Life-Cycle Assessment and Optimization Framework for Sustainable Urban Farming Systems

With the growing population and continuous urbanization, sustainable and secure food production is increasingly important in future urban development. Various advanced farming systems have been developed. The economic performance and environmental impact are important decision criteria for the deployment of such systems. In order to assess and improve the sustainability of urban farming systems, a holistic decision-support framework combining life cycle assessment and optimization is proposed in this work.

After defining the goal and scope of the life cycle assessment and optimization, the life cycle inventory that contains the data of energy and material flows around the system boundary in different phases of the system life cycle is tabulated as the data input for the assessment and optimization of the farming system. The economic performance and environmental impact are evaluated and modeled using the life cycle assessment approach and serve as two objective functions in the optimization of the farming system. Moreover, constraints in the optimization are required to be formulated based on the local market conditions (e.g. demand and price of products, the price of equipment and utilities, and land availability). Decision variables in the optimization including the design of the farming facility, types and amount of crops to be planted and the operating conditions of the farming system can be determined to maximize the economic benefit and minimize the negative environmental impact.

A case study on the design and assessment of a novel modularized urban leafy-vegetable farming system in Singapore utilizing fertilizer derived from beer residue is carried out as a demonstration of the proposed framework. The result of the case study shows the optimized modular vertical farm is promising to be adopted in the urban area for multiple benefits including green and economical urban vegetable supply, waste valorization, and efficient land utilization.