Mitigating Climate Change at the Carbon Water Nexus: A Call to Action for the Environmental Engineering Community

Abstract

Environmental engineers have played a critical role in improving human and ecosystem health over the past several decades. These contributions have focused on providing clean water and air as well as managing waste streams and remediating polluted sites. As environmental problems have become more global in scale and more deeply entrenched in sociotechnical systems, the discipline of environmental engineering must grow to be ready to respond to the challenges of the coming decades. Here we make the case that environmental engineers should play a leadership role in the development of climate change mitigation technologies at the carbon-water nexus (CWN). Climate change, driven largely by unfettered emissions of fossil carbon into the atmosphere, is a far-reaching and enormously complex environmental risk with the potential to negatively affect food security, human health, infrastructure, and other systems. Solving this problem will require a massive mobilization of existing and innovative new technology. The environmental engineering community is uniquely positioned to do pioneering work at the CWN using a skillset that has been honed, solving related problems. The focus of this special issue, on “The science and innovation of emerging subsurface energy technologies,” provides one example domain within which environmental engineers and related disciplines are beginning to make important contributions at the CWN. In this article, we define the CWN and describe how environmental engineers can bring their considerable expertise to bear in this area. Then we review some of the topics that appear in this special issue, for example, mitigating the impacts of hydraulic fracturing and geologic carbon storage, and we provide perspective on emergent research directions, for example, enhanced geothermal energy, energy storage in sedimentary formations, and others.

Reactive Transport Simulation of Fracture Channelization and Transmissivity Evolution

“…S ubsurface rock formations increasingly play a role in environmental protection because they can be used for containment of greenhouse gases as in geologic carbon sequestration, for disposal of voluminous waste streams, for extraction of renewable energy as in geothermal systems, and as reliable barriers in oil and gas operations (Smith et al , 2013a; Clarens and Peters, 2016; Mouzakis et al , 2016; Soong et al , 2018). Fractures in subsurface formations are of interest because they may enable fluid migration especially in the tight formations that serve to contain fluids and inhibit their migration (Cherubini et al , 2013; Dearden et al , 2013; Ramadas et al , 2015; Day-Lewis et al , 2017).…”

Targeted Permeability Control in the Subsurface via Calcium Silicate Carbonation

“…The experimental setup for these experiments was described previously. 31 Briefly, 15 mg of pseudowollastonite powder was placed in 0.75 cm 3 Teflon boats with 1 g of sand and 0.5 mL of DI water, either with or without 0.1 M NaOH. The samples were reacted in a stainlesssteel pressure vessel at 1.1 MPa CO 2 at a given experimental temperature and time.…”

“…The subsurface environment has traditionally been the source of most of our energy but a growing number of applications seek to use it to offset the environmental impacts of energy production. − Geologic carbon storage (GCS), enhanced geothermal energy (EGS), and compressed air energy storage leverage some of the unique characteristics of the subsurface (e.g., its size, temperature, and pressure) to store fluids or extract heat. − Because of the pressure gradients associated with fluid injection/production, strategies are needed to control fluid flow in target formations. Geophysical and/or geochemical alteration of the subsurface environment can create new and undesirable pathways for fluid migration. , In EGS, these are often referred to as thief zones, and undermine the economic viability of production.…”

Hyperbolic Reformulation Approach to Enable Efficient Simulation of Groundwater Flow and Reactive Transport

“…Reactive transport models (RTMs) are widely used to investigate coupled physical and biogeochemical processes in natural and engineered systems [28]. Mechanistic insights gained with RTMs have broad relevance for water, energy, and the environment with applicability from the critical zone to the deep subsurface [18,6]. RTM simulations are underpinned by the numerical solution of a set of mixed differential and algebraic equations that often have significant computational costs [28].…”