There is energy in the waste, wood and manure
Many things can work as a biofuel. There are solid biofuel such as wood, straw or elephant grass. There are also liquid biofuel, such as alcohol from grain or oil from rapeseed and finally there is biogas from manure from cows or pigs.
Biofuel does not hurt the climate as much as oil, coal and gas. Biofuel release only the amount of CO2 that plants marches, as they lived. Biofuel also renews itself, because there will always grow new plants.
But there are some problems lurking here
When we use biofuels, we also draw material from the major circle of life. The biofuel we use should have been left in the ground and fed into new plants. So we risk starving the ground when we spend large amounts of biomass
There are also problems when the crop of bioalcohol and other biofuel will be worth more than crops for food and hungry mouths. The food prices are rising - and that impacts especially those who already have too little.