OIL PALM NANOCELLULOSE

OIL PALM (Elaeis guineensis) is among important commodity in Malaysia since long ago. Currently there are more than 1.4 million hectare of oil palm grown in Malaysia as one of the largest palm oil producers in the world. However, the Oil Palm Empty Fruit Bunch (OPEFB) is considered the cheapest natural fiber with good properties and exists abundantly in Malaysia. It has great potential as an alternative main raw material to substitute woody plants as an important industry. Currently it was told that the well-known Polymeric Hydrogel has gathered a lot of interest due to its three-dimensional (3D) cross-linked network with high porosity. However, for some issues regarding its performance such as poor interfacial connectivity and mechanical strength have been raised so that nanocellulose has been introduced. In some research done by many local institutions in which the plantation of oil palm in Malaysia is discussed to show the potential of OPEFB as a nanocellulose material in hydrogel production is potentially develop. Nanocellulose can be categorized into three nano-structured celluloses in which it differs in the processing method. The most popular nanocellulose hydrogel processing methods are in few techniques. The 3D printing method is taking the lead in current hydrogel production due to its high complexity and the need for hygiene products. Some of the latest advanced applications are used to show the high approach of commercialization potential of nanocellulose hydrogel products. There are challenges and future direction of nanocellulose hydrogel. OPEFB claimed has met the requirements of the marketplace and product value chains as nanocellulose raw materials in many ways for the hydrogel applications. This article at "Anim Agriculture Technology" I am happy to discuss about the potential of the oil palm nanocellulose hydrogel for implementation in Malaysia for the future and reading purposes.

The word 'Nanocellulose' in oil palm industry are not new for many researchers. Nanocellulose is a renewable nanomaterial with many potential applications in advanced materials, biomedical, and food packaging. It has outstanding properties like being lightweight, stiff, non-toxic, a high tensile index, and is most abundant on Earth. It can be derived from any resource material such as lignocellulosic fibers or so-called natural fibers that can be found in 2000 plant species. Natural fibers consist of three main components include cellulose, lignin, and hemicellulose. Other components such as the extractives of polar and non-polar components can also be extracted from natural fibers. In other words, the natural fibers are composed of cellulose microfibrils that are structured in a matrix together with lignin and hemicelluloses components. Natural fibers depend very much on the cellulose type that is related to crystalline composition. The mechanical properties of natural fibers are influenced by the organization of crystalline composition. A single cell of natural plant fibers has a 1 - 50 mm length and 10 - 50 m diameter that are formed from the cellulose microfibrils. The microfibrils are formed of 30-100 cellulose molecules with a diameter of 10-30 nm. Many types of extraction methods are applied to isolate the fibers from the natural plant stem.

Microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC) are two types of common cellulose with a particle size diameter that ranges from 10 to 50 μm and 3 to 5 nm, respectively. In addition, MCC is isolated via sulfuric acid (H2SO4) treatment, while CNC is isolated via acid hydrolysis. In terms of structure, MCC has crystalline structures of multi-sized cellulose microfibril aggregates that appear in bundles, while NCC exists as whiskers or known as rod-shaped in crystalline regions. Nanocellulose can be categorized into three nano-structured cellulose: (i) CNF, (ii) CNC, and (iii) BNC. These nanocelluloses differ based on the method of production. To date, huge numbers of research have used OPEFB as the raw material to produce CNF and CNC. However, study on bacterial nanocellulose, which is made of OPEFB cellulose nanofibrils that involve bacteria or enzymatic polymerization is not available. The CNF and CNC can be self-prepared via chemical, mechanical, or combination methods. Most studies have incorporated nanocellulose in the manufacture of composites, paper, or film. However, to address the issue of low mechanical strength, absorbability, or transparency of the regenerated cellulose membrane or the hydrogel, the incorporation of nanocellulose is very practical. The mechanical strength is successfully enhanced by employing nanocellulose as the additive. These improvements can be applied for high-end applications such as for water filtration, mulching mat, wound healing patch, and other applicable products. The increase in some properties like mechanical strength will have a significant impact on the usage of the products. Unnecessary pretreatments or processes that will increase the production cost could be eliminated. For instance, in the papermaking process, the addition of nanocellulose can reduce the beating revolution which will indirectly reduce the energy consumption and production costs. At the same time, a better fiber bond can still be achieved.

Cellulose Nanofibers (CNF) from OPEFB ar the CNF prepared by hydrolyzing OPEFB with sulfuric acid has an average width of 1–3.5 nm by varying the time of hydrolysis. A longer period of hydrolysis produces nanofibers with better yield, lower degree of polymerization, and crystallinity. The CNF extracted from OPEFB using chemo-mechanical processes such as H2SO4 hydrolysis and high-pressure homogenization produced CNF with sizes of 5 to 10 nm. CNF can also be extracted from OPEFB through the ultrasound effect during the stages and can be obtained after the soda-anthraquinone pulping and bleaching processes. An ultrasound equipped with the frequency of 20 kHz and the output power of 700 W was used to produce CNF with a diameter of 5 to 23 nm. MFCs can be prepared using two different techniques: ammonium persulfate oxidation and sulfuric acid hydrolysis. Both techniques produced MFCs of long and network-like fibrils with widths ranging from 8 to 40 nm. One study isolated CNF from OPEFB via the thermal-chemical process followed by nano-grinding treatment. The produced nanocellulose had a morphological dimensional change from 8.25 μm to 17.85 nm. Another study also used the isolation of OPEFB to produce lignocellulose nanofibers (LCNFs) by applying multi mechanical stages with varied vibration milling times. The external surface of the produced nanofibers was uneven, irregular, folding, and unsmooth, with an optimal size of 53.72-446.80 nm. The cellulose OPEFB fiber can be converted into MFC and CNF through peracetic acid delignification followed by enzyme hydrolysis. The enzyme hydrolysis can be used as a method to transform cellulose into MFC, but it does not have the capability to become a nanocellulose. Hastuti et al. (2019) characterized CNF derived from OPEFB that could produce by 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)/NaBr/NaClO. The crystallinity indices (CrIs) were identified to range from 34% to 55% by using x-ray diffraction (XRD). High-performance nanomaterials like TEMPO-oxidized CNF were successfully prepared with good characteristics from low-quality biomass waste such as OPEFB. Other recent work prepared nanocelluloses from chemically purified celluloses of oil palm empty fruit bunch (CPC-OPEFB) by using acid hydrolysis. The nanocelluloses from CPC-OPEFB were prepared with sulfuric acid treatment at the concentration of 67 wt% at 40 ± 1 °C for 10, 20, 30, and 40 min. The particle size analysis proved that the diameter of the obtained nanocelluloses was affected by the hydrolysis time. The best hydrolysis time to obtain the smallest diameter of CNFs from CPC-OPEFB was 30 min.

