Spending 50% of the energy you harvest to keep up production isn't something that will fundamentally change life as we know it. A process that produces 100 joules with no energy invested is no different from a process that produces 200 joules that requires you to use 100 joules to extract it. The bottlenecks are still the same for all renewable energy sources - manpower, land, and the geographical locations suitable for the production of this kind of thing.
For things like biodiesel, saying that you need to spend 50% of the energy you harvest to keep up production is the same as saying that you need to double the land over a native calculation that does not use energy consumption at all. Those estimates are typically well below the amount of land we farm today, let alone the land mass of the planet.
Biodiesel production in the US today - 5000 gallons per acre per year. Oil consumption of the planet today - 93 million barrels per day. Combine the two numbers, and you would need 750 million acres, which is around 0.6 million sq km. Double that to account for the 50% of energy figure that you quote, and we are looking at 1.2 million sq km. That amounts to around 10% of global farmland, which is a lot, but not enough to change the way the way the world works.