I would like to address this from a slightly different perspective. Energy is the great enabler. With sufficiently cheap energy this could be viable, possibly e

I would like to address this from a slightly different perspective. Energy is the great enabler. With sufficiently cheap energy this could be viable, possibly even for staple crops. In addition, cheaper energy would make available many other processes which are currently cost-prohibitive and greatly assist in raising the standard of living of every human on the planet. Too much attention is given to classifying energy sources as "renewable" or "green", rather than the less restrictive criteria of sustainability and cost. As an example, fission power with a closed fuel cycle, using either uranium or thorium and possibly incorporating seawater extraction could accomodate all of humanity's energy demands for hundreds of millenia at current consumption rates. Nuclear power is already fairly cheap, but I do not think it overly optimistic to expect that economies of scale and automation could make it much cheaper. Yet the United States still refuses to even reprocess spent fuel, and one of the most promising projects -- the Integral Fast Reactor -- was cancelled in 1992 by the Clinton presidency when it was almost complete.