Category Archives: Bioenergy
Bamboo fiber preparation methods can be divided into two types:
1. Mechanical method
2. Chemical method
Mechanical methods give natural bamboo fibers and involve flax production whereas chemical methods are of two types namely Bamboo Viscose Rayon method and Bamboo Lyocell method.
The preparation of rough and fine bamboo fiber is different. Rough bamboo fiber preparation does not involve harsh treatments like the use of bleaches and acids and soaking in oil. Preparation of rough bamboo fiber involves the following steps (Yao and Zhang 2011; Fig. 2.1):
1. Cutting of the stem
4. Fermentation with the enzyme
The preparation of fine bamboo fiber is much similar to that of rough but also includes additional steps. The overall process involves (Yao and Zhang 2011):
2. Fermentation with enzyme
3. Wash and bleach
4. Acid treatment
5. Oil soaking
The abaca-reinforced composites offer an eco-friendly material for many industrial applications with the same strength and qualities as provided by synthetic fibers or glass fibers. The excellent example is provided by the use of abaca composites in car manufacturing by Chrysler-Daimler. Moreover, the production of these fiber composites is energy-efficient as it has been found to save 60 % energy besides reducing CO2 emissions. Moreover, abaca plantations have been used to prevent soil erosion and in promoting biodiversity rehabilitation by intercropping abaca plants in monoculture plantations or rainforests. Waste material produced from abaca plants is also used as organic fertilizers to replenish the soil fertility.
Because of high lignin content, kapok fiber is not easily attacked by ordinary cellulolytic bacteria (Nilsson and Bjordal 2008) and shows better antibacterial property (Han 2010). Liu et al. (2007) investigated the anti-moth, anti-mite, and antibacterial properties of kapok battings. The results of anti-moth test showed that the mean value of weight loss of kapok batting was smaller than reference sample obviously, and the damage grade of surface of kapok batting was 2A. In the anti-mite test, the mite expelling rate was 87.54 %, which proved the anti-mite property of kapok batting. For antibacterial test, kapok batting was confirmed to possess both the bactericidal effect and bacteriostatic effect on Escherichia coli. But in contrast, it did not have these effects on Staphylococcus aureus.
Interface modification of natural fibre-polymer matrix composites is a common duty before composite fabrication because the chemical nature of fibre and polymer matrix is different, i. e. natural fibre possesses hydrophilic nature, whereas polymer matrix possesses the hydrophobic nature. A number of researchers and manufacturers tried to improve compatibility between polymer matrix and natural fibres by various techniques such as using compatibilizer, by matrix modification, by applying hybrid filler and by chemical treatments of filler. Among them chemical surface treatments of natural fibre have been reported to significantly improve the interface bonding of fibre-matrix including bleaching, alkaline treatment, silane treatment, acetylation, grafting with vinyl monomers, isocyanate and different coupling agents (Khan et al. 2009; Rosa et al. 2011). Alkali treatment enriches cellulose content of OBF around 75-80 % due to extraction of pectin and water extractives during treatments along with hemicelluloses from the fibre surface. The fibre became less dense and less rigid which provides the fibrils more capability of rearranging themselves along the direction of tensile deformation. The observations have also been reported for mercerized coir, flax, sisal and bamboo fibre (Varma et al. 1984; Sreenivasan et al. 1996; Sreekumar et al. 2011; Sharma et al. 1995; Das and Chakraborty 2006). Alkali treatment creates micropore on fibre and finally developed rough surface topography. Similar phenomenon happened when fibres were treated with NaClO2 (bleaching). Fibre turns into whitened, more floppy and fibrillated after this treatment. Cellulose percentage as well as crystallinity also increases due to removal of huge amount of lignin and impurities. However, surface coating is developed when the bleached fibre was modified by vinyl monomers. Sometimes fibrillated fibre becomes defibrillated. Modified fibre behaves like compatible reinforcing fibre with several hydrophobic polymer matrices for producing high-performance composites (Khan and Alam 2013).
The percent of elements present in OBF can be determined by an Elemental Analyzer. The main elements in untreated, alkali-treated and bleached OBF are C, H and O which are mainly for cellulose, lignin and hemicelluloses (Table 10.1). The modified fibre by acrylonitrile (AN) monomer shows trace amount of N. It may come from the CN group of acrylonitrile monomer. It is seen that the percentage of C, O and H in all types of fibre is almost the same. Hence, the fibre is not degraded upon the chemical treatments (Fig. 10.2).
