Characterization of Lignocellulosic Biomass for Bioenergy : A Review

Characterization of Lignocellulosic Biomass for Bioenergy : A Review

Sayali Deshpande1, Rushika Marathe1, Hanumant Jaybhaye1, Ankita Kakde1 , Vaishnavi Dhote2

1* Students Department of Civil Engineering,

TSSMs Bhivarabai Sawant College of Engineering and Research , Narhe ,411041, Pune, India

2* Faculty, Department of Civil Engineering,

TSSMs Bhivarabai Sawant College of Engineering and Research , Narhe ,411041, Pune, India

Abstract:- As population is increasing day by day, the demand for energy is also increasing and at the same time depletion of fossil fuels has generated the prerequisite for development of sustainable technologies based on renewable economic sources. Biogas is one is economically feasible, which might benefit the future energy supply demands as well as contributing to a reduction of green house gas emission. Traditionally livestock dung has been utilized as feedstock biogas production but due to unavailability, imbalance and failure occurs in large scale biogas plants, lignocellulosic biomass has attained huge attention. Lignocellulosic biomass acknowledged as the most abundant low cost resources for renewable energy generation across the globe. Energy crops

,saw dust, agricultural residues or waste vegetables , woody plants fall under this category. In many cities the lignocellulosic biomass disposed off openly, which origins environmental pollutions as well as root cause for many diseases. So that we used it as feedstock in biogas. To evaluate the prospective of a variety of lignocellulosic biomass as biogas feedstocks, the characterization of different types of lignocellulosic biomass( saw dust, nut shell, rice straws, corn straw, bagasse ) abundantly found was investigated. The lignocellulosic biomass was characterized for volatile matter, moisture content ash content, total solids, fixed carbon content.

Keywords: Characterization, Biogas, lignocellulose,

1. INTRODUCTION

   Lignocellulosic materials are the most promising feedstock as natural and renewable resource. Among many of the developing countries, its a routine practice that such agricultural wastes are not been fully discarded and then have become a major source of ecological pollution Naturally, cellulose, hemicellulose and lignin are the major constituents of plant cell walls and among all of them, cellulose is the most common and abundant component of all plant matter. From the last several years, there is an increasing demand for industrial important enzymes. In such scenario, cellulase is being used in many of the industrial applications mainly but not limited in the field of cotton processing, paper recycling, agriculture and in the field of research and development. lignocellulosic biomass continues to attract global interest as a sustainable alternatives to fossil carbon resources to produce second generation biofuels and other biobased chemical without compressing global food security. Thus included agricultural wastes such as cereal straw, wheat straw, bagasse, corn straw , etc. Enzymatic hydrolysis of such agricultural wastes provides an environmentally friendly means of depolymerizing cellulose and other carbohydrates at high yields .

   Fig. 1 composition of biomass( Reference: google )

2. LIGNOCELLULOSIC BIOMASS Lignocellulosic materials including agricultural wastes, forestry residues, grasses and woody materials have great potential for bio-fuel production. Typically, most of the agricultural lignocellulosic biomass is comprised of about 10% – 25% lignin, 20% – 30% hemicellulose, and 40% – 50% cellulose. Cellulose is a major structural component of plant cell walls, which is responsible for

   mechanical strength and chemical stability to plants. While, hemi-cellulose macromolecules are often re- peated polymers of pentoses, and hexoses. Due to the genetic variability among different sources hemicellulose macromolecules are also vary in structural composition. Lignin contains three aromatic alcohols produced through a biosynthetic process and forms a protective seal around the other two components i.e. cellulose and hemicelluloses. In general, the com- position of lignocellulose highly depends on its source whether it is derived from the hardwood, softwood, or grasses. Lignocellulosic biomass has a complex internal structure and comprised of a number of major compo- nents that have, in turn, also complex structures. Table shows the typical chemical compositions of all these three components in various lignocellulosic materials that vary in composition due to the genetic variability among different sources.(Advances in lignocellulosic biotechnology: University of Gujrat )

