Biogas - Class XI

Answer is B.

Biogas is characterized based on its chemical composition and the physical characteristics which result from it. It is primarily a mixture of methane (${ CH } _{ 4 }$) and inert carbonic gas (${ CO } _{ 2 }$). However the name 'biogas' gathers a large variety of gases resulting from specific treatment processes, starting from various organic waste - industries, animal or domestic origin waste, etc . 
Hence, the statement is false.

Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The gas obtained by the fermentation of biomass is called biogas.

Biogas is a type of secondary energy because biomass (primary energy) is used to produce biogas by anaerobic digestion into more efficient and higher value fuel.Biogas is also called gobargas as made by waste remains of plants and animals.

Major gases released from biomass are methane ($CH _4$), carbon dioxide ($CO _2$), hydrogen ($H _2$) and hydrogen sulphide ($H _2S$).

Biogas is a mixture of gases consists primarily methane and carbon dioxide  that produced by the breakdown of organic substance into such gases  in complete lack of oxygen. This biogas production can only be done by anaerobic breakdown of biomass. As methanogens are also anaerobic bacteria. The correct answer must be 'Both (b) and (c).

The technology of biogas production from cow dung was developed in India largely due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi & Village Industries Commission (KVIC) .

Biogas is also commonly known as gobar gas. The biogas is produced due to anaerobic decomposition of the organic waste matter from the plants and animals with the help of microorganisms. The composition of biogas is methane and carbon dioxide. There are traces of hydrogen, nitrogen, hydrogen sulphide and carbon monoxide. The major component is of methane which accounts for 50-70%. Methane forms the clear and non-polluting gas and commonly used as a fuel.

• Biogas is a mixture of mostly methane and carbon dioxide with trace amounts of other gases and is considered as a valuable renewable energy source.
• Methane comprises of 45-70% of biogas and thus biogas is inflammable. It produces a deep blue flame and can be used as an energy source.

Methanogens break down cellulosic material anaerobically to produce methane, carbon dioxide, and hydrogen.

Methanogens, which are responsible for biogas production, belong to the domain Archaebacteria.

Methanogens are anaerobic archaea that produce methane as a metabolic byproduct. They are capable of utilizing various substrates, including acetate, formate, and methanol, to generate methane.

Biogas production is an anaerobic process involving three main stages: hydrolysis, acidogenesis/acetogenesis, and methanogenesis. It requires the absence of oxygen to function.

• Methanogens are present in the rumen of cattle that is present in dung as well. Methanogens acts on the cellulose content of the and  It helps in the production of methane gas that is a component of biogas.
  
• Hence Methanogens acts on cellulose and release biogas is a correct statement.
• So, the correct answer is 'Methanogens acts on cellulose and release biogas'.

The breakdown of complex polymers like cellulose into simpler monomers is the rate-limiting step in anaerobic digestion. This hydrolysis step is often the slowest part of the process.

Biogas formation uses organic waste to produce methane gas for energy, while the remaining slurry is a nutrient-rich byproduct used as organic manure.

The development of biogas technology in India was a collaborative effort involving the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC).

The odour is due to the gases produced  by the bacteria Methanogens which belong to Archaebacteria.

(a) Fermenting malted cereals produces ethanol (iii). (b) Swiss cheese production involves CO2 release (v). (c) Myocardial infarction is associated with blood clots (i). (d) Biogas involves sludge digestion (ii).

Methanogens are anaerobic bacteria (not aerobes) that recycle inorganic nutrients and are found in the rumen of cattle to aid in cellulose digestion.

The order of bacteria active in the conversion of organic wastes into biogas is hydrolytic, acetogenic, methanogenic. 

Hydrolytic- Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives which are used by bacteria.

Acetogenic- Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. These bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide.

Methanogenic- The methanogens convert the product of acetogenic step to methane and carbon dioxide. The produced gas consisting of methane, carbon dioxide, and traces of other ‘contaminant’ gases is known as biogas.

So, the correct answer is 'Hydrolytic $\rightarrow$ Acetogenic $\rightarrow$ Methanogenic'.

The Biogases produced during sewage treatment are

Cytophaga is a genus of Gram-negative bacillus. Cellulomonas is a genus of Gram-positive bacillus. They have the ability to digest cellulose. They are called as cellulolytic bacteria. They are involved in biogas production. 

Biomass is biological material derived from living, or recently living organisms. In the context of biomass for energy this is often used to mean plant based material, but biomass can equally apply to both animal and vegetable derived material.
Hence, the non-usable animal or vegetable products are collectively called Biomass.