Nipa is believed to have originally spread across all continents, including Europe, Africa, the Americas, Asia, and Australia. However, climate change and the loss of genotypes adapted to varying environmental conditions have since limited its distribution [30]. Currently, Nipa exhibits a pan-tropical distribution primarily in the Western Indo-Pacific region, extending from southeastern India and Southeast Asia to northern Australia and the Pacific Islands, including the Solomon Islands, Marianas, and Caroline Islands. Despite also being found on Iriomote Island in the Ryukyu, Japan, which represents the northernmost limit of its range, Nipa’s growth is restricted in regions with lower temperatures [8]. This tropical palm thrives in warm, humid climates with temperatures ranging from a minimum of 20ºC to a maximum of 32–35ºC and requires monthly rainfall levels exceeding 1,000 mm [31]. Additionally, Nipa flourishes in brackish environments such as estuaries, tidal river areas, and coastal regions [6, 7].

Nipa (Nypa fruticans Wurmb) is the sole species in the genus Nypa, within the Arecaceae family and the subfamily Nypoideae [6, 7], distinguishing it from other palm families [8]. It is a stemless palm that can reach up to 10 meters in height, with underground rhizomes and rosettes of leaves and inflorescence stalks emerging above ground. The palm features erect, stiff, pinnate leaves that can extend up to 9 meters and are composed of two rows of pinnae, each 60–130 cm long. The leaflets are alternating, stiff, lanceolate, and upward-pointing from the base, with up to 120 leaflets per leaf. Nipa is a monoecious plant, having distinct male and female flowers. Its inflorescences appear seasonally, with one shoot producing 3–4 spadices. The sap can be tapped prior to flowering. Each flower develops into a single-seeded fruit that is ovoid in shape, with a soft, homogeneous, and edible mesocarp [31, 32]. Thus, the development potential of Nipa lies in its sap and mesocarp production.

Certain key information is essential for developing the potential of Nipa palm in Indonesia. Firstly, accurate data on its distribution is needed, although it is confirmed that this plant is a highly adaptive species and an integral part of mangrove forest ecosystems [30]. Based on this initial insight, recalculated land cover data from the Ministry of Environment and Forestry (MOEF) serves as the foundation for identifying the presence of mangrove forests in Indonesia [23], as illustrated in Fig. 1. MOEF reports that mangrove forests are distributed across the Indonesian archipelago [23], Further studies have confirmed the presence of Nipa within Mangrove forests in Aceh Province [14, 33], Jambi [26], South Sumatra [27, 34], West Kalimantan [35], East Kalimantan [36], West Java [37], Central Java [15], East Java [13], North Sulawesi [38], Papua and West Papua [39], although it is also believed to be present in other provinces.

A key challenge remains, as there is still no data on the exact area of Nipa coverage. The only available data used as a reference is the primary and secondary mangrove forest area from 2012 to 2019, according to the Ministry of Environment and Forestry’s (MOEF) land cover recalculation and mapping, as shown in Table S1. Based on this data, the total area of mangrove forests across Indonesia in 2018 was 2,788,600 hectares [23]. Using an estimation approach by Irawan et al., assuming Nipa covers 30 percent of the mangrove area [40], Nipa is estimated to cover approximately 837,000 hectares in Indonesia in 2018. The data also indicate that the reduction in Nipa area correlates with the decline in Indonesia’s mangrove forests. In 2013, the estimated area of Nipa was 877,710 hectares, decreasing to 836,580 hectares in 2018, reflecting a 5 percent reduction over five years.

The existence of Nipa is threatened by disturbances to the mangrove ecosystem. Recent studies indicate a 30 percent reduction in Indonesia’s mangrove forests between 1980 and 2005, with a deforestation rate of 18,209 hectares per year from 2009 to 2019 [41]. Human activities such as population growth, residential expansion, aquaculture, agriculture, mining, and excessive wood harvesting are the primary causes of this degradation [9, 42], posing a significant threat to Nipa sustainability [14, 15]. Therefore, preserving mangrove forests is crucial for securing the future of Nipa as a renewable energy source.

Nipa sap is harvested through a tapping process, which involves cutting the fruit bunch and making thin, tapered incisions (1–2 mm) on the stalk (Fig. 2a). To maximize sap yield, pre-treatments such as bending, swinging, jerking, and hitting the stalk are necessary to remove mucus and P protein that obstruct sap flow [43]. These treatments should be conducted for at least 25 days [13]. Additionally, Prasetyo et al. noted that frequent submersion of Nipa trees in water can also affect sap production [13]. The tapping process to obtain Nipa sap is shown in Fig. 2b.

