2.4.1 Durability

The durability of bamboo fiber reinforced polypropylene can be increased by hybridizing it with small amount of glass fiber (Thwe and Liao 2002a). Bamboo glass fiber reinforced polypropylene composites have a very high fatigue resis­tance, which results in its extremely good durability (Thwe and Liao 2003).

The durability of bamboo fiber depends on high tensile strength, flexural strength, tensile load, moisture absorption, and molding capacity (Thwe and Liao 2002a). Unlike vegetal materials, bamboo durability is not affected by high pH. Bamboo fibers are set into concrete prisms and exposed to wetting and drying for 24 h. Then speci­mens without concrete and specimens with concrete are immersed in tap water. Different mechanical properties are measured after 7, 15, 30, 45, and 60 cycles. The results showed that there is no considerable change in these mechanical properties. These aggressive tests thus attest the durability of bamboo fibers (Lima et al. 2008).

The following extraction methods can be used to obtain bagasse fibers from sugarcane.

4.3.1 Atmospheric Extraction Process to Obtain Bagasse Fibers

There are various mechanical and chemical methods are available for the extraction of the bagasse fibers. Bagasse was put down on the surrounds of an open but sheltered in a sugar factory for duration of minimum two weeks. To satisfy uniform drying process the layer of bagasse was turned over a day. The moisture content was calculated for arbitrarily selected specimens of fibers. The results showed a uniform level of mois­ture less than 15 %. Small fibers and impurity were separated through a sieve process using a 2 ft by 2 ft wooden frame having a screen with 1/16 in eye dimension.

4.3.2 Chemical Extraction

It has been noticed that the most dominant factors for the extraction process are alkaline concentration, reaction time, incorporation, and presence of steam explo­sion. The extraction process tooks place at atmospheric pressure. For the alkaline extraction, an atmospheric process is employed. In this process an LSU designed
atmospheric reactor was used (Fig. 4.4). From previous studies, it is observed that a 2.0 N NaOH solution needed for the removal of a remarkable amount of lignin. The capacity of the reactor was 200 L. Reactor first heated the solution to the boiling point at 100 °C and then gradually screened bagasse is fed to the reactor. The fiber/liquid ratios were maintained at 1:10. After approximately 90 min the whole amount of bagasse delignifies and collected at the other hand of the reactor. The extracted fibers were washed thoroughly with water and left (to dry) in a con­trolled environment for two days with a relative humidity of 65 % and a temperature of 71 °C (Collier and Arora 1994).

After the leaf fiber was obtained, ten fiber samples in green condition weighing approximately 100 g were randomly selected. Then the samples were taken to the laboratory where they were put to dry into an oven at 103 °C for 24 h to determine the moisture content (Eq. 7.1). The moisture content of the waste from fiber extraction was also determined by means of Eq. 7.1.

, . Green weight (g)- Dry weight (g)

Moisturecontent (%)= x100 (7.1)

Green weight (g)

7.2.4 Fiber Color and Color Change

Fiber color was tested during three stages of fiber production. These were as follows: (1) after the fiber came out of the scrapping machine, when the fiber was in green condition; (2) after the application of the three bleaching treatments; and (3) after fiber drying. Color was measured with a Hunter Lab spectrophotometer, miniScan XE Plus model, to obtain parameters L*, a*, and b*. Since colorimeter diameter in its measuring area is 1 cm, fiber rolls of the appropriate thickness were prepared in order to fit the hole totally. Color change (AE*) was determined with the difference between the color of the fiber obtained with the prototype machine and the color after treatment (with water, peroxide, or hypochlorite). The value of AE* for color of the fiber obtained with the prototype machine and fiber color after drying was also obtained. To determine AE*, the ASTM D 2244 (ASTM 2012) standard was used. This standard defines AE* as the net color variation after a period and is obtained by means of Eq. 7.2.

( 7.2 )

where AE*: pineapple fiber color change; AL: L* fiber color after scrapping-L* after washing or after fiber drying; Aa: a* fiber color after scrapping-a* after wash­ing or after fiber drying; Ab: b* fiber color after scrapping-a* after washing or after fiber drying.