Fig. 10.2 Methods of chemical treatment of okra bast fibre
The effects of chemical treatment of OBF on the physical properties are given in Table 10.1. The quality of OBF mainly depends on its physical properties, for example, fineness, moisture regain and densities (Majumdar 2002). OBF is a multicellular fibre. The unit cell of OBF is formed with plenty of cellulose molecules. These are attached with each other in longitudinal direction to produce long continuous filaments. The filaments are sometime attached with neighbouring filaments with intermolecular hydrogen bonding or any other loosely attached bond to form a mesh-like structure. But attachments by week bonding between the cellulosic filaments are not sufficient to form high stiff fibre. The cementing materials (lignin and hemicelluloses) give stiffness by staying in between the gaps of the cellulosic filaments.
Table 10.1 reveals that the fineness of the fibre increases after chemical treatments especially in the case of alkali and bleaching treatments. Hemicelluloses are composed by p-cellulose and y-cellulose carbohydrates. These both types of carbohydrates are soluble in alkali. So, it is supposed that hemicelluloses of the fibre are partially or completely washed out in alkaline medium. On the other hand, bleaching operation is frequently performed in textile industries to remove lignin from cellulosic yarn. A part of hemicelluloses is also removed during bleaching. Splitting of the cementing materials trends to be lesser diameter as well as mesh size. Mukherjee et al. (1993) also reported the reduction of fineness value due to the removal of lignin on bleaching. Further modification through AN-grafting has given surface coating onto OBF. Thus, the fibre diameter is increased slightly. The densities of untreated, alkali-treated, bleached and AN-grafted fibres are 1.15, 1.40, 1.40 and 1.32 g/cm3, respectively, showing that the surface treatments have significant effect on fibre density (Aquino et al. 2007; Bledzki and Gassan 1999).
Hydrophilic nature of cellulosic fibres is a great barrier to achieve strong adhesion with hydrophobic polymer. The presence of hydroxyl (-OH) groups in OBF cellulose is the main cause of moisture absorption of natural fibre which tends to poor wettability. To achieve better wetting of fibre in matrix, those hydrophilic hydroxyl (-OH) groups of cellulose should be blocked by suitable modification. The surface chemical treatment of OBF significantly decreased moisture absorption, concomitantly increasing the wettability between fibres and polymer. As seen in Table 10.1, untreated OBF contains 4-6 % of moisture, while both alkali-treated and bleached fibres contain larger amount of moisture (6-7 %). Due to the removal of hemicellulose, pectin, waxes and fats, fibre becomes floppy, i. e. it contains more pores. Therefore, moisture can easily diffuse in these pores, and hence increases moisture content. On the other hand, moisture affinity is significantly decreased when OBF is modified by AN monomer.
The tensile strength and modulus of untreated and treated OBF are determined from the average of ten fibres of each modification; the values are shown in Table 10.1. Alkali-treated and bleached fibres have shown an appreciable reduction in tensile strength. This decrease may be attributed to considerable delignification and break down of fibre took place during the chemical treatments. The elongation at break in these fibres does not vary much. The AN-grafted OBF brings about a considerable improvement in tensile strength (TS) and tensile modulus (TM). This may be attributed to the fact that AN-grafted OBF may create orderly arrangement of fibrils by surface coating via cross-linking reaction (Rout et al. 1999).
Some algae have the capability to obtain nutrition by both autotrophic and heterotrophic methods. This means light energy is not a primary need for mixotrophs as cell growth can occur by digesting organic material. These cultures are shown to lessen photo inhibition with enhanced growth rates as compared to autotrophic and heterotrophic cultures. This is because cultivation of mixotrophs utilizes both photosynthetic and heterotrophic elements, which decreases loss of biomass and reduces the quantity of organic substrate consumed.
22.214.171.124 Photoheterotrophic Cultivation
This mode of cultivation refers to the process in which alga requires light energy and obtains carbon from an organic source. Unlike mixotrophs, photoorganotrophs cannot grow without light energy. Although this process can enhance the production of certain useful light-regulated metabolites, this mode of cultivation is not preferred in case of procedures like biodiesel production.
Lignocellulosic materials are economically cheap, perfect precursors to produce activated carbon. Due to the abundance of cellulosic biomass in the nature they are usually used to produce activated carbon as the catalytic active site in these catalysts are chemically bound, as a result both the biodiesel and glycerol by-product will be free of catalysts contaminants (Emrani and Shahbazi 2012). For biomass derived CBSC, the body is often amorphous and owns aromatic structure. Moreover, conventional solid acids bearing single functional groups are different from the biomass derived CBSC. CBSC possess high density of nearly neutral phenolic — OH in addition to Brpnsted acid sites (-SO3H and — COOH), as shown in Fig. 15.4 (Kang et al. 2013).
