Proof of concept of a novel in tandem biofilter photobioreactor system for valorization of volatile organic compounds: mineralization of methanol vapors coupled with use of CO₂ as a carbon source for Arthrospira maxima growth

Abstract

BACKGROUND Methanol, a common air pollutant, can be converted to CO2 by biofiltration. In turn, biofilter CO2 streams, contributing to the greenhouse effect, could represent a zero‐cost carbon source for microalgal production. To assess the potential of the combination of both bioprocesses, cultivation of Arthrospira maxima, a major source of added‐value natural products, was carried out with three different carbon sources (bicarbonate mineral medium, CO2 from ambient air, and CO2 from a methanol biofilter outlet). RESULTS Methanol vapors were almost completely treated in the biofilter, achieving an elimination capacity of 148 ± 18 g m−3 h−1 for an inlet load of 157 ± 12 g m−3 h−1, while producing an average of 152 ± 42 g m−3 h−1 of CO2. Compared to cultivation in classic bicarbonate mineral medium, the resulting CO2 concentration in the biofilter outlet (0.5 ± 0.1% (v/v)) allowed for a 20% higher final production of A. maxima (1.3 g dry weight (DW) L−1 of medium). Moreover, the cultivation of A. maxima significantly reduced the carbon footprint of the biofilter, with a fixation rate of 302 mg CO2 L−1 h−1. Additionally, enriched CO2 concentrations coming from the biofilter outlet allowed for a 117% higher A. maxima productivity rate than ambient air (76.5 ± 2.9 vs. 35.3 ± 1.3 mg DW L−1 d−1). CONCLUSION Substantial reduction of the cost of microalgae production and treatment of gaseous contaminants can be carried out in tandem. Further optimization of hybrid bioprocesses could represent a win–win opportunity from both environmental and economic viewpoints. © 2021 Society of Chemical Industry (SCI).