The sheet moulding process is completed in two steps. First, long sheet of composites is prepared with unique thickness, and then the sheets are passed through the different dimensional moulds to prepare various products. Short natural fibre is added with constant weight on carrier foil (conveyer). Resins and fillers are laid from a hopper on fibre. The mixture is then passed through the several ball mills. The prepared composite sheets are rolled with foil. The rolled composite sheets are further moulded for producing different products. Behzad and Sain (2005) estab­lished a novel processing method of natural fibre-thermoset acrylic resins with very short curing step (10 min). The final product has higher mechanical properties but needed huge establishment cost.

10.3.2.4 Pultrusion

The pultrusion technique is often investigated for natural fibre and thermoset resins (Akil et al. 2009). The yarn rolled roving is passed through the resin bath. A hot die helps them convert into profile (Van de Velde and Kiekens 2001). The profile then flows in profile drawer for completing cure process. The prepared composite has greater mechanical properties, but the production rate is not satisfactory. Among the above-mentioned processes, the compression moulding is a more viable method for fabrication of short OBF-PF resins in small-scale production. Short dried OBF with different weight fraction (9, 19, 29 and 38 wt%) is initially mixed thoroughly with PF resin. Composites are made using a stainless steel mould at 150 °C and 50 kN pressure. The curing is completed at room temperature for 24 h keeping the constant pressure 10 kN. The specimens for tensile and flexural tests are made by a cutting machine.

The hybrid system is a cultivation method comprising of two stages and utilizes both open ponds and PBR for different growth phases. The first stage of cultivation is completed in a photobioreactor where uninterrupted cell growth occurs in a pollution-free environment under controlled conditions. The second stage of cultivation occurs in open ponds and is intended to expose the culture to ecological and nutrient stresses. This enhances the production of desired lipid product.

The methods, which are presently being profitably used for algae cultivation, are raceway ponds and tubular PBR. Open ponds are a much cheaper method for algal cultivation. Setup and maintenance are also easier. Open ponds require less energy as compared to PBR. Open ponds are, however, less efficient as compared to PBR. Contamination, losses due to evaporation, temperature vacillation, inept mixing, and light limitations are some of the malfunctions associated with open pond systems.

Straw recovery is one of the major challenges for sustainable sugarcane cultivation. Sugarcane straw can contribute to the improvement of soil properties such as soil erosion, incorporation of organic matter, and conservation of soil moisture and increase the biological activities in soil. On the other hand, sugarcane straw may help to increase the incidence of pest. However, straw recovery from field is not that simple due to technological and economic challenges related to handling and trans­portation. High investment is required for straw transportation from the field to the power plant. At present, some initiatives and developments have been done to trans­portation of straw. The best option for removing the straw from the field to industry has been shown in Fig. 16.1.

Sugarcane straw recovery depends on many factors especially harvesting proce­dure, sugarcane topping, variety, height and crop age, climatic condition, and soil. Sugarcane straw can be recovered from 24 to 95 % through mechanical harvesting (Paes and Hassuani 2005). There are some ways to recover the straw from the sugarcane field.

Algal biomass can be produced as a by-product of high rate algal ponds (HRAPs) running for waste water treatment (Park et al. 2011). The HRAPs are raceway-type open ponds with depths in the range of 0.2-0.5 m, retention times (HRT) ranging from 3 to 10 days (that depends on growth rate of test algae), and paddle wheel to provide mixing (Park and Craggs 2010; Craggs et al. 2012). In such systems algal photosynthesis releases oxygen which is required for degradation of organic matter by heterotrophic bacteria.

The concept of using HRAPs for waste water treatment and algal biomass pro­duction for purposes of energy production (biofuel) was presented by Rupert Craggs and his colleagues working at National Institute of Water and Atmospheric Research Ltd. (NIWA), New Zealand. The HRAPs keep the advantages of simplicity and economy, overcoming the disadvantages of other systems including poor effluent quality and limited nutrient and pathogen removal (Craggs et al. 2012).

