A recent Economist article asks the question of vertical farming, "Does it really stack up?" In theory, it's a win-win-win concept for the environment, feeding growing urban populations locally, and increasing space for agriculture without more land use. But the reality is that vertical farming is costly energy-wise due to the need for artificial lighting and insufficient space for renewable energy installations on skyscrapers. While many designs exist, no large scale vertical farm has been built yet. However, Will Allen's Growing Power did receive approval this year from the Milwaukee city planning commission to build a five story greenhouse, perhaps marking a step toward the fruition of the first vertical farm.