Comparison of Resource Efficiency of Systems for Management of Toilet Waste and Organic Household Waste

Using a system analysis approach compares different systems for handling and treatment of toilet waste and organic household waste. Design issues considered are source separation of urine, use of vacuum toilets and advanced nutrient recovery processes such as Reverse Osmosis (RO). All of the studied systems have low emissions of eutrophying compounds. Other environmental effects are mainly related to the amount of exergy used at each system. Source separating of urine is favourable if only a moderate (> 50 %) recycling potential for nutrients such as N and K is required. However, if higher recycling potential is required systems using nutrient recovery processes such as RO/evaporator are probably to prefer. For vacuum systems, the maximum amounts of flush water must be below 10 lit/p,d to make them reasonable efficient in terms of exergy consumption. The low-flush systems are less sensitive to the use of flush water.