For the Limits to Growth archetype, the leverage point is to remove the limiting condition, an approach that is sometimes referred to as “removing the bottleneck.” In this case, the limiting condition is the available resources (Fig. 2). One strategy to address this leverage point is to increase available resources by incorporating renewable and locally accessible resources. To be specific, the implementation of geographically appropriate wastewater-based resource recovery systems can increase available resources because such systems provide alternative sources for water, energy, and nutrients, other than virgin sources. Technology innovations are promoted in order to synergize the recovery of resources, including water, energy, and nutrients with the treatment of human-generated wastewater [
8,
40–
43]. The use of reclaimed wastewater for agriculture irrigation is a strategy that is now implemented worldwide: 2.0 ×10
5–4.5 ×10
5 km
2 in the world are now irrigated with reclaimed wastewater [
16]. Wastewater also contains nitrogen and phosphorus from human waste and food [
7,
44]. Small cities in developing regions surrounded by agricultural zones provide great opportunities for reclaiming both water and the nutrients embedded in wastewater [
44]. In terms of energy, the embedded energy content of typical municipal sewage in the US has been estimated to be 1.74–1.93 kW·h·m
-3 or 0.45–0.50 kW·h per 1000 gallons (assuming 500 mg·L
-1 chemical oxygen demand (COD)) [
45,
46]; this value is several factors greater than the energy expenditure values reported for the conventional treatment of wastewater (0.3–0.6 kW·h·m
-3) [
47,
48]. Thus, it may be possible for municipal wastewater treatment to achieve energy neutrality or even net energy production through onsite energy generation technologies [
46,
49] and continued use of sanitation technologies that make use of photosynthesis [
44].