Sustainability Requirements

The first requirement for sustainability is a stable population.

If we merely state that the sustainability of future generations is not compromised, we have said nothing about what is required. We don't know what future generations require; but, if we leave them with the same capacity to produce energy and the same size stockpiles of natural capital that we have, we have certainly achieved sustainability.

Assuming that one can live in a civilized society in which nuclear reactions do not occur, the conservation of matter holds. Then, conservation measures and aggressive recycling are sufficient to satisfy the natural capital requirement with fresh extraction etc. making up the slight unavoidable deficits for thousands, perhaps millions, of years without running out. We may consider this part of the problem solved.

Then, I say, sustainability depends upon an adequate supply of renewable energy. Everything else is in principle solved. Of course, achieving a stable population of intelligent human beings is very difficult, but we know what we have to do.

Thus ERoEI for the production of energy is crucial.  Currently we do not have a truly renewable energy technology.  It is necessary to compute ERoEI in such a way that, if an isolated community in which everything can be done because everything required of nature is available inside the borders of the community, I say, if such a community produces nothing for export except energy, that is, nothing crosses the border - not material, not people, only standard 110 volt AC 60 Hz single-phase electric current (and perhaps none of that), then the requirement for sustainability is ERoEI no less than 1.0.