Scientists recently tested the effect of funneling carbon dioxide-rich exhaust toward a vegetable garden, and the results were (literally) huge.
A team of agricultural researchers at Boston University came up with the idea while brainstorming ways to make urban environments more sustainable. As cities become denser, humans require more resources, and climate change worsens, buildings will likely require modifications to serve multiple purposes and recycle resource byproducts. Busy lecture halls with indoor climate control systems, it turns out, are a perfect example of such modifications. The building's exhaust contains high levels of CO2, which plants convert to energy during photosynthesis.
Rather than releasing that CO2 into the environment uncontrolled, the researchers thought to direct their building's exhaust toward an experimental rooftop garden. The garden, nicknamed BIG GRO, contained beds of spinach and corn. While both are common edible plants, corn photosynthesizes in a way that requires less CO2 than spinach, allowing it to serve as a control while the spinach ideally revealed the system's advantages and disadvantages.
[...] The plants that had been exposed to the building's exhaust had grown up to four times larger than the plants placed next to a control fan. The spinach in particular had quadruple the biomass of its control; the corn, despite its own special brand of photosynthesis, had two to three times the biomass of its control. Though the corn's growth causes the team to think the extra CO2 wasn't the only reason their experiment succeeded, there's now concrete reason to believe rooftop farms like BIG GRO could benefit from buildings' otherwise wasted exhaust.