The use of grape residues as a renewable energy source for combustion presents various problems. One of these is the excessive production of carbon monoxide and nitrogen oxides. Analyses and combustion tests were performed on white and red grape pomace as well as grape stems. To verify the possibility of a reduction in emissions, straw of Miscanthus sinensis was added to mixtures with red grape pomace. Emission concentrations of carbon monoxide and nitrogen oxides were determined on a grate combustion device with a nominal thermal output of 8 kW under steady-state conditions. In addition to these emission concentrations, the excess air factor and the flue gas temperature were monitored. The results show a high energy content in grape residues. In red grape pomace, the gross calorific value of dry matter reached 22.17 MJ kg⁻¹. Unfavourable properties included high ash and nitrogen contents. During combustion tests on all types of grape residue, the emission concentrations of carbon monoxide were above the legal limit for the combustion of solid fuels. The addition of Miscanthus straw improved the behaviour during combustion. The maximum content of grape pomace in the mixture capable of meeting legislative emission requirements was 50% wt.

Residual biomass from guava (Psidium guajava L.), a common and widespread fruit tree native to Latin America, has been analyzed in the present research in order to determine the biomass quality and its potential use for energy purposes. Obtained biomass was grinded and compacted into the form of fuel briquettes. Determinations of solid biofuel parameters, i.e., physical, mechanical and chemical properties such as calorific value, moisture, ash content, volatile matter, mechanical durability, contents of the main chemical elements and heavy metals were performed according to international standards. As a result, not inconsiderable traces of heavy metals were found, with a concentration of zinc 4.57 mg kg⁻¹ as the highest. Guava’s moisture content (9.8%) comfortably fulfilled the minimum standard requirements and the net calorific value as received (17.11 MJ kg⁻¹) met the average value of a wood. However, measured sulphur content (0.063%) as well as ash content (3.74%) exceeded the maximum allowed limits for the graded wood briquettes and, therefore, guava wood briquettes should be rather categorized as non-woody A class briquettes. The results of the study can contribute significantly to the knowledge of guava wood properties and its potential as renewable solid fuel since there is little published data about it.

Viability of some African agricultural by-products as a feedstock for solid biofuel production | Musa Bappah, Jiří Bradna, Jan Malaťák, Petr Vaculík | Agricultural Journals

Pellets produced from raw or torrefied shredded logging residues have been investigated in the study. The research material came from pine and spruce stands in Poland, Slovakia, Czechia and Hungary. Torrefaction temperatures (T_t) of 250, 300, and 400 °C were applied. Before pressure agglomeration, 3% wheat flour was added to the torrefaction material as a binding agent. Pellets with a diameter of 8 mm were produced at constant humidity, compaction pressure (P) of 140 or 180 MPa and agglomeration temperature (T_a) of 100, 120 or 140 °C. The produced pellets were assessed for their physicomechanical parameters (density, radial compressive strength, compression ratio, modulus of elasticity), chemical parameters (extractive compounds, cellulose, lignin) and energy parameters (ash content, elemental composition, calorific value). The results were subjected to basic statistical analysis and multi-way ANOVA. The produced pellets varied in physical, mechanical, chemical and energy properties. A significant effect of torrefaction temperature, agglomeration temperature and compaction pressure on the results was observed. In terms of physicomechanical parameters, the best pellets were produced from the raw material, while in terms of energy parameters, those produced from the torrefied material were superior. Pellets of satisfactory quality produced from torrefied logging residues could be obtained at T_t = 250 °C, T_a = 120 °C and P = 180 MPa. Pellets with specific density of approximately 1.1 g·cm⁻³, radial compressive strength of 3–3.5 MPa, modulus of elasticity of 60–80 MPa and calorific value of 20.3–23.8 MJ·kg⁻¹ were produced in the process.

This paper focuses on the comparison of traditional and digital side mirrors in passenger cars during parallel and perpendicular parking maneuvers. The study was conducted on a closed testing ground, where data were collected through field measurements involving a relatively homogeneous group of drivers. The primary aim of the research was to evaluate how the use of digital mirrors affects parking speed and accuracy compared to traditional mirrors, and whether this new technology offers tangible benefits in terms of usability and safety. The key parameters, such as the time required to complete the parking maneuver and the accuracy of the vehicle’s positioning within the parking space, were recorded during the measurements. The data obtained from this research were then subjected to Pearson’s Chi-squared test to evaluate the drivers’ dependence and comfort with the digital side mirror technology. The analysis of the collected data revealed statistically significant differences between the two types of mirrors, with results indicating lower accuracy and higher time consumption when parking with digital mirrors compared to traditional ones. Based on these findings, it can be concluded that digital side mirrors, although representing a modern technological advancement, may have limited practical usability in terms of safety and efficiency, particularly in maneuvers requiring a high degree of precision. Therefore, the study highlights the need for further research and optimisation of this technology to ensure it can be fully utilised in everyday driving, providing drivers with comparable or greater comfort and safety than traditional side mirrors.