## 3 Results and Discussion
40\% BHA + 10\% BH + 10\% BBM + 40\% BM + BE} \\ \hline \multirow{2}{*}{9} & \multirow{2}{*}{31.19} & 37.09 \(\pm\) & 12.87 \(\pm\) & \multirow{2}{*}{7.92 \(\pm\) 0.18} & 10.94 \(\pm\) & 511.68 \(\pm\) & 497.82 \(\pm\) & \multirow{2}{*}{5.68 \(\pm\) 0.26} & \multirow{2}{*}{5.82 \(\pm\) 0.54} & \multirow{2}{*}{10.30 \(\pm\) 0.18} \\  & & 0.44 & 0.20 & & & & & & & & \\ \hline \multirow{2}{*}{10} & \multirow{2}{*}{32.10} & 4 of BHA:BH:BBM:BM = 2:2:2:4 (composition V) were weaker than granules from the raw material ratio BHA:BH:BBM:BM = 4:1:1:4 (composition VII). Analogous results can be seen in the case where MS was used as a binder. This means that BM and a higher BHA content increases the strength of the granules, and the waste from the buckwheat groat industry determines their plasticity. However, the origin of the binder does not significantly affect the strength of the granules. Based on the obtained data, it can be stated that the strength of the granules of the commercial fraction of compositions V-VIII is sufficient to spread them widely and to use the spinner disk at a high speed (\(>\)800 rpm) [61]. Another parameter of fertilisers that is important in determining properties such as granule static strength and bulk density is the moisture content of the commercial product. The moisture of mineral NPK fertilisers cannot exceed 2-3% [62; 63], but when producing fertilisers from organic and biodegradable materials and using binders such as MS or BE, it was not possible to dry them up to the limit specified for mineral fertilisers. The moisture content of the granules was directly related to the size of the granules, i.e., larger granules had a higher moisture content. However, the difference was small. The moisture content of the commercial product also depends slightly on the binder used. With BE (compositions V and VII), the moisture content of the granules was slightly higher than with MS (compositions VII and VIII) at 4.39-6.80% and 3.26-6.17%, respectively. Because, like all solid materials, fertilisers are compacted during transport or longer storage [64], the tapped bulk density of both fractions was measured, and it was found that the numerical value of this parameter depends very little on the size of granules. The bulk density of the raw materials (ground to particles smaller than 1 mm) was quite low and different: 503.2 kg/m\({}^{3}\) of BHA, 476.7 kg/m\({}^{3}\) of BH, 497.5 kg/m\({}^{3}\) of BBM, and 680.71 kg/m\({}^{3}\) of BM. This is in accordance with [PERSON]'s statement: typically, fluffy and dry materials such as dry sawdust, straw, grass, and shredded paper are lighter than 200 kg/m\({}^{3}\)[65]. However, after they are mixed, moistened with a binder, and granulated, the difference between the produced granules of the same compositions was small. As can be seen from Table 2, the data of bulk density vary: between 435.7 g/cm\({}^{3}\) and 503.0 kg/m\({}^{3}\) for composition V; between 489.7 kg/m\({}^{3}\) and 521.0 kg/m\({}^{3}\) for composition VI; between 497.8 kg/m\({}^{3}\) and 567.8 kg/m\({}^{3}\) for composition VII; between 551.2 kg/m\({}^{3}\) and 619.9 kg/m\({}^{3}\) for composition VIII. Analysing the influence of the composition, it can be stated that the tapped bulk density of the biofertilisers with the use of greater amounts of BHA and MS; however, the change is not significant. Similar bulk density is an important and positive factor, because, in this case, a constant storage volume is required, segregation during transportation is reduced, and the uniform spreading of fertilisers in the fields is ensured. A high bulk density is very important in packaging and transportation and is desirable as it can significantly reduce costs. However, since it is determined not only by the chosen granulation method but also by the raw materials, which in this case are light, the bulk density of the produced biofertilisers is not very high and does not equal the density of mineral NPK fertilisers, which is 900-1100 kg/m\({}^{3}\) depending on the kind [66].