Quantitative Inherent Safety Assessment of Crude Palm Oil Production Using the NuDIST Methodology

Abstract

Crude palm oil (CPO) is the most widely consumed vegetable oil globally due to its high agricultural productivity and its increasing use in the food and energy sectors. However, its production process involves intensive operations, severe temperature and pressure conditions, and work environments that increase the risk of industrial accidents, highlighting the need for rigorous process safety assessments from the early design stages. Traditionally, these analyses have relied on inherent safety indices, which, while allowing for quick comparisons, have limitations related to subjectivity and the simplification of complex phenomena. In this context, the present study aims to evaluate the inherent safety of the CPO production process using the Numerical Descriptive Inherent Safety Technique (NuDIST), a quantitative approach based on logistic functions. The methodology considers chemical safety parameters—flammability, explosiveness, toxicity, and reactivity—and process safety parameters—temperature, pressure, heat of reaction, and process inventory—applied to an industrial process with a capacity of 30 t/h of fresh fruit bunches (FFB). The results indicate that linoleic acid is the substance that contributes most to chemical safety, with a Chemical Safety Total Score (CSTS) of 26.14, while process inventory dominates process safety, reaching a Process Safety Total Score (PSTS) of 101.95. The total NuDIST score obtained was 128.09, demonstrating that the process risks are mainly associated with operating conditions rather than the hazards of the substances. Comparisons with other industrial systems reveal that CPO extraction is inherently safer than processes such as chitosan production from shrimp exoskeletons and six (6) possible routes for methyl methacrylate (MMA) production. Taken together, these findings position NuDIST as a robust and objective tool for strengthening the safe and sustainable design of agro-industrial processes.

1. Introduction

The increase in the use of vegetable oils is driven by population growth, the need to incorporate renewable energy sources that contribute to mitigating greenhouse gas emissions, and the sustained development of the biofuels industry [1]. In this context, palm oil has become the most consumed vegetable oil globally, due to its high productivity per unit of cultivated area [2]. Oil palm has yields of around 4 to 4.5 tons per hectare, a figure considerably higher than those of other oilseed crops, which explains its predominant position in the world market [3]. The five main countries that produce it are Indonesia, Malaysia, Thailand, Colombia, and Nigeria [4]. Furthermore, the growing demand for this oil is not only due to its use in the food industry, but also due to its wide versatility, particularly in the production of biodiesel, which makes it a strategic input for both the food and energy sectors [5].

Palm oil is extracted from the fully developed mesocarp of the fruits produced by the African oil palm (Elaeis guineensis). These fruits are drupes that develop in compact, elongated, and pointed clusters [6]. Obtaining this oil requires a chain of operations that begins with the establishment and management of oil palm plantations [7]. Upon reaching maturity, the fresh fruit bunches (FFB) allow the production of two distinct oilseed products: crude palm oil (CPO), which is recovered from the fruit mesocarp, and palm kernel oil (PKO), which is derived from the inner kernel of the fruit [8]. Within this framework, the production of CPO comprises several successive stages, including the reception, weighing, and selection of the bunches, their placement in cages, sterilization, and separation of the fruit through dehulling and threshing [9]. Subsequently, the process includes the digestion and pressing of the material, followed by oil clarification, recovery of the kernels, and, as a final stage, drying [10]. However, it is essential to begin the process by thoroughly understanding the inherent dangers; the crude palm oil production sector involves labor-intensive operations, exposure to high temperatures, and often inadequate working environments, which together increase the likelihood of workplace accidents and adverse health effects [11]. Therefore, a security analysis is required to determine potential risks in the system and propose effective prevention or mitigation measures to improve the process.

In this regard, evaluating process safety during the initial design phase helps select the safest route from among several alternatives. A process pathway that minimizes the use of dangerous substances and operates under milder conditions will naturally lead to a facility that is intrinsically safer and more straightforward to manage [12]. Most safety assessment methods for the process design stage are based on indices such as the PIIS (Prototype Index for Inherent Safety) [13] or the ISI (Inherent Safety Index) [14]. Although safety indices such as PIIS and ISI allow for a quick comparison of design alternatives, they have significant drawbacks: they rely on weightings that do not always adequately represent the complexity of the process, they can oversimplify risk phenomena, and, above all, they introduce a high degree of subjectivity into the qualitative evaluation, since the assignment of scores depends on the evaluator’s judgment. This subjectivity can lead to inconsistent or poorly reproducible decisions among different analysts. To overcome these limitations, it is necessary to complement or replace these indices with more objective numerical quantification methods that incorporate quantifiable hazard metrics, such as the Numerical Descriptive Inherent Safety Technique (NuDIST), based on logistic functions, thus enabling more rigorous, comparable, and data-driven evaluations [15].

Accordingly, this study aims to assess the inherent safety of the crude palm oil production process through the application of the NuDIST methodology, which is based on a study that analyzes inherent safety in the petrochemical industry [15], and it has been implemented in bioprocesses such as the production of chitosan from shrimp exoskeletons [16]. It should be emphasized that, despite the existence of several investigations addressing inherent safety in crude palm oil production processes using methods such as ISI [17] and HIRA (Hazard Identification and Ranking) assessments [18], this is the first study to focus on the NuDIST approach. This research aims to address this knowledge gap by applying the NuDIST methodology to the crude palm oil production process. This provides a comprehensive and novel analysis that integrates chemical and operational parameters within a continuous mathematical framework. Its main advantage over inherent safety index-based methods lies in the incorporation of the logistic function as the basis for assigning chemical and process safety scores, making it a solution for assessing inherent safety that overcomes some of the drawbacks of earlier indices. This approach enables the transformation of qualitative or categorical variables into a continuous and mathematically consistent scale, thereby eliminating the subjective scaling problem inherent in index-based methods [15]. In this way, NuDIST offers a quantitative framework that more accurately reflects the actual variability of hazard parameters and provides a more robust and comparative assessment of intrinsic safety.

