Life Cycle Assessment of the Cultivation of Lettuce in a Hydroponic System Using the Nutrient Film Technique

Author

Raquel Jordan, Clemson UniversityFollow

Date of Award

8-2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Science

Committee Chair/Advisor

Michael Carbajales-Dale

Committee Member

David Ladner

Committee Member

Jeffrey Adelberg

Abstract

Hydroponic systems are an emerging method of soilless crop cultivation typically done inside a greenhouse where nutrients are delivered dissolved in water rather than being supplied from the soil. Potential benefits of hydroponic systems include reduced irrigation requirements, higher crop yield per area, and the ability to grow crops year-round in nontraditional areas such as urban settings, cold climates, and sites with contaminated soil. However, hydroponic systems tend to have high energy requirements for lighting and climate control, which can yield significant environmental impacts. To explore the environmental impacts of cultivating lettuce in a nutrient film technique (NFT) hydroponic system, a life cycle assessment (LCA) was conducted based on a case study of a greenhouse farming operation that agreed to provide data for the project. The functional unit was 1 year of production at the greenhouse, or 32603 kg of lettuce. The system boundary was from raw material extraction to when the finished product arrived at the distributor. OpenLCA was used along with the ecoinvent database for modeling. ReCiPe 2016 v1.03, midpoint (H), was the impact assessment method used. The results of the impact assessment for one year of lettuce production were 1.90 x 10⁵ kg CO₂ eq for climate change, 2.27 x 10⁴ m²a crop eq for land use, 1800 m³ for water use, and 44 kg P eq for freshwater eutrophication. Electricity for lighting and climate control (Scope II), and natural gas for heating (Scope I) were the overwhelming contributors to climate change. Land use was mainly from the upstream impacts of cardboard production for packaging, followed by the direct land area that greenhouse facility occupies. Water use was 56% from water loss from the plant via transpiration. Upstream impact from electricity was the second highest contributor to water use. Freshwater eutrophication was driven by electricity. Coal is used in the electricity grid in the Southeast region of the United States, and the treatment of waste from coal mining has freshwater eutrophication impacts. When compared to traditional open-field growth of lettuce, the hydroponic system at the greenhouse facility had higher impacts in all four categories considered. Results of previous studies vary due to differing system boundaries, locations, and electricity grids. The results of the LCA for the greenhouse agree with some studies and disagree with others. The results confirm that electricity for climate control and lighting is a hot spot for the hydroponic cultivation of crops, and that using more renewable energy can decrease the environmental impacts of hydroponics. Further research should be done to refine the results and to be representative of greenhouses of other sizes and locations.

Recommended Citation

Jordan, Raquel, "Life Cycle Assessment of the Cultivation of Lettuce in a Hydroponic System Using the Nutrient Film Technique" (2025). All Theses. 4568.
https://open.clemson.edu/all_theses/4568