Disadvantages of biofuels are; food production decline, unsustainable land use, labor costs, low energy density, high water demand, induced deforestation, and corrosiveness.
Examples of biofuels are; fuelwood, ethanol, biodiesel, biogas, bioether, methanol, and biobutanol. They differ from each other slightly in physicochemical properties.
Types of biofuels are; first (1st), second (2nd), and third (3rd) generation biofuels respectively. These can also be referred to as the generations of biofuels, they are classified based on source.
Species richness vs diversity shows that species richness only evaluates the number of species, while diversity evaluates both species number and relative abundance.