Cultivation of green microalgae by recovering aqueous nutrients in hydrothermal carbonization process water of biomass wastes

• Published in: Journal of water process engineering 2021-04, Vol.40, p.101783, Article 101783
• Main Authors: Tarhan, Seray Zora, Koçer, Anıl Tevfik, Özçimen, Didem, Gökalp, İskender
• Format: Article
• Language: English
• Subjects: Botryococcus braunii; Chlorella minutissima; Engineering Sciences; HTC process water; Microalgae cultivation; Nutrient recovery; Reactive fluid environment
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2020.101783

[Display omitted] •Process water from hydrothermal carbonization (HTC) of orange and olive pomaces can be used for microalgae cultivation.•Aqueous nutrients in the HTC process water can be recovered by microalgae cultivation.•TOC, TN and TP values in the HTC process water are decreased via microalgae cultivation.•Microalgae cultivated in the HTC process water can be valorized for various applications. The main aim of this study is to investigate the usability of the process water obtained from the hydrothermal carbonization (HTC) of two different types of biomass waste for microalgae production. In this context, the process waters released as a result of hydrothermal carbonization of olive and orange pomace were diluted in different proportions (50×, 100×, 200×, and 400×) and used in the cultivation of Chlorella minutissima and Botryococcus braunii microalgae. It was observed that the growth rates were higher and the doubling times were shorter at low dilution rates for both microalgae species. The highest growth rate and the shortest doubling time values were found as 0.130 g/L/day and 5.33 day, respectively, for Chlorella minutissima microalgae cultivated in the HTC process water of olive pomace. It was also observed that the process water dilution rate had no specific effect on microalgae biochemical characteristics. It can be concluded that the aqueous phases from HTC of orange and olive pomaces can be a good source of nutrients for different types of microalgae, opening a sustainable, cost effective and environmentally friendly approach for microalgae cultivation and, at the same time, for the cleaning of the otherwise biochemically toxic HTC process waters.