Finally, this research addresses a key sustainability challenge associated with the palm oil industry: the need to produce a strategic input for the food and energy sectors under safer, more efficient, and more resilient conditions, reducing the risk of industrial accidents that can generate significant social, environmental, and economic impacts. By applying the NuDIST methodology, the study directly contributes to the social and environmental dimensions of sustainability by promoting the design and operation of inherently safer processes from early stages. This translates into a lower probability of catastrophic events, protection of workers, and a reduction in material and energy losses. In this sense, the results support the Sustainable Development Goals (SDGs), particularly SDG 9 (Industry, Innovation and Infrastructure), by fostering more robust and efficient industrial processes; SDG 12 (Responsible Consumption and Production), through the optimization of inventory and resource use; and SDG 8 (Decent Work and Economic Growth), by strengthening safety in intensive agro-industrial environments. Furthermore, by identifying that the main opportunities for improvement are concentrated in the operating conditions and the inventory of the process, the study provides concrete information to guide optimization strategies that reinforce the overall sustainability of the palm sector.

2. Materials and Methods

A safety evaluation using the NuDIST methodology, founded on logistic functions, was applied to a crude palm oil (CPO) extraction system. The process corresponds to a single-product physical operation with a throughput of 30 tons per hour of African palm fresh fruit bunches (FFB), equivalent to 240,000 tons annually assuming 8000 operating hours, resulting in an annual production of 54,056 tons of crude palm oil, i.e., achieving an approximate production yield of 22.52%. The data on operating conditions were taken from the existing literature on the process [19].

Figure 1 shows a fishbone diagram to provide a general cause-and-effect analysis related to materials, equipment, method, measurement, environment, and personnel; this justifies the use of the NuDIST methodology to assess the inherent safety of the crude palm oil (CPO) production process.

The cause-and-effect diagram allowed for structuring the identification of threats under the NuDIST approach, integrating technical, operational, human, and environmental factors. This classification facilitated the evaluation of undesirable scenarios and the systematic analysis of risks in crude palm oil production.

2.1. Process Description

Figure 2 illustrates the process flow and key equipment units involved in crude palm oil production. Fresh fruit bunches (FFB) from African oil palm are introduced at a throughput of 30,000 kg/h (stream 1), at 303 K and atmospheric pressure, with an oil content of 7282 kg/h. The bunches are transferred from the feed hopper to closed horizontal sterilizers using wagons, where sterilization is performed with 8175 kg/h of saturated steam (stream 4) at 421 K and 4 atm. This step aims to deactivate lipase enzymes to minimize free fatty acid generation and to promote hydrolysis of the palm rachis, facilitating softening of the mesocarp. As a result, 26,696 kg/h of sterilized bunches are obtained at 406 K and 3 atm (stream 5), along with 10,063 kg/h of condensate at 358 K and 1 atm (stream 2) and 1416 kg/h of excess steam at 421 K and 4 atm (stream 3) [4].

Following sterilization, the treated bunches are conveyed to a rotary drum for separation, producing 18,927 kg/h of fruits (stream 7) and 7769 kg/h of rachis (stream 6), both at 406 K and 3 atm. The recovered fruits are then transferred to the digestion stage, where reheating facilitates oil liberation during pressing and enhances pulp–nut separation. This step involves mechanical maceration with the injection of 1350 kg/h of steam (stream 8) at 421 K and atmospheric pressure. The digested material, with a flow rate of 20,277 kg/h at 378 K and 1 atm (stream 9), is subsequently introduced into a horizontal press fitted with a perforated cylindrical basket. In this unit, 8582 kg/h of an oil-rich liquor (stream 11) at 378 K and 1 atm is recovered through the mechanical action of two parallel, counter-rotating regressive screw worms, while 11,695 kg/h of press cake at the same conditions is discharged as stream 10 [19].

A water stream of 2535 kg/h at 358 K and atmospheric pressure is introduced into the press liquor (stream 12) to reduce its viscosity, thereby facilitating subsequent oil separation and purification. During the static clarification step, carried out by gravity settling, approximately 90% of the oil is recovered (5078 kg/h at 365 K and 1 atm). This fraction overflows from the clarifier and is transferred (stream 16) to the drying unit. The final 10% of the oil is recovered during the dynamic clarification stage by means of centrifugation. In this step, the heavier settled fraction is fed to the centrifuge (stream 13, 6711 kg/h at 365 K and 1 atm), whereas water and high-density solids are expelled through the nozzles (stream 14, 6040 kg/h at 375 K and 1 atm). At the same time, an oil-rich fraction containing lighter solids concentrates in the central zone and is removed via a discharge outlet. This flow is recirculated to the static clarification unit along with the press liquor (stream 15, 671 kg/h at 365 K and 1 atm). As a final treatment, the oil undergoes drying to minimize residual moisture and impurities (stream 17, 8 kg/h at 333 K and 1 atm). Given the high outlet temperature, this operation is performed under vacuum to enhance water evaporation. The resulting dehydrated palm oil is then conveyed to storage as the final product (5070 kg/h at 333 K and 1 atm) through stream 18 [4].

