Environmental impact and nutritional improvement of elevated CO₂ treatment: A case study of spinach production

The agriculture sector is known to be the one of the major contributors to global greenhouse gas (GHG) emissions. At the same time, global climate changes have affected the agriculture sector. In order to strengthen the sustainable development of agriculture, it is important to promote environmentally friendly farming and simultaneously increase the economic value. To improve the productivity of agriculture, technical advancements have occurred. Among those, we have focused on CO₂ treatment in cultivation. We aimed to clarify the effectiveness of the elevated CO₂ treatment of spinach based on GHG emission and the economic value using the eco-efficiency score. We assumed that nutrition could represent the value of the vegetable. We measured weights, vitamin C, and CO₂ emissions of elevated CO₂ treatment and conventional production. We used life cycle assessment (LCA) to estimate CO₂ emissions. CO₂ emissions of a 100-g bouquet of spinach were estimated from agricultural inputs, farming, transport, and distribution center processes at a model spinach farm in Japan. CO₂ emission of elevated CO₂ treatment was 29.0 g-CO₂, and was 49.0 g-CO₂ for conventional production. The net weight of a bouquet of elevated CO₂-treated spinach was 1.69-fold greater than that of conventional production. Vitamin C per 100 g spinach produced via elevated CO₂ treatment was 15.1 mg, and that of conventional production was 13.5 mg on average. Finally, based on the above results, we assessed the eco-efficiency scores of the elevated CO₂ treatment and conventional production of spinach, enabling integration of the nutritional value and the environmental impact. The score showed that elevated CO₂ treatment (0.76) was 2.9-fold more efficient than conventional production (0.26). This study suggested that elevated CO₂ treatment could enhance growth and nutritional value of spinach, and further contribute to CO₂ reduction.