Investigating the energy-water-carbon nexus of mega-scale chemicals production from Appalachian shale gas

This paper is concerned with techno-environmental modeling of large-scale chemicals production from Appalachian shale gas and investigates its environmental impacts. We first develop shale gas supply and plant design models to estimate pipeline distances, numbers of wells, well-sites, gathering systems needed in the near/mid-term, as well as the plant-level energy and materials balances. Next, we conduct a life cycle analysis (LCA) to evaluate the energy-water-carbon nexus in terms of energy consumption (eta(le)), freshwater footprint (eta(lw)), and greenhouse gas emissions (eta(ghg)). The results show, based on a mass-based allocation approach, the eta(le), eta(lw), and eta(ghg) are 13.8-17.2 GJ/t olefins, 3.31-4.28 kg/kg olefins, and 0.83-1.17 kg CO2-eq/kg olefins, respectively. However, if we use an economic value based allocation method, these values are updated to 37.4-28.7 GJ/t olefins, 7.28-9.42 kg/kg olefins, and 1.80-2.49 kg CO2-eq/kg olefins, respectively. The values of eta(ghg) indicate that shale gas can be categorized as a low-carbon feedstock based on a mass-based allocation approach, or high-carbon feedstock based on an economic value-based allocation approach.