Global warming and pollution are the twin crises experienced globally. Biological offset of these crises are gaining importance because of its zero waste production and the ability of the organisms to thrive under extreme or polluted condition. In this context, this review highlights the recent developments in carbon dioxide (CO2) capture from flue gas using microalgae and finding the best microalgal remediation strategy through contrast and comparison of different strategies. Different flue gas microalgal remediation strategies discussed are as follows: (i) Flue gas to CO2 gas segregation using adsorbents for microalgal mitigation, (ii) CO2 separation from flue gas using absorbents and later regeneration for microalgal mitigation, (iii) Flue gas to liquid conversion for direct microalgal mitigation, and (iv) direct flue gas mitigation using microalgae. This work also studies the economic feasibility of microalgal production. The study discloses that the direct convening of flue gas with high carbon dioxide content, into microalgal system is cost-effective.

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Hydrogen (H 2 ) produced from biological methods is a potential option to meet the growing clean energy needs. The present study aimed to produce biohydrogen by dark fermentation from nuisance aquatic weed, Eichhornia crassipes, using facultative anaerobic bacteria. A total of 12 bacterial strains were isolated from different wastewater sources and were screened for the potential of H 2 production using glucose as carbon source. Ten strains showed the H 2 -producing potential and were identified up to the generic level by biochemical tests. Two strains with higher H 2 production were sequenced using PCR technique and identified as Proteus mirabilis and Pseudomonas aeruginosa and selected for the studies with E. crassipes as the substrate. It was found that P. aeruginosa could produce 19.54 ± 0.03% of H 2 from 2% acid (H 2 SO 4 ) treated substrate which was comparatively higher than that of 4 and 8% treatments. P. mirabilis also yielded better results of 5.42 ± 0.02% H 2 f or 2% acid (H 2 SO 4 ) treated substrate than 4 and 8% treatments. In total, 33.52 ± 0.04% of H 2 was produced by P. aeruginosa for the substrate treated with 2% alkali (NaOH). It was noted that with respect to P. mirabilis 4% alkali treated substrate yielded a higher percentage of H 2 (20.23 ± 0.03%) compared to the other two concentrations. The results indicate that alkali treated substrate produced comparatively higher amount of H 2 than that of acid treated substrates. Regarding efficiency, P. aeruginosa was found to be more competent than P. mirabilis.

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