The components of biomass | Basic concepts | 1. Cellulose | 2. Hemicellulose | 3. Lignin

Five primary components of biomass are mainly: cellulose, hemicellulose, lignin, volatiles, and ash.

Cellulose

It is a substance that is the main part of the cell walls. Since it is made by all plants, it is probably the most abundant organic compound on earth. Aside from being the primary building material for plants, cellulose has great utility in industry.

  • Formula: (C6H10O5)n, where n is the degree of polymerization and represents the number of glucose groups
  • It is an important structural component of the primary cell wall of green plants.
  • It is strong, crystalline, and resistant to hydrolyze.
  • Cellulose is an unbranched polymer.
  • It is a very complex carbohydrate and consisting of 3,000 or more glucose units.
  • Tasteless, odorless, and hydrophilic
  • Insoluble in water
  • Biodegradable
  • The melting point is 260-270 0C

     

    Showing the components of biomass
    Figure: Showing the components of biomass. Sources 1, 2 

Alpha cellulose: It is a major component of wood and paper pulp. It may be separated from other components by soaking the pulp in a 17.5% solution of sodium hydroxide solution under conditions of the test.

  • It has the highest degree of polymerization and is most stable.
  • Undegraded
  • High molecular weight cellulose

Beta-cellulose: It is the soluble fraction that is reprecipitated on acidification of the solution.

Gamma-cellulose: It is the fraction remaining in the solution. Gamma-cellulose consists mainly of hemicellulose.


Hemicellulose

It is one of the numbers of heteropolymer (matrix polysaccharides) present with the cellulose cell wall of all terrestrial plants.

  • It is strengthening the cell wall of plants by interaction with cellulose.
  • It has an amorphous structure with little strength, can be easily hydrolyzed.
  • It consists of shorter chains – 500–3,000 sugar units.
  • It is an unbranched polymer.
  • Gamma-cellulose consists mainly of hemicellulose

Holocellulose

is the total carbohydrate fraction (cellulose and hemicellulose) of the raw material.


Lignin

It is an important organic polymer present in abundant quantity in cell walls of It has many biological functions such as water transport, mechanical support, and resistance to various stresses.

  • Natural phenolic polymers

  • High molecular weight

  • Complexity in composition and structure

  • Reduction in the accumulation of lignin in plants may increase the production of biofuels.

  • Most important is the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily.

 

Types of lignin: The most important types of lignin are as given below:

  • Milled Wood Lignin:
  • Soda Lignin:
  • Steam Explosion Lignin:
  • Dilute Acid Lignin:
  • Hydrolyzed Lignin:
  • Organosolv Lignin:
  • Kraft Lignin: This type of lignin is the main by-product of the Kraft pulping process. Kraft lignin is only soluble in the alkaline solution above pH 10. It is used to burn for the generation of electricity in paper mills due to low reactivity.
  • Lignosulfonates: This type of lignin is the important by-product of the sulfite process, generally used as additives, dispersant agent, binder, complexing and emulsifying agents.
  • Acid Soluble Lignin: It is the lignin fraction that is soluble in 72% sulphuric acid.
  • Klason Lignin: It is the amount of insoluble residue material after removing the ash by concentrated acid hydrolysis (72% H2SO4) of the plant tissues. Klason Lignin constitutes the major mass proportion of the lignin content for most biomass samples, with the remainder of lignin being classified as acid-soluble lignin.

Total Lignin = Klason Lignin + Acid Soluble Lignin

Klason Lignin = Acid Insoluble Residue – Acid Insoluble Ash


Acid Insoluble Residue: It is the amount of a sample that is not hydrolyzed by 72% sulphuric acid.

Acid Insoluble Residue = Klason Lignin + Acid Insoluble Ash

Acid Insoluble Ash: It is the amount of sample that is not hydrolyzed by 72% sulphuric acid and is not subsequently volatilized upon the incineration of this acid-insoluble residue.


Read more interesting articles:

  1. ANN in chemical engineering
  2. Basics in photocatalysis
  3. Statistics for research

Sources:

1.       http://cameo.mfa.org

2.       https://research.cnr.ncsu.edu

3.       https://en.wikipedia.org

4.       https://www.ncbi.nlm.nih.gov

5.       http://polymerdatabase.com

6.       https://www.celignis.com

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