Climate change, dwindling resources, and population growth are the most hotly debated issues of the 21st century. However, these three conditions are interdependent, and they have conspired to create a looming crisis in global food production. The most repeated statistic is that the earth's population will increase from 7.2 to 10 billion people by 2050, with half of them living in cities. The consensus among prognosticators is that natural resources, particularly water, will be severely depleted in many regions in the world before 2050. Add recurrent droughts, biblical floods, and food-borne diseases, and the global food supply may already be stressed to its limits.
Corporations, governments, and universities are investing tremendous amounts of money in and effort on developing new technologies for a range of solutions. The most intense efforts of late involve controlled-environment agriculture (CEA). Aquaculture, aquaponics, and hydroponics are types of CEA that have been around for decades. New techniques, particularly vertical farming and building-integrated agriculture (BIA) have more recently gained traction and captured the public's imagination. Meanwhile, mainstream media report on every CEA experiment, from the far-fetched to the practical.
Both vertical farming and BIA fit easily into current trends in urban design. Taller buildings are being touted as the architectural solution to achieve the urban density necessary for a sustainable future. Farming vertically follows the same logic as furthering urban density—much more production on a much smaller footprint. It's being tried in Singapore, Canada, Sweden, and increasingly in the U.S. Dickson Despommier, professor of microbiology and public health in environmental sciences at Columbia University, is credited with coining the term. His 2010 treatise, The Vertical Farm: Feeding the World in the 21st Century, is both popular and somewhat controversial. Despommier believes that multi-storied farms in densely populated cities "offer the sustainable production of a safe and varied food supply (year-round crop production)."
If Despommier's thesis is controversial, it's because not everyone believes that growing vertically in cities is economical or practical. "The horticultural viewpoint is complex and limiting, especially regarding the location of CEA enterprises," explains Cary A. Mitchell, professor of horticulture at Purdue University. "Plants are completely dependent upon light, temperature, water, mineral nutrients, and carbon dioxide. Without enough of any of these environmental factors, crop production and yield go nowhere. Energy for lighting and thermal control can be showstoppers, depending on cost and, again, location. Thus, lighting becomes a major limiting factor, especially in urban areas with high electrical rates."
And yet Mitchell, who has worked with NASA on growing crops in space, is involved in looking for ways to solve the energy-consumption issue, which is critical to the success of vertical farming. Purdue was part of a collaboration with the University of Arizona, Michigan State, and Rutgers to study the potential of LEDs in greenhouses, funded in part by a Specialty Crop Research Initiative grant from the USDA. Nine-foot-tall towers fabricated by ORBITEC, the project's industrial partner, were erected to grow high-wire tomatoes. They studied plants lit with LEDs and high-pressure sodium lamps and discovered that the yield was the same no matter which lighting source was used. However, the LEDs used about 25 percent of the energy of traditional lamps. This reduction in energy consumption is critical to the success of any CEA system.
Building-integrated agriculture is a harder sell right now. In this scenario, occupants work in mixed-use high-rises enclosed by a vertically integrated greenhouse (VIG). The facades of such buildings have double skins, creating a void within which trays containing plants can be suspended on cables. Planting and harvesting occur at the bottom level of systems modules that can rise as high as 10 or 20 stories. An adaptive control system alters the angles between rows of plants in the manner of a venetian blind, maximizing solar absorption diurnally and seasonally. Occupants benefit from solar mitigation—and perhaps psychological comfort.
New York–based architects Kiss + Cathcart have designed several successful VIG prototypes for hydroponic food production but are still looking for an opportunity to go beyond demonstration projects to real commissions. "It is not easy to find the right project and a client open to this kind of innovation," admits Kiss, "but I believe we will have one or more projects in the coming year that qualify." It does seem reasonable to think that a hybrid application such as this, with office workers and crops sharing the same area, would work well and have a smaller footprint.
Advocates of vertical farming believe that it will replace the single-story greenhouse, which has been the dominant CEA paradigm for decades. "Evolution of CEA will largely be determined by economics—what makes sense and what makes money!" says Mitchell. "If a magical new plant-based food source—call it 'druthers'—were to be discovered that satisfies all of the health and nutritional requirements of the human diet and could be grown productively in CEA, the entrepreneurial human spirit would go viral and produce druthers wherever and however it would be profitable. Let's just hope that the crop will be environmentally friendly and not promote more population growth, which is the real problem!"