Fermentative hydrogen production from cheese whey with in-line, concentration gradient-driven butyric acid extraction

• Published in: International journal of hydrogen energy 2020-09, Vol.45 (46), p.24453-24466
• Main Authors: Dessì, Paolo, Asunis, Fabiano, Ravishankar, Harish, Cocco, Francesco Giuseppe, De Gioannis, Giorgia, Muntoni, Aldo, Lens, Piet N.L.
• Format: Article
• Language: English
• Subjects: Biohydrogen; Butyric acid; Dairy wastewater; Pertraction; Selective extraction; Waste biorefinery
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.06.081

Hydrogen (H2) generation from cheese whey with simultaneous production and extraction of volatile fatty acids (VFAs) was studied in UASB reactors at two temperatures (20 and 35 °C) and pH values (5.0 and 4.5). The extraction module, installed through a recirculation loop, was a silicone tube coil submerged in water, which allows concentration-driven extraction of undissociated VFAs. Operating conditions were selected as a compromise for the recovery of both H2 and VFAs. Batch experiments showed a higher yield (0.9 mol H2 mol−1 glucoseeq.) at 35 °C and pH 5.0, regardless of the presence of the extraction module, whereas lower yields were obtained at pH 4.5 and 20 °C (0.5 and 0.3 mol H2 mol−1 glucoseeq., respectively). VFAs crossed the silicone membrane, with a strong preference for butyric over propionic and acetic acid due to its higher hydrophobicity. Sugars, lactic acid and nutrients were retained, resulting in an extracted solution of up to 2.5 g L−1 butyric acid with more than 90% purity. Continuous experiment confirmed those results, with production rates up to 2.0 L H2 L−1 d−1 and butyric acid extraction both in-line (from the UASB recirculation) and off-line (from the UASB effluent). In-line VFA extraction can reduce the operating costs of fermentation, facilitating downstream processing for the recovery of marketable VFAs without affecting the H2 production. [Display omitted] •Cheese whey fermentation was studied in UASB rectors with in-line VFA extraction.•Butyric acid was selectively extracted from the broth using a silicone membrane.•Sugars, lactic acid, and nutrients are retained by the silicone membrane.•HPR up to 2 L L−1 d−1 and butyric acid extraction up to 2.5 g L−1 were achieved.•pH 4.5 enhances VFA migration through the silicone membrane but decreases H2 yields.