As the global population rise, climate conditions get more and more unpredictable, natural resources deplete; cities need to take action in order to sustain healthy living conditions as well as to ensure food safety. Currently, cities are solely dependent on external sources and suburban areas for natural resources and food as well as waste management. This linear metabolism results in cities consuming 60-80% of natural resources and producing 50% of waste globally. (Tsui et al., 2021) This problem can be overcome by introducing urban farming into cities by utilising waste and underused space as a resource for urban food production. Waste can be circulated in the city in order to generate a network of waste producing functions and farms. There are urban farming systems which can digest waste and produce supplements for urban food production. However, the quest of choosing an urban farming system based on existing vacant spaces and waste flows is a complicated task. The complexity is a result of variables in the equation which may effect decision making such as different systems, waste types, vacant space characteristics as well as the size of spaces and the quantity of available waste. Moreover, in sites consisting of numerous vacant spaces and waste sources decision making is even more complex and laborious. If human designers were to perform this task then they would need to iterate countless times for each vacant space, each waste source close to it and each potential urban farming systems. However, when it comes iterating and repeating the same steps, computers are explicitly faster, time-efficient and error free. Therefore a decision making tool which can assist designers to choose urban farming systems based on existing conditions can be a practical resource. This paper investigates how to integrate urban farming into cities by utilising under-used spaces and existing waste sources via using a decision making tool. The design rules and the methodology are formed based on literature review regarding different farming systems, varying waste flows and computational approaches. A prototype of the tool is generated and tested on 2 case studies in order to showcase the potential of such an approach combining food production with waste management.