## 4 Conclusions  
An inherent safety assessment methodology was applied to the large-scale production of chitosan from shrimp wastes to identify the presence of hazardous associated with chemical substances and process operation. The selected numerical descriptive inherent safety (NuDIST) technique was focused on three chemical parameters (flammability, explosiveness, and toxicity) and three process parameters (temperature, pressure, and heat of reaction). According to the results, ethanol was the most dangerous chemical with CSTS of 170.65 while the other ranked chemicals reported similar CSTS values around 99-102. The parameter associated with the process was estimated at 209.20, therefore, on an industrial scale, the implementation of the process to obtain chitosan from shrimp exoskeleton is considered relatively safe; however, constant control is necessary to minimize risks of explosion and fire, specifically in the stages of depigmentation and demineralization. A NuDIST total score of 380.20 was obtained, representing a light level of risk, and consequently this process design is inherently safer than other processes in petrochemical industry with moderate risks. The replacement of ethanol by vegetable oils in the depigmentation stage must be addressed as future work to estimate improvements in the safety performance of the process at large scale. The mass integration of residual streams containing agents such as NaOH and HCl should be considered within the design to reduce its consumption and waste generation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Safety Parameters Per Stage** & **HR Score** & **Temperature Score** & **Pressure Score** \\ \hline Deacetylation & 99.90 & & \\ \hline Demineralization & 100.00 & 0.3826 & 0.8163 \\ \hline Deproteinization & 8.10 & & \\ \hline Total & 208.00 & 0.3826 & 0.8163 \\ \hline Total safety score of the process (PSTS)max & & 209.20 & \\ \hline \hline
**NuDIST Score** & & 380.20 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Process safety assessment for the large-scale production of chitosan from shrimp wastes. Figure 6: Comparison of NuDIST results for chitosan production and other processes. **Author Contributions:** Conceptualization, A.D.G.-D. and K.A.M.-S; methodology, D.A.M.-G. and D.C.-C.; software, A.D.G.-D.; validation, A.D.G.-D., A.Z., and D.C.-C.; formal analysis, D.A.M.-G. and A.D.G.-D.; investigation, D.A.M.-G. and D.C.-C.; resources, A.D.G.-D., D.A.M.-G., D.C.-C., and K.A.M.-S; data curation, A.D.G.-D. and A.Z. ; writing--original draft preparation, D.A.M.-G., A.D.G.-D., and D.C.-C.; writing--review and editing, K.A.M.-S., A.Z., and A.D.G.-D.; visualization, A.D.G.-D. and A.Z. ; supervision, A.D.G.-D. and A.Z. ; project administration, A.D.G.-D.; funding acquisition, A.D.G.-D. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Acknowledgments:** Authors express their gratitude to the University of Cartagena and Sapienza University of Rome for providing support to conduct this research. **Conflicts of Interest:** The authors declare no conflict of interest. * [PERSON] (2016) [PERSON] Production of chitin and chitosan from shrimp shell wastes. _J. Bangladesh Agric. Univ._**2016**, _14_, 253-259. [CrossRef]
* [PERSON] et al. (2016) [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] Improvement of chitosan production from Persian Gulf shrimp waste by response surface methodology. _Food Hydrocoll._**2016**, _59_, 50-58. [CrossRef]
* [PERSON] et al. (2016) [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] Potential Anti-Atherosclerotic Properties of Astaxanthin. _Mar. Drugs_**2016**, _14_, 35. [CrossRef] [PubMed]
* [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON]; [PERSON] Astaxanthin Production from Haematococcus pluvialis: Effects of Light Wavelength and Salinity. _Contemp. Eng. Sci._**2017**, _10_[PERSON] 1739-1746.