Krebs & Sisler LP, a Winnetka, Illinois energy research firm, unveiled a method of purifying water using carbon dioxide (CO2), which the company proposes as a way of using the large amounts of CO2 captured in new “clean coal” technologies. The method, says Krebs & Sisler, also rapidly grows algae, that can be used as a food supplements, farm animal feed supplements, or alternative fuels.
In its process, the company says salt water, sewage and industrial wastewaters are purified while biomass is produced by the concurrent use of photosynthesis and photocatalysis. Photosynthesis is the process of using light to convert carbon dioxide into organic compounds such as sugar, while photocatalysis uses light to accelerate chemical transformations.
In this case, light emitting diode (LED) lighting combines with CO2 and balanced nutrients to grow a biomass from species of algae such as Spirulina, which require CO2. The biomass growth rate in deep well-lighted enclosed cells is expected to exceed 100 times the natural rate because all factors related to culturing the algae can be optimized in this continuous hydroponic process.
The algae biomass absorbs minerals dissolved in water and also the minerals contained in organic and inorganic compounds when they are released by the photochemical action of photocatalysis. Photosynthesis then purifies the water by absorbing minerals, given sufficient light, CO2, nutrients, and time.
The resulting biomass is 50% carbon and may be dried for fuel, a farm animal feed supplement, or human nutrient because of its high protein (60%) and carbohydrate (20%) values plus vitamin A, B and E content. The oxygen bound in CO2 is released to fortify the atmosphere for human and creature respiration and for fuel combustion.
Krebs & Sisler say that this process requires thousands of tons per day of low-cost CO2. The recent development of oxygen combustion for power plants could provide free CO2 for water purification facilities sited nearby as well as produce electric power with few CO2 emissions.
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