Life cycle assessment of treatment and handling options for a highly saline brine extracted from a potential CO2 storage site

Abstract

Carbon dioxide (CO2) injection in deep saline aquifers is a promising option for CO2 geological sequestration. However, brine extraction may be necessary to control the anticipated increase in reservoir pressure resulting from CO2 injection. The extracted brines usually have elevated concentrations of total dissolved solids (TDS) and other contaminants and require proper handling or treatment. Different options for the handling or treatment of a high-TDS brine extracted from a potential CO2 sequestration site (Mt. Simon Sandstone, Illinois, USA) are evaluated here through a life cycle assessment (LCA) study. The objective of this LCA study is to evaluate the environmental impact (EI) of various treatment or disposal options, namely, deep well disposal (Case 1); near-zero liquid discharge (ZLD) treatment followed by disposal of salt and brine by-products (Case 2); and near-ZLD treatment assuming beneficial use of the treatment by-products (Case 3). Results indicate that energy use is the dominant factor determining the overall EI. Because of the high energy consumption, desalination of the pretreated brine (Cases 2 and 3) results in the highest EI. Consequently, the overall EI of desalination cases falls mainly into two EI categories: global warming potential and resources–fossil fuels. Deep well disposal has the least EI when the EI of brine injection into deep formations is not included. The overall freshwater consumption associated with different life cycle stages of the selected disposal or treatment options is 0.6–1.8 m3 of freshwater for every 1.0 m3 of brine input. The freshwater consumption balance is 0.6 m3 for every 1.0 m3 of brine input for Case 3 when desalination by-products are utilized for beneficial uses.