Research

Our group’s current research focuses on the development of novel nano-scale materials for combined CO₂ capture and conversion as well as innovative CO₂ utilization and storage options based on unique carbonate chemistry involving silicate minerals while recovering valuable materials such as rare earth elements. We are also working on a new concept of urban mining where we recover metals (e.g., copper and gold) and energy from electronic wastes and industrial wastes (e.g., ashes from waste-to-energy plants and slags from steelmaking plants). Founded on these new materials and reaction schemes, we create innovative fuel synthesis pathways using unconventional energy sources such as marine biomass and municipal solid wastes while minimizing environmental impacts, specifically by reducing CO₂ emission. In particular, the combined capture and conversion of CO₂ to dense energy carriers provides innovative long-term energy storage potential that is needed for current intermittent renewable energy systems.

For over a century, society has dumped waste CO₂ into the atmosphere, oblivious to its damage to the environment. Whereas other waste “spills” are directly remediated (e.g., Gulf Oil Spill of 2010) by concerted actions, widespread dumping of CO₂ into the atmosphere remains a staple of modern society. This is because ending this large-scale practice requires a massive reinvention of the global economy. Specifically, we need to create a cyclic CO₂ economy, whereby we mine CO₂ from the air and store it to create negative emissions while converting a fraction of it to goods required by humanity. Because CO₂ in the air is globally uniform, this resource is equitably available to the whole planet.

Park group aims to create a New Circular Carbon Economy by capturing and converting greenhouse gas CO₂ into platform molecules for current and future fuels, chemicals and polymers, nutrients, and pharmaceuticals needed by humanity in a carbon-neutral, and eventually, carbon-negative manner. Coupling direct air capture CO₂ with a hybrid electro-bio catalytic CO₂ conversion technology is a truly transformational approach towards negative emission technologies (NETs) that has a great potential to achieve great carbon and energy efficiencies. A cyclic carbon economy was not possible in the past, since it requires cost-effective renewable energy. With the recent rapid deployment of solar and wind energy, there is now a great synergy between renewable energy and CO₂-to-chemicals and fuels technologies to replace fossil carbons in our materials, chemicals, and fuel with CO₂ harvested from the air.

Our convergent research toward circular carbon engineering aims to integrate DAC, bio- and electro-chemical disciplines to create highly integrated, hybrid reaction systems that can work with intermittent renewable energy. We focus on developing novel multi-functional DAC materials, bio/electro-catalysts, and integrated systems needed to capture CO₂ from the air, purify it, and deliver it to liquid media, where hybrid electrochemical and biological reactions will convert the CO₂ into platform molecules and products using renewable energy and carbon-free hydrogen.

• Development of Liquid-like Nanoparticle Organic Hybrid Materials (NOHMs)-based Electrolyte Systems for Combined CO2 Capture and Conversion
• Next Generation Fiber-Encapsulated Nanoscale Hybrid Materials for Direct Air Capture with Selective Water Rejection
• Development of NOHMs with Encapsulated Design for Innovative Direct Air Capture
• Encapsulated Metal-Organic Frameworks (MOFs) for unique MOFs Delivery System for CO2 Capture and Improved Long-term Stability
• Energy-efficient regeneration of CO2 capture materials via non-thermal energy transfer

Innovative Carbonate Chemistry for Sustainable Built Environment and Unconventional Resource Recovery

Engineered carbon mineralization is better known as a potential technology for storing CO₂ with a great long-term stability. Geologic storage is an important component of global efforts to mitigate emissions and reduce the concentration of atmospheric carbon dioxide. Permanent, solid storage of CO₂ in inert, non-toxic environmentally benign minerals, via carbon mineralization in mafic and ultramafic rocks, has long been considered as a storage option, in part because by storing it in solid state in subsurface environments, it may reduce the potential cost of monitoring mobile forms of CO₂. Mineralization occurs naturally during weathering of Mg- and/or Ca-rich, Al-poor materials (e.g., “ultramafic rocks” composed mainly of the minerals olivine, serpentine, brucite, and/or wollastonite). In the Park group, we focus on the potential for the same kinds of chemical reactions to be used not only for storage, but for removal of significant quantities of CO₂ from air.

