1. Introduction
Hibiscus cannabinus, commonly known as kenaf, is an annual fiber crop belonging to the Malvaceae family [1]. Renowned for its cellulosic fiber, kenaf presents both economic and ecological opportunities [2]. Boasting exceptional productivity in biomass production, this agronomic crop has the potential to reach a height of 3 m and a width of over 5 cm within just three months from seed sowing [2]. Kenaf demonstrates remarkable adaptability, having been successfully cultivated in diverse environments worldwide, including China, Russia, and India, with minimal to no input required [3]. Its cultivation has been proven to be feasible in many parts of the world [3].
Typically, kenaf is composed of 74% stalk and 26% foliage by weight, featuring an upright growth habit that results in a substantial central stalk, which is the primary repository of usable fibers in the plant [4,5]. The kenaf stalk consists of two distinct parts: the bark, known as bast, constituting approximately 35% of the stalk’s weight on average; and the core, which comprises the remaining 65% [4]. Both bast and core exhibit unique properties suitable for various applications [4]. The bast, characterized by long fibers averaging 2–3 mm in length, possesses a high crystalline fiber pattern composed of 69.2% cellulose, 2.8% lignin, 27.2% hemicellulose, and 0.8% ash [2]. The core resembles wood and consists of shorter fibers, with an average length less than 1 mm, composed of 32.1% cellulose, 25.2% lignin, 41% hemicellulose, and 1.8% ash [2].
The predominant applications of kenaf involve the utilization of fibers from the plant’s stalk. However, every part of the plant holds industrial value, including the leaves, as forage, and the seeds, as a source of oil [5]. Kenaf is one of the oldest cultivated crops; it can be utilized across various industries, including both traditional sectors and emerging areas of industry and agriculture. While there has been extensive research on specific industrial applications of kenaf, this article focuses on the variety of traditional and modern applications exhibiting the greatest potential utility for commercial application in the future and highlights their economic and ecologic benefits, with the aim of promoting kenaf cultivation in different countries and its application in new areas.
2. History
Kenaf was originally domesticated and utilized in sub-Saharan Africa more than 6000 years ago, where it played a pivotal role, primarily as a cordage crop for textile manufacturing and as livestock feed, throughout most of its history [3,6,7]. By the early 1700s, kenaf had spread to India, where it was actively cultivated for cordage purposes [3,6,7]. Subsequently, in 1900, kenaf found its way to China via Taiwan, continuing its use in textile and rope production [6,7,8]. Kenaf production was initiated in Russia in 1902. During the 1930s, kenaf was cultivated in the USSR and Asia, primarily for fiber crop purposes in cordage and textile manufacturing [6,7].
During the 1940s, research on and production of kenaf was initiated in the United States to supply cordage for World War II, addressing disruptions in fiber supplies [3,9]. In the 1960s, as USDA researchers assessed various species, aiming to meet future fiber demands, kenaf stood out as an excellent source of cellulosic fibers for a diverse range of paper products [3,10]. Global kenaf production peaked in 1985, reaching 2.8 million mt [7]. However, a decline ensued in the early 1990s, attributed to competition from significantly cheaper synthetic fibers and other fiber crops like southern pine, which had established processing systems [11]. Global kenaf production dwindled to less than 753,000 mt in 1995 and continued to decline over the next two decades [7].
3. Modern Production
Kenaf, predominantly cultivated in developing nations at present, is poised for adoption as a renewable industrial fiber source in developed economies [7]. Currently, India and China are the leading nations in kenaf production [12]. In recent years, annual kenaf production has been estimated at just over 200,000 mt annually (Table 1), with India and China contributing 49% and 21%, respectively, to this total [12]. Kenaf production has long been dominated by developing nations, with over 95% of modern production attributed to developing countries [12]. Although the current kenaf market is relatively modest, rapid expansion is anticipated due to the versatile applications of this renewable fiber source, such as use in biocomposites and as a potting medium, particularly if the crop is adopted for use by developed nations. Some projections suggest that the global kenaf market is expected to reach a value of $854 million USD by 2025 [13].