Carbonised Material (AC)
/ CO I O» CO
: о : о л; o)o r MX ‘ О “
-г ‘ о
Pyrolysis Carbonisation Sulfonation SO3H-Carbon(Catalyst)
Fig. 15.5 Preparation of SOaH-carbon (Konwar et al. 2014, with permission)
Petroleum-based fuels are no more sustainable for industrial and transportation purposes due to emission of green-house gases (GHGs) and other poisonous gases from their burning, increasing demand and depleting natural resources. Moreover, CO2 (a GHG) buildup due to their combustion, is a serious environmental threat. These facts are leading towards the development of alternative energy sources for ensured environmental sustainability. Therefore, renewable raw materials which include edible plants/seeds (mustard, corn, canola, palm oil, soybean, sunflower, coconut) and non-edible plants/seeds oils (jojoba, castor, jatropha, pongame, Citrus reticulate, Cucumis melo, Moringa oleifera) and waste oils have been explored for the biodiesel production (Rashid et al. 2008, 2011, 2012, 2013; Sharma et al. 2009; Yadav et al. 2009; Diaz and Borges 2012). However, there are several limitations with these resources; (1) competition with human food demand, (2) use of arable land, (3) requirements of huge amounts of fresh irrigation water, (4) lower yield of biofuel molecules, (5) long cultivation periods and low seasonal production (e. g., once a year). Alternatively, microalgae have received massive attention as an alternative, among the many options. They are presumably the cheapest source among all other renewable sources for biodiesel production (Chisti 2007; Petkov et al. 2012).
Microalgae are tiny (unicellular or filamentous) photosynthetic factories and their photosynthetic competence is remarkably higher than terrestrial plants. Growth rate and oil productivity of microalgae is considerably higher (Fig. 18.1) than the oil productivity of the best available oil producing crops (Chisti 2007; Wu et al. 2012). They are believed to produce up to 300 times more oil than traditional energy crops on the basis of acreage usage (Chisti 2007; Schenk et al. 2008). The average lipid
(Wu et al. 2012)
contents of microalgae range between 1 and 70 % (~30 %, when grown in waste water) but under the optimized conditions some species (Botryococcus braunii) can yield up to 80 % of oil (Table 18.1) on dry biomass basis (Schenk et al. 2008; Wu et al. 2012). Moreover, they lack lignin in contrast to higher plants, so are easily degradable. Most importantly, they do not compete with food crops and can be cultivated using non-arable (saline, sodic, water-logged soils) lands, saline/waste water, and artificial beds, e. g., compact bioreactors (Musharraf et al. 2012). They produce remarkable quantity of polysaccharides (sugars) and proteins along with the lipids, so the left-over biomass (after oil extraction) may be exploited for production of bio-ethanol, biogas, bio-fertilizers as well as to enhance to protein and mineral contents of the animal feed (Gill et al. 2013). Microalgae have potential to
sequester the atmospheric CO2 at the rate as high as 1.8 kg of CO2 per kg of dry biomass (Wang et al. 2008). This makes the algal fuels carbon neutral and in certain cases algal fuel production may earn salable carbon credits to meet Kyoto targets.
The specific gravity ofbamboo varies between 0.4 and 0.8 depending on its anatomical structure. The specific gravity of 1-year-old bamboo is very low as compared to
3- or 5-year-old bamboo culms. The average specific gravity increases about 58 % from 1 to 3 years of age. The specific gravity value of outer layer of bamboo is observed to be twice than that of inner layer (Li 2004). The specific gravity of bamboo fiber reinforced plastic composite is measured as 0.924 (Jain et al. 1993).
Bamboo fiber extracted by steam explosion method has a very high specific strength. The specific strength of steam exploded bamboo fiber is equivalent to conventional glass fiber (Okubo et al. 2004). The specific strength of bamboo fibers is higher than plastics, which makes them a very good choice for preparation of many substances including furniture (Lakkad and Patel 1981). Bamboo fiber’s specific strength when compared with specific strength of mild steel is 3-4 times higher. Bamboo fiber reinforced plastic composites possess a very high specific strength (Jindal 1986). The specific strength of bamboo fibers can be increased by making a composite with maleic anhydride grafted polyethylene (Mohanty and Nayak 2010). A remarkable increase in specific strength of bamboo fibers is observed when they are reinforced with aluminum alloy sheets (Li et al. 1994).
