Drawing the line between fossil and renewable energies seems much easier than estimating the maturity level of each energy production technology. However there were some tangent cases in the article I published on June, 11th and I will come back on those.
The first one is ligneous biomass, which you maybe noticed I put in both categories. Indeed, the thing with ligneous biomass is the length of its regeneration cycle which is the time a tree needs to grow. If the use of ligneous biomass exceeds the forests capacity to grow new trees again, this energy source turns from renewable to fossil fuel…
The next tangeant case was nuclear energy, which is divided in three cases according to which fuel is used :
- Uranium, used in conventional nuclear fission, is though little-known so without a doubt a fossil fuel since uranium is relatively rare on Earth. According to some previsionnists, we might run out of it around the end of the century.
- Thorium, which as I mentioned in a comment on my article doesn’t appear in the matrix, is a promising alternative to uranium in nuclear fission. It is indeed 3-4 times more abundant than uranium, 3-4 times more effective in producing nuclear energy and generating 10-100 times less radioactive waste, which obviously makes it much greener. So you might be tempted to classify it as renewable but I finally decided to put it in the fossil category for two reasons. First, the thorium stock is indeed finished, although much greater than the uranium one. Second because production of thorium is often linked to extraction of rare earths, process of which it is a residuum. And rare earths definitely are a fossil ressource
- Finally, deuterium, the basis for nuclear fusion, is an abundant element in salted water, which covers around 70% of the planet’s surface. There is little apprehension concerning its coming to an end. So deuterium is available in almost infinite quantities, at least regarding the human activity timespan. However, this is not quite enough to decide if it is renewable or not but as for now, I still couldn’t make it clear for sure. That’s why I decided to temporarily put it in the renewable category, and I will keep you up to date when I find more about it. And if you have any information to add, I will be happy to read your comments.
That was it for the criteria separating fossil from renewable fuels. In my next article, I will come back on the issue of being green for an energy and explain how, to me, it relates (or not!) to the caracteristic of being renewable for an energy source.