The cost–greenhouse gas emission nexus for water distribution systems including the consideration of energy generating infrastructure: an integrated conceptual optimization framework and review of literature

The increased release of greenhouse-gas (GHG) emissions associated with human activities causing climate change is one of the most significant problems faced by human-kind. Water distribution systems (WDS), whilst providing an essential service to society, are responsible for the generation of significant amounts of GHGs. In response, the minimization of GHG emissions associated with WDSs has become a research focus. In this paper, a critical review of previous research is provided, summarizing research progress and highlighting research needs in this emergent and important area. This is done within the context of the water distribution system cost-emissions nexus (WCEN) conceptual framework, which is a novel conceptual framework that considers the interaction between all components required to accurately evaluate the costs and greenhouse gas (GHG) emissions associated with water distribution systems (WDSs) in an integrated fashion. Key findings from this review indicate that future research should (1) include the use of time-dependent emissions factors (EFs), which would allow the scheduling of pumps at times of lower emissions intense energy to be considered; (2) include the modeling of seasonally variable water demands; (3) include greater consideration of the hydraulic simulation process, such as using seasonal extended period simulations; (4) include greater consideration of the management of pumping operations at the design stage, instead of solely focusing on changes in infrastructure design to reduce costs and GHG emissions; (5) include consideration of the effects that external policies, such as carbon taxes and present value discounting, have on the trade-offs between costs and GHG emissions.