Maximization of bio-hydrogen production from winery vinasses using on-line feedback control

Abstract

Continuous biohydrogen production by dark fermentation valorizes organic effluents like winery vinasse (WV), being an economical alternative to fossil fuels, to produce clean and renewable hydrogen. Trickling bed reactors (TBR) operated with low hydraulic retention time (HRT) favor hydrogen production. However, its large-scale application has still been limited in the literature due to possible operational risks and costs. To maximize the hydrogen production rate (HPR) rapidly, an innovative on-line feedback control was evaluated using WV in a TBR. Based on continuous HPR measurements, the strategy alternates the operation between a high HRT of 5.5 h and a low HRT of 3 h (an organic shock load) by detecting either a peaking phenomenon during the transient or the steady state after it. Use of the controller increased the mean HPR to 177.5 ± 12.3 mLH2⋅Lreac−1⋅h−1 from 93.9 ± 9.9 mLH2⋅Lreac−1⋅h−1 under a usual fixed HRT operation, and only 91.5 h were needed to automatically find the optimal mean HRT at 3.76 ± 0.15 h. Bacterial community and metabolite analysis helped explain the increase in hydrogen yield (1.1 ± 0.4 mmol H2gCODadded−1) by a cross-feeding interaction between lactic acid and hydrogen-producing bacteria.