Retrofitting Unused Spaces for Urban Agriculture: Transforming a Nonfunctional Cold Room into a Controlled Environment Growth Chamber for Lettuce Cultivation

Growth chambers are vital in controlled environment agriculture (CEA), enabling precise regulation of environmental conditions for year-round crop production, especially in urban areas with limited arable land. This study retrofitted a nonfunctional cold room into a plant growth chamber with controlled temperature, humidity, and CO2 levels to evaluate lettuce (Lactuca sativa) growth under three LED treatments: broad-spectrum white, combined white and far-red, and narrow amber (598 nm). Environmental parameters were controlled at 21 °C during the day and 19 °C at night, with 65% relative humidity, and 800 ppm CO2. After 40 days, plants under combined white and far-red LEDs produced the tallest shoots (21.8 ± 0.3 cm) and highest leaf count (23.7 ± 0.9). No significant differences were observed among treatments for fresh mass, dry mass, head diameter, or relative chlorophyll content. The findings demonstrated the feasibility of retrofitting a nonfunctional cold room into a controlled environment growth chamber capable of supporting lettuce cultivation under the tested conditions.