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Aug
27

“The natural conversion of sunlight to electric charge that occurs in all green-plant photosynthesis after 1 billion years of natural selection may already be the highest net emergy possible

“The natural conversion of sunlight to electric charge that occurs in all green-plant photosynthesis after 1 billion years of natural selection may already be the highest net emergy possible.” – Howard T. Odum

3 comments

  1. John Poteet
    John Poteet says:

    There's a harsh thought. If that's the bottom line then the Earth can support about 500 million people at first world standards of living once fossil fuels are gone.

  2. Chris George
    Chris George says:

    I think we could likely manage about 2 billion at the standard of living of a 1990 Frenchman.

    Assuming, of course, we can grow enough food in whatever the new climate settles out at and that we don't destroy too much of the biosphere before the population stabilizes.

  3. Edward Morbius
    Edward Morbius says:

    I've been thinking of plants, and modeling various industrial solar PV or solar thermal designs. By the time you get to producing a synfuel (say, Fischer-Tropsch) and then burning that (storage or transport), you're not much ahead of plants in terms of total solar energy conversion. Maybe 10% at the high end, as low as 2-3% at the low, which is comparable to plant growth (1-3% solar conversion to cellulose / starches).

    Plants also build themselves, repair themselves, provide their own transport systems, defend themselves against pests, and provide their own structural support — all of which I consider "plant services" which humans would otherwise have to provide.

    Plants do generally have fairly specific growing conditions, and require nutrients and fertilizer, which limit growth potential.

    I'm still really not sure that humans, building structures and equipment which will need replacement on a 20-40 year basis (most PV systems), maybe longer for solar thermal, though I kind of doubt it, can beat that.

    On carrying capacity, I've been looking over a few refs this evening, and that's sobering stuff. But I tend to fall in the general range you guys are talking about: 500m to 2 billion. I figure a standard of living of roughly early-to-mid 20th century in terms of resource consumption. If you scale your infrastructure right that's actually not horrible, and could be quite pleasant. Other alternatives … not quite so much.

    +Chris George I've missed seeing your posts, found a bunch looking for Paul Chefurka refs after +John Poteet shared some links earlier.

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