Last time, I published a mapping of energy resources, classifying them according to their conventionality and renewability. I bet you might have been surprised at how I classified some of them as conventional or not. Indeed, I have myself, as some energy sources were not so easy to put in this or that box and this exercise made me realize how not so simple our energy ressources model is after all. So today I’ll review these choices with you, and tell more about the most surprising cases.
It’s rather obvious to figure out that nuclear fission, conventional oil and coal types as well as natural and town gas are conventional energies. What can seem more surprising is to list out water and biomass. However, both have been part of our energy mixes for a while. Hydroelectricity (in forms such as hydroelectric dams or pumping stations) account for about 15% of our mix worldwide and around 83% of our renewables production mix. And don’t you remember how your parents or grand-parents were buying steres of wood in autumn? Or how you are maybe still doing in your countryside house? Just the same, passive solar energy is centuries-old, being used in optimizing the way homes are oriented and build.
Let’s now turn to unconventional energy sources. We’ve heard a lot lately about unconventional oil and gas, so you probably weren’t surprised to find bituminous sands or shale gas there. But maybe you didn’t know there were unconventional coal types. Peat and graphite are respectively very low (less than 55%) and very high (more than 95%) carbon-intensity coal types that just now become exploitable in economic terms. By the way, I have to mention that lignite (55-75% carbon-intensity coal) is now experiencing an extraction boom. Although it has been long exploited before, bituminous and sub-bituminous coal, more carbon-intensive, slowly replaced it, and it’s only recently that exploitation costs and revenues made it more interesting to turn to lignite too.
About nuclear fusion, I just have to say there’s no doubt about the relevant classification since the technology is only at the research stage. All other renewables are not very surprisingly unconventional since they’re not very well established yet. I’ll simply finish with adding that fermentescible biomass is different from ligneous biomass in the means they are converted into energy. Biochemical processes (methanation) are used for the first while thermal processes are used for the latter (combustion, gasification or pyrolysis).