4. Kenaf Applications
4.1. Paper
Kenaf has a distinctive combination of lengthy bast and short core fibers, rendering it a suitable material for the production of a diverse array of paper products [14]. The entire kenaf plant stalk has long been recognized as a viable fiber source for paper pulp [5,10,15]. Field trials in the southeastern United States have shown kenaf fiber yields per acre per year of three to five times more than southern pine [14]. The choice of pulping the bast and core fibers together or separately depends on the specific process and intended application [5,16]. Combining bast and core fibers in the pulping process yields a paper akin to newsprint, while separating and pulping the bast alone results in a higher quality paper suitable for use as premium stationery or filter paper [5,16].
The quality of kenaf plant bast, as utilized in paper-pulp production, has been likened to that of softwood [5]. In comparison to softwood pulp, kenaf bast pulp exhibits similar tensile strength, but surpasses softwood pulp in tear strength and bulk fiber [5,16]. Kenaf offers several processing and cultivation advantages over softwood trees, particularly the predominant paper-pulp crop in the southern United States, Pinus taeda, or southern pine. Kenaf’s annual growth cycle is notably faster than the 17-year maturation period of southern pine, with kenaf reaching a height of up to 6 m within 5–7 months in suitable climatic conditions [16]. Kenaf also boasts comparable yields, with reported yields ranging from 11 to 18 metric tons of dry-stalk biomass per hectare [3].
The harvesting and processing of kenaf fiber for paper requires considerably less time, heat, energy, and chemical treatment compared to that of southern pine, which is primarily attributed to kenaf’s fiber orientation and lower lignin content [16,17]. Kenaf bast fibrils align parallel to the fiber axis, facilitating easier mechanical processing, in contrast to the spiral orientation found in softwoods [17]. Additionally, kenaf bast exhibits significantly lower lignin content, measured at 3%, compared to southern pine’s over 26%, resulting in less byproduct during processing [2,17,18]. Some researchers estimate that a complete substitution of pine with kenaf in U.S. paper-pulp production systems could result in annual energy savings exceeding 4.64 billion kWh/year [17].
Kenaf stalks not only serve well in the production of various paper products, but also offer ecological and economic advantages over conventional paper-pulp sources such as southern pine. In terms of production, kenaf’s annual growth cycle contrasts with the multi-year timeline of southern pine, reducing the risk of crop loss from climatic events like damaging storms and hurricanes. From an economic standpoint, kenaf processing requires less energy input than southern pine due to its fiber orientation and lower lignin content, resulting in a comparatively lower cost for kenaf pulp processing. Although kenaf’s current use in paper pulp is limited, the future holds promise as the focus shifts toward more ecological alternatives.
4.2. Biocomposites
Natural-fiber composites sourced from plants and animals, like cotton, jute, and sheep’s wool, distinguish themselves from synthetic counterparts comprising glass and carbon [2]. These natural-fiber composites present numerous advantages over synthetic alternatives, including reduced tool wear, lower density, cost-effectiveness, availability, and biodegradability [2,19,20]. In manufacturing processes, natural fibers prove non-abrasive to mixing and molding equipment, in contrast to the effects of synthetic fibers, thus minimizing tool wear and production costs [2]. With a lower density than their synthetic counterparts, natural fibers find specialized uses, typically boasting, on average, half the density of glass-derived synthetic fibers [2,20]. Natural fibers, readily produced to meet demand, surpass the availability of synthetic fibers, which necessitate substrates for production [2].
Historically, processing costs of synthetic fibers were lower than those of natural fibers, but research advancements over the past two decades have significantly narrowed the gap [2,11]. Today, plant fibers generally cost about a quarter of the cost of synthetic fibers derived from glass. The reported costs of kenaf fiber per kilogram range from USD 0.44 to 0.55, while synthetic glass fibers stand at USD 2.00 per kilogram [2]. Crucially, natural-fiber composites, composed of plant fibers, undergo easy breakdown by various organisms, earning them recognition as a renewable resource [2].
