The conflating of “renewable” with “sustainable” is not a perfect pairing. Consider the definition of sustainable, “of, relating to, or being a method of harvesting or using a resource so that the resource is not depleted or permanently damaged.” While renewable fuels offer the possibility of renewed sources of energy, they do not automatically represent a sustainable option.
Many biofuels demonstrate this principle. The input of resources needed to convert corn into ethanol is not sustainable. Ethanol, while renewable, has less energy per gram or gallon than oil and natural gas. Any oil used in the production of ethanol results in a decreased availability of energy. The 2nd Law of Thermodynamics tells us as much. Using one source of energy to generate another (as in the case of electricity) always results in less energy available after converting from the original to the “secondary” source.
The reason any of this matters is that while there is no energy crisis, it is often said that there is a crisis in how we use energy. I would extend this and argue there is a problem with the types of energy we use. Nonrenewable sources are often energy rich, they contain lots of energy for their mass (or weight), but they cannot be reconstituted. Nuclear energy is the most energy dense source that we currently use. However, there are numerous issues associated with using fuel rods to power our country, not to mention Japan’s recent tragedy. As Germany recently decided, the cost is not worth the abundance of energy generated by nuclear sources. Their transition to renewable fuels is admirable, but how they go about it will be a big question.
Many of the renewable technologies on the market today rely on rare earth elements. While these are not necessarily rare, the monopoly of some countries on their production and the extractive measures needed to produce them make wind power, for instance, less “sustainable” although it is a renewable source of energy. Similar issues exist for solar panels. The silicon that serves as the main semiconductor in photovoltaic arrays (much like they do in computers), has to be mined. Is it feasible that renewable materials that are sustainably harvested can replace minerals and other extracted goods? Human ingenuity may well hold the answer.
Unfortunately though, renewable energy cannot handle the load itself. Maybe it will be able to some day when innovations like Bloom Energy Boxes are affordable enough for the average individual. Until then there is a need for a mixed energy portfolio.
[Image source]