Additionally, it is necessary to identify the representative substances in the crude palm oil (CPO) extraction process to determine the NuDIST chemical safety parameters. The chemicals involved, with their respective CAS numbers, are specified in

Table 1. Representative components in the crude palm oil production process.

Representative Components	CAS Numbers	References
Water	7732-18-5	[20]
Calcium oxide as ash	1305-78-8	[21]
Silica	7631-86-9	[22]
Cellulose	9004-34-6	[23]
Hemicellulose	9025-56-3	[24]
Lignin	9005-53-2	[25]
Palmitic acid	57-10-3	[26]
Oleic acid	112-80-1	[27]
Linoleic acid	60-33-3	[28]
1,3-dipalmitoyl-2-oleoylglycerol	1867-91-0	[29]
Tripalmitin	555-44-2	[30]
Triolein	122-32-7	[31]

.

Finally, it is necessary to analyze the operating conditions, such as temperature and pressure, of the different stages of the crude palm oil (CPO) extraction process to determine the NuDIST process safety parameters.

Table 2. Operating conditions of the streams in the crude palm oil production process.

Stream	Temperature (K)	Pressure (atm)
1	303.15	1.00
2	420.85	4.40
3	358.15	1.00
4	420.85	4.40
5	406.32	2.72
6	406.32	2.72
7	406.32	2.72
8	420.85	1.00
9	378.19	1.00
10	378.19	1.00
11	378.19	1.00
12	358.15	1.00
13	365.15	1.00
14	375.46	1.00
15	365.15	1.00
16	365.00	1.00
17	332.58	1.00
18	332.58	1.00

contains the process operating conditions, showing a pressure range of 1.00 to 4.40 atm and a temperature range of 303.15 K to 420.85 K, categorized as safe operating conditions or conditions with no risk of death.

2.2. Numerical Descriptive Inherent Safety Technique (NuDIST) for Inherent Safety Assessment in Crude Palm Oil Production Process

The method, based on logistic functions, as introduced by Ahmad et al. [15], has two main components: chemical safety and process safety. With regard to the chemical safety parameters, four were evaluated—flammability, explosiveness, toxicity, and reactivity—whereas those related to process safety were temperature, pressure, heat of reaction, and process inventory, all analyzed within the same logistical function that distinguishes the method.

The use of the NuDIST technique is justified over conventional index-based methods due to its ability to reduce the subjectivity inherent in discrete scoring by employing continuous logistic functions based on quantifiable parameters. Unlike traditional indices, NuDIST transforms chemical and operational variables into a consistent mathematical scale, improving the reproducibility and comparability of results across processes. This feature is particularly relevant in palm oil production, where complex physical operations and variable operating conditions predominate. Furthermore, NuDIST allows for a more precise identification of dominant risk factors, differentiating between chemical and process contributions. Therefore, its application provides a more robust and objective assessment of inherent safety compared to conventional index-based approaches.

2.2.1. NuDIST Total Score

The NuDIST Total Score is determined separately for each process route under evaluation. Accordingly, every route analyzed with this methodology is assigned a specific overall score that combines both the Chemical Safety Total Score (CSTS) and the Process Safety Total Score (PSTS), such that the NuDIST Total Score represents the cumulative contribution of these two components [15], as shown in Equation (1).

$$\mathrm{N}\mathrm{u}\mathrm{D}\mathrm{I}\mathrm{S}\mathrm{T} \mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{S}\mathrm{c}\mathrm{o}\mathrm{r}\mathrm{e}=\mathrm{C}\mathrm{S}\mathrm{T}\mathrm{S}+\mathrm{P}\mathrm{S}\mathrm{T}\mathrm{S}$$

(1)

The overall score calculated for each route plays a key role in the classification process of alternatives, as it enables the identification of the safest option among them. In this context, a lower NuDIST Total Score reflects a route with reduced hazard potential relative to those with higher values. Consequently, the chemical safety and process safety scores must first be evaluated in order to obtain the final NuDIST Total Score [15].

2.2.2. Chemical Safety Total Score (CSTS)

The Chemical Safety Total Score (CSTS) is calculated according to Equation (2). The CSTS calculation is based on the worst-case scenario [32]. The worst-case scenario describes the situation with the highest possible risk [14]. For each substance, the flammability (S_FL), explosiveness (S_EXP), toxicity (S_TOX), and reactivity (S_R) scores are aggregated, and the highest resulting value is taken as indicative of the most critical chemical, representing the dominant contribution to chemical safety within the process analyzed [15].

$$\mathrm{C}\mathrm{S}\mathrm{T}\mathrm{S}={\left({\mathrm{S}}_{\mathrm{F}\mathrm{L}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{E}\mathrm{X}\mathrm{P}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{T}\mathrm{O}\mathrm{X}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{R}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}$$

(2)

Flammability is defined as the ease with which a material burns in air [33]. In this approach, the flammability parameter (S_FL) is determined using the liquid’s flash point, which corresponds to the minimum temperature at which sufficient vapor is released to create an ignitable mixture with air [34]. The tendency of a liquid to ignite is governed by its lower flammability limit and by how readily it generates vapors across typical temperature ranges [14]. Therefore, liquids that ignite at lower temperatures pose a higher hazard than those with higher flash point values [15]. This parameter is calculated using Equation (3), where the term x is the flash point in °C for the substances in the process under study.