Industries like the automotive, construction, sports, and leisure industries, and other mass-production sectors, are rapidly expanding their utilization of natural fibers in biocomposites, emphasizing sustainable, renewable, and reinforced materials. Plant fibers, being naturally composite materials, consist of a rigid, crystalline cellulose microfibril-reinforced amorphous lignin and hemicellulose matrix [2]. The bast of kenaf emerges as a potential reinforcing fiber in biocomposites due to its durability, toughness, and high aspect ratio compared to other fibers, boasting a tensile strength of up to 11.9 GPa and a modulus as high as 60 GPa [2]. Beyond their mechanical properties, natural fibers from plants like kenaf also offer ecological advantages over synthetic counterparts. Kenaf fibers, recognized as a renewable resource, do not contribute to CO2 emissions [2]. Biocomposites incorporating kenaf fiber are also more energy-efficient than their synthetic counterparts, requiring 15 MJ to produce 1 kg of kenaf fiber compared to the 54 MJ needed for 1 kg of glass fiber [2].
The main hurdle for the incorporation of plant fiber composites, including materials like kenaf, into commercial applications is the constrained processing temperatures required to prevent fiber degradation [21]. Plant fiber composites necessitate processing temperatures below 200 °C, thereby restricting their application to the production of common thermoplastics such as polyethylene, polypropylene, polyvinyl chloride, and polystyrene [21]. Despite the limited range of products that can be derived from plant fibers, these products account for 70% of the consumption in the thermoplastics industry, indicating the potential for a substantial impact from the widespread adoption of plant-based fibers [21].
Existing research has demonstrated that kenaf stands as an optimal fiber source for biocomposites, showcasing various favorable physical properties and ecological benefits over synthetic alternatives. Several industries have already embraced the incorporation of plant fibers like kenaf into biocomposites, such as the automotive parts manufacturing industry [2]. Anticipated future research and a growing focus on renewable inputs are expected to further enhance the utilization of kenaf in biocomposites in the times ahead.
4.3. Oil Absorbent
Oil spills continually present a significant ecological threat worldwide. Remediation processes for oil spills are typically intricate and costly [22]. Various methods, including mechanical, chemical, and biological approaches, are employed to address oil spills [22,23]. Chemical treatment involves the use of dispersants, surface-washing agents, emulsion breakers, and gelling agents [24]. Biological treatments employ microbes to degrade spilled oil [25]. Mechanical methods include transferring oil from the spill site to containers using oil sorbents or skimmers [23].
When opting for mechanical methods in oil spill treatment, absorption using synthetic or natural fibers is generally considered an efficient and cost-effective choice [23,26]. Despite the effectiveness of synthetic fibers, their lack of easy biodegradability makes natural fibers preferable in oil spill clean-up due to their readily biodegradable and non-toxic nature [23]. The kenaf plant’s core, known for its exceptional absorbency, offers an ecologically friendly alternative to synthetic fibers, given its biodegradability [5,27]. Ground kenaf core has demonstrated superior oil absorption compared to other natural fiber-based oil absorbents like sisal, coco coir, and loofa sponge [22]. While the economic impact of utilizing ground kenaf core as an oil absorbent may be modest in terms of increasing crop production, the ecological advantages of this application are evident and noteworthy.
4.4. Potting Medium
In recent years, there has been a growing interest in the use of alternative potting media within the horticulture industry, driven by escalating costs and the diminishing availability of popular substrates like peat and coco coir [28]. Traditional potting media commonly used in the horticulture industry, such as peat, perlite, and coco coir, are not locally produced in most container-plant production regions. Consequently, they must be transported, leading to increased costs and a negative environmental impact [29]. Additionally, the use of peat is deemed ecologically irresponsible as a potting medium due to its non-renewable and limited resource nature [30]. This has led to a reduced supply and much higher costs for greenhouse and nursery growers.
Kenaf presents itself as an environmentally and economically sustainable alternative to some frequently used potting media components. Being highly adaptable, different kenaf cultivars can be cultivated in nearly every container-plant production region. The ground stem of the kenaf plant, particularly the core, has demonstrated its suitability as a potting medium for plant production on multiple occasions. Wang [29] found that three foliage plants, Brassaia actinophylla, Hibiscus rosa-sinensis, and Pittosporum tobira, flourished when grown in a mix of 70% ground kenaf core and 30% peat, outperforming two commercial controls. Reichert and Baldwin [31] similarly demonstrated that greenhouse annuals grown in a ground kenaf core–peat medium performed as well as those in a 100% peat-based medium. They also showed that the kenaf core–peat medium proved more cost-effective to produce. Webber et al. [32] concluded that the ground core of the kenaf plant can effectively replace traditional potting media, contingent on factors such as the fineness of its grind, its percentage in the growing media, and the growth requirements of specific crops. Although further research is needed to optimize the use of ground kenaf as a potting medium in commercial-scale production systems, past experiments have already demonstrated its potential as a viable alternative.
