Waste-derived Volatile Fatty Acids Research Articles

How to develop a bio-based phosphorus mining strategy for eutrophic marine sediments: Unlocking native microbial processes for anaerobic phosphorus release

This study examined the anaerobic release of phosphorus (P) from two different Baltic Sea sediments (B and F), focusing on the impact of initial concentration of externally introduced waste-derived volatile fatty acids (VFA) as the carbon source, temperature, pH, and mixing conditions. The first batch bioreactor set was operated to demonstrate the effect of VFA on anaerobic P release at different concentrations (1000–10000 mg/L as COD) at 20 °C. A notable P release of up to 15.85 mg/L PO4–P was observed for Sediment B at an initial carbon concentration of 10000 mg COD/L. However, VFA consumption in the bioreactors was minimal or no subsequent. The second batch bioreactor set was carried out to investigate the effect of temperature (20 °C-35 °C), pH (5.5, 7.0 and 8.5) and mixing conditions on P release by introducing lower initial carbon concentration (1000 mg COD/L) considering the potential risk for VFA accumulation in the bioreactors. Maximum P releases of 4.4 mg/L and 3.5 mg/L were for Sediment B and Sediment F, respectively. Two-way ANOVA tests revealed that the operation time and pH and their interactions were statistically significant (p < 0.05) for both sediments while the effect of mixing was not statistically significant. Most of the sulfate was reduced during batch bioreactor operation and Desulfomicobiaceae became dominant among other sulfate-reducing bacteria (SRB) possibly shows the importance of SRB in terms of anaerobic P release. This study gives an insight into future implementations of phosphorus mining from eutrophic environment under anaerobic conditions.

Pilot-scale production of mcl-PHA by Pseudomonas citronellolis using acetic acid as the sole carbon source

Medium-chain-length polyhydroxyalkanoates (mcl-PHA) are biobased materials with promising properties for environmentally friendly applications. Due to high production costs, which are related to the cost of the carbon sources combined with conversion insufficiencies, currently only small quantities are produced. This results in a lack of reliable data on properties and application potential for the variety of polymers from different types of production strains. This study investigated the potential for the production of mcl-PHA from volatile fatty acids (VFA) at a larger scale, given their potential as low-cost and sustainable raw material within a carboxylate-platform based biorefinery. Pseudomonas citronellolis (DSMZ 50332) was chosen as the production strain, and acetic acid was selected as the main carbon and energy source. Nitrogen was limited to trigger polymer production, and a fed-batch process using a pH-stat feeding regime with concentrated acid was established. We report successful production, extraction, and characterization of mcl PHA, obtaining a total of 1.76 kg from two 500-litre scale fermentations. The produced polymer was identified as a copolymer of 3-hydroxydecanoate (60.7%), 3-hydroxyoctanoate (37.3%), and 3-hydroxyhexanoate (2.0%) with a weight average molecular weight (Mw) of 536 kDa. NMR analysis indicates the presence of unsaturated side chains, which may offer additional possibilities for modification. The results confirm that there is a potential to produce significant amounts of mcl-PHA with interesting rubber-like properties from waste-derived VFA.

Towards improved conversion of wet waste to jet fuel with atomic layer deposition-coated hydrodeoxygenation catalysts

The conversion of wet waste-derived volatile fatty acids into jet fuel-range hydrocarbons is a promising route for increasing the production of sustainable aviation fuel; however, the cost and moderate alkane selectivity of Pt-based hydrodeoxygenation catalysts present challenges for commercialization. To address this, we used atomic layer deposition to apply TiO2 overcoats to Pt/Al2O3 catalysts and create new interface sites that exhibited 8 times higher site time yield of the desirable n-alkane product than uncoated catalyst. Through TPR/TPD, XPS, CO DRIFTS, and DFT calculations, we found that the increased selectivity of the ALD-coated catalyst was due to the creation of O vacancies at the Pt-TiO2 interface under reducing conditions, resulting in new Ti3+ acid sites near the active metal. Maximum conversion and alkane selectivity during HDO was achieved with an ALD-coated 0.5% wt Pt catalyst, indicating that TiO2 ALD can be used to maximize the utility of precious-metal catalysts.

The Effect of Sequential and Simultaneous Supplementation of Waste-Derived Volatile Fatty Acids and Methanol as Alternative Carbon Source Blend for Wastewater Denitrification

Supplementation of alternative carbon sources is a technological bottleneck, particularly in post-denitrification processes due to stringent effluent nitrogen levels. This study focuses on enhancing the sustainability of wastewater treatment practices by partially replacing conventionally used fossil-derived methanol with organic waste-derived volatile fatty acids (VFAs) in moving bed biofilm reactors (MBBRs). In this regards, results of denitrification batch assays with sequential or simultaneous addition of VFA effluent from acidogenic fermentation of potato starch residue (AD-VFAPPL) and chicken manure (AD-VFACKM), simulated synthetic VFAs solutions (sVFAs), and methanol as carbon source were presented and discussed. Although methanol has proven superior in the conversion of nitrate to nitrite, VFAs are more effective when it comes to reducing nitrite. Although solely added AD-VFAPPL had a slower denitrification capability (0.56 ± 0.13 mgNOx-N removed/m2/day) than methanol (1.04 ± 0.46 mgNOx-N removed/m2/day), up to 50% of the methanol can be replaced by waste-derived AD-VFAPPL and achieve comparable performance (1.08 ± 0.07 mgNOx-N removed/m2/day) with the pure methanol. This proves that the co-addition of VFAs together with methanol can fully compete with pure methanol in performance, providing a promising opportunity for wastewater treatment plants to potentially reduce their carbon footprint and become more sustainable in practice while benefiting from recovered nutrients from waste.