3. PROPERTIES OF CELLULOSE

   Plant biomass contains 40% to 50% of cellulose molecules which are fibrous in nature, insoluble, crystalline polysaccharide. Being the most abundant and easily available carbohydrate polymer all around the earth which isa major polysaccharide constituent of plant cell wall, composed of repeating (1,4)-D-glucopyranose units, which are attached by -1,4 linkages with an average molecular weight of around 100,000 [12]. Naturally cellulose molecules are exists as bundles which aggregated together in the form of micro-fibrils order i.e., crystalline and amorphous regions [3,13,14]. The structure of one.

   chain of the cellulose polymer is presented in Figure 1 Cellulose has attracted worldwide attention as a re- newable resource that can be converted into bio-based products of commercial interests. Therefore, cellulose has been used as a potential energy source for a wide variety of organisms including fungi and bacteria to ex- tract many useful products e.g., enzymes. (Advances in lignocellulosic biotechnology: University of Gujrat )

4. PROPERTIES OF HEMICELLULOSE

   The second most abundant polymer after cellulose is hemicellulose which is heterogeneously branched in nature. The backbone of the hemicellulose polymer is built up by sugar monomers like xylans, mannans and glucans, with xylans and mannans being the most common [15], in this case xylanases are the enzymes involved in its degradation. Similar to cellulases the xylanases can act synergistically to achieve hydrolysis, predominant enzymes within this system are endo 1, 4 b-xylanases which attack the polysaccharide backbone, and b-xylosidases. Hemicellulosic biomass contains 25% to 35% of hemi- cellulose, with an average molecular weight of <30,000. Cellulose and hemicellulose binds tightly with non-co- valent attractions to the surface of each cellulose micro- fibril. Hemicellulose, degrade quickly due to its amorph- ous nature [16]. Among other important aspects of the structure and composition of hemicellulose are the lack of crystalline structure, mainly due to the highly bran- ched structure, and the presence of acetyl groups con- nected to the polymer chain. (Advances in lignocellulosic biotechnology: University of Gujrat )

5. PROPERTIES OF LIGNIN

   Lignin is generally the most complex and smallest fraction, representing about 10% to 25% of the biomass. It has a long-chain, aromatic polymer composed largely of phenyl propane units. Lignin acts like a glue by filling the gap between and around the cellulose and hemicellulose. complexion with the polymers. It is present in al- most all kind of cellulosic plant biomass and acts as a protective sheet against cellulosic and hemicellulosic components of the biomass

   materials. Lignin is consists of multifarious and large polymer of phenyl-propane, methoxy groups and non- carbohydrate poly phenolic substance, which bind cell walls constituent together [16]. Among them phenypropanes are the main blocks of the lignin share in biomass residues. These phenylpropanes denoted as 0, I, II methoxyl groups attached to rings give special

   structure I, II and III. These groups depend on the plant source which they are obtained. Structure I exist in plants (grasses) and structure II found in the wood (con- ifers) while structure III present in deciduous wood. (Advances in lignocellulosic biotechnology: University of Gujrat )

   Biomass	Cellulose	Hemicellulose	Lignin	Reference
   Wheat straw	35	29	21	Naik et al. (2010)
   	34	24	14	Adapa et al. (2009)
   Rice straw	39	24	6	Chandra et al. (2012)
   Corn stover	43	24	11	Zeng et al. (2011)
   Sugarcane bagasse	35	24	22	Rezende et al. (2011)
   	45	28	23	Sun and Cheng (2002)
   Switchgrass	36	31	6	Greenhalf et al. (2012)
   Poplar wood	44	32	21	Meng et al. (2012)
   Eucalyptus chips	45	15	26	Emmel et al. (2003)

   Table . Cellulose, hemicellulose and lignin (wt%) content of different biomass

   Fig. Conversion process schematics and valorization of lignocellulosic biomass residues, such as tall grass, bagasse, rice husks, wood chips, and organic landfill waste. Pretreatment of these biomass depolymerizes the complex lignin and cellulosic structures and separate lignin from cellulose and hemicellulose via hydrolysis. Subsequent fermentation and/or chemical treatment converts them into valuable energy and chemical products.( Ref: Google )

6. PROXIMATE ANALYSIS

   It is the most often employed practice for biomass characterization. It determines the weight percentage of moisture, volatile matter(VM), fixed carbon(FC) and ash content of a biomass. Characterization using proximate analysis is easy and time saving as it requires as of standard laboratory equipments, however ultimate analysis is utmost important for accurate results of major elements such as carbon (C), hydrogen(H), Nitrogen(N), sulphur (S), and oxygen(O) present in biomass. Moisture content of rice straws found lowest amongst the all lignocellulosic biomass. Volatile content of bagasse found height. Ash content of peanut shell is found lowest. Comparative low moisture content feedstock is preferred using thermal conversion process, while bio-conversion can utilize biomass with high moisture content. Ash the incombustible solid mineral matter of the biomass, mainly contains oxides of silica(Sio), alumina(Alo), iron(FeoO), calcium(CaO), and Magnesium(MgO).