4.5. Livestock Feed
Kenaf leaves have been used as a livestock feed for centuries. In general, the kenaf plant exhibits high protein levels, with crude protein content ranging from 14% to 34% in the leaves, 2% to 12% in the stalk, and 6% to 23% in the whole plant [3,33,34,35,36,37]. The notably high protein content in the leaves makes them a desirable livestock feed, and kenaf has demonstrated effective ensilage, allowing for the storage of this food source [3,38]. Moreover, studies indicate that kenaf leaves exhibit satisfactory digestibility, featuring a high percentage of digestible protein [3,38]. Kenaf finds applications as feed for a diverse range of livestock. It has been favorably used as a supplement in a rice ration for sheep and serves as a suitable feed source for Spanish goats [3,36,39]. Reported kenaf foliage yields have reached as high as 5796 kg per hectare [40]. However, leaf biomass yield and crude protein content vary among kenaf cultivars [4,33]. Also, the leaf biomass percentage and percentage of crude protein decrease as the kenaf plant increases in height and maturity, because the lower leaves senesce [4]. Therefore, cultivar selection and harvest time are factors to consider if kenaf is to be cultivated for forage production. Although utilizing kenaf as livestock feed may not be the most economically or ecologically impactful application, employing kenaf leaves for this purpose enables the utilization of a plant part that would be discarded in most applications where only the stalk is utilized.
4.6. Biomass Energy
Biomass is a considered to be a completely renewable resource and has seen its use progressively increase in the production of energy [41,42,43,44,45]. Kenaf biomass can be used as a source of energy through multiple applications, including as a biofuel, for the generation of methane, and as solid fuel for thermochemical energy applications (combustion, gasification, and pyrolysis) [42,43]. Kenaf has been shown to be an efficient source for the generation of different types of biofuels, including bioethanol, biodiesel, biogas, and biohydrogen, due to its high levels of cellulose and low lignin content [42]. Kenaf biomass can be subjected to pretreatment/hydrolysis for fermentation to ethanol. A pilot study on ethanol produced from kenaf found that a single kg of kenaf is capable of producing around 18,000 kJ of energy, and theoretical calculations have estimated a level of 256 L of biofuel production per metric ton of biomass [42]. Kenaf biomass can be hydrothermally liquefied to generate bio-crude/bio-oil [42,43,46]. It has also been shown to be an advantageous feedstock with respect to methane production through anaerobic digestion [43]. In addition to biomass energy applications that require processing, kenaf has been shown to be an efficient solid fuel as combustion feedstock for applications such as use in boilers, with advantages over alternatives due to its high volatility and reactivity [43,47]. Also, biochar produced from pyrolysis of kenaf can be used as a solid fuel, as a soil amendment, or as pre-material for activated carbon production [48]. While kenaf biomass holds promise as a source of biomass energy through many different paths, additional research and adequate supporting infrastructure is still required before this crop can be adopted on a commercial scale as a source of renewable bioenergy.
4.7. Additional Uses
In addition to the utilizations already discussed in this article, numerous other applications have been discovered for kenaf. While they are not yet suitable for adoption on the industrial scale in the immediate future, additional research into these applications holds promise for their future integration into commercial systems in the decades to come. These applications include the utilization of kenaf for medicinal use [49,50,51,52,53], for use as a source of seed oil [5,54,55,56,57,58,59,60,61,62], and as a filtration aid [63].
