Bio-Energy Generation from Synthetic Winery Wastewaters

In Spain, thewinery industry exerts a great influence on the national economy. Proportional to the scale of production, a significant volume of waste is generated, estimated at 2 million tons per year. In this work, a laboratory-scale reactor was used to study the feasibility of the energetic valorization of winery e uents into hydrogen by means of dark fermentation and its subsequent conversion into electrical energy using fuel cells. First, winery wastewater was characterized, identifying and determining the concentration of the main organic substrates contained within it. To achieve this, a syntheticwinery effluentwas prepared according to the composition of thewinerywastewater studied. This e uent was fermented anaerobically at 26 C and pH = 5.0 to produce hydrogen. The acidogenic fermentation generated a gas e uent composed of CO2 and H2, with the percentage of hydrogen being about 55% and the hydrogen yield being about 1.5 L of hydrogen at standard conditions per liter of wastewater fermented. A gas e uent with the same composition was fed into a fuel cell and the electrical current generated was monitored, obtaining a power generation of 1W h L1 of winery wastewater. These results indicate that it is feasible to transform winery wastewater into electricity by means of acidogenic fermentation and the subsequent oxidation of the bio-hydrogen generated in a fuel cell

BIOLOGICAL METABOLITES RECOVERY FROM BEVERAGE PRODUCTION SOLID RESIDUES THROUGH ACIDOGENIC FERMENTATION

Acidogenic fermentation was applied to evaluate the potential recovery of biological monomers as precursors in bio-plastic production. Three residual organic substrates from high-volume beverage sectors (coffee, orange juice, beer) were assessed: spent coffee grounds (SCG), orange peels (OP), and brewers\u2019 spent grains (BSG). Batch fermentation tests were set up. SCG and OP were studied as single substrates and combined to evaluate yields of target monomers (volatile fatty acids, ethanol, lactate) and to reveal interactions between the matrixes. NaOH pre-treatment was applied to SCG to enhance disruption of the lignocellulosic cell wall. BSG was studied without pre-treatment and following acid or alkaline pre-treatment, with acidogenic fermentation being initiated with two different initial pH values (7; 9). Acetogenic fermentation was achieved with all substrates, although with different yields of target monomers. In terms of total biological metabolite production, following alkaline pre-treatment, OP and BSG, both fermented at an initial pH 9, showed the best performance, yielding 62.6 g and 62.0 g target monomers per litre substrate. For all substrates, acetic and butyric acids were the most abundant products. In the case of OP fermentation, butyrate accounted for 57% (35.8 g/L) of the total. The BSG test with the highest total yield also achieved the highest acetate yield (36.7 g/L). The results confirm that OP and BSG should be considered a priority sustainable feedstock for the supply of biological monomers, particularly if polyhydroxyalkanoates are to be produced. SCG are better suited to aceto-oriented approaches, such as the production of polyvinyl acetat

Production of polyhydroxyalkanoates from cheese whey - pH effect on the acidogenic fermentation stage and nutrient needs of the culture selection stage

Dissertação para obtenção do Grau de Mestre em Biotecnologi

Acidogenic fermentation of brewer’s spent grain towards polyhydroxyalkanoates production

