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Comment by lifeonlars | Hacker News Reader

A ratio of fuel calories to food calories isn't that useful a metric unless you have similar numbers for all the conventional methods of producing food at scale.

It's not like 1 is a goal: we can't eat fossil fuels (or solar energy), and we know that eating either plants or animals is never going to yield all the energy they absorbed during their lives.

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There are similar numbers for conventional farming, and historical estimates too. There's a whole field of study on the EROI of agriculture. And yes, for all of human agriculture until roughly the industrial revolution, the EROI was over 1. By definition. 1 unit of labor + sun better equal at least 1 unit of food! When solar energy is the only external input and all mammalian labor provides the rest (which must be fed by the same crops that you're trying to grow), if you got less crop calories than it took to run the farm, you and your livestock would be dead.

Since the choice is not between these new types of farming and pre-industrial-revolution agriculture, that comparison doesn't matter much..

And even pre-industrial agriculture had specific elements which had a yield of less than 1 by this metric, in order to make specific things that humans wanted to eat. Since most humans don't like a diet of grass and oats, the huge excess calorie yield from those crops could subsidize low-yield farming of vegetables, meat and other delicacies.

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