Biogas is a better fuel than animal dung-cakes. This is because of the following reasons :
(i) Biogas burns without smoke, whereas the burning of animal, dung-cakes produces a lot of smoke.
(ii) Animal dung-cakes leave residue like ash, whereas biogas leaves no residue.
(iii) The calorific value of biogas is much higher than that of animal dung-cakes.