$${\mathrm{S}}_{\mathrm{F}\mathrm{L}}=100\times \left(1-\left({\displaystyle \frac{1}{1+3.77{\mathrm{e}}^{-0.024\mathrm{x}}}}\right)\right)$$

(3)

Explosiveness, defined as a chemical’s propensity to generate an explosive mixture with air, is determined by the span between its lower and upper explosive limits [14]. When the concentration is below the lower explosive limit (LEL), the mixture does not contain enough fuel to ignite, whereas concentrations above the upper explosive limit (UEL) are excessively rich to sustain combustion [34]. Therefore, within this methodology, the explosiveness parameter (S_EXP) increases as the gap between the lower and upper explosive limits becomes larger, reflecting a higher explosion potential. Because both limits are reported on a volumetric percentage basis, a 50% difference between the LEL and UEL is considered a reference midpoint, representing a neutral state that is neither particularly safe nor especially hazardous [15]. This parameter is calculated using Equation (4), where the term x is the difference between the UEL and the LEL in volume percent (vol%) for the substances of the process studied.

$${\mathrm{S}}_{\mathrm{E}\mathrm{X}\mathrm{P}}=100\times \left({\displaystyle \frac{1}{1+1096.63{\mathrm{e}}^{-0.14\mathrm{x}}}}\right)$$

(4)

Toxicity refers to the capacity of a substance to produce adverse effects in living organisms. One commonly used measure for assessing chemical toxicity is the Threshold Limit Value (TLV), as defined by the American Conference of Governmental Industrial Hygienists (ACGIH). In the present methodology, the Short-Term Exposure Limit (TLV-STEL) is selected to quantify the toxicity parameter (S_TOX), since it is better suited to represent short-duration exposure and acute toxic effects [34].

The TLV-STEL represents the highest airborne concentration to which employees may be exposed for a short duration of up to 15 min without experiencing severe irritation, lasting or irreversible tissue damage, or narcotic effects that could elevate accident risk, compromise self-protective abilities, or markedly reduce work performance, as long as such exposures occur no more than four times per day, are separated by intervals of at least 60 min, and do not result in exceeding the daily Threshold Limit Value—Time Weighted Average (TLV-TWA) [34]. A chemical with a lower TLV-STEL is associated with greater toxic hazards, whereas substances with higher TLV-STEL values pose comparatively lower toxicity risks [15]. This parameter is calculated using Equation (5), where the term x is the TLV-STEL in ppm for the substances in the process under study.

$${\mathrm{S}}_{\mathrm{T}\mathrm{O}\mathrm{X}}=100\times \left(1-\left({\displaystyle \frac{1}{1+403.4288{\mathrm{e}}^{-0.012\mathrm{x}}}}\right)\right)$$

(5)

In this method, the NFPA (National Fire Protection Association) reactivity rating is used to calculate the reactivity parameter (S_R). This rating is available in the Material Safety Data Sheet (MSDS) for the chemical product. The NFPA developed the hazard classification system known as the Hazardous Materials Diamond (NFPA 704). This system uses colors and numbers to quickly communicate the hazards of a material, where yellow represents the hazard of reactivity (instability) with water on a scale of 0 to 4 [35]. The hazard index for reactivity is summarized in

Table 3. Hazard classification index: reactivity [35].

Score	Indication	Explanation
0	Stable	Remains stable and shows no reaction upon contact with water.
1	Caution	May undergo a reaction when exposed to heat or water, although without violent behavior.
2	Warning	Prone to instability or capable of undergoing a violent reaction upon contact with water.
3	Danger	Could become explosive when exposed to mechanical shock, elevated temperatures in confined environments, or contact with water.
4	Extreme Danger	Material that can detonate, undergo rapid explosive decomposition, or react violently under normal temperature and pressure conditions.

. This parameter is calculated using Equation (6), where the term x is the NFPA reactivity rating score for the substances in the process under study.

$${\mathrm{S}}_{\mathrm{R}}=100\times \left({\displaystyle \frac{1}{1+270.43{\mathrm{e}}^{-2.8\mathrm{x}}}}\right)$$

(6)

2.2.3. Process Safety Total Score (PSTS)

To calculate the Total Process Safety Score (PSTS), the scores for the temperature (S_T), pressure (S_P), heat of reaction (S_HR), and process inventory (S_PI) parameters are added together [15], as shown in Equation (7). When a process route involves more than one reaction step, the individual module scores corresponding to each reaction stage are taken into account.

$$\mathrm{P}\mathrm{S}\mathrm{T}\mathrm{S}={\left({\mathrm{S}}_{\mathrm{T}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{P}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{H}\mathrm{R}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}+{\left({\mathrm{S}}_{\mathrm{P}\mathrm{I}}\right)}_{\mathrm{m}\mathrm{a}\mathrm{x}}$$

(7)

In this context, temperature represents an indicator of the amount of thermal energy that can potentially be released [36]. Operating at elevated temperatures poses intrinsic safety concerns, as high thermal levels expose the plant to increased thermal stress [14]. Therefore, processes operating at elevated temperatures pose greater hazards compared to those running at lower temperature levels [15]. The temperature parameter (S_T) is calculated using Equations (8) and (9), for operating temperatures above 25 °C and below 25 °C, respectively, where the term x is the highest temperature in °C recorded in the process under study.

$${\mathrm{S}}_{\mathrm{T}>25°\mathrm{C}}=100\times \left({\displaystyle \frac{1}{1+403.43{\mathrm{e}}^{-0.012\mathrm{x}}}}\right)$$

