S06 - Session O1 - Experimental and numerical assessment of carbon sequestration in horticultural crops inside a Mediterranean naturally ventilated greenhouse.

Authors: Francisco Domingo Molina Aiz *, Mireille N. Honore, Hicham Fatnassi, Alejandro López-Martínez , Diego Luis Valera-Martinez, María ngeles Moreno-Teruel

The main objective of this work was to evaluate the CO 2 sequestration of two greenhouse horticultural crops. The spatial distribution of the photosynthetic activity of crops in a naturally ventilated greenhouse was modellised using Computational Fluid Dynamics (CFD). The CFD model allowed to simulate plants photosynthesis distribution from the solar radiation and CO 2 concentration. Simulations were validated through measurements carried out in a multispan greenhouse of the University of Almeria (Spain), equipped with new side vents and an internal double roof. A tomato crop was cultivated from February to July, and cucumber from September to December 2021. Measurements in the greenhouse included the main outside and inside climate parameters (air temperature, humidity and velocity, solar radiation and CO 2 concentration), photosynthetic activity and photosynthetically active radiation (PAR) in plant leaves. Three experimental methods were used to estimate carbon sequestration: - Carbon plant content was calculated from the annual dry weight of fruits, leaves and shoots. - The instantaneous carbon sequestration was estimated from the CO 2 absorbed by plants measured with a portable photosynthesis analyser and from the leaf area index. - The whole-canopy instantaneous carbon absorption by crop photosynthesis was estimated using the greenhouse as an open-chamber system, measuring air velocity and CO 2 concentration in all ventilation openings. We obtained a carbon sequestration of 298-348 g/m 2 for the tomato in spring-summer cycle and 383-417 g/m 2 for the cucumber in autumn-winter. Maximum photosynthesis rate for the tomato was of 14.1 μmol CO 2 m -2 s -1 with a PAR of 590 μmol m -2 s -1 at the leaf level (measured in June). For the cucumber, the maximum photosynthesis was 15.4 μmol CO 2 m -2 s -1 with 649 μmol m -2 s -1 of PAR (in November). The lower values of PAR radiation and photosynthesis in the summer was a consequence of the whitewashing of the greenhouse cover.