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.

Using unconventional plant fibres, such as okra, as the filler for conventional thermosetting matrices can be considered a preliminary step towards the fabrication of fully biodegradable composites. The use of thermosets enables a reflection on a

Table 11.2 Decomposition temperatures for selected natural fibres (De Rosa et al. 2010a)

number of aspects. These include, for example, the possible maximum amount of fibres leading to an improvement of the composite properties, before effective impregnation gets hindered by an excessive amount of filler, and the evaluation of effectiveness of chemical treatment to provide a sounder fibre-matrix interface. It needs to be noted that plant fibre composites including kenaf fibres, which are botanically similar to okra, in thermosetting matrices are quite diffuse and a number of studies have been performed. In particular, it was demonstrated that alkali treat­ment with NaOH has some positive effect on fibre density and assists in improving the mechanical interlocking and chemical bonding between polyester resin and the

fibre, resulting in superior flexural and impact properties (Aziz and Ansell 2004). Another significant observation is that kenaf is very suitable to manufacture fabrics, therefore producing composites with a sufficiently high amount of fibres, compati­ble, e. g. with the requirements of the automotive industry as regards the envisaged substitution of fibreglass (Na and Cho 2010). It is not surprising, therefore, that fibres such as okra are having some minor interest for application in thermoset matrix composites.

In particular, unsaturated polyester matrix was reinforced with a maximum of 36 vol% okra fibres: the fibres were defined as “woven” in that the whole usable length of the stem, equal to around 60 cm, is employed to reinforce the composites (Srinivasababu et al. 2009). The fibres were introduced either without treatment or subjected to two different procedures, both including an alkali pretreatment with sodium hydroxide, followed by a long-time (14 h) or short-time (5 min) treatment with a very diluted acid solution of potassium permanganate (Srinivasababu and Rao 2009; Srinivasababu et al. 2009). Both treatments brought to some improve­ment of tensile modulus and especially to a more consistent increase of it with the introduction of a higher amount of fibres, which may depend on their more uniform geometry after treatment. In contrast, tensile strength only shows some improve­ment for the highest volume of fibres introduced (36 %), being reduced at lower volumes of reinforcement with respect to untreated okra fibre composites (Srinivasababu et al. 2009). Another study was performed on the introduction of a limited amount, up to 20 wt%, of okra fibres bleached with sodium hypochlorite, in a Bakelite matrix. Here, the introduction of fibres did not result in an increase of tensile and flexural strength with respect to the pure matrix, even for the maximum amount of fibre introduced and the situation was not substantially improved by bleaching, although this treatment did lead to an increased strength of the fibres alone (Moniruzzaman et al. 2009).

To summarize these results, the problems linked to the reduced interface strength and to the anomalous section of the okra fibres, as extracted from the bast, appear still limiting factors for possible applications as reinforcement for semi-structural components.

Gravity sedimentation is a simple process used for the separation of algae in water and wastewater treatment, which is often supported by flocculation to upsurge the effectiveness of gravity sedimentation (Chen et al. 2011). Another model of gravity sedimentation procedure is flotation, which is considered more effectual and advan­tageous as compared to sedimentation and can capture the bits with thickness of less than 500 pm (Yoon and Luttrell 1989). The operative and efficient methods for harvesting of algal biomass include centrifugation and chemical precipitation (Chen et al. 2011). These procedures are not economically practicable for harvesting of algae due to high procedure charge of centrifugation or chemical flocculants for the production of biogas. Filtration also appears to have great prospective for condens­ing algal biomass from bulk culture, integration of different techniques such as floc­culation, gravity sedimentation, or flotation can also be done. For biogas production, concentrated slurry is considered as a good substrate for anaerobic digestion (Prajapati et al. 2012, 2013). The consumption of wet algal biomass reduces the water necessity, which is required in excessive amount for the digestion of conven­tional biomass, for biogas production.

The rate of a chemical reaction changes due to the participation of heterogeneous catalyst. The product generally desorbs from the surface of the catalyst and diffuses away after the completion of reaction. The catalytic site determined the surface area of the catalyst and hence it is very critical and important. Adsorption and desorption are the two phenomena associated with the heterogeneous catalysts functions. The two processes help in the reaction of molecules to make them attract and attach to one another. Homogeneous catalysts are in the same phase as the reactants. When catalysis in a single liquid phases this type of catalyst is called homogeneous cataly­sis. Table 15.3 shows the comparison of main advantages/disadvantages of homoge­neous vs. heterogeneous catalysts. A main disadvantage of homogeneous catalysts is the problem of their recovery from the reaction medium because of its hygro­scopic nature along with its hazardous nature for the environment as compared to heterogeneous catalysts; this led to flourishing activity attempting to heterogenize homogeneous catalysts.

