Unlike open raceway ponds, where risk of contamination is distressing, single spe­cie culture may be grown in closed photo-bioreactors (CPBs) without any contami­nation risk. Huge quantities of algal biomass have been produced using CPBs for fuel production previously using different types of CPBs, including tubular, col­umn, and flat-panel (Fig. 18.3) (Sanchez Miron et al. 1999; Pulz 2001; Carvalho et al. 2006).

A tubular photo-bioreactor comprises of an array of straight transparent (plastic or glass) tubes. This tubular array also called as a solar collector captures the sun­light. The solar collector tubes are generally <0.1 m in diameter. Tube diameter is limited because light does not penetrate too deeply in the dense culture broth that is essential to ensure higher biomass productivities in the CPB. Microalgal broth is circulated from a reservoir to the solar collector and back to the reservoir making it a continuous operation. Capturing of sunlight may be enhanced through the orienta­tion of the collector facing sun pathway and through the use of transparent pipes or flat panels as solar collectors. Alternatives of tubular photo-bioreactors exist in con­sidering flaws related to tubular photo-bioreactors (Carvalho et al. 2006; Pulz 2001)

but these alternatives are not commonly used for mass culture. Technically, achiev- ability of tubular photo-bioreactors is maximum by artificial illumination (Pulz 2001) but costly than natural source of light (sun).

The CPBs require cooling during day-light hours; temperature control at night is also useful, in a way. For example, the loss of biomass due to respiration at night may be reduced by lowering the temperature at night. Outdoor tubular photo­bioreactors are effectively and inexpensively cooled using heat-exchangers. This may be achieved by placing a heat-exchange coil in the degassing column. Evaporative cooling by water sprayed on tubes (Terry and Raymond 1985) is also used and has demonstrated successfully in dry climates. Large tubular photo­bioreactors have also been sited within temperature controlled green-houses (Pulz 2001), but doing so is not worthwhile for economical production of biodiesel.

The tensile strength of bamboo fibers is observed as 56.8 MPa, which is higher than that of aluminum alloy (Amada and Untao 2001). Bamboo fibers reinforced poly­propylene composites and bamboo glass fiber reinforced polypropylene hybrid composites, when exposed to water, show a decrease in tensile strength and elastic modulus (Thwe and Liao 2003). The high density bamboo fibers are shown to have increased tensile strength when fabricated with maleated polyethylene contents (Han et al. 2008). The tensile strength of bamboo fiber obtained from bamboo fiber blocks is higher than that of separated fiber bundles. This is due to interaction between components in bamboo in which parenchyma cells can pass loads (Shao et al. 2010).

Poly butylene succinate bamboo fiber (PBS/BF) composite has a tensile strength of 21 MPa. When bamboo fiber esterified with maleic anhydride is added in the concentration of 5 %, the tensile strength increases to 28 MPa (Lee and Ohkita 2005). Alkali treated bamboo fiber reinforced composite is shown to have a reduc­tion in tensile strength (Kushwaha and Kumar 2010). Bamboo fiber reinforced plas­tic composites have a measured tensile strength of 102.6 MN m-2 (Jain et al. 1993). The tensile strength of bamboo fiber reinforced epoxy resins is calculated to be

200.5 MN m-2 (Jain et al. 1992). The tensile strength of short bamboo glass fiber reinforced polypropylene composites is best at the fiber length of 1-6 mm (Thwe and Liao 2002b).

The tensile strength of outer periphery of bamboo fibers is approximately 160 kg mm-2 and that of inner periphery is approximately 45 kg mm-2 (Ray et al. 2005). The tensile strength of steam exploded bamboo fiber can be increased by impregnation and reduction in number of voids (Okubo et al. 2004). Green compos­ites made from bamboo fibers show the tensile strength of 330 MPa at the fiber volume of 70 %. This tensile strength is observed to be higher than that of the com­posites prepared from biodegradable resins (Cao and Wu 2008). The tensile strength of permanganate treated bamboo polyester fibers is increased by 58 % and that treated with benzoyl chloride is 71 % (Kushwaha and Kumar 2010).

The tensile strength of bamboo fiber reinforced poly propylene composite after aging of 1,200 h at 25 °C temperature is reduced by 12.2 % and that of bamboo glass fiber reinforced poly propylene composite is reduced by 7.5 %. The strength reduction can be suppressed by using MAPP residues (Thwe and Liao 2003).