We are motivated by examples of extensive, natural carbon mineralization that occurs during weathering of ultramafic rocks. Most ultramafic rocks at and near the Earth’s surface are “peridotites” that come from the upper mantle, where the most abundant minerals are Mg-rich olivine (Mg_1.8Fe_0.2SiO₄) and pyroxenes (Ca,Mg,Fe)₂Si₂O₆. Mantle peridotite is brought to the surface by plate tectonics together with faulting and erosion. It is very far from equilibrium with the atmosphere and oceans, and reacts rapidly to form Mg-hydrates (serpentine Mg₃Si₂O₅(OH)₄, brucite Mg(OH)₂), iron oxides, and carbonates (magnesite MgCO₃, dolomite CaMg(CO₃)₂, calcite CaCO₃). Our research seeks to make feasible the implementation of subsurface carbon sequestration into solid carbonates at large scales needed for significantly reversing global warming by evaluating the key feedbacks, reaction rates and other basic parameters in carefully controlled experiments and modeling.

Concrete is the most widely used infrastructural material due to its superior mechanical properties and versatility. Unfortunately, concrete and aggregates as well as other construction materials have large environmental footprints including massive CO₂ emissions. Furthermore, our infrastructure is rapidly gaining. Thus, there is a unique opportunity that can address both issues of CO₂ emissions and sustainable construction materials development–utilizing captured CO₂ in the production of construction materials.

Park group members develop sustainable concretes and construction materials that exhibit reduced embodied carbon through partial replacement of cement with end-products of carbon sequestration technology, with tailored physical and chemical properties. Our key scientific and engineering questions are focused on the chemically enhanced extraction of alkaline metals (i.e., Ca and Mg) from industrial wastes (i.e., waste concretes and fly ash and bottom ash from power plants) to form solid carbonates, and their use and behavior in concrete as an alternative binder. The new scientific and engineering advancements and discoveries from these research efforts have led to the sustainable pathways towards the decarbonization of our built environment while incorporating new manufacturing technologies such as 3D printing.

• Carbon mineralization in peridotite for CO₂ removal from air and solid storage: Chemo-mechanical feedbacks and kinetics
• Carbon Storage Assurance Facility Enterprise (CARBONSAFE)
• Assessment of the CO2 Mineralization Potential of Tamarack’s Ultramafic Bowl-Shaped Intrusion
• Sustainable Construction Materials with Integrated Upcycling of Waste Materials and Carbon Sequestration
• A novel approach to CO₂ Brick Production Integrated with Simultaneous Recovery of Rare Earth Elements from Carbon Intensive Industrial By-Products

Recovery of Critical Minerals and Rare Earth Elements for Clean Energy Transition

To achieve the rapid clean energy transition, there is an urgent need for the sustainable supply of energy-relevant critical minerals and rare earth elements. Valuable energy-critical metals such as platinum group metals (PGMs) and Ni occur in low concentrations in mafic and ultramafic ores with complex mineralogy. PGM concentration, for example, is < 5 ppm (g/ton) disseminated in a large number of mineral phases (there are over 350 minerals that carry PGMs). These ores often contain low, but economically important, concentrations of other energy-critical metals such as Co and Cu. Traditional processing routes for these ores are energy and water intensive and require complex flow sheets and large amounts of diverse chemicals. Even then, a significant number of values end up in tailings because these values are disseminated in waste rock and not liberated; adequate liberation would require further extensive comminution which is both highly impractical and vastly uneconomical.  There is thus a long-standing research need for innovative separation and extraction technologies for recovery and purification from both ores and tailings—especially from the latter, which have accumulated in vast ponds for many decades. Yet these mafic and ultramafic ores and their tailings, containing high concentrations of Mg, Ca, and Fe minerals (providing high carbon sequestration potential), provide a unique opportunity for developing innovative technologies in sustainable mining through the combination of energy-efficient carbon mineralization pathways for CO₂ utilization and storage, in addition to renewable energy-driven recovery of metals.

We envision a paradigm shift in sustainable mining by developing a more energy-efficient, highly integrated, renewable-energy-driven CO₂ sequestration and metal recovery technology for ores and especially tailings allowing tandem metal valorization and carbon sequestration. Specifically, our innovative concept aims to develop an autogenous, reactive comminution reactor system using Stirred Media Mills (SMM) that can provide excellent liberation of value minerals from host rock, thereby significantly enhancing their recovery and simultaneously also generate high specific-surface-area Mg/Ca/Fe (or Mg-Ca-Fe) silicate mineral particles for rapid leaching and continuous removal of Si-rich passivation layers on these silicates. In addition, this approach significantly reduces energy consumption in comminution (because the SMM will be operated at low speeds since the objective is not a targeted PSD) and can be coupled with sustainable carbon mineralization, flotation and electrochemical recovery of key energy minerals using selective redox pathways. Park group members also combine novel reactor designs with electrochemical separation technology driven by renewable energy, creating a new pathway to recover energy-relevant materials from a wide range of unconventional resources including electronic wastes and waste-to-energy plant ashes.