Thorough Investigation of the Effects of Cultivation Factors on Polyhydroalkanoates (PHAs) Production by Cupriavidus necator from Food Waste-Derived Volatile Fatty Acids

Volatile fatty acids (VFAs) have become promising candidates for replacing the conventional expensive carbon sources used to produce polyhydroxyalkanoates (PHAs). Considering the inhibitory effect of VFAs at high concentrations and the influence of VFA mixture composition on bacterial growth and PHA production, a thorough investigation of different cultivation parameters such as VFA concentrations and composition (synthetic and waste-derived VFAs) media, pH, aeration, C/N ratio, and type of nitrogen sources was conducted. Besides common VFAs of acetic, butyric and propionic acids, Cupriavidus necator showed good capability for assimilating longer-chained carboxylate compounds of valeric, isovaleric, isobutyric and caproic acids in feasible concentrations of 2.5–5 g/L. A combination of pH control at 7.0, C/N of 6, and aeration of 1 vvm was found to be the optimal condition for the bacterial growth, yielding a maximum PHA accumulation and PHA yield on biomass of 1.5 g/L and 56%, respectively, regardless of the nitrogen sources. The accumulated PHA was found to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with the percentage of hydroxybutyrate in the range 91–96%. Any limitation in the cultivation factors was found to enhance the PHA yield, the promotion of which was a consequence of the reduction in biomass production.

Potential of food waste-derived volatile fatty acids as alternative carbon source for denitrifying moving bed biofilm reactors

Fossil-based materials such as methanol are frequently used in the denitrification process of advanced biological wastewater treatment as external carbon source. Volatile fatty acids (VFAs) produced by anaerobic digestion of food waste, are sustainable compounds with the potential to act as carbon sources for denitrification, reducing carbon footprint and material costs. In this study, the effectiveness of food waste-derived VFAs (AD-VFA) was investigated in the post-denitrification process in comparison with synthetic VFA and methanol as carbon sources. Acetic acid had the highest rate of disappearance among single tested VFAs with a denitrification rate of 0.44 g NOx-N removed/m2/day, indicating a preferential utilization pattern. While AD-VFA had a denitrification rate of 0.61 mg NOx-N removed/m2/day, sVFA had a rate of 0.57 mg NOx-N removed/m2/day, indicating that impurities in AD-VFA did not play substantial role in denitrification. AD-VFA proved to be promising carbon source alternative for denitrification in wastewater treatment plants.

Feasibility of nanofiltration process for high efficient recovery and concentrations of food waste-derived volatile fatty acids

Various methods exist for the recovery of volatile fatty acids from organic mixed waste effluents, and among them, the membrane filtration process holds a great promise over other recovery methods due to their simplicity, sustainability and high efficiency. Hence, in this study, nanofiltration experiments were carried out using two commercial nanofiltration membranes of 200–300 Da and 300–500 Da under various pH (4, 5.4, 7 and 9) at constant pressure (15 bar) and temperature of 20-21 °C in order to achieve a higher amount of volatile fatty acids from the real mixed food waste-based effluent. Results showed that solution pH plays an important role in the physicochemical parameters such as total solids removal rate was above 80 % at pH 4, chemical oxygen demand, ammonia and phosphorus removed to some extent at pH 9. Subsequently, the concentration and recovery percentages of volatile fatty acids increased with solution pH 9; in particular, lower molecular weight cut-off membrane, i.e., 200–100 Da, appeared to be more effective with an increased concentration of total volatile fatty acids (16.94 g L−1) and recovery percentage above 90 % at pH 9. Membrane performance was also evaluated and correlated with recovery performance in terms of permeate flux reduction at lower pH. An important finding of this study was the concentration and recovery percentages of volatile fatty acids reached around 96 % after 3rd cycle by conducting a repeated sequencing nanofiltration process, which was identified as a promising option to enhance the recovery percentages of volatile fatty acids.