M. Siti Alwani, H. P.S. Abdul Khalil, M. Asniza, S. S. Suhaily,

A. S. Nur Amiranajwa, and M. Jawaid

Contents

5.1 Introduction……………………………………………………………………………………………………… 78

5.2 Classification of Agricultural Biomass Raw Materials……………………………………………………. 79

5.3 Agricultural Biomass Properties……………………………………………………………………………… 81

5.3.1 Chemical Properties…………………………………………………………………………………. 81

5.3.2 Physical Properties………………………………………………………………………………….. 81

5.3.3 Mechanical Properties………………………………………………………………………………. 83

5.4 Biomass Raw Material Design and Network……………………………………………………………….. 84

5.4.1 Biomass Fibre Design………………………………………………………………………………. 84

5.4.2 Biomass Fibre Network…………………………………………………………………………….. 86

5.5 Current and Future Applications of Agricultural Biomass………………………………………………. 91

5.5.1 Future Potential of Biocomposite Industry………………………………………………………. 91

5.5.2 Value Chain of Biocomposite Industry…………………………………………………………… 92

5.6 Agricultural Biomass Raw Materials for Sustainable Economical Development………………………. 93

5.7 Conclusions…………………………………………………………………………………………………….. 96

References………………………………………………………………………………………………………….. 97

M. Siti Alwani • H. P.S. Abdul Khalil (*) • M. Asniza • A. S. Nur Amiranajwa School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia e-mail: akhalilhps@gmail. com

S. S. Suhaily

School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia Product Design Department, School of the Arts, Universiti Sains, Penang 11800, Malaysia M. Jawaid

Department of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia

Department of Chemical Engineering, College of Engineering, King Saud University, Riyadh 11451, Saudi Arabia

K. R. Hakeem et al. (eds.), Biomass and Bioenergy: Processing and Properties,

DOI 10.1007/978-3-319-07641-6_5, © Springer International Publishing Switzerland 2014

Abstract Nowadays, the depletion of natural resources, growing population and raising environmental concerns have raised a tremendous interest in finding a sus­tainable alternative for creating new materials that are environmental friendly. Agricultural biomass is the plant residue left in the plantation field after harvesting. This lignocellulosic material possesses a composition, structure and properties that make them suitable to be used in various conventional and modern applications. This renewable plant waste is abundant, biodegradable, low cost and low density that could be a principal source for production of fibres, chemicals and other industrial products. The uses of these materials are not only limited to composite, paper and textile applications, but are also progressing immensely to many other unlimited applications such as medical, nano technology, biofuel and pharmaceutical. These expanding applications of agricultural biomass would not only help in reducing the environmental pollution but also provide an opportunity in developing renewable and sustainable material to be used in various advanced applications in the future. This would also help in generating employment and contributing to the improvement of people’s livelihood. The aim of this chapter is to discuss different types of agricul­tural biomasses with its present applications and future potentialities.

Keywords Agricultural biomass • Properties • Fibre design • Fibre network • Applications

5.1 Introduction

The widespread concern over increasing fossil fuel prices, global warming issues, environmental pollution and green house effects have stimulated a tremendous interest in the use of renewable materials that compatible with the environment. A way of addressing this sensitive issue could be through promoting the biomass from agricultural as an important alternative source for raw materials in the compo­sition of various products and applications.

Biomass such as agricultural crops is the largest of cellulose resource in the world. Approximately 2 x 1011 tons of lignocellulosics is produced annually com­pared to 1.5 x 108 tons of synthetic polymers (Pandey et al. 2010). Biomass is a clean source of energy as it releases carbon dioxide (CO2) as it burns but the gas released is recaptured by the growth of the same materials. This material considered as the most abundant waste after harvesting. After harvesting the fruit for food, most of the biomass is traditionally wasted for which it is normally left in the plantation field as organic fertilizer, mixed with the rejected fruits to make animal feed or is open-burnt. Utilization of these wastes could solve the disposal problem and reduce the cost of waste treatment (Goh et al. 2010).

Compared to glass fibre, biomass offers many advantages due to their unique characteristic such as low cost, low energy consumption, zero CO2 emission, low abrasive properties, low density, biodegradability, non-toxicity and their continuous availability (Guimaraes et al. 2009) . However, biomass fibres also have certain drawbacks especially when considering its application in composite. They have high moisture absorption and poor compatibility with polymer matrix which is responsible for poor mechanical and thermal properties. Modification or treatment of the fibre is needed to enhance the performance of biomass in different multiple applications (Pandey et al. 2010).