Studies by Tamunaidu et al. [44] in Thailand, Van Nguyen et al. [45] in Malaysia, and Prasetyo et al. [13] in Indonesia found that the main components of Nipa sap are sugars, including sucrose, glucose, and fructose, making it a potential feedstock for sugar-based bioethanol [46] (Table 1).

The data indicate that the highest total sugar content in Nipa sap, at 16.98%, was recorded in a study from Thailand [44], while the highest sucrose content, at 12.74%, was observed in a study conducted in Indonesia [13]. Notable but statistically insignificant variations were identified across three studies. Firstly, total sugar content in Nipa sap varied, with Prasetyo et al. attributing fluctuations to weather conditions; periods of high rainfall and water-logging tend to lower sugar production [13]. Secondly, differences in sucrose, glucose, and fructose content were noted, with Prasetyo et al. emphasizing that sap freshness is crucial, as tapping, storage, and preservation processes can lead to sucrose hydrolysis into monosaccharides (glucose, fructose) within 24 hours [13]. Lastly, Van Nguyen et al. reported inorganic elements, such as potassium (K) at 0.24%, chlorine (Cl) at 0.24%, and sodium (Na) at 0.08%, in Malaysian Nipa sap—elements not detected in other studies. While potassium is common in other plant saps (e.g., coconut), the sodium and chlorine levels are heavily influenced by soil and water conditions. Since Nipa palms thrive in brackish water with high salinity, this contributes to their seawater tolerance, underscoring their potential in saline agriculture [45].

Nipa fruits begin to grow two months after the flowering period and take 180 days to mature. The fruits are oval or round, measuring 12–16 cm in length and 5–10 cm in width, syncarpous with hexagonal carpels, and light chestnut brown in color [31, 32]. The mesocarp, obtained by halving the fruit and removing the husk, is initially clear, gelatinous, and sweet with a slightly oily, tannin-like taste when young [12]. As the fruit matures, the texture hardens, the color turns opaque white, and it becomes moisture-resistant [27]. A sample of the Nipa mesocarp is shown in Fig. 2c.

Studies by Osabor et al. [11] in Nigeria, Chau Sum et al. [47] in Malaysia, and Prasetyo et al. [13] in Indonesia found that carbohydrates are the main component of Nipa mesocarp, making it suitable as a starch-based bioethanol feedstock [46] (Table 2). Data show that the highest carbohydrate content, measured at 51.08±1.71%, was reported in the study in Nigeria [11]. The data also reveal variations in carbohydrate content across the three studies, indicating that high carbohydrate content tended to be accompanied by low moisture. Factors influencing these variations include fruit maturity, as moisture content decreases with fruit aging [47], and soil characteristics as well as nutrient content [13].

Nipa oil is derived from the mesocarp through either wet or dry methods [48]. The wet method involves grinding the mesocarp, adding water (60ºC), pressing (2000 kgf), and heating the emulsion (105ºC) until the oil separates. The dry method involves drying the mesocarp in an oven (70ºC) for 24 hours, followed by pressing the dried mesocarp (2000 kgf) to extract the oil. Additionally, Nipa oil can be obtained through extraction using the Soxhlet method [12, 49]. Nipa oil has a light aroma and is thicker than coconut oil, making it less prone to flowing [12].

Studies on the physicochemical properties of Nipa oil have been conducted by Hamzah [48] in Indonesia, Tabinas [12] in the Philippines, and Moon et al. [49] in Bangladesh (Table S2). The data from these studies show that Nipa oil exhibits specific physicochemical properties, with the highest saponification value (195.22 mg KOH/g) and iodine value (88.94%) reported in the study in the Philippines [12], while the FFA value (9.17%) was found in Bangladesh [49]. These physicochemical characteristics indicate Nipa oil’s potential as a biodiesel feedstock based on its saponification value, FFA value, and iodine value [50]. Tabinas noted that Nipa oil’s high fat content makes it suitable for biodiesel production [12, 51]. Further discussion on these parameters and their impact on biodiesel production will be elaborated in the next section.

