If I may offer a science-fictional scenario for techno-cornucopianism, the limit for earth-based society is when it becomes something like a living system which can reproduce its components from the local resources. The elements of carbon, hydrogen, oxygen and nitrogen (CHON) are available just about everywhere in various proportions, and it is essentially impossible to run out of silicon, aluminum, magnesium, and many others because they form such a large fraction of the crust or dissolved oceanic solids.
Energy available to such a society is a substantial fraction of the sunlight reaching Earth's surface. This is many times more than we use today, so even if a society based on such bio-mimic systems must plateau it will do it at a far higher level than the present. The real issue is what happens if it becomes unstable. That depends on how the designers choose to build the system. A conventional industrial model can collapse from inter-dependency on parts, but if the bio-mimic systems are self-reproducing, the technological capability can sustain itself through a collapse of part of the system and rebuild afterward. This is what we've seen with life for hundreds of millions of years.
I believe that our level of understanding will let us get to this state within the next century, perhaps the next 50 years. All we have to do is keep going. Right now our technological systems are in the state of auto-catalytic RNAs dependent on the supply of molecular building blocks from natural processes. When we can synthesize anything we need from soil, air, water and sunlight, we will have broken through a great many resource limits.
We're going to have a contraction of oil supply henceforth, but if we can use electrified rail, battery vehicles and different living patterns to remove the need for that oil supply, we can still live well. Replacing coal with nukes removes most of the impact of electricity on the environment. Project Better Place has a plan for continuing something very close to BAU, though that's not a requirement to avoid a collapse. What we need is the vision (like PBP) and the will to pursue it. "If we don't change the direction we're going, we're likely to wind up where we're headed."
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