(8)

$${\mathrm{S}}_{\mathrm{T}<25°\mathrm{C}}=100\times \left(1-\left({\displaystyle \frac{1}{1+0.0025{\mathrm{e}}^{-0.012\mathrm{x}}}}\right)\right)$$

(9)

Operating at elevated pressures significantly raises the level of energy stored within the facility [14]. The simultaneous presence of elevated pressures, high temperatures, or corrosive substances creates significant challenges for equipment and construction materials, while high operating pressures also increase the likelihood of chemical leaks [36]. Therefore, processes operating at elevated pressures pose greater hazards compared to those running at lower pressure levels [15]. The pressure parameter (S_P) is calculated using Equation (10), where the term x is the highest pressure in bar recorded in the process under study.

$${\mathrm{S}}_{\mathrm{P}}=100\times \left({\displaystyle \frac{1}{1+148.41{\mathrm{e}}^{-0.2\mathrm{x}}}}\right)$$

(10)

A large reaction enthalpy is a chemical characteristic that enhances the likelihood of explosive behavior [14]. A positive reaction enthalpy corresponds to an endothermic process, whereas a negative value is associated with an exothermic one. Consequently, the heat of reaction parameter (S_HR) is described using two separate logistic functions: one applied to values below 0 kJ/mol for exothermic reactions, and another applied to values above 0 kJ/mol for endothermic reactions. In both cases, reactions involving substantial heat release or absorption may pose significant safety concerns [36]. Accordingly, within this approach, larger scores are assigned as the heat of reaction deviates further from zero [15]. This parameter is calculated using Equations (11) and (12), for endothermic and exothermic reactions, respectively, where the term x is the highest heat of reaction in kJ/mol recorded in the reactions of the studied process.

$${\mathrm{S}}_{\mathrm{H}\mathrm{R}>0\mathrm{k}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}}=100\times \left({\displaystyle \frac{1}{1+601.85{\mathrm{e}}^{-0.016\mathrm{x}}}}\right)$$

(11)

$${\mathrm{S}}_{\mathrm{H}\mathrm{R}<0\mathrm{k}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}}=100\times \left({\displaystyle \frac{1}{1+403.43{\mathrm{e}}^{0.006\mathrm{x}}}}\right)$$

(12)

Maintaining smaller inventory levels helps limit the potential severity of accidents [14]. However, at the early design stage, accurately defining the exact inventory requirements for each chemical involved in the process is challenging. Consequently, the process inventory parameter (S_PI) is estimated by using the reaction yield as a proxy to approximate the amount of chemical inventory required for plant operation [36]. Yield refers to the quantity of the target product obtained under ideal conditions, assuming complete conversion of the limiting reactant and the absence of competing side reactions [37].

Yield is commonly expressed as a percentage (%). A higher yield reflects a larger fraction of the target product being obtained, which generally means a reduced requirement for raw materials. In contrast, a lower yield suggests greater material losses and is associated with an increased potential for hazardous outcomes [15]. This parameter is calculated using Equation (13), where the term x is the production yield in percentage (%) of the process under study.

$${\mathrm{S}}_{\mathrm{P}\mathrm{I}}=100\times \left(1-\left({\displaystyle \frac{1}{1+1339.43{\mathrm{e}}^{-0.12\mathrm{x}}}}\right)\right)$$

(13)

3. Results and Discussion

3.1. Chemical Safety Total Score (CSTS) of the Crude Palm Oil (CPO) Production Process

First, NuDIST parameters were calculated for the chemical safety assessment of each of the substances involved. For simplicity, twelve (12) chemical substances are considered in this process: water, calcium oxide and silica, which represent the ash content of the biomass; cellulose, hemicellulose and lignin, which represent the cellulosic material of the palm bunch; palmitic acid, oleic acid and linoleic acid, which represent the fatty acids present in palm oil; and 1,3-dipalmitoyl-2-oleoylglycerol, tripalmitin and triolein, which represent the triglycerides present in palm oil (see Table 1).

In this regard, to calculate the flammability parameter, the flash point of the chemical substances involved was first determined. In this case, only palmitic acid (113 °C), oleic acid (189 °C), linoleic acid (112 °C), and triolein (330 °C) have a recorded flash point, while the other substances do not. Because linoleic acid has the lowest flash point, it contributed the most to the flammability parameter, with a score of 20.41 after performing the calculation with Equation (3). On the other hand, to calculate the explosivity parameter, the UEL, LEL, and their difference were determined for the chemical substances involved; however, none of them have this information recorded, so no score is generated for the explosivity parameter after performing the calculation with Equation (4). Similarly, to calculate the toxicity parameter, the TLV-STEL of the chemical substances involved must first be determined; however, no substance presents the recorded indicator; therefore, there is no score in the toxicity parameter after performing the calculation with Equation (5).

Finally, to calculate the reactivity parameter, the NFPA reactivity rating of the chemicals involved was first determined. In this case, water, silica, cellulose, hemicellulose, lignin, palmitic acid, oleic acid, 1,3-dipalmitoyl-2-oleoylglycerol, tripalmitin, and triolein have an NFPA reactivity rating of zero (0), while calcium oxide and linoleic acid have an NFPA reactivity rating of one (1). After performing the calculation with Equation (6), it was discovered that water, silica, cellulose, hemicellulose, lignin, palmitic acid, oleic acid, 1,3-dipalmitoyl-2-oleoylglycerol, tripalmitin and triolein contribute a score of 0.37 to the reactivity parameter, while calcium oxide and linoleic acid contribute 5.73 to this parameter.