The energy constituents of J. curcas are wood, fruit as whole and parts of fruit such as shells, seed husks, and kernel (Singh et al. 2008) which are direct sources of fuel. All these products have different energy values. The energy value of these products increases upon processing, but unless a use for by-products is found a decrease in overall energy availability occurs. A schematic illustration of these energy components is shown in Fig. 17.1.

Several pretreatment processes combine physical and chemical elements. The most common of physicochemical pretreatments used are steam explosion: SO2-steam explosion, Liquid hot water, ammonia fiber explosion (AFEX), Microwave pretreat­ment, Ultrasound pretreatment, and carbon dioxide (CO2) explosion.

Steam explosion is the most widely employed physicochemical pretreatment for lignocellulosic biomass. It is a hydrothermal pretreatment in which the biomass is subjected to pressurized steam for a period of time ranging from seconds to several minutes, and then suddenly depressurized. This pretreatment combines mechanical forces and chemical effects due to the hydrolysis (autohydrolysis) of acetyl groups present in hemicellulose. Autohydrolysis takes place when high temperatures promote the formation of acetic acid from acetyl groups; furthermore, water can also act as an acid at high temperatures.

Addition of dilute acid in steam explosion can effectively improve enzymatic hydrolysis, decrease the production of inhibitory compounds, and lead to more complete removal of hemicellulose.

The most important factors affecting the effectiveness of steam explosion are particle size, temperature, residence time, and the combined effect of both tempera­ture and time (Alfani et al. 2000). Higher temperatures result in an increased removal of hemicelluloses from the solid fraction and an enhanced cellulose digestibility; they also promote higher sugar degradation.

AFEX involves liquid ammonia and steam explosion. A typical AFEX process is carried out with 1-2 kg ammonia/kg dry biomass at 90 °C pH values (<12.0) during 30 min. It reduces the lignin content and removes some hemicellulose while decrys — tallizing cellulose. The important advantages of AFEX include: (1) producing neg­ligible inhibitors for the downstream biological processes, so water wash is not necessary (Mes-Hartree et al. 1988); and (2) requiring no particle size reduction. However, ammonia must be recycled after the AFEX pretreatment based on the considerations of both the ammonia cost and environmental protection. Therefore, both ammonia cost and the cost of recovery processes drive up the cost of the AFEX pretreatment (Holtzapple et al. 1992).

Carbon dioxide (CO2) explosion acts similar to steam and ammonia explosion: high-pressure CO2 is injected into the batch reactor and then liberated by an explo­sive decompression. It is believed that CO2 reacts to carbonic acid (carbon dioxide in water), thereby improving the hydrolysis rate. The glucose yields in the later enzymatic hydrolysis are low (75 %) compared to steam and ammonia explosion. Overall however (CO2 ) explosion is more cost-effective than ammonia explosion and does not cause the formation of inhibitors as in steam explosion.

The date palm biodiversity is obvious all around the world where about 5,000 date palm cultivars can be found (Jaradat and Zaid 2004). Based on botanical descrip­tions, about 1,000 cultivars can be found in Algeria, 400 in Iran, 370 in Iraq, 250 in Tunisia, 244 in Morocco, and 400 in Sudan, as well as many additional cultivars in the other countries (Benkhalifa 1999; Osman 1983; Zaid and De Wet 1999). The date palm trees (Phoenix dactylifera L.) is the tallest Phoenix species, it can be found with heights of more than 30 m and has fruit reaching up to 100 mm x 40 mm in size. The fruits are very tasty and nutritious (Jaradat and Zaid 2004). Date palms have characteristics that adapt them to varied conditions. Date palm trees can grow well in sand, but it is not arenaceous. It can also grow well where soil water is close to the surface because they have air spaces in their roots. Although date palm tree can grow well in saline conditions, it can do better in higher quality soil and water. The leaves of the date palm are adapted to hot and dry conditions, but it is not a xerophyte and requires abundant water (Benkhalifa 1999; Jaradat and Zaid 2004).

