Potential for nutrient recovery and biogas production from blackwater, food waste and greywater in urban source control systems

In the last decades, the focus in waste and wastewater treatment systems has shifted towards increased recovery of energy and nutrients. Separation of urban food waste and domestic wastewaters using source control systems could aid this increase; however their effect on overall sustainability is unknown. To obtain indicators for sustainability assessments, five urban systems for collection, transport, treatment and nutrient recovery from blackwater, greywater and food waste were investigated using data from implementations in Sweden or northern Europe. The systems were evaluated against their potential for biogas production and nutrient recovery by the use of mass balances for organic material, nutrients and metals over the system components. The resulting indicators are presented in units suitable for use in future sustainability studies or life cycle assessment of urban waste and wastewater systems. The indicators show that source control systems have the potential to increase biogas production with more than 70% compared to a conventional system and give a high recovery of phosphorus and nitrogen as biofertilizer. The total potential increase in gross energy equivalence for source control systems was 20-100%; the greatest increase shown for vacuum-based systems.