Elevating Carbon Dioxide in a Commercial Greenhouse Reduced Overall Fuel Carbon Consumption and Production Cost When Used in Combination with Cool Temperatures for Lettuce Production

Greenhouses that are well sealed can result in carbon dioxide (CO 2 ) drawdown and suppressed plant growth. While growers can add supplemental CO 2 , it is unknown how supplemental CO 2 fits within the framework of sustainable crop production in greenhouses. In this study, supplemental CO 2 was used in combination with reduced temperatures to evaluate the productivity of ‘Grand Rapids’ lettuce ( Latuca sativa ) compared with a traditionally maintained, warmer, and well-insulated greenhouse without supplemental CO 2 at a commercial facility. Simulations using Virtual Grower software based on identical greenhouses compared fuel use and carbon (C) consumed because of heating and CO 2 supplementation. Models were verified with measurements in a well-sealed commercial greenhouse; CO 2 quickly decreased to below 300 ppm in a nonsupplemented greenhouse containing plants. Supplemental CO 2 boosted total leaf number and mass of lettuce even though temperatures were maintained 3 °F lower in elevated CO 2 than in the traditional management scenario. Maintaining a cooler greenhouse but adding CO 2 decreased total carbon (C) consumed (by combined fuel use and CO 2 supplementation) by 7% during the 3-month season that required a well-sealed greenhouse. Additionally, fuel savings because of lower temperature set points paid for the cost of adding CO 2 . The use of CO 2 enrichment should be considered as a tool in sustainable systems when its use can counteract the plant growth and development reductions brought on by lowered temperatures.