The date palm tree is characterized by numerous offshoots produced at its trunk’s base. The trunk of the date palm tree is covered with persistent grayish leaf bases. It is surmounted by a handsome array of pinnate divided long leaves and needle sharp fronds. Usually, around 10-20 new leaves are produced annually. The leaves of the date palm are subtended by a cylindrical sheath of reticulate mass of tough, fibrous material, at their bases. These together form a tight protective envelope for the terminal bud (Benkhalifa 1999; Dakheel 2003). A young actively bearing date palm tree showing offshoots is shown in Fig. 1.2 and fruit of the date palm is seen in Fig. 1.3 . Detailed morphological traits of date palm tree leaf can be shown in Fig. 1.4. where different parameters of the leaf can be demonstrated like the leaf length, thickness, angle, length of leaflet part, rachis thickness, leaf lets number as well as others (Salem et al. 2008).

Once the date palms’ fruit are harvested, large quantities of date palm rachis and leaves wastes accumulated every year in agricultural lands of different countries. These amounts of important and valuable biomass wastes are of potential interest in different countries since they can be considered as new cellulosic fiber sources. Thus, innovative ways of valorizing this abundant renewable resource should be found (Chandrasekaran and Bahkali 2013). One of these ideas is to use such natural fibers in natural fiber composites suitable for different industrial applications. This can be one way of meeting the increasing demand in renewable and biodegradable materials. Therefore, the agricultural residues of date palms mainly rachis and leaves can be viewed as sources of reinforcing fibers for polymeric matrices in com­posite. The competitiveness of the date palm fibers in forming natural composites suitable for automotive industrial applications was demonstrated (Al-Oqla and Sapuan 2014). On the other hand, several studies proved that date palm fibers have the potential to be an effective filler in both thermoplastics and thermosetting mate­rials to be used in different industrial applications (Abdal-hay et al. 2012; Agoudjil et al. 2011; Al-Oqla and Sapuan 2014).

Key to the diagram

Parameter Label

Leaf length Leaf width Leaf angle Spinctcd part length Length of lcaflcted part Petiole width

Rachis thickness between the last spine and the first leaflet

Leaf lets number

Terminal leaflet length

Terminal leaflet width

Ventral angle of middle leaflet

Middle leaflet width

Middle leaflet length

Leaflets spacing index at the middle

Angle of leaflets on both sides of

terminal one

Spine number SN

Middle spine width WS

Middle spine length LS

PW

Fig. 1.4 Detailed morphological traits of date palm tree leaf (Salem et al. 2008)

Date palm tree can produce annually large number of natural fibers that can be utilized in different industries. It is estimated that the annual date palm agricultural wastes are more than 20 kg of dry leaves and fibers for each date palm tree (Al-Oqla and Sapuan 2014). Moreover, the date palm tree produces another type of wastes as date pits which are about of 10 % of the date fruits (Barreveld 1993). Unfortunately, these agriculture wastes are not properly utilized in any biological process or industrial applications, in most of countries, despite of their contents of potential amount of cellulose, hemicelluloses, lignin, and other compounds. Typical date palm fibers can be seen in Fig. 1.5.

Natural bamboo fibers have some of the excellent properties, which make it a very potent material to be used in textile industry. Refined bamboo fibers with low non — cellulosic content can be used in textiles (Liu et al. 2011). Bamboo fiber luster is closer to that of silk. It can be used for knitting and weaving purposes (Yi 2004). Study on bamboo fibers revealed that its chemical composition is same as that of all the bast fibers, which means cellulose content is in majority and lignin content is present in small amount. The structural properties of bamboo are different from those of other textile producing plants. Bamboo is shown to have high potential in textile industry (Yueping et al. 2010). They are used for the formation of socks, under wears, T-shirts, bathing suits, bathing suit cover ups, towels, Sleep wear, face masks, sani­tary napkins, bed sheets, pillows, baby diapers, bullet proof vests, table cloth, blinds, and mattresses. Bamboo fibers are observed to have excellent characteristics for spinning and weaving (Hengshu 2004). Dyeability of bamboo can be enhanced by plasma treatment. Longer the treatment time, higher the roughness and hence higher is the dyeability, which leads to increase in potential to be used as textile.

Biodegradable/bio-based polymeric products is based on renewable plant and agri­cultural biomass as a basis for sustainable portfolio with eco-efficient products that can compete in markets, which currently dominated by petroleum-based products. Through intensive research and development, the large quantities of biomass have now found applications in commercially viable bio-based products. The utilization of lignocellulosic materials from biomass for a number of value-added products is very significant through chemical, physical and biological innovations to invent such innovative and competitive products in various fields, as shown in Fig. 5.9.