How to Re-Balance the Nitrogen Metabolism of the Atlanta-Chattahoochee System?

Abstract

Multi-sectoral Systems Analysis (MSA) of the Atlanta-Chattahoochee system is proposed. It has three objectives: (i) to identify the major fluxes of nitrogen (N) entering, leaving, and circulating within an urbanrural system; (ii) to quantify the benefits of implementing changes of technology in that system; and (iii) to assess the relevance, or redundancy of the system’s features – sectors, processes, and flows – for attaining proposed goals for improving the eco-efficiency and ecoeffectiveness of the system. MSA uses Substance Flow Analysis (SFA) to track the paths of N through a structured model comprising five socio-economic sectors, i.e., water, energy, food, forestry, and waste management. It incorporates a set of eco-effectiveness indicators, to assess the health of the nitrogen metabolism of the system, as well as a Regionalized Sensitivity Analysis (RSA) procedure for identifying economic and policy priorities for rebalancing the flows of N. The capabilities of such a framework are illustrated in the context of the Atlanta- Chattahoochee system under different scenarios for three candidate technological solutions: (a) urine separating toilets, (b) pyrolysis of poultry litter, and (c) capturing power plant flue gas for algae production. The results show that MSA can be useful for understanding the nitrogen metabolism of the city-watershed system while also indicating which innovative technologies might be most effective in “re-balancing” that metabolism.