Environmental impact from circular and self-sufficient neighbourhoods from a life-cycle perspective

Increased self-sufficiency and circularity are often presented as means to decrease the environmental impact from urban resource management, but more knowledge is needed about how this approach in fact compares with conventional systems from a life-cycle perspective when resource consumption and emissions from both the production and for running the processes are included. This paper presents the results from a life-cycle assessment for energy, water, and wastewater systems in a Swedish, urban neighbourhood where local, more self-sufficient and circular systems, including solar power, rainwater harvesting, and resource recovery from wastewater, were compared to conventional, centralized systems. The analysis revealed that the cases with local systems had a lower marine eutrophication and land use impact, but they did not decrease the environmental impact in terms of global warming, mineral resource depletion, and freshwater eutrophication in this site with well developed, efficient conventional systems. There were however differences between the subsystems, such as a lower global warming potential for local wastewater management due to avoided impacts from resource recovery. Local systems also had advantages under certain conditions, such as in neighbourhoods with large infrastructure networks per person and long distances to connect to the existing infrastructure grids. For planners and decision-makers, this study indicates that self-sufficiency is currently rather motivated by other benefits than decreased environmental impact in places with similar conditions to this study. It also highlights that these systems are more worthwhile from an environmental perspective in the above-mentioned conditions or in sites with larger environmental impact from the conventional systems. For producers, some key areas for improvement to decrease the environmental impact include production of photovoltaic modules and batteries for electricity, leakage of refrigerant from heat pumps for the heat supply, production of the storage tank for rainwater collection, production of expanded clay as filter material for the greywater treatment, production of sodium hydroxide for blackwater treatment, and emissions in operation for both greywater and blackwater treatment.