The specific strength ofbamboo decreases with increase in age. The best strength is observed in the bamboos of 3-6 years (Li 2004). The strength is also observed to increase with height. The strength increases from central to outer part (Li 2004). BZB is seen to have a higher specific strength than many of the commercially available wood fibers (Nugroho and Ando 2000).
The second generation biofuel technology for the production of ethanol is cellulosic ethanol technology. Cellulose plants are the main source for the production of cel — lulosic biofuels. They have categorized it as “energy crops” rather than the crops for food production. Some of the examples are perennial grasses and trees, like switch grass and Miscanthus. Another source of cellulosic biomass is residues (crop) such as stems and leaves.
Generally it has been observed that the lignocellulosic biomass is the main feed stock for ethanol and includes various materials like agricultural residues such as corn stover, husks, bagasse, woody crops, waste paper and municipal and industrial wastes. Environmental issues can be resolved by using or disposal of agricultural waste residues and other wastes for the production of bioethanol. There is no interference of the lignocellulosic feedstocks with food security and are important in terms of energy security in all areas, environmentally and also agricultural development and employability.
Two different processing methods can be used for the production of ethanol from lignocellulosic biomass. These are as follows:
• Biochemical Method—In this method before fermentation, enzymes and other micro-organisms are used for the conversion of cellulose and hemicellulose part of the feedstocks into sugars for the production of ethanol.
• Thermo chemical Method—In this method pyrolysis/gasification technologies are used to produce a synthesis gas (CO+H2) from which a range of long carbon chain biofuels, such as synthetic diesel, can be reformed.
The main compositions of the lignocellulosic biomass are lignin, polysaccharides cellulose, and hemicellulose. It is generally seen that the use of lignocellulosic biomass becomes difficult because of the stability of the polysaccharides and it became difficult to ferment the pentose sugars by Saccharomyces cerevisiae. Hydrolysis of the polysaccharides must be undertaken for the conversion of lignocellulosic biomass to biofuels, or broken into simple sugars by using acid or enzymes. To overcome these problems several biotechnology-based approaches are being used which include development of strains of Saccharomyces cerevisiae, which is used to ferment pentose sugars. Generally the biochemical routes are used to produce ethanol from lignocellulosic biomass. The three main steps involved for the production of ethanol are pretreatment, hydrolysis of enzymes, and fermentation. In detail, first the pretreatment of Biomass is undertaken to enhance the advancement of enzymes. After pretreatment hydrolysis of biomass can be undertaken to change polysaccharides into monomer sugars, like glucose and xylose.
Simultaneous saccharification and cofermentation (SSCF) process can be used to convert pretreated biomass into ethanol. Generally it is assumed that the pretreatment is an important step used to improve the enzymatic hydrolysis of biomass. The basic step involved in this process is that it modifies the physical and chemical properties of biomass and ultimately enhances the enzyme access and efficacy l eading to modification in crystallinity and degree of polymerization (cellulose). This process also increases the internal surface area and pore volume of pretreated biomass leading to facilitate substantial improvement in enzymes accessibility. Enzymatic hydrolysis step also enhances the rate and yield of monomeric sugars.
Table 7.3 presents the results of the productivity tests for the prototype scrapping machine for A. comosus leaves. The tests found that the prototype machine has an average processing capacity of 113 A. comosus plants/hour, with a slightly superior capacity in the case of the second crop plantations than in the first crop plantations (Table 7.3). Such difference may be explained by the higher amount of leaves present in the second crop plants (105) compared with the quantity of leaves in the first crop plants (an average of 69).
As for productivity, it is possible to process an average of 178 pineapple leaves kg/hour, with the second crop plantations showing again the highest productivity. This level of productivity allows the production of an average of 17.2 fiber kg (in green condition) per hour. This is the equivalent of an average dry fiber final weight of 4.9 kg/h.
Evaluation of performance of other types of machines (Banik et al 2011; Das et al 2010) shows that this model presents lower performance than that of systems developed in Asia, which have a more advanced technology for this kind of processing. Banik et al (2011), for example, report equipment capable of producing 25 fiber kg/hour; Das et al (2010) also report that high-performance technical equipment for industrial production can process 1,500 green fiber kg/day. In these cases, however, the machines, although more powerful, are more expensive.