In the past few decades, the development of new materials that involve natural resources as the raw material, especially as a composite material, has accelerated. Nowadays, a large number of interesting applications are emerging for these materi­als due to recent progress in technological advances, biomass material development, genetic engineering, and composite science technology that offer significant oppor­tunities for an exploration and development of improved materials from renewable resources which can be used in various applications such as biocomposites, pulp and paper, construction, automotive, medical, packaging, aerospace, pharmaceuti­cal and biomass energy production (Lau et al. 2010).

Nadendla Srinivasababu, J. Suresh Kumar,

K. Vijaya Kumar Reddy, and Gutta Sambasiva Rao

Contents

8.1 Introduction……………………………………………………………………………………………………. 126

8.2 Materials and Methods……………………………………………………………………………………….. 128

8.2.1 Pure Splitting Method…………………………………………………………………………….. 128

8.2.2 Chemical Treatment……………………………………………………………………………….. 129

8.2.3 Fiber Characterization……………………………………………………………………………… 129

8.2.4 Fabrication and Testing of Composites…………………………………………………………. 130

8.3 Results and Discussion………………………………………………………………………………………. 131

8.3.1 Physical and Mechanical Properties of Fiber……………………………………………………. 131

8.3.2 Fiber Morphology………………………………………………………………………………….. 131

8.3.3 Tensile Properties…………………………………………………………………………………. 133

8.3.4 Flexural Properties…………………………………………………………………………………. 135

8.3.5 Impact Properties…………………………………………………………………………………… 137

8.3.6 Dielectric Properties……………………………………………………………………………….. 138

8.4 Conclusions……………………………………………………………………………………………………. 138

References………………………………………………………………………………………………………….. 139

N. Srinivasababu (*)

Department of Mechanical Engineering, Vignan’s Lara Institute of Technology and Science, Vadlamudi 522 213, Andhra Pradesh, India e-mail: cnjlms22@yahoo. co. in

J. S. Kumar ♦ K. V.K. Reddy

Department of Mechanical Engineering, JNTUH College of Engineering, Hyderabad 500 085, Andhra Pradesh, India

G. S. Rao

Mechanical Engineering Department, V. R. Siddhartha Engineering College, Vijayawada 520 007, Andhra Pradesh, India

K. R. Hakeem et al. (eds.), Biomass and Bioenergy: Processing and Properties,

DOI 10.1007/978-3-319-07641-6_8, © Springer International Publishing Switzerland 2014

Abstract Natural fibers and their composites play a vital role in the fabrication of various components in automobile and structural components because of their supe­rior specific performance. In order to satisfy day-to-day requirements in various sectors, new eco-friendly materials are introduced which are reinforced with renew­able, cheap, and easily available natural fibers. A new leaf fiber, i. e., Indian date leaf (IDL), is introduced in this work and extracted by “pure splitting method” (PSM). Initially, the fiber is characterized for its density and tensile behavior. Surface morphology of the fiber is also examined by using JEOL JSM scanning electron microscope (SEM). Using IDL and IDL CT fibers as reinforcement in the polyester matrix, the composites are fabricated by wet lay-up technique. The fabricated com­posite specimens are tested to determine mechanical and dielectric properties as per ASTM procedures. Chemically treated IDL fiber exhibited 25.69 %, 4.6 % more tensile strength and modulus than untreated ones, and the stress vs. strain curves are drawn for all tested specimens. The specific tensile strength of chemically treated IDL FRP composites is 1.38 times higher than untreated IDL FRP composites whereas specific tensile modulus of IDL FRP composites is 1.04 times higher than treated IDL FRP composites at maximum fiber volume fraction. Chemically treated IDL FRP composites exhibited flexural strength, modulus of 63.47 MPa, 5 GPa under flexural loading, which is higher than untreated FRP composites. IDL FRP composites’ impact strength is 18.94 kJ/m2 at maximum fiber volume fraction. The dielectric strength is clearly decreasing with increase in fiber content, which gives an opportunity for a designer in selecting suitable lightweight material with reasonable insulation. A clear rougher surface at all portions on the surface of chem­ically treated IDL fibers is visualized from SEM image.