Kenaf is notable for the medical potential of its extracts, particularly from its seeds and leaves [49,50,51,52,53]. Its seed oil has been found to possess anti-oxidant, anti-cancer, anti-ulcer, anti-inflammatory, anti-thrombotic, anti-tyrosinase, anti-hyperlipidemia, and hepatoprotective activities in numerous studies [49,50,51,52,53]. Leaves from the kenaf plant have been found to treat a plethora of ailments; however, additional studies are needed to discover their true medical potential [51]. In addition to possessing medical properties, the relatively high oil content of kenaf seeds (23.7%) and a fatty acid composition similar to cottonseed oil suggest that kenaf seed oil can be used as a source of edible oil [54]. Oil derived from the seeds of the kenaf plant has been found to be suitable for cooking and for producing cosmetics [54,55,56,57,58,59,60,61,62]. Kenaf seed oil is also a potential feedstock for biodiesel production through transesterification [64,65]. Once the oil is removed from the seeds, the concentrated seed cake can be used as livestock feed as well [65].
Kenaf core has potential as a filtration aid for swimming pools and spas [63]. Currently, filter-grade diatomaceous earth is used as a filtration aid for these applications, and it is known to be toxic to humans [63]. Lee and Eiteman [63] found that kenaf core could be used as a comparable substitute for diatomaceous earth in these filters, offering a non-toxic sustainable alternative. While research thus far has only shown its application as a filter for use in pools and spas, many other potentially higher value applications for use as a filter could be identified with further investigation. Kenaf core can also be utilized as bedding material for animals (horses, cattle, and poultry). Kenaf core particles were shown to have water retention levels and absorption capacity similar to other commercial bedding materials [66]. Kenaf fibers also have potential application in bioremediation to absorb and accumulate heavy metals from contaminated soils and wastewaters [67]. Although kenaf holds future promise in all these applications, more research is required for their implementation on a commercial scale.
5. Kenaf Compared to Other Fiber Crops
The utilization of a given fiber crop depends upon the intended application, area of cultivation, and other factors such as economic and ecological influences. Kenaf possesses similarities and notable advantages over comparable crops. A comparison of the yields and composition of common fiber crops is shown in Table 2. While lower lignin (2.8%) and higher cellulose (69.2%) content are present in the bast of the kenaf stalk and its core possesses a higher concentration of lignin (25.2%) and hemicellulose (41%), the whole stalk of the kenaf plant possesses a cellulose content of 45–57%, a hemicellulose content of 21.5%, and a lignin content of 8–13% [2]. Comparatively, southern pine displays a slightly lower cellulose (43.6%), higher lignin (26.8%), and similar hemicellulose (21.2%) relative to kenaf [68]. Consequently, for applications such as the production of paper pulp or biocomposites, kenaf represents a more efficient alternative than southern pine, having greater fiber and cellulose yields and, most importantly, lower lignin content, allowing for more efficient processing with less byproduct. Hemp and jute both possess a higher cellulose content than kenaf, 70–74% and 61–71.5%, respectively, with jute having a similar lignin content (12–13%) and hemp a lignin content nearly half that of kenaf’s, at 3.5–5.7% [2]. However, kenaf possesses dry-stalk yields comparable to southern pine and hemp, and greater yields than jute. Dry-stalk yields of 17.9 mt.ha−1.yr−1 have been reported for southern pine [69], 11–17 mt.ha−1.yr−1 for hemp [70], and only 4.3–7.6 mt.ha−1.yr−1 for jute [71]. Additionally, when the bast is separated from the core of the kenaf plant, it possesses 69.2% cellulose and 2.8% lignin [2], which is comparable to those of hemp and jute (Table 2). The remaining core can be used for applications such as potting media substitute or oil absorbent, due to its high hemicellulose content [2,5,27,29,31,32]. Thus, kenaf displays similarities and advantages in its yield and composition that warrant its application, as opposed to alternative fiber crops, in many situations.
6. Discussion
Kenaf, a highly productive annual fiber crop, boasts versatility and can thrive in a diversity of global locations [3]. With a history of human cultivation spanning over 6000 years, kenaf has been traditionally employed for cordage and textiles [3]. However, the last century of research has uncovered a myriad of new applications for this crop, presenting significant potential for expanding its cultivation and utilization. In Malaysia, for example, kenaf has been targeted as a new industrial crop to support diversification of the country’s commodities sector [13,75]. Recognizing the potential of kenaf as a profitable bioresource, the Malaysian government promotes kenaf production with incentives for cultivation and product development, including renewable energy, from kenaf biomass [13,42].
