What is biomass? Explain the principle and working of a biogas plant using a labelled schematic diagram.

(N/A) Biomass refers to the organic matter produced by plants and animals,such as agricultural residues,cow dung,and wood,which serves as a renewable source of energy.
Principle: $A$ biogas plant operates on the principle of anaerobic fermentation. In the absence of oxygen,microorganisms break down complex organic matter (biomass) into simpler substances,releasing gases like methane $(CH_4)$,carbon dioxide $(CO_2)$,hydrogen $(H_2)$,and hydrogen sulfide $(H_2S)$.
Working:
$1$. $A$ mixture of cow dung and water (slurry) is prepared in the mixing tank and fed into the digester.
$2$. The digester is a sealed,oxygen-free tank where anaerobic bacteria decompose the biomass.
$3$. As decomposition occurs,biogas is produced and collects in the gas holder (dome) above the slurry.
$4$. The pressure of the accumulated gas pushes the spent slurry into the overflow tank,which is then removed and used as high-quality manure.
$5$. The biogas is supplied to homes through pipes for cooking and lighting.