## 5 Conclusions  
This research on VOC emission kinetics from stored CRDF in relation to its structural modification indicated:  
* A significant effect of CRDF densification was observed for the maximum emission of total VOC potential, where pelletization decreases maximum emission potential \(E_{0}\) by 86%, while pelletization with a binder reduced \(E_{0}\) by 63%;
* pelletization both with and without a binder modified total VOC emission constant rate \(k\) by only \(\pm 10\%\) in relation to ground CRDF;
* half of maximum VOC potential was released within 2.26 to 2.76 d of storage. Therefore, it is recommended that shorter storage, and potential for venting and treating VOC emissions from CRDF should be explored;
* numerous deviations of emission patterns from the first-order model were noted for individual VOCs. More research in this area is warranted;
* a correlation between VOC boiling point and emission constant rate was not confirmed in all structural CRDF modification cases. More research in this area is warranted; and
* further research on the VOC emission mechanism from CRDF and other biochar types should be developed as a new niche in fundamental and applied biomass science, and waste conversion into high-quality solid fuels with consideration of worker-safety aspects.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2071-1050/11/3/935/s1](http://www.mdpi.com/2071-1050/11/3/935/s1)]([http://www.mdpi.com/2071-1050/11/3/935/s1](http://www.mdpi.com/2071-1050/11/3/935/s1)). The following files were submitted as supplementary materials in zipped folder \"supplementary materials.zip\":CRDF VOCs emission kinetics Sustainability.xlsx, containing detailed results of VOC emissions from stored CRDF, and the emission kinetic modeling.  
**Author Contributions:** Conceptualization, A.B. and A.S.; methodology, A.B., M.M., A.S., and J.L.; formal analysis, A.B., M.M., and J.L.; validation, A.B., M.M., A.S., and J.K.; investigation, M.M. and J.L.; resources, A.B. and A.S.; data curation, M.M., J.L., A.S., and A.B.; writing--original draft preparation, A.B. and M.M.; writing--review and editing, A.B., J.K., A.S., and J.L.; visualization, A.B. and J.K.; and supervision, A.B., A.S., and J.K.  
**Funding:** Authors would like to thank the Fulbright Foundation for funding the project titled \"Research on pollutant emissions from Carbonized Refuse Derived Fuel into the environment\", completed at Iowa State University. In addition, this project was partially supported by the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project no. IOW05556 (Future Challenges in Animal Production Systems: Seeking Solutions through Focused Facilitation) was sponsored by the Hatch Act and State of Iowa funds. The publication is financed under the program of the Minister of Science and Higher Education \"Strategy of Excellence - University of Research\" in 2018 - 2019 project number 0019 / SDU / 2018/18 in the amount of PLN 700 000.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.