Nipa sap has physical characteristics and chemical contents similar to the extract from sweet sorghum stalks, namely sucrose, glucose, and fructose [55]. Based on this similarity, sweet sorghum conversion technology serves as a reference for processing Nipa sap (sugar) as a feedstock into bioethanol through a primary process, fermentation [52]. The stoichiometric calculations for hydrolysis and fermentation reactions are performed based on the chemical composition data of Nipa sap (Table 1) to obtain theoretical ethanol. Disaccharide sugars (sucrose) need to be hydrolyzed into simple sugars (glucose and fructose) according to Eq. (1).

Subsequently, glucose and fructose are fermented into ethanol according to Eq. (2).

The ethanol conversion results from Nipa sap are shown in Table 3.

Assumption: sucrose, glucose, and fructose are produced from 1 gram of Nipa sap.

Theoretical total ethanol from stoichiometric calculations.

n.d. = not detected.

The conversion results of Nipa sap show that the highest theoretical ethanol production, 0.0895 grams, was obtained from the study in Thailand, which also recorded the highest total sugar content [44]. This confirms that the sugar content in Nipa sap feedstock is directly proportional to the ethanol yield. Additionally, Karimi & Chisti stated that the maximum theoretical yield of ethanol from fermentation is 0.51 grams of ethanol per gram of glucose, with lower yields expected in commercial operations [56]. Hence, the ethanol estimation from Nipa sap aligns with theoretical expectations.

Saville et al., in their study, stated that the corn-to-ethanol conversion technology could be applied to other starch-containing feedstocks, although adaptations are needed to account for differences in starch, protein, and β-glucan content [53]. Thus, the bioethanol production process from Nipa mesocarp feedstock follows this approach through two main processes: hydrolysis and fermentation. According to Karimi & Chisti, hydrolysis is necessary because microorganisms cannot effectively break down starch into sugars during fermentation [56].

Theoretical ethanol production estimation is performed using stoichiometric calculations of hydrolysis and fermentation reactions based on the chemical composition data of Nipa mesocarp (Table 2). In this hydrolysis, the carbohydrate (starch) compound formula for Nipa is assumed to be (C₆H₁₀O₅)₅. The hydrolysis reaction of Nipa starch into simple sugars (glucose and fructose) is shown in Eq. (3).

The simple sugars (glucose or fructose) are then fermented into ethanol according to Eq. (2). The ethanol conversion results from Nipa mesocarp are shown in Table 4.

Assumption: carbohydrates are produced from 1 gram of Nipa mesocarp.

Theoretical total ethanol from stoichiometric calculations. The conversion results of Nipa starch show the highest theoretical ethanol yield of 0.2903 grams from the study in Nigeria, where the highest carbohydrate (starch) content was also recorded [11]. This further confirms that the starch mass in Nipa mesocarp feedstock is directly proportional to the ethanol yield.

Before proceeding with the process of converting Nipa oil into biodiesel, it is essential to explain the impact of three parameters (saponification value, iodine value, and FFA) on its quality as a feedstock for biodiesel production. In the previous section, it was noted that a high saponification value (195.22 mg KOH/g) was found in the study in the Philippines [12], indicating shorter fatty acid chains in the structure and suggesting high triacylglycerol/triglyceride content, thus making it a promising feedstock for biodiesel [54].

The high iodine value (88.94%) in the study in the Philippines [12] indicates a high unsaturated fatty acid content, leading to increased nitrogen oxide emissions and lower thermal efficiency in engines [57]. Conversely, the low iodine value (14.53%) found in the study in Bangladesh is more suitable as a biodiesel feedstock [49]. In addition, a high FFA value (9.17%) in the study in Bangladesh indicates lower oil quality due to high Free Fatty Acid content. High FFA in oil complicates the biodiesel production process, as it forms soap (saponification reaction) and makes the final product purification more challenging [54].

Nipa oil shares similar physical and chemical characteristics with palm oil [12, 49]. Based on these considerations, palm oil conversion technology is used as a reference for biodiesel production from Nipa oil through the transesterification reaction, where triglycerides from vegetable oil react with short-chain alcohol (methanol) to produce Fatty Acid Methyl Ester (FAME) and glycerol [54]. The overall process occurs in three stages in chemical equilibrium, forming monoglycerides and diglycerides as intermediates [58]. The transesterification reaction is shown in Fig. S2.

Due to the complexity of the transesterification reaction and limited data availability, estimation of theoretical FAME yield from Nipa oil is excluded in this discussion. However, Dimian et al., in their study, estimated biodiesel production using triglyceride feedstock, finding that 0.884 grams of triolein produced 0.888 grams of FAME, suggesting that triglyceride to FAME conversion is proportional in mass [58]. Although supporting evidence from other studies is needed to validate this claim, these results can illustrate the production of biodiesel or FAME from Nipa oil-based triglycerides.

