Why is the use of biomass to generate heat:
$(i)$ discouraged by burning it directly in ovens (chulhas),and
$(ii)$ encouraged for obtaining biogas through a biogas plant?

(N/A) $(i)$ Burning biomass directly in traditional ovens (chulhas) is discouraged because it is less efficient,produces a lot of smoke,and causes significant air pollution.
$(ii)$ Using biomass to produce biogas is encouraged because it is a highly efficient fuel,burns without smoke,and the spent slurry left behind in the biogas plant serves as an excellent,nutrient-rich manure for crops.