Keywords Indian date leaf fiber • Mechanical properties • Dielectric strength • Scanning electron microscopy (SEM)

8.1 Introduction

Natural fibers, the name itself implies that they are created by nature. The renewable nature of fibers and high specific performance when they are reinforced into the matrix invited the attention of several researchers from the past few decades. Several people made numerous efforts for investigating the performance of fiber and its composites under mechanical, thermal, and electrical loadings at various fiber con­tents. Some of the imperative results related to various natural fiber reinforced com­posites using various fibers and matrices have been reviewed and are highlighted. In order to understand the behavior of IDL FRP composites, focus is made to com­pare the obtained results from the present work with the results which are available in literature on leaf fibers like sisal and pineapple polymer composites.

The pineapple fiber length of 6 mm was found to be optimum in pineapple leaf fiber reinforced LDPE composites when the mechanical properties and process ability characteristics were considered (George et al. 1995). Cardanol derivative of toluene diisocyanate-treated sisal fiber reinforced composites had shown best mechanical performance dimensional stability when compared with the composites reinforced with sisal fiber under same aging conditions (Joseph et al. 1995).

Sisal fiber reinforced polystyrene composites had exhibited marginal increase in tensile strength at 10 mm fiber length, and benzoylation-treated sisal fiber rein­forced composites have shown considerable improvement in tensile properties (Manikandan Nair et al. 1996). After conducting the study on pineapple leaf FRP composites, it was found that the mechanical properties were optimum at a fiber length of 30 mm (Uma Devi et al. 1997). With enhancement in fiber volume in matrix, the tensile strength of henequen fiber reinforced HDPE composites decreases for different processing temperatures, whereas the flexural strength and modulus were increased (Herrera-Franco et al. 1997).

An improvement in the mechanical performance of the composites was observed with the reinforcement of wood fiber in LDPE matrix along with titanate coupling agents (Liao et al. 1997). In order to assess the improved mechanical performance of the FRP composites, acetylated coir/oil palm fibers were reinforced in case 1, whereas in case 2, silane/titanate coupling agents were used (Hill and Abdul Khalil 2000). A comparison of mechanical properties was made among the composites reinforced with abaca (short) and glass fiber prepared by melt mixing and injection molding (Mitsuhiro et al. 2002).

An increase in tensile strength and modulus was observed up to an MAPP con­centration of 35 % weight (Luo et al. 2002). The natural rubber composites were reinforced with bamboo fiber, and their mechanical performance was assessed after the silane coupling agents were added (Ismail et al. 2002). Big blue stem fiber reinforced composites had shown higher strength than wood and are comparable (Julson et al. 2004). A new experiment was conducted and composites were made,

i. e., the use of polyester matrix, modified with coupling agent; flame retardant system; and blend of both as matrices and sisal fibers were reinforced to determine their mechanical properties (Fonseca et al. 2004).

Two investigations on flax and jute fiber reinforced composites were made. In the first case, various maleated PP coupling agents were used in agro-fiber PP compos­ites. In the second case, oxidized PE, MAPP, and newly introduced MaPE coupling agents were used in the composites. The tensile and impact behavior of the compos­ites in both the cases were studied (Keener et al. 2004). The effect of hybridization on the mechanical properties of randomly oriented banana/sisal hybrid FRP com­posites was investigated with the reinforcement of banana and sisal fibers at various volume fractions (Idicula et al. 2005). With the enhancement in NaOH concentra­tion, the mass loss in Phormium tenax fibers was investigated. The composites consisting of epoxy matrix and treated and untreated fibers are tested under flexural load (Roger et al. 2007).

The glass, sisal, and coconut fibers reinforced polyester composites were tested for their mechanical properties after they were exposed in salt spray chamber (Nicolai et al. 2008). The resin transfer-molded banana FRP composites had shown maximum tensile, flexural, and impact properties at 40 % fiber content and had fiber of 30 mm in length (Sreekumar et al. 2008) . The soaking time and molarity of

chemical on the properties of turmeric FRP composites under tensile loading was investigated (Srinivasababu et al. 2010) . The composites manufactured with the reinforcement of vakka and jowar fibers had tested for their mechanical and dielec­tric performance at various fiber volume fractions in the composites (Murali Mohan Rao et al. 2010; Ratna Prasad and Mohana Rao 2011).

Leaf fibers are obtained from mesophyll ofleaves, e. g., sisal, Indian date, etc. In the present work, an attempt is made to introduce a new fiber, IDL. Indian date is called Eetha chettu in Telugu, shown in Fig. 8.1. This belongs to the Arecaceae family, binomially called “Phoenix dactylifera L.” Palm trees are grown extensively in coastal areas, specifically in Gorigapudi village, Guntur Dt., Andhra Pradesh, India. The leaves of the ID palm trees are about 0.5 in. to 1 ft. in length.