This article emphasizes several kenaf applications with considerable prospects in the near term, such as paper pulp, biocomposites, oil absorbents, potting media, and animal feed, and those which require additional research but have potential for commercial impact in the future, such as use as a medicine [5,49,50,51,52,53], as a filtration aid [63], or as a source of biomass energy [42] (Figure 1, Table 3). While today the global cultivation of kenaf is just over 200,000 mt annually, with the vast majority of the contribution coming from developing countries [12], the future holds promise for its cultivation on a larger scale with the adoption of kenaf for application in the utilizations discussed in this article. In particular, kenaf could be incorporated into these applications in developed nations where cultivation is currently extremely limited despite the crop’s obvious economic and ecologic benefits.
The utilization of kenaf in paper pulp holds the promise of reducing production costs, requiring less energy for processing, and mitigating environmental impact by minimizing processing byproducts and decreasing the amount of land required for fiber production [5]. While kenaf has found acceptance as a source of paper pulp in deforested regions like China, challenges such as the absence of processing facilities and competition with established southern-pine processing plants have limited its adoption in regions like the southern United States [17]. In the realm of biocomposites, kenaf’s ecological and economic advantages over synthetic fibers position it for significant expansion, especially as ongoing research refines manufacturing processes and demand increases for natural fibers [2]. The substitution of kenaf in potting media presents immediate potential, given the horticulture industry’s flexibility and willingness to embrace alternatives amid rising media costs and decreasing availability [31]. Further research on potted plant production with a kenaf-based medium could expedite its adoption by the horticulture industry. Although some applications, like the use of kenaf leaves as livestock forage, may seem minor, they also allow for the utilization of byproducts from a crop primarily grown for its stalk. Research has also shown that kenaf shows promise for a variety of medicinal utilizations, most impactfully perhaps as an anti-cancer agent [49,50,51,52,53]; as a filtration aid [63]; as a source of seed oil [5,54,55,56,61]; and as a source of biomass energy [42]. While these applications hold merit for commercial adoption in the future, additional research is required before they can be implemented on an industrial scale.
Compared to other fiber crops, kenaf possesses similarities and advantages in its yield and composition that justify its application over alternatives. Kenaf has a yield and cellulose content comparable to those of southern pine, but possesses a lower lignin content, even as a whole plant, allowing for reduced processing costs and less byproduct in applications such as paper pulp or biocomposites [2,3,5,18,68,69]. Crops such as hemp and jute have higher cellulose content and comparable or lower lignin content in their whole stalk compared to kenaf [2], making them more desirable fibers for applications such as those involving paper pulp and biocomposites, when whole stalks are utilized. However, when the kenaf stalk is decorticated and its bast is separated from its core, the bast of the kenaf plant has a composition comparable to those of jute and hemp [2], while the remaining core is ideal for utilization as a potting media substitute or an oil absorbent, due to its high hemicellulose content [2,5,27,29,31,32]. Depending on the intended applications and its environment of cultivation, kenaf exhibits numerous characteristics that justify its consideration over other fiber crops.
Despite the numerous advantages of kenaf and the multitude of opportunities for its application, several challenges still hinder its adoption on a commercial level. Historically, the low cost and widespread availability of synthetic fibers impeded its acceptance in many industries [11]. However, current trends show a reduction in the cost of producing plant-based fibers and their products, making them comparable to or cheaper than synthetic alternatives [2]. Today, the major obstacles to the commercial adoption of kenaf are the lack of processing facilities and insufficient awareness across the entire supply chain. Although kenaf offers clear benefits, there is a significant lack of the infrastructure necessary to process the plant. For large-scale adoption, it is crucial to establish initial pilot processing facilities followed by full-scale operations. Additionally, awareness of the crop across the supply chain is limited. Many industries are accustomed to established processes and are reluctant to adopt alternatives unless there is a pressing need, or there are clear benefits from introducing new technologies. Kenaf’s economic and ecological advantages will drive its adoption in commercial industries once they are made aware of these benefits. Furthermore, kenaf is unfamiliar to most farmers in developed nations, necessitating education for both industries and farmers. Farmers will need to be encouraged to adopt and cultivate kenaf. In many cases, the cultivation of fiber crops, for example in the United States with southern pine, is only economically viable due to government market support and subsidies. Similar subsidies for kenaf would make its cultivation competitive with other fiber crops. With appropriate infrastructure, education, and financial incentives, the widespread adoption of kenaf can be achieved. The urgent need to reduce greenhouse gas emissions requires a transition from a fossil fuel-based economy to one that uses sustainable bio-based resources, providing opportunities for the economic and ecological benefits of kenaf to be harnessed at a commercial level in the emerging circular economy.
