost-effective and renewable biomass source for thermochemical conversion into valuable biofuels.
Hydrogen is becoming a key part of global plans to cut carbon emissions in power generation, transportation, industrial heat, and integrated microgrid systems. This paper examines the production pathways of hydrogen specifically grey, blue, green, pink, brown/black, and naturally occurring white hydrogen and assesses their techno-economic maturity in relation to projected demand trajectories through 2050. The combustion properties of hydrogen are analyzed comprehensively, highlighting its extensive flammability limits, elevated flame velocities, minimal ignition energy requirements, diffusive-thermal instabilities, and tendencies for NOₓ formation. These characteristics have a big impact on how hydrogen-fired furnaces, spark-ignition (SI) and compression-ignition (CI) engines, and advanced gas turbine combustors are designed and used. In furnaces, using hydrogen-enriched and pure-H₂ operation can greatly lower CO₂ levels, but the burners need to be redesigned to stop flashback and NOₓ. SI hydrogen engines are getting continue to improve, thanks to direct injection, Exhaust Gas Recirculation (EGR), boosting, and knock mitigation. Hydrogen-diesel dual-fuel CI systems, on the other hand, are very efficient and produce less carbon. Gas turbines have problems with flashback, thermoacoustic instabilities, and mixing non-uniformities. This has led OEMs to use multi-nozzle, cluster-type, and low-NOₓ combustor architectures. The study also talks about how hydrogen is used in hybrid renewable microgrids, which use electrolysis, Combined Heat and Power (CHP) units, and thermal recovery to store energy for a long time. Collectively, the findings demonstrate hydrogen’s strong potential to decarbonize multi-sector energy systems.
Waste crosslinked polyethylene (XLPE) can be a source of valuable hydrocarbons for further use. XLPE is widely used material which – unlike polyethylene – is very stable both chemically and mechanically. There-fore, its waste is difficult to process. A very promising way is slow pyrolysis catalyzed by ruthenium (Ru/Al2O3) which allows the conversion of waste into hydrocarbons via degradation of rigid chemical structure of cross-linked material. High hydrocarbon yields (91–92 wt.%) were achieved by slow pyrolysis without or with cata-lyst, but significant changes in the composition of resulting gas and oil were found with the Ru/Al₂O₃ catalyst. To reveal the possibilities of using this catalyst for processing of XLPE at a relatively lower final temperature (max. 480 °C, mostly 450–470 °C), an effect of the catalyst on degradation of XLPE structure and related rheological properties of XLPE melt was investigated. It was found that the activation energy of degradation decreases significantly in the presence of the catalyst and the degradation is greatly facilitated by Ru/Al2O3 at the defect sites of the XLPE structure (the tertiary carbons). By the catalyst, the torque for XLPE melt and the its shear viscosity are significantly reduced already at 250 °C. Thus, Ru/Al2O3 catalyst, even in very small amounts (1 wt.% Ru), significantly promotes the degradation of XLPE structure and reduces the solid pyrolysis residue. This finding greatly facilitates the processing of waste XLPE. The catalytic mechanism of action of Ru is outlined and the equations for the XLPE cleavage are given. The main product of processing, pyrolysis oil, can be used as a clean heating fuel, or oil for further use, or a source of solvents, liquid and solid hydrocarbons, especially paraffin.