Information on the indicators for the chemicals involved in the crude palm oil (CPO) extraction process can be obtained from the CAMEO Chemicals website or the Material Safety Data Sheets (MSDS).

Table 4. NuDIST parameters for the Chemical Safety Total Score (CSTS) applied to the crude palm oil (CPO) production process for Water, Calcium Oxide (CaO), and Silica.

Indicator and Parameter	Chemical Substances
	Water [20]	Calcium Oxide (CaO) [21]	Silica [22]
Flash point (°C)	-	-	-
Flammability (SFL)	0.00	0.00	0.00
UEL (vol%)	-	-	-
LEL (vol%)	-	-	-
UEL-LEL (vol%)	-	-	-
Explosiveness (SEXP)	0.00	0.00	0.00
TLV-STEL (ppm)	-	-	-
Toxicity (STOX)	0.00	0.00	0.00
NFPA Reactivity Classification	0	1	0
Reactivity (SR)	0.37	5.73	0.37
CSTS	0.37	5.73	0.37

,

Table 5. NuDIST parameters for the Chemical Safety Total Score (CSTS) applied to the crude palm oil (CPO) production process for Cellulose, Hemicellulose, and Lignin.

Indicator and Parameter	Chemical Substances
	Cellulose [23]	Hemicellulose [24]	Lignin [25]
Flash point (°C)	-	-	-
Flammability (SFL)	0.00	0.00	0.00
UEL (vol%)	-	-	-
LEL (vol%)	-	-	-
UEL-LEL (vol%)	-	-	-
Explosiveness (SEXP)	0.00	0.00	0.00
TLV-STEL (ppm)	-	-	-
Toxicity (STOX)	0.00	0.00	0.00
NFPA Reactivity Classification	0	0	0
Reactivity (SR)	0.37	0.37	0.37
CSTS	0.37	0.37	0.37

,

Table 6. NuDIST parameters for the Chemical Safety Total Score (CSTS) applied to the crude palm oil (CPO) production process for Palmitic Acid, Oleic Acid, and Linoleic Acid.

Indicator and Parameter	Chemical Substances
	Palmitic Acid [26]	Oleic Acid [27]	Linoleic Acid [28]
Flash point (°C)	113.00	189.00	112.00
Flammability (SFL)	20.02	3.88	20.41
UEL (vol%)	-	-	-
LEL (vol%)	-	-	-
UEL-LEL (vol%)	-	-	-
Explosiveness (SEXP)	0.00	0.00	0.00
TLV-STEL (ppm)	-	-	-
Toxicity (STOX)	0.00	0.00	0.00
NFPA Reactivity Classification	0	0	1
Reactivity (SR)	0.37	0.37	5.73
CSTS	20.39	4.25	26.14

and

Table 7. NuDIST parameters for Chemical Safety Total Score (CSTS) applied to the crude palm oil (CPO) production process for 1,3-Dipalmitoyl-2-Oleoylglycerol, Tripalmitin, and Triolein.

Indicator and Parameter	Chemical Substances
	1,3-Dipalmitoyl-2-Oleoylglycerol [29]	Tripalmitin [30]	Triolein [31]
Flash point (°C)	-	-	330.00
Flammability (SFL)	0.00	0.00	0.14
UEL (vol%)	-	-	-
LEL (vol%)	-	-	-
UEL-LEL (vol%)	-	-	-
Explosiveness (SEXP)	0.00	0.00	0.00
TLV-STEL (ppm)	-	-	-
Toxicity (STOX)	0.00	0.00	0.00
NFPA Reactivity Classification	0	0	0
Reactivity (SR)	0.37	0.37	0.37
CSTS	0.37	0.37	0.51

summarize the NuDIST parameters for chemical safety along with the base indicators used to calculate these parameters. Next, using Equation (2), the Chemical Safety Total Score (CSTS) was calculated for the chemical substances involved in the process, as shown in Table 4, Table 5, Table 6 and Table 7, where water, silica, cellulose, hemicellulose, lignin, 1,3-dipalmitoyl-2-oleoylglycerol and tripalmitin reached the same value (0.37) for the CSTS, surpassed by triolein (0.51), oleic acid (4.25), calcium oxide (5.73), palmitic acid (20.39) and linoleic acid (26.14).

Once the CSTS for each chemical was calculated, the highest result was selected; this value represents the CSTS of the crude palm oil (CPO) extraction process, which is 26.14. Subsequently, the chemical associated with the highest CSTS value was selected; this substance represents the chemical safety of the crude palm oil (CPO) extraction process, and it is linoleic acid. Additionally, the chemical safety parameters associated with the highest CSTS value were selected. This information is summarized in

Table 8. Chemical safety assessment with parameters and total score for the crude palm oil (CPO) extraction process.

Parameters	Score
Flammability (SFL)	20.41
Explosiveness (SEXP)	0.00
Toxicity (STOX)	0.00
Reactivity (SR)	5.73
CSTSmax	26.14
Chemical substance	Linoleic acid

and outlined in Figure 3. From Figure 3, it can be deduced that the only parameters contributing to the highest CSTS are flammability and reactivity, with a Chemical Safety Total Score (CSTS) of 26.14 for linoleic acid.

3.2. Process Safety Total Score (PSTS) of the Crude Palm Oil (CPO) Production Process

Secondly, the NuDIST parameters for the process safety assessment were calculated. To calculate the temperature parameter, the maximum process temperature was first determined to be 420.85 K (147.70 °C) according to Table 2. Equation (8) was then used, since the process temperature is greater than 25 °C, and the calculation was performed, yielding a score of 1.44 for the temperature parameter. Similarly, to calculate the pressure parameter, the maximum process pressure was first determined to be 4.40 atm (4.46 bar) according to Table 2. Equation (10) was then used, and the calculation was performed, yielding a score of 1.62 for the pressure parameter.