2.5.1 Biofuel Production

Bamboo is observed to be more productive as compared to many biofuel producing vegetable plants. Bamboo is suitable for fuel production because it has low alkali index and ash content. Moreover it has low heating value than many of the woody biomass feed stocks. Further research is required on bamboo fibers for commercial­ization of biofuel (Scurlock et al. 2000). Pyrolysis of bamboo in the presence of high temperature steam and inert atmosphere containing nitrogen produces a product. The product when analyzed indicates exploitation of derived char as activated carbon precursor or solid fuel for gasification. The composition of liquid fraction reveals it to be a biofuel (Kantarelis et al. 2010). The treatment of bamboo fibers with cold sodium hydroxide/urea disrupts the recalcitrance of bamboo fibers effectively and leads to generation of highly reactive cellulosic material. This material, on enzy­matic hydrolysis is converted into bio-ethanol. Bamboo fiber derived bio-energy products include charcoal, biofuel, pyrolysis, firewood, gasification, briquettes, pel­lets, and biomass (Li et al. 2010). Bamboo hemi-cellulosic fibers having 2.4 % hemi — cellulose content have been extracted and pulped. The pulp produce can be used to produce biofuel and bio-ethanol after further modification (Vena et al. 2010).

Final properties of biomass fibres are strongly influenced by its individual charac­teristic which played an important factor when considering this material in multidis­ciplinary applications. Biomass fibre properties that are related to vital variables include fibre structure, cell dimension, microfibril angle and defects (Abdul Khalil et al. 2012b). According to John and Thomas (2008), origin, sources, species and maturity of fibres determined the dimension of single cell in biomass fibres. Table 5.2 shows the physical properties of various agricultural biomasses. The prop­erties of end product such as tensile strength, tear strength, drainage, bonding and

stress distribution are highly dependent on the fibre structural characteristic espe­cially on fibre length, fibre width and thickness of cell wall (Rousu et al. 2002; Ververis et al. 2004; Abdul Khalil et al. 2008). Fibre aspect ratio (length/width) is important in determining the suitability of fibre for an exact application in order to reach its maximum potential (Han and Rowell 1997). Biomass fibre cell wall struc­ture is composed predominantly of polysaccharide-rich primary (P) and secondary wall layers (S1, S2 and S3) (Abdul Khalil et al. 2008). This thick multilayered and sandwich-like structure of bonded cell wall layers provide strength, toughness and collapse resistance to the structure (Smook 1992). Moreover, lumen structure influ­enced the bulk density of fibres and its size affects the thermal conductivity and acoustic factor of fibre in end product (Liu et al. 2012).

Adapted from: (1) Joseph et al. (1999), (2) Rowell et al. (2000), (3) Mohanty et al. 2005, (4) Reddy and Yang (2005), (5) Wathen (2006), (6) Andre (2006), (7) Abdul Khalil et al. (2007), (8) Satyanarayana et al. (2007), (9) Omotoso and Ogunsile (2009), (10) Yueping et al. (2010), (11) Ahmad (2011), (12) Kiaei et al. (2011), (13) Jawaid and Abdul Khalil (2011), (14) Sadegh et al.

(2011) , (15) Zimniewska et al. (2011), (16) Abdul Khalil et al. (2012a), (17) Jawaid et al. (2012), (18) Kalita et al. (2013), (19) Shah (2013), (20) Moya et al. (2013), (21) Mershram and Palit (2013), and (22) Nguong et al. (2013)

Unidirectional tensile, flexural, impact, and dielectric fiber reinforced polyester composite test specimens are fabricated by wet lay-up technique (Srinivasababu et al. 2010). All the fabricated composite specimens are conditioned as per ASTM D 618-05 Procedure A in an environmental chamber, supplied by the Narang Scientific Works Pvt. Ltd., New Delhi. The physical dimensions of all the specimens are measured as per ASTM D 5947-06 Test Method A. The tensile and flexural tests are conducted on specimens as per ASTM D 5083-02 and ASTM D 790-07, respec­tively, on Electronic Tensometer supplied by Kudale Instruments Pvt. Ltd., Pune. The Charpy impact test is conducted on specimens using Computerized Izod/ Charpy Impact Tester, supplied by the International Equipments as per ASTM D
6110-08. The dielectric test is performed on composites using the Dielectric Strength Tester according to ASTM D149-97a step-by-step test, supplied by Rectifiers & Electronics, New Delhi.