Cellulose, considered as one of the most abundant renewable polymeric material (Brinchi et al. 2013), is naturally organized as microfibrils linked together to form cellulose fibres, in which every single filament consists of several cells of cellulose- based crystalline microfibrils connected by lignin and hemicellulose (Siqueira et al. 2010) . Cellulose consists of p-D — glucopyranose units linked together by (3-1-4- linkages, containing hydroxyl groups able to form hydrogen bonds, playing there­fore a major role in directing the crystalline packing and also governing the physical properties of cellulose (John and Thomas 2008).

Cellulose cannot be considered uniformly crystalline, but ordered regions dis­tributed throughout the material, called crystallites, can be found in its structure. The linear association of these components is a microfibril, and can be considered the elementary unit of the plant cell wall. These microfibrils are found to be 10-30 nm wide, indefinitely long, and they can contain approximately 2-30,000 cellulose molecules in cross section. Individual cellulose nanocrystals (CNC) and cellulose microfibres (Fig. 11.4) can be isolated from crystalline cellulose core breaking down these crystalline regions (Oke 2010; Kalia et al. 2011).

There is a wide range of cellulose-based particle that can be considered different depending on cellulose source and extraction processes. Two main families of nano­sized cellulosic particles can be found: the first one consists of CNC or nanowhis­kers (CNW) and the second one is the microfibrillated cellulose (MFC) (Belgacem and Gandini 2008; Lu et al. 2008; Brinchi et al. 2013). In this section, our attention

Fig. 11.4 Scheme of main steps needed to prepare CNC from natural sources

will be given to the extraction of CNC from natural sources, their specific properties and final application in polymeric matrices. CNC can be extracted from a variety of cellulosic sources, such as plants, bacteria and algae. The extended literature on this subject confirms that commonly studied source materials are represented by wood, plants, microcrystalline cellulose or bleached pulp because of their extensive avail­ability and high content of cellulose. Essentially, CNC can be easily prepared from commercial microcrystalline cellulose or from filter paper, because of their purity and availability in laboratories (Klemm et al. 2011) and they can be isolated using a two — stage procedure, as shown in Fig. 11.4. The first one is a pretreatment of the source material, in which complete or partial removal of hemicelluloses and lignin, with consequent isolation of the cellulosic fibres, is obtained. The second treatment— generally a chemical hydrolysis—is able to remove the amorphous regions of the cellulose polymer, thus yielding a highly crystalline structure.

Azizi Samir et al. (2005) reported that even high-purity cellulose crystals starting from crystalline domains can be obtained, and together with these a non-crystalline state (amorphous) of the cellulose can be found. These cellulose amorphous regions are randomly oriented in a spaghetti-like arrangement having a lower den­sity if compared to nanocrystalline regions (de Souza Lima and Borsali 2004; Saxena and Brown 2005). These amorphous regions are easily subjected to acid attack and they can be removed leaving intact crystalline regions (de Souza Lima and Borsali 2004) . De Souza Lima and Borsali (2004) described how cellulose amorphous regions can be disrupted for the production of CNC. Going more into detail, hydronium ions can easily penetrate these amorphous domains, promoting the hydrolytic cleavage of the glycosidic bonds and isolating individual crystallites. Dong et al. (1998) firstly studied the effect of hydrolysis conditions on the proper­ties of resulting CNC. They have shown that longer hydrolysis times lead to shorter monocrystals with increased surface charge. Indeed, Beck-Candanedo et al. (2005) studied the properties of CNC obtained by hydrolysis of softwood and hardwood pulps. They considered the influence of hydrolysis time and acid-to-pulp ratio in order to obtain CNC. From their analysis, they explained how reaction time is cer­tainly one of the most important parameters to be considered for the acid hydrolysis of wood pulp, since too long reaction times can completely depolymerize the cel­lulose, up to yielding its component sugar molecules.

