Understanding EROEI – or Energy Return On Energy Invested – should be on every school curriculum, but isn’t. Simply put, it’s the amount of energy we as a species can play with. Back in the days when you could poke a hole in the ground and oil would gush out of it skywards, getting hold of plenty of energy was easy. In fact, for every blob of oil you used for locating, drilling and transporting the stuff, you got between 100 and 200 similarly-sized blobs of the same quality back. The way this energy value was expressed was by way of EROEI; thus, sweet onshore crude oil could be said to have an EROEI of 100 to 200. These were the low hanging fruit days that made the 20th century boom. Once all the low hanging fruit was gone we had to move a bit further up the tree. […]