Algae Production CO2 Absorber with Immobilized Carbonic Anhydrase
Low-cost CO2 supply is necessary to achieve algal biofuel cost metrics; and high CO2 capture and utilization (CCU) efficiency are necessary to achieve algal biofuel cost, life-cycle, and production quantity metrics. The focus of this project is on developing a low cost, high efficiency method for CCU from flue gas for use in production of algae biofuel and commodity bioproducts. A CCU process was developed and demonstrated that met or exceeded all of the project goals: 83% CO2 capture efficiency from flue gas; 97% utilization efficiency in algae cultivation; $21/metric ton (mt) projected cost of CO2 capture and supply at full-scale; TRL-5 technology maturity. The state-of-the-art approaches to CO2 supply for algae from industrial sources are (i) to distribute the flue gas directly or (ii) to concentrate and compress the CO2 prior to distribution. Both of these conventional methods require an expensive distribution and control system to provide CO2 to thousands of acres of algae ponds. The first method has major technical barriers – (i) technology must be invented to prevent ground level release of the flue gas, (ii) maintaining cultivation facilities during utility outages, and (iii) diurnal, daily weather, seasonal variations in CO2 utilization by the algae limit the capture efficiency to less than 10%. Even without these barriers, the distribution system is expensive, and a large amount of energy is required to compress the flue gas, so the approach is too expensive for producing algal biofuel and commodity co-products. The second method, capturing and compressing carbon dioxide, overcomes the technical barriers noted above because the carbon dioxide is purified to avoid ground level flue gas emissions and it can be stored as liquid carbon dioxide to accommodate variations in supply and use; however, this method is even more expensive because capture and compression costs are added to the cost of the vast distribution and control network. Global Algae Innovations (Global Algae) new CCU process overcomes all of these obstacles. The approach utilizes sodium bicarbonate in the media as a shuttle so that CO2 is readily captured from flue gas, and no separate gas distribution and control system is required because the CO2 is distributed to the ponds in the growth media. Figure 1 illustrates the key process blocks and a summary of the key reactions. Figure 2 provides photographs of the key components used to implement this CCU process at the 8-wetted acre open raceway algae farm operated by Global Algae. The CO2 is recovered 24 hours per day with only 2.5 inches of water pressure drop on the flue gas, and the carbonated media can be stored indefinitely in a covered pond until it is needed for cultivation. The new process is incorporated into Global Algae’s Department of Energy (DOE) funded integrated biorefinery project for scale-up of algae biofuel process as well as eight other DOE projects and one Department of Agriculture (USDA) project. The technology is included in Global Algae’s technology package that will be broadly licensed through a franchise model. Additionally, nine new high pH algae strains were isolated that are being used on four other DOE projects.
- Research Organization:
- Global Algae Innovations, Inc., San Diego, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Bioenergy Technologies Office
- DOE Contract Number:
- EE0007092
- OSTI ID:
- 1581442
- Report Number(s):
- DOE-GAI-07092
- Country of Publication:
- United States
- Language:
- English
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