Carbon dioxide can be not just stored, but used as a raw material for making valuable products, such as motor fuels, fodder proteins and amino acids, and bioactive compounds, as well as for growing microalgae. The proposed basic and related technologies are waste-free. The by-product is oxygen.
The suggested CO2 processing method turns carbon dioxide into a basis for microalgae feed using special bioreactors. The microalgae are then processed as well. As compared to other carbon dioxide chemical bonding methods, the proposed technology features low energy consumption, it does not use expensive catalysts and does not require any hydrogen supply. Photosynthesis with microalgae is up to 400 times more efficient in converting solar energy and carbon dioxide into biomass and oxygen than foliage plants, since the specific surface of microalgae is several-fold higher.
The proposed technology is highly flexible. The same bioreactors are suitable for growing various microalgae species and strains to select the best match for subsequent processing into a final product.
Depending on the geographic location of the bioreactor production facility, fresh recirculated water or seawater can be used as a microalgae growth ambient. See our selected freshwater microalgae species (Schedule 1) and Table 2 seawater species most suitable for producing a specific final product (Schedule 2).
Schedule 1. Freshwater microalgae to convert CO2 into commercial products.
*In 2018, global astaxanthin production amounted to about USD 600 mln . The key factors contributing to the astaxanthin consumption growth are the fodder industry expansion, higher demand for organic aquaculture feeds, and growth of the market for food additives and cosmetics products [Astaxanthin Market Growth Projections Statistics 2019–2026 Global Market Insights, Inc.] Astaxanthin is used for cattle/pig/poultry breeding; it significantly improves chicken survival rate [F. H. Comhaire, Y. El Garem, A. Mahmoud, F. Eertmans, F. Schoonjans. Combined conventional/antioxidant “Astaxanthin” treatment for male infertility: a double blind, randomized trial // Asian Journal of Andrology. — 2005-09. — Vol. 7, iss. 3. — P. 257—262. — ISSN 1745-7262 1008-682X, 1745-7262. — doi:10.1111/j.1745-7262.2005.00047.x.]
Schedule 2. Sea microalgae to convert CO2 into commercial products.
The simplified diagram below shows the carbon dioxide bio-processing:
Average process metrics for processing 1 ton of CO2:
- Energy consumption: 6 kWh;
- Motor fuel output: up to 0.36 ton;
- Bioactive substances output (if produced): up to 0.62 ton;
- By-product (oxygen): up to 0.64 ton;
- Bioreactor footprint (1 t/h СО2): 6 m2
- Total equipment footprint (1 t/h СО2), excluding the bioreactor footprint: 2.1 m2
Note. The technology is most suitable for processing carbon dioxide produced by thermal power plants and chemical production facilities. In this case, dump low-energy heat further improves the CO2 to biomass conversion efficiency.