Comparison of environmental condition, productivity, and resources use between GREENBOX and Greenhouse for growing lettuce

Abstract

<b><sc>Abstract.</sc></b> <b>Over 50% of the world's population lives in urban areas, which is only projected to increase, leading to the expansion of food deserts. GREENBOX farming has been proposed to grow fresh produce in urban areas to meet the increasing demand for sustainable and local food production. Studies have shown that GREENBOX technology can provide desired environmental conditions inside the boxes located in urban buildings for growing vegetable crops. This study compared the environmental conditions, productivity, and water consumption between GREENBOX and conventional greenhouses. Two modular GREENBOXES, equipped with LED lighting, hydroponic growing platform, and climate controls, were located in warehouse conditions, and we used a greenhouse bay (glass glazed, equipped with supplemental lighting, and fully controlled by an Argus Titan control system) for comparison purposes. Forty-eight (48) heads of butterhead Rex lettuce (Lactuca sativa) were grown over a 30-day growing cycle. We collected environmental data (light, temperature, relative humidity, and CO₂ concentration), crop growth data (wet weight, dry weight, Leaf Area Index, and Specific Leaf Area), and water consumption, over all four seasons. Both GREENBOXES and the greenhouse provided the desirable environment for lettuce growth, and grew well toward full canopy at harvest. The environmental variables were all within the optimum range for lettuce growth. However, the GREENBOX environment was largely independent of the natural weather and consequently much less variable. The range of the daily temperature variation is only a few degrees in the GREENBOXES, while in the greenhouse was over 20°C. The relative humidity in GREENBOX was mainly in the range of 50-60%, compared to 60-80% in the greenhouse. The CO₂ concentration was slightly lower in the GREENBOXES than in the greenhouse. Statistical analysis revealed a higher level of productivity (but not statistically significant) in the GREENBOX over the greenhouse, with higher values over the warmer seasons (spring and summer). The water use was consistently lower in the GREENBOX. We believe that GREENBOX is advantageous over the greenhouse in urban settings because it can be used in food production to provide similar or better environmental conditions to vegetable crops but do not require any open lands.</b>