Research Highlights: The correlations between seed mass and the remaining physical properties were determined in selected fir species, and a method for seed sorting was proposed to promote uniform germination and emergence. Background and Objectives: Information about the variation and correlations between the physical properties of seeds is essential for designing and modeling seed processing operations such as seed separation. The aim of this study was to determine the range of variation in the physical properties of seeds in eleven fir species, and to analyze the correlations between these parameters to improve the seed sorting process. Materials and Methods: Terminal velocity, thickness, width, length, the angle of external friction and mass were determined in the seeds of 11 fir species. The measured parameters were used to calculate the geometric mean diameter, three aspect ratios, sphericity index and the specific mass of each seed. Results: The seeds of Sierra white fir where most similar, whereas the seeds of balsam fir differed most considerably from the seeds of the remaining fir species. In the majority of the analyzed fir species, seed mass was most strongly correlated with terminal velocity, followed by thickness. Conclusions: Fir seeds should be sorted primarily with the use of mesh sieves with longitudinal openings to obtain fractions with similar seed mass and to eliminate the need for dewinging.

Relationships between the physical properties of seed and their germination capacity and energy is an important consideration for separating seeds of the highest or lowest quality. The objective of this study was to determine the correlations between the selected aerodynamic, geometric, frictional and mass parameters of cultivated radish (Raphanus sativus L.) seeds and their germination capacity for the purpose of improving seed quality. The parameters were determined for graded and discarded radish seeds and impurities were separated by a gravity separator. A germination test was performed, its results were verified every 12 hours, and the germination rate index was determined. A statistical analysis revealed that germinated and non-germinated seeds from the graded fraction did not differ significantly. In the discarded fraction, germinated seeds were characterized by higher terminal velocity (by approx. 10%), thickness (by approx. 9%) and mass (by approx. 26%) in comparison with non-germinated seeds. Significant positive correlations were noted between the germination time vs terminal velocity and mass of discarded seeds. Thus, the separation of radish seeds should take place in two stages using a gravity separator and a pneumatic separator. A vertical stream of air with the speed of approx. 8 m s -1 allows recovery of around 37% of discarded seeds that contain approx. 86% of healthy germs. The resulting seed mixture is characterized by greater germination energy and capacity than the seed fraction graded on a gravity separator only.

The aim of the described research was to assess the suitability of onion husk waste as a material for the production of solid fuels in the form of granules (pellets). Due to the low susceptibility to thickening of onion husks, the addition of a binder in the form of potato pulp was used (waste with a high starch content). Both wastes were subjected to elemental analysis determining the content of C, H, N, S, Cl, and their HHV (High Heating Value) and LHV (Low Heating Value). Mixtures containing the addition of 10%, 15%, and 20% potato pulp to onion husks were subjected to granulation in a “flat matrix–thickening rollers” operating system at three rotational speeds of the granulator matrix a 170, 220, and 270 rpm. The influence of the potato pulp addition and matrix rotational speed on the quality of the obtained pellet was determined. The highest quality product was combusted in a low-power boiler with a retort grate, and the content of CO, CO2, SO2, NO, and HCl in the exhaust gas was determined. The highest quality granulate was obtained from a mixture containing 10% potato pulp, which was compacted at 170 rpm matrix, where the kinetic strength was 99.50% and the density was about 650 kg·m−3. The results of the combustion emissions from onion husk granules exceed the requirements of the EcoDesign Directive with the greatest being the case of CO.

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