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> It is likely that the efficiency can be improved a lot What makes you think that? I thought internal combustion engine efficiency is widely believed to have

• Brian_K_White 6y ago
  Internal combustion, or any form of combustion, is only one way to get energy back out of a hydrocarbon. And a hydrocarbon cycle doesn't necessarily have to be all that efficient to be practical, if the primary energy input is renewable, and the cycle is largely closed (IE, a plant somewhere consumes the same stuff the vehicle produces). The portability, safety, ease of handling, and rapid simple refill of hydrocarbons outweighs a lot of other factors at the point of use for some jobs, mainly vehicles. Most other energy-consuming jobs can use a wide variety of other forms of energy, so this is mostly about vehicles, not energy usage in general. This is why your furnace doesn't burn gasoline. Anyway what they're saying is that entire cycle can probably be improved a lot from what we can manage today. We can surely continue discovering new and better ways to make a fuel cell that consumes a hydrocarbon. And we are definitely still discovering a variety of different ways to synthesize hydrocarbons. Some have a lot of overhead like planting corn and eventually getting a small quantity of a low-density hydrocarbon (alcohol). Some are more direct bulk inustrial processes that are fairly cyclic and lower overhead than farming. We already have a variety of examples of both the consumer and generator parts of the cycle and we are definitely not done discovering all the possibilities.