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Carbon dioxide (CO2) concentrations affect the growth rate of plants by increasing photosynthesis. Increasing CO2 in controlled environment agriculture (CEA) provides a means to boost yield or decrease daily light integral (DLI) requirements, potentially increasing profitability of growing operations. However, increases in carbon dioxide concentrations are often correlated with decreased nutritional content of crops. The objectives of this experiment were to quantify the effects of carbon dioxide on the growth, morphology, and nutritional content of two lettuce varieties, ‘Rex’ and ‘Rouxai’ under four CO2 concentrations. Applied CO2 treatments were 400, 800, 1200, and 1600 ppm in controlled environment chambers with identical DLI. Lettuce was germinated for eight days in a greenhouse, then transplanted into potting mix and placed in a growth chamber illuminated by fluorescent lights. After 21 days, lettuce was destructively harvested, and fresh weight and plant volume were measured. Anthocyanins, xanthophylls, chlorophyll, and mineral concentration were measured. The lettuce fresh and dry weight increased with increasing CO2 concentrations, with the greatest increases observed between 400 and 800 ppm, and diminishing increases as CO2 concentration further increased to 1200 and 1600 ppm. Violaxanthin was observed to decrease in ‘Rouxai’ with increasing CO2 concentration. Largely, no significant differences were observed in lutein, anthocyanins, and mineral content. Overall, increasing concentrations of carbon dioxide can significantly increase the yield for lettuce in controlled environments, while not significantly reducing many of the nutritional components. 

In recent years, new forms of high-tech controlled environment agriculture (CEA) have received increased attention and investment. These systems integrate a suite of technologies – including automation, LED lighting, vertical plant stacking, and hydroponic fertilization – to allow for greater control of temperature, humidity, carbon dioxide, oxygen, and light in an enclosed growing environment. Proponents insist that CEA can produce sustainable, nutritious, and tasty local food, particularly for the cities of the future. At the same time, a variety of critics raise concerns about its environmental impacts and energy use, high startup costs, and consumer accessibility challenges, among other issues. At this stage, however, relatively little research has explored actual consumer knowledge and attitudes related to CEA processes and products. Guided by theories of sense-making, this article draws from structured interviews with local food consumers in New York City to examine what people know and think about high-tech CEA. From there, it explores the extent to which CEA fits into consumer conceptualizations of what makes for “good food.” Key findings emphasize that significant gaps in public understanding of CEA remain, that CEA products’ success will depend on the ability of the industry to deliver on its environmental promises, and that concerns about “unnatural” aspects of CEA will need to be allayed. Given the price premium at which high-tech CEA products are currently sold, the industry’s expansion will depend in large part on its ability to convince value-oriented food consumers that the products meet the triple-bottom-line of economic, social, and environmental sustainability goals. 

Lighting is a major component of energy consumption in controlled environment agriculture (CEA) operations. Skyscraper farms (multilevel production in buildings with transparent glazing) have been proposed as alternatives to greenhouse or plant factories (opaque warehouses) to increase space-use efficiency while accessing some natural light. However, there are no previous models on natural light availability and distribution in skyscraper farms. This study employed climate-based daylight modeling software and the Typical Meteorological Year (TMY) dataset to investigate the effects of building geometry and context shading on the availability and spatial distribution of natural light in skyscraper farms in Los Angeles (LA) and New York City (NYC). Electric energy consumption for supplemental lighting in 20-storey skyscraper farms to reach a daily light integral target was calculated using simulation results. Natural lighting in our baseline skyscraper farms without surrounding buildings provides 13% and 15% of the light required to meet a target of 17 mol·m−2·day−1. More elongated buildings may meet up to 27% of the lighting requirements with natural light. However, shading from surrounding buildings can reduce available natural light considerably; in the worst case, natural light only supplies 5% of the lighting requirements. Overall, skyscraper farms require between 4 to 11 times more input for lighting than greenhouses per crop canopy area in the same location. We conclude that the accessibility of natural light in skyscraper farms in dense urban settings provides little advantage over plant factories. 

We assess the landed costs and selected environmental outcomes of conventional field-based and representative CEA supply chains (greenhouses and plant factories) for leaf lettuce delivered to wholesale markets in two US cities. Simulation modeling using heat balance methods was used to assess CEA energy use. Landed costs of field-produced lettuce from California were less than half those from CEA systems. “Best case” analysis suggests few plausible assumptions under which urban-based CEA supply chains have landed costs comparable to field-based supply chains. Energy use and Global Warming Potential (GWP) were also generally larger for CEA supply chains, although a CEA greenhouse had only slightly higher values for GWP if located near its delivery location. Additional analysis of more automated systems in peri-urban areas is merited.