The Planting of Blocks
Recent years have fostered a renewed interest in trying to grow crops in the belly of urban development—the textbook antithesis of agriculture in comparison to its traditional, American roots in rural soil. Cities like Detroit, flush with vacant land and no one eager to fill it, have embraced urban farming as a way to give purpose to otherwise neglected plots while creating fresh produce and the jobs needed to grow it. The city of Boston recently released a call for proposals for three sites to serve as pilot projects for urban farming plots. According to Mayor Manino, urban farming presents an opportunity for local, small scale enterprise that can help fuel new farmer’s markets.
The fascination for farming in cities bears a greats deal of latent merit. For as bountiful as cities are in human capital, they are sinks for natural resources—including food. Virtually all food served in cities is brought in from its surrounding environs to bring sustenance to their high concentration of residents. As a country we have grown accustomed to shipping food as far as it needs to travel in order for it to be continuous and available regardless of its source or growing season. In 2001 the U.S. imported 68.2% of its shellfish, 21.4% of fruit, juices and nuts and 15.5% of vegetable oils.
In the case of cities the very distance that food needs to travel makes even the most sustainably grown produce laced with resources (and associated cost) for packaging and transportation. Studies estimate that it can require up to seven calories of input energy to process and move food for ever one calorie produced. Bringing fresh food closer to its largest source of demand would help further improve the inherent efficiency of cities.
Efficient Doesn’t Always Mean Cheap
Especially in urban environments, the very density-driven demand that makes a sustainable source of food production attractive also makes construction very expensive. The deeper into the city one goes the more demand for consistent food production, but the taller the farm most likely has to be in order to justify the fixed cost of the land that sits beneath it. When all of the factors are gathered together the swift rise of pro forma price tags can quickly extinguish the excitement of potential investors.
But despite how expensive it is to build in the city, it is not a rare event. Even in the recession new high rise towers are built because the programs within them (usually commercial or residential) have developed proven models for generating attractive returns for developers. Using some of these other urban uses as a catalyst for developing test beds for vertical farms could make the first generation of farming centers more viable while creating a residential amenity for a sustainably-minded clientele.
Residential space most likely stands a better chance of being paired with farming square footage. First of all, it rents and sells at a premium compared to its commercial brethren. Vertical green space, though universally attractive, could be valued as more of an amenity to a living room rather than a conference room. The garden wall that was planned for green tower, One Bryant Park, meant to create a green facet of exterior to address the park below, never actually materialized, most likely due to a corporate client wondering how much return there was in such an installation. For the same reason we see more balconies on residential buildings than corporate ones, what could be thought of as miniature greenhouses could be aptly placed next to a home. Here in New York, most tenants are willing to pay some degree of a premium for rooftop space or a private terrace. It seems likely that private gardens could generate a similar demand.
When it comes to building tall structures, there is a certain degree of critical mass that makes expanding the scope of an existing project more economical than starting a new one from scratch. Foundations, a concrete superstructure, elevators, fire stairs and exterior cladding are components that all urban buildings need—including vertical farms. Adding one more service elevator to a bank of three is easier than creating one by itself and other building systems could find similar success. Vertical farming space could take a seemingly parasitic role on new tall buildings in order to make themselves more plausible.
Growing Residential Symbiosis
Then again, the relationship may be much more reflexively beneficial. If a building of apartments and a vertical farm can each be thought of as constructed ecologies, there are numerous ways that a vertical column of green space can play a valuable role in making a building more sustainable. To start, a bar of floor area devoted to planting (say on the southern face where buildings get the most sun and take on the most heat) could serve as a buffer to help control the temperature of the apartments behind them. “Double walls” are becoming more commonplace in architecture today as tools for efficiency. Buildings like the Cambridge Public Library have a pair of walls on the same exterior face with an air space between them whose air flow can be controlled to store or release heat depending on the weather. A column of linked vertical gardens is essentially an occupiable, double-skin wall where moisture and temperature are regulated independently. In the winter, it stores the heat that it captures and keeps the cold farther away from living space to lower its cooling load. In the summer, the stack of air can be vented at the top to move hotter air out of the building.
Plants are commonly known as great natural air filters, making an enclosed garden space an opportunity to filter air coming in or out of the building, not unlike the “orangery” that Thomas Jefferson designed for his home, Monticello. Air can be drawn through the farm to come out cleaner and healthier on the other side—a boon for cities that are often plagued with air quality as a source for ailments like asthma (New York being a prime example).
Having many uses (and reuses) for water, it only makes sense for buildings to harvest all of the rainwater they can to reduce the amount of potable freshwater they need for non-drinking purposes: flushing toilets, cooling tower make-up, sidewalk cleaning. Plants can find great uses for cisterns full of rainwater but when they’re done with it, the water is just as useful to the building as it was to start with—maybe moreso—but in the process we have cultivated food.
And what to do with this food? One possibility is that apartments on each floor could have garden space (a coveted amenity for many in the city, myself included) that they manage themselves to supplement their own consumption of fresh produce. Another option would be that all of the spaces are collectively managed by a farming company with a portion of the food going to residents and the rest being sold at local farmers markets or to restaurants. In either case, the waste produced could be paired with food waste from the building and composted in the cellar, with the methane produced used to create power via a fuel cell and the compost returned back up to the plants for nutrients—reducing the net waste load on the city around it.
Perhaps the least quantitative but most obvious benefit is who would not want to have a greenhouse outside your living room or kitchen 100 feet in the air? A room with a city view is great but a tempered garden with a city view has to be fantastic. Even if it came at a premium I have to believe there would be plenty of buyers interested in having fresh food and green space as part of their city home.
Though the farming space would be a smaller part of the floor plate than a holistic vertical farm would yield, its construction would also be a fraction of the cost. Another reality of theoretical vertical farms is that sunlight would need to be supplemented with ultraviolet bulbs on full floors given the limited amount of square feet that have direct access to the southern face of building. On the contrary, in this model farming is reserved to the prime space on each floor while the rest is made up of homes that can suffice with indirect light from the other three directions. With proven models of maintenance and yield, in time full towers could be financed for food production.
Given the scale of endeavor that vertical farms inherently command, it is difficult for them to get out of their own way towards being realized. Pairing vertical farming with vertical living could give us more food in more cities much sooner. As for what something like this could actually look like? More on that to come…