(Question 1 points 3).
Food fuel is the fuel in which we use farmland or crops for bio-fuels production to the detriment of the food supply. whereas, mechanical fuel is a material used to produce energy when it is burned. Petroleum products (gasoline, kerosene, and bunker B) are the best being used as a mechanical fuel worldwide.
(Question 2 points 3).
This is because they are lightweight, spread easily, less volatile and are relatively persistent in the environment.