Polyhydroxyalkanoates (PHA) are fully biodegradable polyesters, synthesized by microorganisms from renewable resources, which reveal an alternative to petroleum-based plastics. Its production by mixed microbial cultures, unlike pure cultures, allows the use of industrial by-products in the absence of sterility conditions, potentially reducing process costs. The study described focused on the valorization of a waste from a brewery industry, brewer’s spent grain (BSG), through organic acids production, towards PHA production. PHA production using mixed microbial cultures involves three steps: (1) acidogenic fermentation of BSG for organic acids production, (2) selection of the mixed cultures able to accumulate PHA and (3) PHA production. In order to extract the sugars necessary to produce organic acids (phase 1), pre-treatment methods such as acid hydrolysis and subcritical water have been studied. Acid hydrolysis was selected for further experiments as the hydrolysis yield on sugars reached was higher than using subcritical water (0.152 g total sugars g BSG-1 versus 0.008 and 0.020 g total sugars g BSG-1 at 200 °C and 230 °C, respectively). Afterwards, the pH (5.0, 5.5 and 6.0) and organic loads (10, 20 and 30 gCOD L-1) effect on the acidogenic fermentation of hydrolyzed BSG was studied in batch. It was verified, regardless of the condition, that the most produced acids are acetic and butyric. As pH and organic load affects the fermentation products profile, it is possible to manipulate PHA composition. At last, the acidogenic fermentation of hydrolyzed BSG was studied in a continuous mode, using an expanded granular sludge bed reactor (EGSB). Due to the reduced operating time, it was not possible to reach stability. However, it was observed that sugars were consumed to produce organic acids. This revealed the potential of EGSB to be used for BSG acidogenic fermentation towards PHA production

Acidogenic Fermentation Towards Valorisation of Organic Waste Streams into Volatile Fatty Acids

Anaerobic acidification of eight organic streams (cheese whey, sugarcane molasses, organic fraction of municipal solid wastes (OFMSW), glycerol, soapy slurry, winery wastewater, olive mill effluent, and landfill leachate) was evaluated in batch experiments to determine their acidogenic potential and examine the composition of the produced volatile fatty acids (VFA). Cheese whey, molasses and OFMSW presented the highest acidogenic potentials (0.3 to 0.4 gVFA per g of chemical oxygen demand fed, CODfed) with the predominance of acetic, n-butyric and propionic acids. A further experimental set was applied to cheese whey, by varying food-to-microorganism ratio (F/M) and initial alkalinity. Maximisation of VFA production (up to 0.63 gVFA g–1CODfed) was obtained for an initial alkalinity of 5 – 7 g L–1 as CaCO3 and F/M ratios of 2 – 4 gCOD g–1VSS. Moreover, it was demonstrated that low F/M ratios combined with high alkalinity supply can shift the VFA profile by increasing the production of propionic and n-valeric acids. The results are useful towards optimal designs for acidogenic processes based on the composition of the VFA produced, since the control of the acidification products is crucial for valorisation in some applications

Influence of feedstock mix ratio on microbial dynamics during acidogenic fermentation for polyhydroxyalkanoates production

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] The nature of microbial populations plays an essential role in the production of volatile fatty acids (VFA) during acidogenesis, the first stage in polyhydroxyalkanoates (PHA) production using mixed cultures. However, the composition of microbial communities is generally affected by substrate alterations. This work aimed to unravel the microbial dynamics in response to a gradual change in the feedstock composition in an acidogenic reactor, with subsequent PHA production. To achieve this, co-digestion of cheese whey and brewery wastewater (BW) was carried out for the production of VFA, in which the ratio of these feedstocks was varied by gradually increasing the proportion of BW from 0 up to 50% of the organic content. Bacteria such as Megasphaera, Bifidobacterium or Caproiciproducens were the most abundant in the first stages of the co-digestion. However, when BW reached 25% of the organic load, new taxa emerged and displaced the former ones; like Selenomonas, Ethanoligenens or an undefined member of the Bacteroidales order. Accordingly, the production of butyric acid dropped from 52 down to 27%, while the production of acetic acid increased from 36 up to 52%. Furthermore, the gradual increase of the BW ratio led to a progressive drop in the degree of acidification, from 72 down to 57%. In a subsequent approach, the VFA-rich streams, obtained from the co-digestion, were used as substrates in PHA accumulation tests. All the tests yielded similar PHA contents, but with slightly different monomeric composition. The overall results confirmed that the microbiome was altered by a gradual change in the feedstock composition and, consequently, the VFA profile and the monomeric composition of the biopolymer also did.The current investigation has been financially supported by both the Spanish Ministry of Science and Innovation and European FEDER funds (PID2020-117805RB-I00 project). The authors, belongin to the BIOENGIN group, thank Xunta de Galicia for financial support to Competitive Reference Research Groups(ED431C 2021/55). B. Lagoa-Costa would also like to thank the financial contribution of INDITEX Group and the technical support of Dr. Ben Allen and Dr. Tom P. Curtis, from Newcastle University, during his internship. Funding for open access charge was provided by Universidade da Coruña/CISUGXunta de Galicia; ED431C 2021/5