In the making of film a study by Lani et al. (2014) that has prepared nanocellulose from OPEFB fiber that had a 4 - 15 nm diameter. The nanocellulose was applied to reinforce the polyvinyl alcohol/starch blend films, and 5% (v/v) of nanocellulose formulated the best nanocomposites with the tensile strength of 5.694 MPa. Salehudin et al. (2014) incorporated nanocellulose extracted from OPEFB to enhance the mechanical properties of starch-based polymers. The CNF was prepared by hydrolyzing OPEFB with 64% H2SO4 at 45 °C for 90 min and obtained nanofibers with diameters of 50 to 90 nm. The incorporation of 2% nanofiber enhanced the starch-based film up to 28% in terms of tensile strength. Another study found that 1 wt% of OPEFB nanocellulose reinforced poly (vinyl alcohol)-α-chitin composite films were improved by 57.64% and 50.66% of tensile strength and young’s modulus, respectively.  Nanocellulose is also used in preparing nanopaper. Ferrer et al. (2012) prepared dissimilar cellulose pulps of sulfur-free chemical treatments of OPEFB. The pulps were microfluidized to obtain CNF, which was used to manufacture nanopaper via an overpressure device. The nanopaper had lesser water absorption, higher tensile strengths (107-137 MPa), and higher elastic modulus (12-18 GPa). A superadsorbent was produced from OPEFB for water remediation through sulfuric and phosphoric acid hydrolysis with activated carbon. The occurrence of sulfonic groups achieved better remediation capabilities on the NCS compared to NCP. The performance was doubled compared to the sample of rice-straw NC by having a metal adsorption capability to Pb2+ with 86% efficiency and 24.94 mg/g adsorption capacity.

The Cellulose Nanocrystal (CNC) from OPEFB studied successfully isolated MCC from OPOPEFB-total chlorine free pulp. The acid hydrolysis method was applied using the TCF pulp bleaching that was done via the oxygen-ozone-hydrogen peroxide bleaching sequence. The produced MCC had 87% of crystallinity, which had good thermal stability. CNC was also isolated from OPEFB-total chlorine free bleached pulp by the acid hydrolysis of 58% sulfuric acid concentration continued by ultrasonic treatment. The optimal hydrolysis time was 80 min for CNC with dimensions of 150 nm in length and 6.5 nm in diameter. It was proven that the CNC could be practically produced from chlorine free pulp, which are known as environmentally benign processes as they save energy and reduce chemical usage. Pujiasih et al. (2018) focused on the silylation of MCC from OPEFB via the aminosilane compound synthesized through the aminolysis of 3-glycidoxypropyltrimethoxysilane with ethylenediamine. Three steps were involved: (i) bleaching process, (ii) alkaline treatment, and (iii) acid hydrolysis. Budhi et al. (2018) used OPEFB as raw material to obtain CNC. They managed to produce 44.8% yield of CNC from dried OPEFB with a diameter of about 140 nm and crystallinity index at 73.3%. Septevani et al. (2019) synthesized and able to be characterized nanocellulose obtained from OPEFB via strong H2SO4 and mild acid (H3PO4) hydrolysis at 50 °C for 3.5 h. A rod-like and long filament-shaped nanocellulose was obtained from the strong and mild acid hydrolysis, respectively. The degree of crystallinity was higher from the strong acid hydrolysis (96%), compared to that of the mild acid hydrolysis (86%). As an initiative to reduce the agglomeration problem was carried out and the CNC from OPEFB was prepared using the TEMPO (2,2,6,6-Tetramethylpiperidinyloxy or 2,2,6,6-Tetramethylpiperidine 1-oxyl)-oxidation reaction method. The drying and solvent exchanged techniques were applied in the post-treatment step, and the agglomeration of NCC due to the hydrogen bonding among cellulose linkages was minimized. From another study showed that the application of 1-10% CNC as a reinforcement material in the composite exhibited good transparency and visibility by obtaining more than 80% of visible light transparency at 550 nm. The CNC from OPEFB was produced by using chemical pulping such as soda pulping, followed by the 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) oxidation reaction method. The produced NCC was used to enhance the polylactic acid (PLA) biopolymer film matrix by 0-20% of loadings. The NCC had a rod-like shape of 2-6 nm in width and 200-500 nm in length. We hope this article able to provide information to all. Thanks.

Rewrite by,

M Anem,

Putrajaya,

Malaysia.

(November 2022).