Emphasizing the previous discussion, Nipa processing focuses on the production of first-generation biofuels, which are based on sugar, starch, and fat feedstocks. According to Capodaglio and Bolognesi, this generation of biofuels commonly uses feedstock derived from agricultural food crops, which often sparks controversies related to supply and rising food prices [2]. A breakthrough by Hao et al. introduced a new category, termed generation 1.5 biofuels, which use non-food agricultural crops (cassava) as feedstock [59]. According to Ruan et al., the advantages of this generation of biofuels include the availability of large quantities of feedstock, ease of production with existing technology, and the absence of competition with food needs [60]. This description aligns closely with Nipa, a non-food crop available in large quantities and with existing conversion technology, positioning it as a generation 1.5 feedstock for advanced biofuels, which will be further discussed in section 3.4.

Building on the previous discussion of Nipa-based biofuel production (bioethanol and biodiesel), a review of innovative bioenergy methods is essential for advancing this area. Reviewing recent studies will offer insights into technological advancements and identify potential growth opportunities. Table S3 presents the latest research on bioenergy, relevant to Nipa’s development prospects, including the use of non-food crop feedstocks for biofuel, advancements in production technologies to improve efficiency, and the role of Microbial Electrochemical Systems (MES) in conserving energy and recovering products from production waste.

The table highlights that non-food agricultural crops used for biofuel production continue to capture researchers’ interest, as they bypass the food-versus-fuel dilemma. Some examples of these crops include cassava [61], sweet potato [62], sweet sorghum [63], Jerusalem artichoke [64], and sago [65] for bioethanol production, and non-edible oils from castor [66], karanja [67], cottonseed [68], mahua [69], and rubber seed [70] for biodiesel production.

To enhance bioethanol output, research advancements are focused on genetically engineered microorganisms that improve fermentation efficiency [71], as well as the adoption of methods like continuous fermentation [73], SSF (Simultaneous Saccharification and Fermentation) [74], CBP (Consolidated Bioprocessing) [75], and membrane technologies [72]. In biodiesel production, the efficiency of transesterification efficiency is improved by using nanocatalysts [76], natural heterogeneous catalysts [77], and ionic liquid catalysts [79], along with techniques like supercritical reaction technology [78] and ultrasonic-assisted transesterification [80].

Microbial Electrochemical Systems (MES) also show high potential for energy conservation and product recovery from Nipa biofuel production waste. This waste contains organic residues that can be processed to produce bioelectricity via MFC [81], SMFC [82], MDC [85], and MRC systems [86], methane and hydrogen via MEC [83, 84], and valuable chemicals via MESC [87]. This overview of current bioenergy trends highlights promising development pathways for Nipa-based biofuel applications.

Fuel import dependency, as the first indicator of energy sustainability, arises primarily from the inability to domestically produce sufficient energy to meet consumption demands. In this context, Prasetyo et al. propose integrating Nipa bioethanol into national fuel production to increase supply [13]. In the first scenario, the national fuel supply includes only oil fuel and biodiesel. In the second scenario, bioethanol from Nipa is added (Fig. 3). The simulation uses 2022 fuel production and import data from the MEMR [88].

Fuel production with bioethanol is calculated as production without bioethanol (53,436 thousand kL) plus estimated bioethanol from Nipa (13,330 thousand kL). Fuel imports with bioethanol are calculated as imports without bioethanol (27,861 thousand kL) minus estimated bioethanol from Nipa (13,330 thousand kL).

Simulation results with the two scenarios show that without Nipa bioethanol integration (Scenario 1), total fuel production is 53,436 thousand kL with imports of 27,861 thousand kL. Conversely, with Nipa bioethanol integration (Scenario 2), total fuel production increases to 66,766 thousand kL (an increase of 24.95%), and imports decrease to 14,531 thousand kL (a decrease of 47.86%). This underscores the influence of Nipa bioethanol in increasing supply, reducing fossil fuel imports, and contributing to energy security.

Dependence on fossil fuel consumption, as the second indicator of energy sustainability, is closely related to the availability of alternative fuels. Therefore, further exploration of Prasetyo et al.’s [13] simulations is needed to understand the impact of Nipa bioethanol production on fuel consumption. Data on fuel production, consumption, and imports in Indonesia for 2022 (Table S4) serve as the basis, with additional elaboration on consumption breakdowns [88]. Simulation results with two scenarios of fuel consumption with and without bioethanol are shown in Table S5.