Now, to calculate the heat of reaction parameter, the process heat of reaction was first determined. According to the description of the crude palm oil (CPO) extraction process, this is a single-product physical process, meaning no significant chemical reactions occur. Therefore, a score of zero (0) was obtained for the heat of reaction parameter due to the lack of chemical reactions, eliminating this parameter’s contribution to the Process Safety Total Score (PSTS). Finally, to calculate the process inventory parameter, the production yield was first determined, which is 22.52% according to the description of the crude palm oil (CPO) extraction process. Subsequently, Equation (13) was used to perform the calculation, yielding a score of 98.90 for the process inventory parameter.

Table 9. NuDIST parameters for the Process Safety Total Score (PSTS) applied to the crude palm oil (CPO) production process.

Indicator and Parameter	Process Data and Scores
Maximum temperature (°C)	147.70
Temperature (ST)	1.44
Maximum pressure (bar)	4.46
Pressure (SP)	1.62
Heat of reaction (kJ/mol)	-
Heat of reaction (SHR)	0.00
Production yield (%)	22.52
Process inventory (SPI)	98.90

summarizes the NuDIST parameters for process safety along with the base indicators used to calculate these parameters.

The next step is the calculation of the Total Chemical Safety Score (TSSS). For this, Equation (7) was used, and the calculation was performed, obtaining a value of 101.95. The results are summarized in

Table 10. Process safety assessment with parameters and total score for the crude palm oil (CPO) extraction process.

Parameters	Score
Temperature (ST)	1.44
Pressure (SP)	1.62
Heat of reaction (SHR)	0.00
Process inventory (SPI)	98.90
PSTS	101.95

and outlined in Figure 4. From Figure 4, it can be concluded that the parameter that contributed most to the TSSS is the process inventory, with a score of 98.90.

3.3. NuDIST Total Score of the Crude Palm Oil (CPO) Production Process

Once both parameters were obtained, for both the chemical and process parts, the NuDIST Total Score was calculated using Equation (1), obtaining a value of 128.09.

Table 11. CSTS, PSTS, and NuDIST Total Score for the crude palm oil (CPO) extraction process.

Type of score	Value
Chemical Safety Total Score (CSTS)	26.14
Process Safety Total Score (PSTS)	101.95
NuDIST Total Score	128.09

summarizes the results obtained for the CSTS, PSTS, and the NuDIST Total Score, which are outlined in Figure 5, and shows that the PSTS (101.95) contributes more to the total NuDIST score (128.09) than the CSTS (26.14), representing over 70% of the total. This implies that crude palm oil extraction is less safe due to the process’s operating conditions, compared to the chemical substances involved.

This study explicitly analyzed potential threats to process safety, addressing both chemical and process safety. Regarding chemical safety, intrinsic parameters of representative process substances (flammability, reactivity, toxicity, and explosiveness) were evaluated, with linoleic acid identified as the primary contributor to chemical risk due to its flash point and NFPA classification. Process safety, on the other hand, was examined based on extrinsic process parameters, including temperature, pressure, inventory, and the presence of chemical reactions. The results show that the greatest threats are associated with operating conditions and the high process inventory level, rather than the intrinsic hazards of the compounds. This comprehensive approach clearly defines the dominant sources of risk and reinforces the suitability of the NuDIST methodology for assessing the inherent safety of the system.

Now, this methodology, by assigning specific numerical values, is a relative, not an absolute, indicator and does not define universal limits to determine whether a chemical process is inherently safe, unlike the ISI methodology, which has been implemented for crude palm oil extraction processes [17]. Therefore, to generate an appropriate diagnosis, the value obtained for the evaluated process must be compared with the value obtained for other processes calculated using the same methodology.

Table 12. Comparison of CSTS, PSTS, and the NuDIST Total Score for the crude palm oil (CPO) extraction process, chitosan production [16], and six (6) methyl methacrylate (MMA) production routes [15].

Process	CSTS	PSTS	NuDIST Score
Crude palm oil (CPO) extraction	26.14	101.95	128.09
Chitosan production [16]	170.65	209.20	380.20
Six (6) methyl methacrylate (MMA) production routes [15]
1. Acetone cyanohydrin (ACH)-based route	258	241	499
2. Propionaldehyde (C2/PA)-based route from ethylene	342	232	574
3. Methyl propionate (C2/MP)-based route from ethylene	330	163	493
4. Propylene (C3)-based route	332	199	531
5. tert-Butyl alcohol (TBA)-based route	240	131	371
6. Isobutylene (i-C4)-based route	240	92	332

presents a comparison of the results obtained in several studies, including the CSTS, PSTS, and NuDIST Total Score for the crude palm oil (CPO) extraction process, chitosan production, and six (6) methyl methacrylate (MMA) production routes.

According to the results obtained for the crude palm oil (CPO) extraction process, this process is inherently safer than other processes evaluated using the NuDIST technique, such as the chitosan production process from shrimp exoskeletons proposed by Zuorro et al. [16], where a NuDIST Total Score of 380.20 was obtained, almost three times higher than the score obtained for CPO extraction (128.09). This is mainly due to the presence of inherently more unsafe chemicals in chitosan production from shrimp exoskeletons, such as ethanol, which yielded a CSTS of 170.65 [16], more than six times higher than that obtained for CPO extraction (26.14). Furthermore, the PSTS in chitosan production from shrimp exoskeletons is 209.20 [16], more than double that for CPO extraction (101.95), as shown in Table 12.

