What is biomass? Name the reaction that takes place in the biogas plant. Write the main constituents of biogas. List two reasons for considering biogas an ideal fuel for domestic use.

(N/A) Biomass is the organic matter produced by plants or animals,which serves as a renewable source of energy.
The reaction that takes place in a biogas plant is an anaerobic decomposition (or fermentation) reaction.
Main constituents of biogas:
$(i)$ Methane $(CH_{4})$
(ii) Hydrogen $(H_{2})$
(iii) Hydrogen sulphide $(H_{2}S)$
(iv) Carbon dioxide $(CO_{2})$
Reasons for considering biogas an ideal domestic fuel:
$(i)$ Biogas burns without smoke,causing less pollution.
(ii) It leaves no residue like ash,unlike wood,charcoal,or coal.