• Integrated CO2-facilitated hydrometallurgical and electrochemical technology for sustainable mining and recovery of critical elements from wastes and ashes
• Integrated Reuse and Co-Utilization of Slag, Sludge and Dust With Inherent Heavy Metal Capture and Nanoscale Calcium Carbonate Production as an Enhanced Fluxing Agent in Steel Plants (INSIGHT)
• A novel approach to CO2 brick production integrated with simultaneous recovery of rare earth elements from carbon intensive industrial by-products
• Innovative Stirred Media Mill Reactor with Integrated Carbon Mineralization and Electrochemical Separation of Critical Metals (critical SMM-e)
• Energy-Relevant Elements Recovery from CO2-Reactive Minerals during Carbon Mineralization

Ocean-Based Solutions for Climate Change

We work on a number of innovative approaches to develop ocean-based solutions for climate change mitigation. Since oceans constitute the largest natural sink of CO₂, technologies that can enhance carbon storage, or even CO₂ capture, in the ocean are highly desired. In the Park group, we develop technologies such as alkalinity enhancement and biologically inspired CO₂ hydration reactions that can shift the equilibrium of ocean water to pump more carbon into this natural sink. Our approaches provide valuable insights into how we can harvest and convert CO₂ captured by the ocean into chemicals, fuels, and materials using renewable energy such as off-shore wind. Through these emerging and innovative technologies, organic and inorganic carbon from ocean-based solutions can replace fossil-derived carbon and create a new carbon economy. It is critical to develop these ocean-based CCUS technologies without unintended environmental or ecological consequences, which will create a new engineered carbon cycle that is in harmony with the Earth’s system.

Another emerging area of ocean-based solutions is the use of marine biomass as bioenergy source, also known as blue carbon. Seaweed and salt-tolerant algae are among less investigated types of bioenergy sources that is available worldwide, compared to the global oil distribution. They can also be farmed in regions where algal biomass is currently by using brine instead of freshwater. Compared to terrestrial biomass, seaweed has a high average CO₂ sequestration rate (36.7 ton hectare⁻¹ year⁻¹, seven times greater than that of conventional lignocellulosic biomass), rapid growth rate (harvested up to six times per year even without fertilizer), and does not compete with land-based food crops if grown in the sea.

Thermochemical conversion pathways of biomass (e.g., gasification, pyrolysis and liquefaction) are attractive because of rapid reaction kinetics but are challenged by the need for dry feedstock. Seaweeds and algae that have a high-moisture content (80-90%), generally need to be dried before their conversion. Thus, an effective energy conversion technology that can convert wet and salty biomass into efficient energy fuels and energy carriers (e.g., H₂) with high purity with reduced environmental footprints continues to be desired.

In the Park group, we are investigating an alkaline thermal treatment (ATT) reaction, which directly converts wet and salty seaweeds to high purity hydrogen in the presence of hydroxide (i.e., NaOH) and a gas-reforming Ni/ZrO₂ catalyst. This particular reaction is less studied but very interesting in terms of its moderate reaction conditions (i.e., ambient pressure and temperature < 500 °C) that would allow the development of distributed biomass conversion systems without the need of a skilled operator. As shown in Figure, the overall ATT reaction is designed to push all the energy towards the H₂ product, while the carbon in the seaweed is captured and stored as solid carbonates. If the purity of produced H₂ is high enough to eliminate any subsequent gas cleaning steps, the overall biomass conversion technology would have a great potential to be sustainable. The biomass carbon captured in a form of solid carbonate can be stored with long-term stability in geologic formations, and if so, the overall ATT technology could achieve net carbon-negativity leading to a BioEnergy with Carbon Capture and Storage (BECCS) potential.

• Alkaline Thermal Treatment of Seaweed for High-purity Hydrogen Production with Carbon Capture and Storage Potential
• Novel Artificial Oyster Reefs produced via Carbon Mineralization for Storm Wave Energy Dissipation in a Sea Level Rise Environment
• Suppressed Growth of Green Noctiluca blooms, Salps and Jellyfish and Enhanced CO2 Storage via Ocean Alkalinity Addition