In comparison with other processes, such as the methyl methacrylate (MMA) production proposed by Ahmad et al. [15], CPO extraction is also considered an intrinsically safer process, as the lowest score obtained in this process was 332. In fact, MMA production, among the three processes compared, is the most unsafe because four (4) of the six (6) possible extraction routes exceed a NuDIST Total Score of 390 [15], as shown in Table 12. From Table 12, it can also be concluded that the PSTS for route 6 (92) is lower than that obtained for CPO extraction (101.95), making the latter less safe in terms of process safety. However, the chemical safety (CSTS) for route 6 (240) is more than 9 times higher than that for CPO extraction (26.14), demonstrating that MMA production, in each of its routes, is inherently less safe than CPO production [15].

Figure 6 presents a bar chart comparing the three processes previously discussed: CPO, chitosan, and MMA production. This chart reaffirms that the crude palm oil extraction process is the most intrinsically safe of the three systems. It is worth noting that the crude palm oil extraction process is identified in Figure 6 by the blue bar with the red label.

Based on the comparison of the three processes, chitosan and methyl methacrylate (MMA) production serves as a relevant benchmark because it represents industrially established systems that combine harsh operating conditions with the handling of inherently hazardous chemicals. In the case of chitosan, the comparison is pertinent due to the use of reagents such as ethanol, which exhibit high levels of flammability, toxicity, and reactivity, reflected in high CSTS values. Meanwhile, MMA production routes involve highly volatile and combustible compounds, broad explosive ranges, and, in some cases, high-heat chemical reactions, significantly increasing the inherent risk of the process in terms of CSTS and PSTS. These characteristics result in both processes exhibiting considerably higher NuDIST scores than crude palm oil extraction. Therefore, its inclusion as a reference allows for contextualizing the comparative results and highlighting that the observed differences are not accidental, but rather a direct consequence of the nature of the substances handled and the severity of the operating conditions. In this sense, the comparison strengthens the interpretation of the results by demonstrating that the greater inherent safety of the CPO extraction process is primarily due to its physical nature and the use of less hazardous compounds.

Finally, based on the results obtained using NuDIST, the generated information can directly support various design and operational decisions at the crude palm oil production plant. In particular, the high values associated with the process inventory parameter help guide decisions related to optimizing material balances. Likewise, the scores related to temperature, pressure, toxicity, flammability, explosiveness, and reactivity can serve as criteria for selecting appropriate equipment capacities, construction materials, and safer operating margins. At the operational level, the results facilitate the prioritization of adjustments to critical operating conditions that influence the overall process risk. Similarly, the results allow for the evaluation of process redesign alternatives focused on improving production performance.

4. Conclusions

In the context of sustained global demand for palm oil and the need to strengthen the sustainability and safety of agro-industrial systems, this study addressed the inherent safety of the crude palm oil (CPO) production process. The operational complexity of the process, characterized by high material loads, elevated temperatures, and an intensive sequence of physical operations, poses significant challenges in terms of industrial risk. In response to this problem, the main objective was to apply the Numerical Descriptive Inherent Safety Technique (NuDIST) methodology to quantify the chemical and process safety of the system objectively. This methodology allowed for the analysis of both the intrinsic properties of the substances involved and the critical operating conditions, employing logistic functions that reduce the subjectivity typical of traditional indices. The results showed that chemical safety is dominated by linoleic acid, which achieved the highest Chemical Safety Total Score (CSTS) with a value of 26.14, primarily due to its contribution to the flammability (20.41) and reactivity (5.73) parameters, while the other compounds presented significantly lower levels of risk.

On the other hand, the process safety analysis showed that the Process Safety Total Score (PSTS) reached a value of 101.95, representing more than 70% of the NuDIST Total Score (128.09), indicating that operating conditions have a greater influence than the nature of the chemical compounds. In particular, process inventory was the dominant factor, with a score of 98.90, associated with a low production yield of 22.52%, while the maximum operating temperature (147.7 °C) and maximum pressure (4.46 bar) contributed moderately with values of 1.44 and 1.62, respectively. A comparison with other industrial processes evaluated using NuDIST, such as chitosan and methyl methacrylate (MMA) production, confirmed that CPO extraction is inherently safer, exhibiting total scores approximately threefold lower than the other processes compared. Taken together, these findings highlight the usefulness of NuDIST as a robust and quantitative tool to support decision-making in the early stages of design and optimization, and underscore the need to focus future improvement strategies on optimizing process production yield to further strengthen the inherent safety of the palm oil sector.

Based on the NuDIST results and the process review, potential safety risks in palm oil production can be comprehensively assessed. Conventional or more widely recognized methods, such as HAZOP (Hazard and Operability Study) and ISI, qualitatively identify risks associated with operating conditions, while unconventional approaches, such as NuDIST, provide objective and continuous quantification at early design stages, demonstrating that, in crude palm oil (CPO) production, the main threats arise from operating conditions and not from inherent hazards of the substances. Finally, the study was limited to steady-state and nominal operating conditions, without considering dynamic scenarios, operational failures, seasonal variability of raw materials, or external events. These limitations open the possibility for future work to incorporate dynamic analyses and probabilistic approaches for a more comprehensive assessment of the inherent safety of the process.