Faculty Publications
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Item Plasma-Activated Water as Nitrogen Source for Algal Growth: A Microcosm Study(Institute of Electrical and Electronics Engineers Inc., 2021) Sukhani, S.; Punith, N.; Ekatpure, A.; Salunke, G.; Manjari, M.; Harsha, R.; Chanakya, H.N.; Lakshminarayana, R.Nitrogen is one of the most critical nutrients affecting algal cell biomass growth and thereby plays a crucial role in algal growth economics. Conventionally, all man-made nitrogen (N) sources are based on hydrogen derived from fossil fuels. This investigation examines the effect of a new N source, i.e., plasma-activated water (PAW), on yields of algal biomass. The N uptake rates of the algae for PAW were determined and it was compared with the conventional N sources. Four treatments of N source in duplicates were run to evaluate the potential of algae cultivation in batch microcosms (5 L). Mixotrophic algal cultures from a nearby eutrophied lake were incubated for 1 week with nitrate-N (NaNO3), nitrite-N (NaNO2), nitrate+nitrite (NaNO3+NaNO2), and PAW as sole N source in basal Bold's media. Even though the cultures were not axenic, steady increase in chlorophyll and biomass was observed for all the cases studied. The highest biomass yield was observed in nitrate-N fed cultures, at an average of 32.5 mg/( \text{L}\cdot day), followed by a combination of nitrate+nitrite [27.1 mg/( \text{L}\cdot day)], PAW-N [26.6 mg/( \text{L}\cdot day)], and nitrite-N [22.5 mg/( \text{L}\cdot day)] fed cultures. Nitrogen uptake rates were similar in all cultures studied. The highest rates observed were in nitrite-N [4.05 mg/( \text{L}\cdot day)], closely followed by PAW [3.56 mg/( \text{L}\cdot day)]. The results suggest that PAW can be utilized as a N source with pre-exposed cultures. The algal biomass yields of PAW were comparable to conventional sources although cultures with PAW showed signs of better uptake of N. © 1973-2012 IEEE.Item Effect of solvent pre-treatment on microwave assisted pyrolysis of Spirulina (Algal Biomass) and Ficus benghalensis (Lignocellulosic Biomass) for production of biofuels: comparative experimental studies(Springer Science and Business Media Deutschland GmbH, 2025) Varma, J.V.; Sridevi, V.; Musalaiah, M.; King, P.; Hamzah, H.T.; Tanneru, H.K.; Ramesh, R.; Malleswari, G.B.The study focuses on the comparison of microwave-assisted pyrolysis (MAP) of Spirulina, (algal biomass), and aerial roots of Ficus benghalensis (lignocellulosic biomass) as feedstocks for biofuel production. Solvent ethanol was used to pretreat feedstocks. The experiments were carried out using a microwave power of 450 W, considering both fresh and solvent-pretreated feedstocks. Solvent-pretreated Spirulina demonstrated a high bio-oil yield of 56.1 wt. % and a biochar yield of 13.5 wt. %, whereas for solvent-pretreated Ficus benghalensis, the corresponding yields were 35.4 wt. % and 12.3 wt.%. Both solvent-treated and fresh algal biomass feedstocks showed higher yields than lignocellulose biomass. Pre-treatment of feedstocks showed positive results on microwave energy consumption and pyrolysis index. The average heating values were 27.3 0C/min for pretreated Spirulina and 46.2 0C/min for pretreated Ficus benghalensis. Fourier Transform Infrared (FTIR) characterized the obtained bio-oils and biochar. The FTIR results indicated the presence of distinctive functional groups such as N=C=O, O=C=O, N-O, and S=O in MAP of Spirulina bio-oil, and C=C and C-I stretching in MAP of Ficus benghalensis bio-oil. The FTIR results for biochar were consistent across both feedstocks, showing common functional groups such as C-Cl, C=C, C-H, O-H, C-F, and S=O. However, in the case of Spirulina, an extra functional group, C=N, was also detected. Pre-treatment of microalgal biomass is essential for the maximal recovery of biofuel precursors packed inside the complex microalgal cell wall. It was concluded that pre-treatment is an efficient way to improve the yield and composition of bio-oil with low microwave power and short microwave irradiation time. Efforts are still required to develop an economical and environmentally benign pre-treatment approach to facilitate 100% biomass conversion to added-value products. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.