It stands to reason that since we breathe in oxygen and exhale carbon dioxide, which plants utilize to generate glucose for sustenance, our breath may serve as fertilizer. Indeed, according to Boston University researchers who recently studied the use of carbon dioxide from classrooms as fertilizer for their rooftop garden.
According to Popular Mechanics, the study’s authors used rooftop exhaust vents from a school building to recycle carbon dioxide for use by plants in an experimental BIG GRO rooftop garden. They discovered that some of the spinach plants in the same area grew to be four times the size of a control group.
According to a news statement from the study’s principal author, Sarah Buckley, who is currently a student at the University of Cambridge, “We wanted to see whether there was a resource in buildings that was underutilized that might be exploited to produce plants in rooftop farms.” The success of rooftop farms and the consequent viability of their installation atop buildings may be increased by creating more favorable conditions that encourage development.
The research was published in Frontiers in Sustainable Food Systems under the title, “Enhancing crop growth in rooftop farms by repurposing CO2 from human respiration within buildings.”
According to the study, an increase in vegetation in metropolitan areas could help with some of the environmental issues associated with farming and pollution.
The researchers divided their maize and spinach plants into two groups: one that received carbon dioxide exhaust fanning and the other that did not. Although both are quite widespread and tasty, corn and spinach were chosen because they each have a unique photosynthetic pathway adaptation that enables them to carry out unique versions of the light-independent processes.
In comparison to spinach plants close to the control fan, those next to the two rooftop exhaust vents that fanned them with carbon dioxide doubled their biomass. The spinach still expanded to be twice the size of the control plants even after strong winds limited the amount of carbon dioxide that reached the plants, but there are still some unanswered problems.
According to Buckley, there are still a lot of features of this system that need to be figured out before it can be put into use, like the best air application design and the potential size of the boosted growth effect. Additionally, growth slows down as wind speed rises, therefore the ideal wind speed would have to be determined and incorporated into the system design.
The study’s findings suggest preliminary support for a theoretical system that would introduce a more circular carbon cycle within buildings by diverting high concentrations of CO2 from human respiration to a rooftop farm, where it could be put to practical use to grow food that humans could consume and breathe in again. In order to increase the feasibility of rooftop farms as an urban greening technique, plant growth should be improved. This will make them more productive and maybe able to withstand harsher circumstances.
According to Popular Mechanics, the researchers monitored the carbon levels on the rooftop and in the 20 study-related classrooms. According to Buckley, the classrooms and rooftop exhaust vents both had elevated carbon levels when people were present inside the facility.
According to Buckley, CO2 levels typically exceed the acceptable limit of 1,000 parts per million in classrooms and 800 parts per million, which is high enough to promote plant growth near rooftop exhaust vents.
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However, not all growth outcomes were indisputably caused by carbon dioxide exposure. In contrast to spinach, which has a similar photosynthetic system, maize has a distinct photosynthetic pathway, therefore it benefits less from carbon dioxide. For instance, the corn exposed to the exhaust fans was two to three times larger than the control plants. The elevated temperatures from the exhaust fan may have contributed to its rapid growth.
In a recent study conducted by French scientists and published in the journal Trends in Plant Science, The decline of plant mineral nutrition under rising CO2: physiological and molecular aspects of a bad deal, it was discovered that plants like spinach grown in environments with higher carbon dioxide concentrations have lower nutrient levels. These plants use the most prevalent C3 photosynthesis pathway, which is the pathway used by almost all trees.
Depending on the amount of carbon dioxide, these plants may contain five to twenty-five percent less potassium, iron, and other minerals. This may suggest that as carbon levels rise due to global warming, plants may become less nutrient-dense. However, the French study found that an increase in plant biomass would still be advantageous for lowering atmospheric carbon dioxide levels and assisting with current food needs.
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Buckley hopes that the study carried out by her research group will result in the BIG GRO system being improved and used with rooftop farms and gardens.
Hopefully, additional rooftop farms will be erected if that occurs. According to Buckley, they may offer a wide range of environmental and social advantages, including energy savings for the building, carbon drawdown, climate mitigations, urban heat reduction, opportunities for building communities, local food production, and advantages for aesthetic and mental health.