Kenaf, one of the oldest cultivated crops, can be utilized across various industries, including both traditional sectors and emerging areas of industry and agriculture. Harvesting time and crop management can be adjusted according to the intended use of the crop. This article describes the range of traditional and modern uses for kenaf with the greatest potential for future commercial applications and also discusses those that have commercial promise with additional research. Kenaf’s adoption across various applications holds the potential for substantial positive environmental impacts, particularly in areas like biocomposites, potting media, and more recently, as a sustainable source of biomass energy, where renewable resources can replace non-renewable ones. While current knowledge highlights numerous kenaf applications, future research holds the promise of not only expanding its use in known applications but also of unveiling novel ones and advancing applications such as kenaf’s use as a medicine to the point where they are commercially viable. The ongoing exploration of kenaf’s potential applications signifies a dynamic and evolving landscape for this versatile crop.
Conceptualization, C.C.A., A.C.W., C.N.M. and D.G.C.; investigation, C.C.A., C.N.M. and A.C.W.; resources, A.C.W. and D.G.C.; writing—original draft preparation, C.C.A.; writing—review and editing, C.C.A., C.N.M., D.G.C. and A.C.W.; supervision, A.C.W. and D.G.C.; funding acquisition, not applicable. All authors have read and agreed to the published version of the manuscript.
The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding authors.
The authors declare no conflicts of interest.
Footnotes
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Enlarge this image.Figure 1. Graphical schematic of kenaf plant parts, including the whole stalk, bast, core, foliage, and seeds of the plant, and their respective utilizations (H = Historical usage).
World production of kenaf and allied fibers [
| 2017/18 | 2018/19 | 2019/20 | 2020/21 | 2021/22 | |
|---|---|---|---|---|---|
| Developing countries | 202.6 | 198.6 | 204.6 | 200.3 | 195.7 |
| Far East | 155.3 | 151.3 | 157.7 | 150.2 | 146.7 |
| China | 50.0 | 45.97 | 52.37 | 45.03 | 41.43 |
| India | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Indonesia | 3.3 | 3.3 | 3.4 | 3.3 | 3.3 |
| Thailand | 0.2 | 0.2 | 0.2 | 0.3 | 0.3 |
| Vietnam | 0.5 | 0.5 | 0.5 | 0.3 | 0.4 |
| Cambodia | 0.2 | 0.2 | 0.2 | 0.3 | 0.3 |
| Pakistan | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Latin America and the Caribbean | 26.0 | 26.1 | 25.6 | 28.5 | 27.3 |
| Brazil | 2.8 | 2.9 | 2.6 | 5.5 | 4.4 |
| Cuba | 11.9 | 12.0 | 11.8 | 11.8 | 11.8 |
| Other | 11.3 | 11.2 | 11.2 | 11.2 | 11.1 |
| Africa | 15.5 | 15.4 | 15.5 | 15.6 | 15.7 |
| Near East | 5.7 | 5.7 | 5.8 | 6.0 | 6.0 |
| Developed countries | 6.8 | 6.8 | 6.9 | 6.8 | 6.8 |
| World | 209.4 | 205.4 | 211.5 | 207.1 | 202.5 |
1 Data in thousand metric tons.
A comparison of dry-stalk yield (metric ton per hectare per year) and content levels of cellulose, hemicellulose, and lignin for common fiber crops.
