Solar greenhouses can be promising candidate for CO2 capture and utilization: mathematical modeling

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Solar greenhouses can be considered as efficient places for biological CO2 capture and utilization if CO2 enrichment becomes a common practice there. As CO2 enrichment is applied only when greenhouses are closed, ventilated greenhouses––which represent a large percentage of greenhouses all over the world––cannot be considered for this practice. Consequently, ventilated greenhouses cannot be considered for CO2 capture and utilization. The aim of this paper is to show––through modeling and simulation––that these ventilated greenhouses can be activated for serving as efficient CO2 capture and utilization places if they are kept closed (to apply CO2 enrichment) and used microclimate control methods alternative to ventilation. The paper introduces a realistic mathematical model in which all the processes and phenomena associated with the biological CO2 capture and utilization by photosynthesis inside greenhouses are considered. The model validity and accuracy were ensured through the good agreement of its numerical predictions with the available experimental results in the literature. The effect of different environmental and planting conditions on the CO2 capturing process (the photosynthesis process) is investigated. A case study was chosen to investigate the effects of the cooling method, cooling temperature, planting conditions, and CO2 concentration level on the cumulative amount of captured CO2 which represents the greenhouse capturing performance. The results show that the capturing performance of greenhouse can be enhanced from value as low as 1.0 g CO2/m2 day for ventilated greenhouses with low planting density to a value as high as 140 g CO2/m2 day for high planting density when alternative microclimate control methods and CO2 enrichment are applied, considering the appropriate plant type. Additional benefits besides CO2 capture are also discussed for the possible increase of the plant productivity and possible lowering of water consumption by plants.