In contrast, lower reaction times will only yield large fibres and aggregates that cannot be easily dispersed. Araki et al. (1998) compared the effects of using both sulfuric acid and hydrochloric acid cellulosic nanocrystals (CNC), demonstrating that sulfuric acid is able to provide more stable aqueous suspensions compared to hydrochloric acid. Recently, CNC with an acicular structure ranged from 100 to 200 nm in length and 15 nm in width were extracted from Phormium tenax leaf fibres by acid hydrolysis (Fortunati et al. 2012d): in the cited paper, CNC extraction pro­cess was studied in terms of yield, thermal and chemical properties of the obtained nanocrystals and the results coming from the analysis of Phormium fibres were com­pared with those obtained extracting crystals from two reference materials, Flax of the Belinka variety and commercial microcrystalline cellulose (Fortunati et al. 2013a, b). Morphological, thermal and chemical characterization of the obtained CNC from different plant sources confirmed that natural fibres offered high levels of extraction efficiency if compared with commercial sources of nanocellulose. On the basis of these results, Fortunati et al. (2013c) extracted from the bast, for the first time in the case of okra (Abelmoschus Esculentus) natural fibre, cellulose micro — and nano­fibres, with a view to obtaining cellulose structures with a high crystallinity and thermal stability. Previously obtained results on thermal and mechanical behaviour of okra fibre indicated it as a possible candidate for use in the production of biode­gradable composites (De Rosa et al. 2010a); however, the use of okra bast fibres in textiles presents a number of drawbacks such as limited rub resistance, scarce colour fastness, sensitivity to wear and it is very much prone to creasing, possibly because of high degree of orientation of cellulose in the fibre. Furthermore, these studies demonstrated that commonly applied chemical treatments, such as bleaching and alkalization, do not substantially generate any improvement to okra fibre properties, indicating that high variability of their mechanical properties limits their use in com­posites (Moniruzzaman et al. 2009; De Rosa et al. 2011).

The possibility of using okra fibres as a source of CNC may be a viable alter­native to employing them in the form of technical fibres. Fortunati et al. (2013d) demonstrated that hydrolysis parameters already applied for extraction of cellulosic fraction starting from microcrystalline material (Fortunati et al. 2012a, b, c) are adequately suitable for hydrolysis starting from a macrofibre, such as okra. In the specific case, the extraction of cellulose was carried out in a two-step procedure in which the holocellulose produced by the action of a first chemical treatment was then exposed to the action of sulphuric acid for further hydrolysis, allowing obtaining CNC in an aqueous suspension.

The use of cellulose nanostructures as a reinforcing phase in nanocomposites has numerous well-known advantages, e. g. low density, renewable nature, a wide variety of filler available through the world, low energy consumption, high specific properties, modest abrasion during processing, biodegradability, relatively reactive surface, useful for the grafting of specific groups (Siqueira et al. 2010). However, cellulose nanoparticles present some disadvantages, for instance, high moisture absorption, poor wettability and incompatibility with most polymeric matrices and limitation in the processing temperature. In fact, lignocellulosic materials start to degrade near 220 °C restricting the matrix types that can be used in association with natural fillers (Wambua et al. 2003). Several reviews have been written on these topics, demonstrating that CNC can be successfully used as filler in nanocomposites, improving mechanical and barrier properties of the matrix (Klemm et al. 2005, 2011; Hamad 2006; Dufresne 2008, 2010; Hubbe et al. 2008; Eichhorn et al. 2010; Habibi et al. 2010; Visakh and Thomas 2010; Siqueira et al. 2010; Duran et al. 2012).

New biopolymer nanocomposites using poly(vinyl alcohol) (PVA) as matrix and reinforced with CNC extracted from okra bast fibres were produced for the first time by Fortunati et al. (2013d). The partial aggregation of cellulose in PVA appears to demonstrate that a good level of compatibility between the hydrophilic crystalline nanocellulose and the polymer matrix was obtained. It has been demonstrated that CNC are able to increase the degree of crystallinity of PVA matrix, specifically the nanocomposites containing 5 wt% of cellulose appeared the most suitable formula­tion, with an increase of 40 % in crystallinity value and of 150 % in the elongation at break with respect to the PVA matrix. The result can be justified considering that this content may lead the available surface area of cellulose to its optimal dimension in the nanocomposite. Moreover, the obtained results showed how okra fibres, and in general bast herbaceous systems, can be applied in the CNC form in nanocom­posite formulations to be used in some industrial areas, such as packaging.

Though algal biomass appears to be a good substrate for the production of biogas, there are certain restrictions due to anaerobic digestion of algal biomass. It has been reported by Sialve et al. (2009) that there are two major problems of microbial flora of anaerobic absorption: sodium ion toxicity and ammonia inhibition.

