Utilisation of CO2 from Sodium Bicarbonate to Produce Chlorella vulgaris Biomass in Tubular Photobioreactors for Biofuel Purposes

Abstract

Microalgae are one of the most promising sources of renewable substrates used for energy purposes. Biomass and components accumulated in their cells can be used to produce a wide range of biofuels, but the profitability of their production is still not at a sufficient level. Significant costs are generated, i.a., during the cultivation of microalgae, and are connected with providing suitable culture conditions. This study aims to evaluate the possibility of using sodium bicarbonate as an inexpensive alternative CO2 source in the culture of Chlorella vulgaris, promoting not only the increase of microalgae biomass production but also lipid accumulation. The study was carried out at technical scale using 100 L photobioreactors. Gravimetric and spectrophotometric methods were used to evaluate biomass growth. Lipid content was determined using a mixture of chloroform and methanol according to the Blight and Dyer method, while the carbon content and CO2 fixation rate were measured according to the Walkley and Black method. In batch culture, even a small addition of bicarbonate resulted in a significant (p ≤ 0.05) increase in the amount of biomass, productivity and optical density compared to non-bicarbonate cultures. At 2.0 g∙L–1, biomass content was 572 ± 4 mg·L−1, the maximum productivity was 7.0 ± 1.0 mg·L–1·d–1, and the optical density was 0.181 ± 0.00. There was also an increase in the lipid content (26 ± 4%) and the carbon content in the biomass (1322 ± 0.062 g∙dw–1), as well as a higher rate of carbon dioxide fixation (0.925 ± 0.073 g·L–1·d–1). The cultivation of microalgae in enlarged scale photobioreactors provides a significant technological challenge. The obtained results can be useful to evaluate the efficiency of biomass and valuable cellular components production in closed systems realized at industrial scale.

Current Advancements in Biofuel Production from Microalgae: Harvesting and Conversion Technologies

“…The biomass yields of various microalgae using open systems and PBRs is mentioned in Tab. 1 [38][39][40][43][44][45][46][47][48][49][50][51][52].…”

Recent Developments on the Performance of Algal Bioreactors for CO2 Removal: Focusing on the Light Intensity and Photoperiods

“…In Ratomski et al [ 19 ], 100 L photobioreactors were utilized to explore the potential of sodium bicarbonate as a cheap CO 2 alternate for the production of Chlorella vulgaris and lipid using gravimetric and spectrophotometric techniques and a well-known Bligh and Dyer method, respectively. A substantial improvement in biomass production was noticed in the presence of bicarbonate in comparison with the samples in the absence of bicarbonate.…”

A novel system integrating electrolysis and ionic membranes (EIMs) enables artificial carbon concentration and alleviation of metal cation stress in microalgae cultivation

“…32 With increasing NaHCO 3 dose, the salinity generated by Na + manifests as a challenge for microalgae cultivation. [33][34][35][36][37][38][39] For example, Chlorella vulgaris ESP-31 was observed to have decreased growth when more than 14.3 mM NaHCO 3 was added to the medium, 37 as was Chlorella zofingiensis. 39 Similarly, Chlamydomonas rheinissima showed significant mortality with a higher concentration of bicarbonate than 0.5 mM of that in the medium.…”

“…[33][34][35][36][37][38][39] For example, Chlorella vulgaris ESP-31 was observed to have decreased growth when more than 14.3 mM NaHCO 3 was added to the medium, 37 as was Chlorella zofingiensis. 39 Similarly, Chlamydomonas rheinissima showed significant mortality with a higher concentration of bicarbonate than 0.5 mM of that in the medium. 40 Therefore, it remains to be addressed to supply total dissolved inorganic carbon (TIC) for microalgae cultivation without cation accumulation and CO 2 release.…”