A critical evaluation of CO2 supplementation to algal systems by direct injection
By N. Langley, S. Harrison, R. Hille. 2012
87 citations recorded by the source corpus.
Abstract Microalgae are currently cultivated on a relatively small scale for nutritional products, supplements and aquaculture feed. In recent years there has been renewed interest in algal bioenergy, which would require cultivation at far greater scales. A key component of large-scale production systems is the delivery of CO 2 to the algal cells, which is often a limiting factor in ponds and air sparged systems. Although many methods of CO 2 supplementation to algal reactors have been investigated, the most commonly suggested method is still the direct injection of CO 2 enriched gas into the growth medium. A sound understanding of CO 2 gas–liquid mass transfer is critical to efficient operation of cultivation systems as mixing and gas compression may represent significant operational expenses. For carbon capture or sequestration through algal culture, CO 2 recovery is equally important, particularly where carbon trading is involved. Chlorella vulgaris was grown in internal loop airlift reactors under varied CO 2 partial pressures in the inlet gas. In these reactors, with an overall mass transfer coefficient of 0.0094 s −1 , an inlet CO 2 partial pressure of 0.0012 atm (1200 ppm CO 2 by volume) was sufficient to overcome any mass transfer limitations. Under these operating conditions, a CO 2 recovery of 26% resulted. Increasing the partial pressure of CO 2 in the inlet gas above 0.0012 atm did not increase the algal productivity and caused significant decreases in CO 2 recovery to 9.7% and 2.1% at inlet CO 2 partial pressures of 0.00325 atm and 0.0145 atm respectively. Much research into algal growth is done without analysis of CO 2 gas–liquid mass transfer, using influent CO 2 partial pressures well in excess of the minimum value required to overcome CO 2 gas–liquid mass transfer limitations, even in poorly mixed systems. This could result in algal growth being optimised under conditions that are not industrially practical or desirable.
Subfields: Renewable Energy, Sustainability and the Environment
View Paper: https://www.semanticscholar.org/paper/7a4c605b20633c92416498906dfc11de59b613e2
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In Renewable Energy, Sustainability and the Environment
Citations in the corpus
- Process Design and Economics for the Production of Algal Biomass: Algal Biomass Production in Open Pond Systems and Processing Through Dewatering for Downstream Conversion (2016, background): “It is well established that in order to promote high biomass growth rates required to achieve economical production of commodity fuel products, supplemental CO2 must be delivered to the cultivation system beyond merely relying on CO2 transfer from ambient air [66,67].”
- Overview of the potential of microalgae for CO2 sequestration (2014, background): “However, when compared to terrestrial plants, microalgae and cyanobacteria have faster growth rates, and their CO2fixation efficiency is also between 10 and 50 times higher (Costa et al. 2000; Langley et al. 2012).”