1. Introduction
The increasing demand for shrimp worldwide has motivated shrimp industries to raise their production capacity generating a higher amount of wastes. Such wastes are mainly composed of cephalothorax, shell, and tail, which represent approximately 50% of the total shrimp weight [
1]. Globally, the waste generation rate is around 1.4 billion ton/year [
2]. Colombia, the Caribbean and Pacific coasts mostly process shrimps according to market needs and have been environmentally affected by the generation of shrimp wastes. The major environmental issues are related to exoskeleton decomposition and attraction of insects, as well as diseases transmitted to humans [
3].
To solve environmental-related problems of shrimp wastes generation, different alternatives such as valorization of residues and production of high-value materials have been proposed. Due to the high content of chitin and carotenoids in shrimp exoskeleton (about 20–30%), shrimp wastes are known as a promising source of chitosan and astaxanthin [
4]. Chitosan is produced by enzymatic or chemical deacetylation of chitin [
5]. This biopolymer is biocompatible, biodegradable, non-toxic, and exhibits a wide range of applications in the textile, pharmaceutical, and food industries, among others [
6]. Chitin and chitosan are of commercial interest because of their high percentage of nitrogen (6.89%) compared to synthetically-substitute cellulose (1.25%) and this makes chitin a useful chelating agent [
7]. Astaxanthin is extracted using alkaline solutions at high concentrations and temperatures, without performing depigmentation processes to take advantage of such byproduct [
8]. It is a red carotenoid pigment classified as a xanthophyll, that occurs naturally in a wide variety of living organisms [
9]. This carotenoid has several applications in the cosmetic, pharmaceutical, medicinal, and health supplement industries [
10].
The extraction procedures for high-value products from shrimp wastes have been the focus of several contributions. Despite these efforts, there is still a knowledge gap in the application of computer-aided assessment tools to evaluate the performance of chitin, chitosan, and astaxanthin production from shrimp exoskeleton and identify improvement opportunities. One of the most important analyses to consider is safety assessment. Major accidents have taken place in several industries causing economic loss, physical damage, and death of employees and loss of reputation and credibility in the industry [
11]. Therefore, the importance of safety analysis becomes evident. The main objective of process safety assessment is to eliminate all hazards, or else to mitigate the consequences of these [
12].
Different metrics have been proposed for quantification and measurement of safety performance. Gerbec [
13] proposed a new universal safety indicator method to support organizational learning in process-safety incident investigation, which was determined from the outcome deficiency observations and root-cause analysis of company incident investigations. Jafari et al. [
12] stated the contribution of the index-based approach to measuring the inherent safety of the chemical process design and performed a systematic review of novel indicators developed within the period 1990–2017. They identified 35 indicators categorized according to the estimation approach (hybrid approach, equational based approach, graphical approach, advanced mathematical approach, risk-based approach, and relative ranking). Some of the most popular have been the fuzzy-logic-based inherent safety index, the process stream index, the integrated inherent safety index, and the fire and explosion index. For early design phases, inherent safety metrics are widely employed, for example, the numerical descriptive inherent safety technique (NuDIST). This metric is a universal safety indicator method to support organizational learning in process safety incident investigation [
14].
According to the contributions shown in
Table 1, there is limited open literature regarding the application of NuDIST assessment methodology in chemical processes whose process data is gathered from modeling and simulation. Despite the efforts of such techniques to overcome the limitations of conventional index-based methods for safety assessment, it was identified that there is a need to explore the use of the NuDIST metric as a decision-making tool for inherent safety designs of additional chemical processes. In this work, the NuDIST methodology is used to evaluate the performance of large-scale production of chitosan from shrimp wastes from a process safety point of view. This is the first time that process safety aspects have been analyzed at the early design phase for a scaled-up process to obtain chitosan. The incorporation of computer-aided simulation allows for the entering of more detailed process data in the calculation of the chemical and process safety index involved in the NuDIST index.
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.