Glycerol as a Raw Material for Hydrogen Production

Sakamoto

et al. 2019

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This study compared the biohydrogen generation by subtropical mixed and pure cultures from the crude glycerol from the biodiesel production using waste cooking oils (WCO). The crude glycerol was pretreated by pH adjustment. The mixed culture was obtained from a subtropical granular sludge of the UASB (Upflow Anaerobic Sludge Blanket) reactor used in the treatment of vinasse from sugarcane of ethanol and sugar industry. It was heat treated in order to inactivate hydrogen-consuming bacteria, which was identified by Illumina MiSeq Sequencing with a relative abundance of 97.96% Firmicutes Philum, 91.81% Clostridia Class and 91.81% Clostridiales Order. The pure culture was isolated from a subtropical granular sludge from UASB reactor of treating brewery wastewater and identified as Enterobacter sp. (KP893397). Two assays were carried in anaerobic batch reactors in order to verify the hydrogen production from crude glycerol bioconversion with: (I) mixed culture and (II) pure culture. The experiments were conducted at 37 C, initial pH of 5.5 for assay I and 7.0 for assay II, with 20 g COD L À1 of crude glycerol. The crude glycerol consumption was 56.2% and 88.0% for the assay I and II, respectively. The hydrogen yields were 0.80 moL H 2 mol À1 glycerol for the assay I and 0.13 moL H 2 mol À1 glycerol for the assay II. Enterobacter sp. preferred the reductive metabolic route, generating 1460.0 mg L À1 of 1,3-propanediol, and it showed to be more sensitive in the presence of methanol from crude glycerol than mixed culture that preferred the oxidative metabolic route with biohydrogen generation. The mixed culture was more able to generate H 2 than pure culture from the crude glycerol coming from the biodiesel production using WCO.

Section: Metabolic Pathway E Oxidative and Reductivesupporting

confidence: 63%

Bioconversion of crude glycerol from waste cooking oils into hydrogen by sub-tropical mixed and pure cultures

Sakamoto

et al. 2019

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“…and Citrobacter sp. [18]. The glycerol metabolism and H 2 production can be driven by two pathways: oxidative and reductive.…”

Section: Compounds Of the Organic Liquid Mediummentioning

confidence: 99%

“…The H 2 production is directly proportional to the generation of volatile organic compounds [44] in liquid medium. In most of the bioconversion of glycerol pathways, along with the different metabolites, H 2 is also produced during oxidative metabolism (Equations (4)e(7) below) [18]. It can be concluded that the generation of highly reduced final products is accompanied by high yields of H 2 [4].…”

Section: Compounds Of the Organic Liquid Mediummentioning

confidence: 99%

“…Most of these studies were conducted in the anaerobic batch reactors, where the produced hydrogen is accumulated in the headspace of the bioreactors [2]. However, the majority of the researches are conducted with raw glycerol from virgin vegetable oils and animal fats [18]. In addition, the application of crude glycerol, from used cooking oils into biodiesel by transesterification processes, with fermentation by mixed cultures for H 2 generation has never been employed.…”

Section: Introductionmentioning

confidence: 99%

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Crude glycerol by transesterification process from used cooking oils: Characterization and potentialities on hydrogen bioproduction

Santana

et al. 2016

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This study evaluated the potential bioconversion of crude glycerol from biodiesel production, applying used cooking oil for biohydrogen production by fermentative bacteria consortia. The pretreatment of crude glycerol was made by pH adjustment. Heat treatment of the inocula and initial pH 5.5 were applied to select hydrogen-producing bacteria and inactivate hydrogen-consumers microorganisms. The inocula tested were: (I) granular sludge from the thermophilic UASB reactor used on the treatment of vinasse and (II) granular sludge from the UASB reactor used on the treatment of sanitary sludge for the assays (1) and (2), respectively. The characterization of crude glycerol presented high levels of alkalinity, methanol and soap that may be inhibitory to biologic processes of H 2 production. The assays were carried in anaerobic batch reactors in order to verify the efficiencies of crude glycerol to H 2 generations by the microbial consortia (20%) at 37 C, initial pH 5.5, with 20.0 g COD L À1 glycerol. The cumulative production of hydrogen for the assays (1) and (2) were, respectively, (mmol H 2 L À1) 28.49 ± 1.55 and 19.14 ± 1.67. The subsequent yields were obtained as follows: 2.2 moL H 2 mol À1 glycerol and 1.1 moL H 2 mol À1 glycerol, respectively. The used cooking oil was an efficient waste for bioconversion of crude glycerol to H 2 production.

“…Glycerol may result in different yields of hydrogen per mole of organic substrate, depending on the route of the fermentation (oxidative or reductive) and the composition of the end products [7,9]. According to Rossi et al, the end products of the fermentation process are mainly volatile organic acids (VFA) such as acetic, propionic and butyric acids; and alcohols as ethanol and 1-butanol [10].…”

Section: Introductionmentioning

confidence: 99%

Determination of alcohols and volatile organic acids in anaerobic bioreactors for H 2 production by near infrared spectroscopy

Santana

et al. 2017

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In recent years, near infrared (NIR) spectroscopy has been investigated as a tool for monitoring anaerobic digesters, but several adversities in its application have been reported. This study proposes the application of NIR for the determination of alcohols and volatile organic acids from H 2 production bioreactors and evaluates different approaches to optimize the prediction models. Partial least squad (PLS) models were developed using samples from anaerobic batch reactors fed with crude glycerol for wastewater treatment. The analytes predicted were: methanol, ethanol, 1-butanol, acetic, propanoic, butyric, isocaproic and total volatile organic acids (VFA). The optimization of the predictive capacity of the models was achieved through the orthogonal signal correction (OSC) preprocessing and the selection of variables performed by the genetic algorithm (GA). The application of the proposed models were based on the following figures of merit: accuracy, precision, linearity, limits of detection and quantitation, measurement interval, sensitivity, selectivity, signal-to-noise ratio and bias. Despite the low selectivity (maximum of 0.12%), the models presented high sensitivity [g À1 ¼ 0.19 (mg L À1) À1 ], low LOQ (1 mg L À1) and correlation between reference and predicted values (r) at least 0.93, except for propanoic acid (r pred ¼ 0.85). The F-test revealed that the selection of variables by GA significantly improved the accuracy and linearity of the prediction models for methanol, acetic acid, isocaproic acid and VFA. NIR spectroscopy has proved to be a powerful tool for monitoring H 2 production bioreactors since provides fast, low cost and multicomponent information.