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. At LCSE, 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.
At LCSE, 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 (LCSE PIs: Alissa Park, Jingguang Chen)
- Electrochemical Production of Renewable Acids and Base for Direct Ocean Capture and Carbon-free Concrete Produciton from Ocean (LCSE PIs: Aaron Moment, Shiho Kawashima, Daniel Esposito, collaboration with Xiao Su at UIUC)
- Novel Artificial Oyster Reefs produced via Carbon Mineralization for Storm Wave Energy Dissipation in a Sea Level Rise Environment (LCSE PIs: George Deodatis, Alissa Park)
- Suppressed Growth of Green Noctiluca blooms, Salps and Jellyfish and Enhanced CO2 Storage via Ocean Alkalinity Addition (LCSE PI: Alissa Park, collaboration with Joaquim Goes at Lamont)