Network Optimization Model for a Sustainable Supply Network for Greenhouses

Meeting the demand for food in arid and water-scarce regions can be economically and environmentally challenging. Uncertainties related to climate change and global warming exacerbates technical challenges for efficient food production. Protected agriculture in the form of greenhouses grow different types of crops in a controlled microclimate offering better conditions for healthy and profitable production. Moreover, CO2 enrichment has also been proven to increase crop yields at low costs, and can be supplied from burning carbon-based resources and transferring the carbon recovered through pipeline networks or tanks. However, the sustenance of CO2 supply to greenhouses requires compliance with the global sustainability standards, and as such there is a need for economically viable and environmentally-friendly networks for the supply of CO2 required by the greenhouses. The objective of this study is to design an optimum supply chain network for a sustainable supply of CO2 to greenhouses. The framework developed is based on an optimisation model solved using integer linear programing (ILP) aiming to minimise the economic cost associated with the operations of the entire supply chain network serving greenhouses. An environmental assessment is also conducted in quantifying the CO2 offset related to the CO2 utilisation in agricultural greenhouse applications. The proposed model was implemented for a case study based in Qatar, comprising of a set of hypothetical greenhouses placed at various locations; a source of CO2 from a biomass based power plant, a distribution centre, and existing pipeline and roadway networks. GIS optimisation models previously developed for the Qatar case study provide locations for greenhouses, pipeline and road transportation routes for CO2 fertilisation as inputs for the proposed supply chain model. The demand for resources, CO2 transport networks, and the distances between the source and greenhouses were assumed to be the constraints impacting the design of the supply chain network. The results obtained indicate the optimal CO2 supply quantities to the greenhouses following a proposed network of pipelines and road routes, with a minimum associated cost of transportation of approximately 0,09$/kg of CO2.