Toxicity of ammonia mainly arises because of excessive C/N ratio of the algal biomass. Free ammonia present during the harvesting procedure barely disturbs the acidogens and mostly hinders acetoclastic methanogens. The range of obstructive concentration of ammonia varies widely (1.7-14 g/L) because there are several other factors contributing to inhibition of ammonia. These factors are nature of the feed, inoculum, operating and functioning conditions, i. e., pH and the presence of antago­nistic ions like sodium ion, calcium ion, and magnesium ion (Angelidaki and Ahring 1993; Chen et al. 2008; Koster and Lettinga 1988; Sialve et al. 2009). Furthermore ammonia when released in the course of hydrolysis of amino acids causes an upsurge in both alkalinity and pH of digester liquid. At elevated concentration of ammonia and alkaline pH, acetate ion, which is the basic substrate for the methanogens, gets trans­formed into ammonium acetate or ammonium bicarbonate leading to the reduction of accessible acetate to methanogens (Shanmugam and Horan 2008, 2009). This reduc­tion of acetate ion and subsequent less development of methanogens due to high ammonia released during algal biomass ingestion can be the main reason of low meth­ane in the headspace biogas (Shanmugam and Horan 2009).

13.4 Conclusions

Algal biomass can prove to be the most promising source of bioenergy to cope with high energy demands. Algal biomass can generate improved quantities of biogas and biodiesel as compared to traditional substitutes. With the latest and more advance technologies, it can successfully replace the conventional feedstock. If the internal and external factors are carefully controlled such as increased water, CO2, light, and sufficient space, the algal feedstock can generate maximum biomass and in turn maximum bioenergy output. The biofuels generated through algal biomass is more environment-friendly with minimum contribution towards global warming. Among different methods of algae cultivation, the most successful is the mixotro — phic production, which possesses both photoheterotrophic and photoautotrophic capabilities. Open and close pond systems are used equally with certain benefits and limitations, however, if the problems associated with production of algal biomass such as cost, temperature maintenance, salinity control, and contamination are elim­inated, algal biomass can be grown to its maximum. Harvesting of algal biomass after mass cultivation plays a vital part in shaping the process budget of algal biofu­els. The harvesting of macroalgae biomass is a simple process as compared to the microalgae harvesting. Due to the diluted nature of algal culture cells and small size, the operating expense of dewatering and harvesting of algal biomass is ele­vated. To resolve this challenge, a number of procedures including chemical as well as mechanical, can be performed which includes centrifugation, flotation, floccula­tion, filtration, screening and gravity sedimentation, and electrophoresis with ben­eficial output. Optimized culture technologies are the key elements to regulate the effective cost of the production of algal biomass for the purpose of biogas produc­tion. With the selection of those algal strains that are rich in oil, there is a great potential of algal biomass in biodiesel and biogas production.

Fermentation is a biological process for ethanol production. The microorganism such as yeasts is the best choice for ethanol production. There are three kinds of processes used in the ethanol production from sugarcane straw. Separate hydrolysis and fermentation is the first process of fermentation where lignocellulosic hydroly­sis and ethanol fermentation have been done separately. Another two methods are simultaneous saccharification and fermentation (SSF) and simultaneous saccharifi­cation and cofermentation (SSCF). To obtain the desired ethanol yields from sugar­cane straw hydrolysates, it is essential that the hemicellulose fraction should be fermented with the same conversion rate for getting the maximum ethanol produc­tion (Lin and Tanaka 2006). Hemicellulose hydrolysate contains pentose and hex — ose sugars. The different types of yeast, fungi, and bacteria can assimilate pentose sugar by conversion of sugarcane straw hydrolysate.

16.5.2 Distillation of Ethanol

The final medium of ethanol production is composed of water and ethanol (Huang et al. 2008). Ethanol recovery is necessary from a fermented substrate. The water and ethanol cannot be separated by conventional method. There are three steps for ethanol purification such as distillation, rectification, and dehydration. The dehy­dration method can be used for producing high concentrated ethanol. Huang et al. (2008) reported that a dehydration process can be realized through azeotropic distillation, extractive distillation, liquid-liquid extraction, adsorption, or some complex hybrid separation methods.

