The rapidly growing literature on biofuels and many initiatives looking for alternative energy sources shows an amazing variety of options proposed by experts and visionaries. All these options are being proposed as feasible and/or highly desirable solutions to replace our use of oil.

In order to ascertain whether or not a certain source of energy would be an appropriate input for a system, one must first carefully observe the characteristics of the energy system. We cannot feed gasoline to humans, or power a refrigerator with pizzas. When refuelling a vehicle in a modern gas station, the driver must first select the appropriate type of fuel: gas or diesel, regular or premium octane rating.

In the same way, US electric plugs with a voltage of 110 volts (V) deliver an energy input incompatible with EU appliances, which require 230V. All these examples clearly show that it is impossible to judge the feasibility and desirability of a potential energy source by studying only its characteristics in terms of a generic determination of the amount of joules (or kilocalories) it can deliver.

Common sense tells us that it is important to check the compatibility of the potential energy source and the system that is supposed to use it. It is therefore hard to understand why many focus only on the characteristics of the production process of the energy input, e.g. the overall output/input ratio of the production process of ethanol from crops. They seem to make a naive assumption: if it can be burned, and if it can be produced with an output/input energy ratio higher than 1, then it is a feasible and desirable energy source for both developing and developed societies.

As a matter of fact, this assumption has been proved wrong by the evolution of the energy sources used by humankind. Wood was almost entirely replaced by coal at the beginning of the Industrial Revolution, even though both can be burned and both have an output/input energy ratio higher than 1 (and much higher than the one achieved with biofuels). In the same way, coal was largely replaced by oil in the middle of 20th century, and in the last few decades, wherever possible, oil has been replaced by natural gas.

This evolution strongly suggests that there are other characteristics that define the quality of an energy source, besides its ability to burn and an output/input energy ratio greater than 1. However, an organic discussion of what makes an energy source high or low quality is never provided by those investing their time in calculating the second decimal of the output/input energy ratio of corn-ethanol production.

For this reason, we strongly believe that it is essential to explore some basic concepts of energetics before getting involved in any discussion of the feasibility and desirability of a large-scale move toward agro-biofuel. This step is a prerequisite if we want to have a more informed discussion about our future energy sources.

This entry was posted under Environment, Technology.