The simplest biofuels (ie ethanol and biodiesel) end up using food or food growing farmland to power cars, which is not a good idea cos we can afford to pay so much that the world’s poor people can’t buy it to eat.

However biofuels as a concept doesn’t always have to do this. You can in theory make ethanol from waste material that you can’t eat; you can grow biofuel crops on land that’s no good for crops (ie salty); you can also do creative things like grow algae with seawater. Lots of potential.

most plants will struggle to get better than 2% efficiency for photosynthesis !!!