At present, anthropogenic systems are synonymous with linear economies that cause wide-spread resource waste and environmental degradation. Urban areas are hotspots for this behaviour due to their high population density and resource consumption. Changing this situation is limited by the lack of a holistic but sufficiently detailed understanding of systems where resource waste is occurring. This study explores the material and substance (nitrogen, phosphorus, and carbon) flow analysis of organic waste and wastewater systems in Christchurch, New Zealand, with the aim of identifying leverage points within the system, which should be targeted for future solutions to encourage circularisation. Results show that the predominant material input into the system is groundwater, infiltrated water, and industrial wastewater. The predominant nitrogen and phosphorus input comes from food products, detergents, green waste, and industrial wastewater. The Christchurch wastewater system was found to be a prime example of a linear economy, where two-thirds of the nitrogen and half of the phosphorus entering the wastewater system is discharged to the ocean. Leakage from the water supply system reduces water resource efficiency, while water infiltration in the wastewater network inflates the quantity of wastewater treated at the centralised treatment plant, limiting nutrient recovery. In the compost facility, 86% of the waste is composted, with one-third of the nitrogen and all the phosphorus exiting as compost, while two-thirds of the nitrogen treated exits through volatilization. The remaining 14% of the organic waste entering the treatment plant is deemed unsuitable for composting. The material and substance flow analysis has resulted in identifying flows with leverage points in the system where there are opportunities to reduce, reuse, or recover materials and substances to encourage circularization. These flows include food product, detergent, unsuitable materials, domestic water supply leakage, wastewater network infiltration, and wastewater treatment plant nutrient recovery
