Compared with an array of solar cells, plants are strikingly poor transducers of the sun’s energy. Energy storage by photosynthesis is approximately <2 watts (W) per m2. The important difference between plants and solar cells is that plants are very cheap. They are able to grow with a moderate supply of water, nutrients and CO2 that they turn into stable organic compounds. No fuel technology is perfect, but the GHG crisis and concern over oil supplies means that diversifying the range of fuel options makes good sense; at the very least, such diversification places humanity on a healthy learning curve (Haug et al., 2011). Continuous increases in energy needs have encouraged governments to search for new alternatives to fossil fuels. The rationale is to facilitate the transition from a fossil-energy based economy to an economy based on renewable sources of energy. Numerous low — emission scenarios have demonstrated that the goals of the Kyoto Protocol cannot be achieved without providing a large role for biofuels by 2050 in the global energy economy. Among the reasons why biofuels are appropriate for such a transition are the following: (i) their simplicity; (ii) their production via well-known agricultural technologies; (iii) their potential for mitigation of climate warming without complete restructuring of the current working energy system; (iv) the use of existing engines for their transportation (even considering the conventional turbofan used in aviation) (Kleiner, 2007; Rothengatter, 2010);

(v) their potential to facilitate worldwide mobilization around a common set of regulations;

(vi) their potential as a directly available energy source with good public acceptance; (vii) their more uniform distribution than the distributions of fossil fuel and nuclear resources; and (viii) their potential to create benefits for rural areas, including employment creation.