   Ignition and combustion problem for use of biomass fuels are mainly due to high moisture and ash content. The cations present in ash content retards the enzymatic scarification of biomass samples, hence washing is recommended in order to remove water soluble and sticky inorganic material before hydrolysis. In biomass fuel, chemical energy is stored in the mainly form of fixed carbon and volatile matter. The ratio released as a gas by heating to 9500c for 7min is volatile matter whereas the non-volatile organic matter which may also contain oxygen with hydrogen excluding the ash and moisture content is fixed carbon. The fixed carbon is used to relate the heating value of the product and co-products. The extent of biomass ignition and gasification as energy source can be estimated with volatile matter and fixed carbon. Content depending on biomass utilization. Fixed carbon and volatile matter provides fuel properties which render comparison of fuel after biochemical production from lignocellulosic biomass. both volatile matter and fixed carbon have positive effects on the calorific value.

   Ultimate Analysis

   Ultimate analysis is defined as the determination of carbon, hydrogen, nitrogen and sulfur in a wide type of organic and inorganic samples, both solid and liquid. Elemental analysis illustrates the biomass composition in respect of the most abundant five elements (C, H, N, S and O) and total mineral matter. Owing to high carbon and low nitrogen and sulphur content (Table 2), poplar wood is considered to be a plausible biomass for green fuel generation. Energy generation from poplar bioenergy system is favored in southern Europe by Gasol et al. (2009), based on energy balance and environmental perspective. Presence of sulphur also hampers the catalytic efficiency by forming metal sulphides. Rapid deactivation of catalyst in presence of small amounts of sulphur compounds has been reported by Sauciuc et al. (2011) during synthesis of synthetic diesel from biomass using Fischer Tropschs process. Since it was having low energy density with high oxygen and acid content (Czernik et al., 2004), a hydrotreatement process was performed at 100 – 200 bar (Zacher et al., 2014) for the production of low oxygen hydrocarbons.( Nadim Akhtar et al 2019 )

7. BIOMASS CHARACTERIZATION Heterogeneity remains an inherent characteristic of biomass. The feasibility and viability of products recovery from biomass depends upon its properties. The two main conversion pathways earlier mentioned are basically used to recover products of value from biomass. The choice of the conversion route also depends on the features of biomass hence characterization is essential to better understand quintessential physicochemical properties of biomass that will determine how suitable the material is for conversion; these properties are keys to the efficient utilization of biomass in bioconversion processes [1, 7]. However, the characteristics of biomass are largely swayed by its primary organic components (cellulose, hemicellulose and lignin), which vary depending on biomass source, species, climaticconditions, etc. Depending on the end use of biomass, characterization of biomass is commonly determined and reported in terms of proximate and ultimate analysis using a variety of analytical tools some of which are described in subsequent sections of this review. This provides vital information for evaluating various application potential of biomass, particularly its energy production potential, which also takes into account heating value when the biomass is used as feedstock in thermochemical conversion processes such as gasification [25]. presents the most important characteristics of various lignocellulosic and non- lignocellulosic biomass materials

8. CONCLUSION

Lignocellulosic biomass, including agricultural and forestry residues is a highly complex heterogeneous material, the composition of which varies tremendously on its habitat, source, range of tolerance for adverse environmental niche conditions, seasonal variation and availability of nutrients.

A sustainable and alternative energy source, in order to be preferred to agricultural residues should be economically viable, environmentally friendly, provide energy security, reducing greenhouse emissions. Under this considerations, the characterization of residual biomasses will play an important role in bioenergy production. Discovering new sources of raw materials for the production of biofuels in a sustainable way is very important, and their characterization is crucial.

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