Why Planting Farms in Skyscrapers Won't Solve Our Food Problems
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One of our colleagues suggested, with his tongue in cheek, an alternative: "What about vertical nuclear energy? We could stack reactors in skyscrapers alongside the farming skyscrapers, to provide the electricity!" Fortunately, no one's going to try that, because just to grow our wheat. we'd have to add another 4000 or so nuclear reactors to the hundred or so currently in the United States.
To have a much greater impact on soil conservation efforts than the displacement of wheat would accomplish, we'd want to take indoors the nation's number-one grain, corn, which occupies about a quarter of our cropped acreage, and some of the most badly abused land. But corn makes wheat's electricity consumption look modest. Because wheat naturally grows mostly in fall, winter, and spring and produces lower yields than summer crops like corn, its light requirement is lower. The U.S. corn crop would require energy for lighting equivalent to 40 times the current US electricity supply.
Maybe trying to satisfy the nation's huge grain requirements with vertical farming is too ambitious. Assume instead that we were to take a more modest approach and grow the national crop of vegetables under lights. If that required a similar level of lighting per unit area to that used for wheat, we would "only" have to double our national electricity generation. But removing all vegetable production from the landscape would preserve no more than 2 percent of our currently cropped soils.
A question of control
Based on its energy requirements for lighting alone, vertical farming would be incapable of substituting for a substantial share of our soil-based agricultural production. But the lighting problem is only the first among many obstacles facing high-rise agriculture. Climate control to achieve suitable growing conditions would add huge energy requirements. And light fixtures would release more energy as heat than as light, which in summer would put huge loads on air-conditioning systems. To maintain the good health of plants grown indoors, humidity and air circulation must be very precisely controlled, often at a high energy cost. And before any of those needs would come the gargantuan resource requirements for construction of the towers themselves.
Then there would be the impracticalities and energy requirements for producing and hauling artificial growth media, fertilizers, water, and other resources hundreds of feet up and getting harvests out of the towers. Pesticides could not be eliminated and would undoubtedly be applied in many situations. If Despommier has ever worked in a greenhouse, he knows that some of the pathogens and insects that damage crops in the field can be excluded, but that many others will flourish. Powdery mildew, aphids, mites, or other pests can easily wipe out greenhouse-grown wheat plants, for example, if chemical control is not used.
The system inevitably would also require an enormous input of manual labor. As a hydroponic model, Despommier points approvingly to 300-plus acres of greenhouses near Willcox and Snowflake, Arizona, in which EuroFresh Farms grows vegetables. Energetically, EuroFresh has no relevance to vertical farming, because it is a horizontal operation that makes good use of Arizona sunshine. But with four employees per cropped acre, it does provide a good example of the large manual labor requirements of a massive, intensive hydroponic operation.
EuroFresh's geographical location is no accident. It lies close to the nation's southern border, and the company employs large numbers of immigrant workers. It also employs inmates from a nearby branch of Arizona State Prison. If EuroFresh is to provide an encouraging example for vertical farming, other questions come to mind. Who will own and control the agricultural high-rises? How and from where will the stoop-labor force for vertical farming be recruited? What will become of the farm families whose central role in the nation's life has been replaced by vertical-farming operations? Will they find themselves migrating to the cities to tend corporate tomato vines?