Background
Carbon dioxide removal (CDR) methods from atmospheric air, including direct air capture (DAC), is essential to limit the spread of global warming. However, current DAC approaches based on thermal and pressure swings are very energy intensive. Moisture-driven DAC using strong-base anion exchange resins (AER) reversibly binds CO2 from ambient air at low humidity and releases it when exposed to moisture. The energy required for compression of CO2 is paid through evaporation of water.
Many current methods of moisture-driven DAC that yield 5-10 kPa CO2 are inadequate for most CO2 utilization process (e.g., CO2 electrolysis, thermochemical synthesis or geologic storage). However, these pressures are ideal for accelerating the growth of plants and photosynthetic organisms, which are carbon-limited when capturing CO2 directly from ambient air. While CO2 capture directly from air into ponds can be accelerated to increase the growth of aquatic photosynthetic organisms using very high pH and alkalinity media, these conditions are not suitable for most strains of microalgae and some cyanobacteria.
High CO2 delivery rates at more modest pH levels and alkalinity suitable for a wide range of microalgae and cyanobacteria can be achieved by delivering concentrated CO2 from industrial waste streams, but this requires costly and complex transportation from the source to the cultivation site, which directly contradicts the need for widespread decarbonization. Also, through traditional means of delivering CO2 to microalgae cultures, between 60 and 80% of the CO2 is lost to the air, which increases the greenhouse gas intensity of biofuels and bioproducts produced during cultivation.
Invention Description
Researchers at Arizona State University have developed AUDACity (DAC polymer-enhanced cyanobacterial bioproductivity), which is methods and systems for capturing CO2 from ambient air using anion exchange resin (AER) particles contained within mesh materials. This enables high surface area of the particles to contact air and deliver the CO2 directly into mildly alkaline liquid medium, which is suitable for significantly accelerating growth of photosynthetic organisms, including cyanobacteria and microalgae, to produce sustainable fuels and other products.
Potential Applications
- Sustainable fuel production
- CO2 removal and utilization
Benefits and Advantages
- Efficient: high growth rates of photosynthetic organisms
- Less expensive: does not require a concentrated CO2 source
- More strains of microalgae and cyanobacteria available: does not require high alkalinity or high pH system
- Sustainable: lowers CO2 loss to ambient air