## 5 Conclusions  
This study examined the potential of 14 polysaccharides and proteins as dust suppressants by testing spray-on treatments at two different biopolymer concentrations on a medium-grained sand and a fine-grained silica sand. Moisture retention tests, penetrometer tests, and crust thickness measurements were performed, and the following conclusions were drawn:  
1. Penetrometer test results on biopolymer-treated medium-grained sand ranged from 1.7 to 34.0 N (control = 1.5 N) and on fine-grained silica sand from 6.7 to 37.9 N (control = 1.7 N), respectively. The results showed that all tested biopolymers formed crusts with significantly differing penetration resistances depending on the biopolymer type (\(p<.05\)). Increasing the biopolymer concentration significantly increased the penetration resistance on medium-grained sand (\(p<.001\)). In contrast, on fine-grained silica sand, it only increased the penetration resistance of protein treatments significantly (\(p<.001\)). Proteins achieved similar penetration resistances as polysaccharides but required higher concentrations.
2. Moisture-retention test results on medium-grained sand ranged from 3.4 to 19.5 wt% (control = 6.9 wt%) and on fine-grained silica sand from 1.0 to 18.2 wt% (control = 2.5 wt%). On both tested soil types, the biopolymer type had a significant effect (\(p<.001\)) on the samples' moisture retention, resulting in it decreasing or increasing relative to the water-treated control. Increasing the concentration increased moisture retention of protein-treated fine-grained silica sand samples significantly (\(p<.001\)).
3. The thicknesses of crusts formed on biopolymer-amended medium-grained sand samples ranged from 0.3 to 8.8 mm (control = 0 mm) and on fine-grained silica sand from 3.2 to 18.1 mm (control = 0 mm). The results showed that the different biopolymers formed crusts of varying thicknesses, with the biopolymer type significantly affecting the crust thickness (\(p<.001\)). On medium-grained sand, doubling the concentration only had a significant effect for protein amendments (\(p<.001\)) and resulted in the crust thickness increasing. On fine-grained sand, increasing the concentration slightly reduced the crust thickness of most treatments because of a lower infiltration depth.  
The results of this study demonstrate that the tested polysaccharides and proteins have the potential to be applied as dust suppressants in industries such as mining. Thereby, biopolymers can contribute to reducing the industry's environmental and human health impacts.  
**Author Contributions:** Conceptualisation, J.L.S. and J.F.; methodology, J.L.S. and J.F.; formal analysis, J.L.S.; investigation, J.L.S.; data curation, J.L.S.; writing--original draft preparation, J.L.S.; writing--review and editing, J.L.S., B.G.L. and J.F.; visualisation, J.L.S.; project administration, J.L.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Data Availability Statement:** Data supporting the findings of this study will be made available from the corresponding author upon reasonable request.  
**Acknowledgments:** We thank Rheinische Baustoffwerke GmbH and Quarzwerke Frechen AG for providing the mine soils used in this study. We thank [PERSON], [PERSON], and [PERSON] for assisting in characterising the soil samples and [PERSON] for designing and printing the 3D-printed splash guard. Last, the authors would like to thank the anonymous reviewers for their helpful comments and suggestions, which improved the manuscript.  
**Conflicts of Interest:** The authors declare no conflict of interest.