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Enhancement of hydrogen and methane production through anaerobic digestion using pre-treatments
Full text linkDark fermentation of organic wastes is considered as a promising process in terms of sustainable waste management and simultaneous biofuel production. Pre-treatment technologies are known as essentials of dark fermentation to overcome obstacles responsible for low H2 yield.
The effect of aerobic pre-treatment of food wastes with different compositions (carbohydrate-rich, protein-rich and lipid-rich) prior to two-stage anaerobic digestion, on H2 and CH4 productions was investigated. The results showed that pre-aeration of food waste did not constitute an effective treatment for the purpose of improving H2 production potential during the first stage of the AD process. However, during the subsequent stage of AD, CH4 yield for protein-rich substrate, increased by 45.6%, thus revealing that carbon conversion to CH4 had an increase after pre-aeration.
In case of inoculum pre-treatment, a novel method using waste frying oil (WFO) was introduced. H2 production from glucose was investigated for inoculum pre-treated with different concentrations of WFO. In the next step, a flux balance analysis model was developed to study the effect of inoculum pre-treatment on H2 producing and H2 consuming metabolic pathways. The results showed that H2 consumption by hydrogenotrophic methanogens that was accounted for about 56% of the loss in the H2 yield in untreated cultures, was negligible when the inoculum pre-treated with WFO.
Moreover, optimization of H2 yield from food waste was performed in the next step of research, using a three-factor three-level Box-Behnken design method. Initial pH, pre-treatment duration and waste frying oil concentration were considered as the experimental factors. The results showed that combination of high WFO concentration, low initial pH and long pre-treatment could result in inhibition of methanogens.
Furthermore, two-stage anaerobic digestion of food waste was performed using the inoculum pre-treated with WFO and total energy yield was compared with three common pre-treatments (heat shock, aeration and alkaline pre-treatment) and untreated cultures. The results showed that inoculum pre-treatment with WFO resulted in higher H2 and CH4 productions compared to alkaline, aeration and heat shock pre-treatment.
Finally, microbial community of inoculum at different stages of dark fermentation (untreated, pre-treated with WFO, washed and fermented) was investigated to understand the effect of inoculum pre-treatment with WFO on H2 producing and H2 consuming microbial populations. The microbial diversity analysis showed that inoculum pre-treatment with WFO did not affect spore-forming H2 producing bacteria. However, it resulted in increased relative abundances of non-spore forming H2 producers which could be considered as an advantage in comparison with harsh pre-treatments such as heat shock
Optimization of hydrogen production from food waste using anaerobic mixed cultures pretreated with waste frying oil
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Evaluation of hidden H2-consuming pathways using metabolic flux-based analysis for a fermentative side-stream dynamic membrane bioreactor using untreated seed sludge
No full textThe degradation of glyphosate is enhanced in a microbial fuel cell: Electrochemical performance, degradation efficiency, and analysis of the anodic microbial community
Full text linkGlyphosate, one of the most used herbicides worldwide, is known as an aquatic contaminant of concern, and has been identified as presenting adverse impacts in agroecosystems, due to a somewhat limited natural chemical and biological degradation in the environment. In this study, we investigated the degradation of glyphosate in microbial electrochemical systems (MESs), and compared the performance and the microbial composition of enriched anodic biofilms with those shown by native microbial communities. The reduction of glyphosate content observed in MESs (approx. 70 %) was much higher than in non-electroactive microbial cultures (approx. 49 %). The analysis of the microbial communities by 16S amplicon sequencing revealed a significant difference between the microbial community composition of MESs anodic biofilms and non-electroactive enriched communities. The anodic biofilms were dominated by Rhodococcus (51.26 %), Pseudomonas (10.77 %), and Geobacter (8.67 %) while in non-MESs cultures, methanogens including Methanobrevibacter (51.18 %), and Methanobacterium (10.32 %), were the dominant genera. The present study suggested that MESs could be considered as a promising system for complete degradation of glyphosate from waters polluted by this herbicide
Pre-treatment technologies for dark fermentative hydrogen production: Current advances and future directions
Full text linkEffect of inoculum pre-treatment on mesophilic hydrogen and methane production from food waste using two-stage anaerobic digestion
No full textPre-treating anaerobic mixed microflora with waste frying oil: A novel method to inhibit hydrogen consumption
No full textEffect of aerobic pre-treatment on hydrogen and methane production in a two-stage anaerobic digestion process using food waste with different compositions
No full textStudy of microbial dynamics during optimization of hydrogen production from food waste by using LCFA-rich agent
No full textIn dark fermentation of food waste, changes in microbial community composition and dynamics were studied, after inoculum pre-treatment with waste frying oil (WFO). The microbial diversity in the raw sludge was the highest, considering that all genera with abundances higher than 0.1% contributed to only 37.42% of the total diversity. After inoculum pre-treatment with WFO, many genera were inhibited; however, no effect was observed on spore-forming fermentative bacteria. In addition, none-spore-forming H2 producers were enriched significantly after inoculum pre-treatment, while spore-forming H2 producing bacteria (e.g. Clostridium spp.) remained almost unchanged. The predominant OTUs after dark fermentation were Clostridium sp. (27.24%), Aeromonas sp. (13.43%) and Chromobacterium sp. (12.00%)
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