In the first scenario, without Nipa bioethanol integration into fuel production, Oil Fuel consumption is 42,062.16 thousand kL (55%), and Biogasoil is 33,905.15 thousand kL (45%) with its two components, Gasoil 23,128.36 thousand kL (31%), and Biodiesel 10,776.79 thousand kL (14%). This scenario indicates that without Nipa bioethanol production as a renewable energy source, fuel consumption is dominated by fossil energy (oil fuel) (Fig. 4a).

In the second scenario, with Nipa bioethanol integration in production, Oil Fuel consumption decreases to 28,731.92 thousand kL (38%), and Biogasoil increases to 47,235.39 thousand kL (62%) with its three components, Gasoil 23,128.36 thousand kL (30%), Bioethanol 13,330.24 thousand kL (18%), and Biodiesel 10,776.79 thousand kL (14%). This scenario illustrates that the presence of substitute fuels from renewable sources (bioethanol) enables a shift in consumption patterns, evidenced by the reduction in oil fuel usage in favor of cleaner energy (Fig. 4b).

Additionally, this scenario shows that with Nipa bioethanol production, the share of oil fuel consumption decreases by 31.69 percent, while Biogasoil increases by 39.32 percent. This further confirms the positive impact of Nipa bioethanol on the environment, reducing fossil fuel consumption, a major source of greenhouse gas emissions (GHG).

The threat to Food Security, as the third indicator of energy sustainability, poses a challenge for conventional biofuels using food crops as feedstock. Studies in Brazil and the United States show a correlation and interconnection between fuel and food prices, where biofuels and food needs share the same sources, causing food prices to follow world oil prices [89, 90]. Indonesia, as the world’s leading palm oil producer, relies heavily on palm oil-based biodiesel to boost its domestic fuel production [88]. Although studies indicate that using palm oil for biodiesel provides economic benefits and does not threaten food security [91], evidence shows that land-use changes tied to palm oil cultivation have led to rising prices for certain food commodities [92].

Regarding the threat to food security from the use of food crops as biofuels, a qualitative sustainability analysis is conducted, particularly through an environmental policy approach. The unsustainability of palm oil as a biofuel is evidenced by its ban in the transportation sector of the European Union (EU) until 2030, as stipulated in the Renewable Energy Directive (RED II), due to high indirect land-use change (ILUC-risk criteria) threatening food security [93]. This EU policy significantly affects Indonesia, particularly due to its international arena stigma.

Solutions to these challenges are offered by the International Energy Agency (IEA) by promoting more sustainable advanced biofuels compared to conventional biofuels, with criteria for feedstock being (1) non-food agricultural crops and (2) not grown on agricultural land [3]. For these purposes, alternative feedstocks that do not potentially pose sustainability issues are required. In this context, the feasibility of Nipa development with its various advantages as a sustainable biofuel source has been affirmed by Prasetyo et al. [13]. Nipa as an advanced biofuel feedstock is supported by its compliance with criteria as a non-food crop and not grown on agricultural land, which are its main strengths.

At the end of this extensive journey, the utilization of Nipa as a biofuel will be underscored and highlighted for its sustainability pillars. Previous discussions have emphasized that Nipa, as a biofuel (bioethanol), contributes to the achievement of sustainable energy systems in Indonesia, although further exploration is required to advance its application. Therefore, the integration of the three pillars of sustainable energy systems, as outlined by the UNECE [28] into the Implementation Guide by the Global Bioenergy Partnership (GBEP) [29], has been conducted with adjustments to the indicators. The results indicate that the utilization of bioethanol, as a component of bioenergy with Nipa as the feedstock, fulfills the three pillars of sustainability: economic, environmental, and social. Firstly, in the economic pillar, Nipa bioethanol, integrated into national fuel production, can reduce fossil fuel consumption. Secondly, in the environmental pillar, the reduction in fossil fuel consumption, switching to bioethanol, has a positive impact on the environment by reducing GHG emissions. Thirdly, in the social pillar, Nipa as a bioethanol source does not create resource competition that threatens the price and supply of the national food basket. Supported by these three pillars of sustainability as a biofuel source, the economic potential of Nipa as a bioresource is unlocked for future utilization.