VOLATILE FATTY ACIDS PRODUCTION FROM URBAN ORGANIC WASTES FOR BIOREFINERY PLATFORMS

Optimization of operational parameter setup for maximizing VFAs production via acidogenic fermentation of main organic urban waste stream

Valuable product production from wood mill effluents

Fibreboard production is one of the most important industrial activities in Galicia (Spain). Great amounts of wastewater are generated, with properties depending on the type of wood, treatment process, final product and water reusing, among others. These effluents are characterized by a high chemical oxygen demand (COD), low pH and nutrients limitation. Aerobic and anaerobic processes have been used for their treatment. Presently, bioplastics production (mainly polyhydroxyalkanoates or PHA) from wastewaters with mixed cultures is being studied. Substrate requirements for these processes are a high organic matter content and low nutrient concentration. Therefore, wood mill effluents could be a suitable feedstock. PHA production from wastewaters is carried out in three steps. First, complex organic matter is converted into volatile fatty acids (VFA) through acidogenic fermentation. Then, VFA are used as substrate in an aerobic sequencing batch reactor (SBR), in which the enrichement of PHA producing bacteria from a mixed culture is favoured. Finally, the sludge from the SBR is fed with a pulse containing high VFA concentrations, resulting in PHA accumulation inside the cells. In this work, the possibility of applying this process to wood mill effluents is proposed. An acidification percentage of 37% and a storage yield (YSTO) of 0.23 Cmmol/Cmmol were obtained

Valorization of sewage sludge for volatile fatty acids production and role of microbiome on acidogenic fermentation

This work explored the production of volatile fatty acids (VFA) through the anaerobic digestion of sewage sludge (SS). The first experiment took place at batch scale to evaluate the combined effect of using a thermal pre- treatment (120 \ub0C, 15 min) and different Substrate/Inoculum ratios (S/I) (1, 2, 4 and 6 g VS substrate/g VS inoculum) on the acidogenic potential of the SS. The results showed that the thermal pre-treatment influenced positively the degree of acidification of the SS at low S/I ratios, reaching maximum of 45%. Afterwards, a continuous lab-scale experiment, was set-up to study two ranges of organic loading rates (OLR): 1300\u20131600 mg COD L 121 d 121 and 2400\u20133500 mg COD L 121 d 121 . The highest degree of acidification (22%) was achieved at the lowest OLR. Analysis of the microbial community in the reactor revealed that OTUs most abundant present genes related with amino acids and carbohydrates fermentation being crucial for VFA production

Enhanced volatile fatty acid production from oil palm empty fruit bunch through acidogenic fermentation - A novel resource recovery strategy for oil palm empty fruit bunch

The glucan-rich fraction, hemicellulosic compounds-rich fraction, and a mixture of both fractions obtained from organosolv pretreatment of oil palm empty fruit bunch (OPEFB) were used as substrates to produce volatile fatty acids (VFAs) in acidogenic fermentation. In this study, the effects of medium adjustment (carbon to nitrogen ratio and trace elements supplementation) and methanogenesis inhibition (through the addition of 2-bromoethanesulfonate or by heat shock) to enhance VFAs yield were investigated. The highest VFA yield was 0.50 \ub1 0.00 g VFAs/g volatile solid (VS), which was obtained when methanogens were inhibited by heat shock and cultivated in a mixture of glucan-rich and hemicellulosic compounds-rich fractions. Under these conditions, the fermentation produced acetic acid as the only VFA. Based on the results, the mass balance of the whole process (from pretreatment and fermentation) showed the possibility to obtain 30.4 kg acetic acid and 20.3 kg lignin with a 70% purity from 100 kg OPEFB