| Crop | Dry-Stalk Yield (mt.ha−1.yr−1) | Cellulose | Hemicellulose | Lignin | ||||
|---|---|---|---|---|---|---|---|---|
| Kenaf | 11–18 | [ | 45–57 | [ | 21.5 | [ | 8–13 | [ |
| Kenaf bast | 69.2 | [ | 27.2 | [ | 2.8 | [ | ||
| Kenaf core | 32.1 | [ | 41 | [ | 25.2 | [ | ||
| Hemp | 11–17 | [ | 70–74 | [ | 17.9–22.4 | [ | 3.5–5.7 | [ |
| Hemp bast | 64.8 | [ | 7.7 | [ | 4.3 | [ | ||
| Hemp core | 34.5 | [ | 17.8 | [ | 20.8 | [ | ||
| Jute | 4.3–7.6 | [ | 61–71.5 | [ | 13.6–20.4 | [ | 12–13 | [ |
| Jute bast | 62.1 | [ | 21.8 | [ | 14 | [ | ||
| Jute core | 34–39.8 | [ | 31.1–37.2 | [ | 24–26 | [ | ||
| Southern Pine | 17.9 | [ | 43.6 | [ | 21.2 | [ | 26.8 | [ |
Commercial uses for kenaf plant parts and a rationale for each of these applications.
| Plant Part | Application | Rationale | Reference |
|---|---|---|---|
| Whole Stalk | Paper Pulp | The whole stalk may be pulped, resulting in newsprint-quality paper. | Webber and Bledsoe [ |
| Biomass Energy | Kenaf biomass can be used as a bioenergy feedstock for biofuel and biogas production, and as solid fuel for combustion, gasification, and pyrolysis. | Saba et al. [ | |
| Biochar | Kenaf biochar can be used as a solid fuel, as a soil amendment, or for activated carbon production. | Khiari et al. [ | |
| Bast | Paper Pulp | Pulping the bast alone creates a higher quality paper than pulping the stalk as a whole. | Webber and Bledsoe [ |
| Biocomposites | Quality biocomposites can be generated using kenaf bast fibers, which offer increased durability and toughness, a high aspect ratio, and ecologic and economic benefits compared to their synthetic counterparts. | Akil et al. [ | |
| Textiles | One of the oldest uses of the crop, the bast of kenaf can be used to produce textiles and cordage. | Webber et al. [ | |
| Core | Potting Media | Ground kenaf core may be effectively utilized as an environmentally and economically sustainable alternative to frequently used potting media components such as peat, depending on the fineness of its grind, its percentage in the growing media, and the growth requirements of a specific crop. | Wang [ |
| Oil Absorbent | The kenaf plant’s core possesses exceptional absorbency and offers an ecologically friendly alternative to synthetic fibers as an oil absorbent. | Webber and Bledsoe [ | |
| Filtration Aid | Kenaf has been shown to be an effective replacement for diatomaceous earth in pool and spa filters. | Lee and Eiteman [ | |
| Animal Bedding | Kenaf core particles were shown to have water retention levels and absorption capacity similar to other commercial bedding materials. | Lips et al. [ | |
| Foliage | Livestock Feed | Kenaf plants, particularly their leaves, exhibit high protein levels, ensilage effectively, and have been shown to be a suitable forage for a variety of livestock. | Webber et al. [ |
| Seeds | Edible Oil | Due to their high oil content and unique fatty acid composition, the seeds of the kenaf plant may be used as a viable source of oil for human consumption or the production of cosmetics. | Webber and Bledsoe [ |
| Medicine | Kenaf seed oil has been found to possess anti-oxidant, anti-cancer, anti-ulcer, anti-inflammatory, anti-thrombotic, anti-tyrosinase, anti-hyperlipidemia, and hepatoprotective properties. | Norhisham et al. [ | |
| Biodiesel | Kenaf seed oil is a potential feedstock for biodiesel production through transesterification. | Rathana et al. [ | |
| Livestock Feed | After oil extraction, the concentrated seed cake can be used as livestock feed. | Szulczyk and Badeeb [ |
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; Wilkie, Ann C 2
1 Department of Environmental Horticulture, University of Florida-IFAS, Gainesville, FL 32611, USA
2 Department of Soil, Water, and Ecosystem Sciences, University of Florida-IFAS, Gainesville, FL 32611, USA