The work on biomass gasification using EFB as biomass is limited in the literature. Ogi et al. (2013) investigated EFB gasification in entrained flow gasifier using steam and steam-O2 as gasification agent. They reported that pure steam gasification is in favor of more hydrogen production compared to steam-O2 for EFB gasification. Because of using steam-O2 the amount of CO2 increased while H2 and CO decreased in the system. Furthermore, TG analysis shows that EFB decomposed easily to the gases in the presence of steam and there is very low amount of tar in steam gasifica­tion of EFB. Furthermore, they observed that the EFB well gasified in the presence of steam compared to the cedar wood under same operating conditions and predicts high gasification rate as well.

Lahijani and Zainal (2011) investigated EFB air gasification in pilot scale fluid­ized bed gasifier. They studied the effect of temperature and equivalence ratio on the product gas composition. They predicted maximum of 20 vol.% hydrogen at 1,323 K. The maximum carbon conversion and cold gas efficiency was predicted 93 % and 72 %, respectively.

Mohammed et al. (2011a, 2011b) studied for hydrogen-rich gas from EFB as biomass in fluidized bed gasifier using air as gasification agent. They investigated the effect of temperature, particle size, and equivalence ratio on the hydrogen pro­duction using bench scale system. They predicted maximum 38.02 vol.% of hydro­gen at 1,273 K. They reported that lower particle size of EFB is in favor of more hydrogen.

Ismail et al. (2011) investigated the effect of CaO on EFB gasification in the presence of O2 and He. They reported that CaO played a very good catalyst for the gasification of EFB. The H2/CO ratio was increased by increasing temperature in the presence of CaO. Furthermore, nanosize of CaO increased 56 % more hydrogen compared to the bulk CaO. Their results showed that the high production of hydro­gen can be obtained at 973 K using EFB in dry conditions via O2-He gasification.

Physical properties of the natural fibers are crucial in determining their suitability for different industrial applications as well as natural fiber composites. Fiber’s length, diameter, and density as well as aspect ratio, thermal conductivity, cost, and availabil­ity are considered as key criteria and properties that can determine the potential usage of any natural fiber type in different industrial applications (Al-Oqla and Sapuan 2014; Al-Khanbashi et al. 2005; Alves et al. 2010). Date palm fiber can be considered as one of the most available natural type comparing to other natural fiber used in polymer composites for automotive industry. It can be estimated that the annual world produc­tion of the date palm fiber is about 42 times more than that of coir and about 20 and 10 times more than hemp and sisal production respectively. On the other hand, the fiber density is one of the most important physical properties that contribute implementing natural fibers in different applications. That is, it can lead to lower weight composites suitable for automotive and space applications. A comparison between the date palm fibers with other natural types regarding the density property is demonstrated in Fig. 1.8. It is noticed that date palm fiber have a lower density as compared to other natural fibers which give it an added value in the field of natural fiber composites.

On the other, hand, several researches had reported the significance of the aspect ratio (length/diameter) on the properties of final composite materials. Studies had investigated and proved that this aspect ratio of the date palm fiber has an intermedi­ate value regarding other natural fiber types which can attribute its usage in different industrial applications (Al-Oqla and Sapuan 2014). Table 1.3 provides useful physi­cal properties of the date palm fibers with other natural types. The physical proper­ties such as length, diameter, density, and micro-fibril angle of the date palm fibers made it potential for wide range of applications (Al-Oqla and Sapuan 2014; Faruk et al. 2012; Sbiai et al. 2010).

Research and investigation regarding use of bamboo fiber for the well-being of human beings is limited because of limited availability and tough extraction pro­cess. The techniques used for bamboo fiber extraction nowadays give low fiber yield or low quality fiber. Studies are further required for improving the extraction, prepa­ration, and processing techniques for bamboo fiber. Bamboo fiber is a potent fiber to be used for many applications. It is an outstanding biodegradable textile material, which does not absorb ultraviolet and infrared rays. For commercializing bamboo based products much research and knowledge is required so that the world may get benefit from an inexpensive source of fibers.

Super strong and durable bamboo is being used presently for flooring and panel­ing. Its stability, hardness, flexibility, and strength are its most remarkable qualities. Bamboo has a bright future as an alternate to wood for formation of furniture and construction material. Bamboo fiber can also serve as an alternate to cement and concrete in near future. As bamboo is easily pulped, it can be used efficiently for paper production and may benefit us with less cost and high availability. Textile industry is expected to get huge advantages from bamboo fibers in near future, as bamboo is lightweight, environmental friendly, and bacteriostatic. Also it is antial­lergenic and soft like silk which makes it best suited for its use in textile industry.