Production of Docosahexaenoic Acid and Odd-Chain Fatty Acids by Microalgae Schizochytrium limacinum Grown on Waste-Derived Volatile Fatty Acids

Heterotrophic microalgae are recognized as a source of bioactive compounds. However, there are still some drawbacks for their use at an industrial scale associated with the high cost of glucose, the main carbon source in heterotrophic cultures. In recent years, significant efforts have been made to investigate more sustainable carbon sources to produce biomass. In this study, the capacity of Schizochytrium limacinum to grow on waste-derived volatile fatty acids and the effect that their use produces on biomass and fatty acids profiles were investigated. Acetic, propionic, butyric, valeric and caproic acid were evaluated independently, as well as in a synthetic mixture (VFA). The use of acetic and butyric resulted in a good biomass productivity, while the use of valeric and propionic acid resulted in higher content of odd-chain fatty acids (OCFA), increasingly investigated due to their potential benefits for human health. The use of industrial waste-derived VFA as a potential carbon source was validated through the utilization of biowaste derived effluents from a volatile fatty acid platform. The biomass produced was of 18.5 g/L, 54.0% lipids, 46.3% docosahexaenoic acid (DHA) and 25.0% OCFA, concluding that waste derived VFA can produce DHA and OCFA in a suitable ratio of DHA/OCFA with potential industrial applications.

Cell Retention as a Viable Strategy for PHA Production from Diluted VFAs with Bacillus megaterium

The production of biodegradable and biocompatible materials such as polyhydroxyalkanoates (PHAs) from waste-derived volatile fatty acids (VFAs) is a promising approach towards implementing a circular bioeconomy. However, VFA solutions obtained via acidification of organic wastes are usually too diluted for direct use in standard batch or fed-batch processes. To overcome these constraints, this study introduces a cell recycle fed-batch system using Bacillus megaterium uyuni S29 for poly(3-hydroxybutyrate) (P3HB) production from acetic acid. The concentrations of dry cell weight (DCW), P3HB, acetate, as well as nitrogen as the limiting substrate component, were monitored during the process. The produced polymer was characterized in terms of molecular weight and thermal properties after extraction with hypochlorite. The results show that an indirect pH-stat feeding regime successfully kept the strain fed without prompting inhibition, resulting in a dry cell weight concentration of up to 19.05 g/L containing 70.21% PHA. After appropriate adaptations the presented process could contribute to an efficient and sustainable production of biopolymers.

Evaluation of the Cultivation of Aspergillus oryzae on Organic Waste-Derived VFA Effluents and Its Potential Application as Alternative Sustainable Nutrient Source for Animal Feed

Considering the projected demand for protein supplementation in animal feed, as well as prioritizing plant-based protein provision for the growing human population, great stress is imposed on conventional protein sources, calling for new sustainable alternatives. In this regard, the production and application of single-cell proteins (SCPs) has proven to be a promising alternative. Therefore, in this study, volatile fatty acids (VFAs) effluents recovered from anaerobically digested FW, CKM, CM, and their combinations were applied for the cultivation of edible filamentous fungi Aspergillus oryzae. The biomass was further evaluated considering its protein, fat and alkali insoluble material contents. The maximum fungal biomass yielded of 0.47 ± 0.00 and 0.37 ± 0.00 g dry biomass/g tVFAsCODeq.consumed, with up to 47% protein and 5% fat content successfully cultivated in shake flasks and bench scale reactors, respectively. In addition to the production of protein-rich biomass, significant reductions in medium COD (25–58%) and ammonium (33–48%) were achieved. The results presented in this research work imply that using waste-derived VFAs for the production of animal feed grade SCP is an innovative approach that can contribute to the economy and sustainability of animal feed production process.

Cultivation of edible filamentous fungus Aspergillus oryzae on volatile fatty acids derived from anaerobic digestion of food waste and cow manure

In a circular economy approach, edible filamentous fungi (single cell protein) can be cultivated on volatile fatty acids (VFAs) derived from anaerobic digestion (AD) of organic-rich waste streams. In this study, the effect of pH, concentration/distribution of VFAs, nutrient supplementation, and type of waste on Aspergillus oryzae cultivation on synthetic VFAs, and actual VFAs derived from AD of food waste and cow manure were investigated. The optimal pH for A. oryzae growth on VFAs were 6 and 7 with maximum acetic acid consumption rates of 0.09 g/L.h. The fungus could thrive on high concentrations of acetic (up to 9 g/L) yielding 0.29 g dry biomass/gVFAsfed. In mixed VFAs cultures, A. oryzae primarily consumed caproic and acetic acids reaching a biomass yield of 0.26 g dry biomass/gVFAsfed (containing up to 41% protein). For waste-derived VFAs at pH 6, the fungus successfully consumed 81–100% of caproic, acetic, and butyric acids.

Waste-derived volatile fatty acids as carbon source for added-value fermentation approaches.

The establishment of a sustainable circular bioeconomy requires the effective material recycling from biomass and biowaste beyond composting/fertilizer or anaerobic digestion/bioenergy. Recently, volatile fatty acids attracted much attention due to their potential application as carbon source for the microbial production of high added-value products. Their low-cost production from different types of wastes through dark fermentation is a key aspect, which will potentially lead to the sustainable production of fuels, materials or chemicals, while diminishing the waste volume. This article reviews the utilization of a volatile fatty acid platform for the microbial production of polyhydroxyalkanoates, single cell oil and omega-3 fatty acids, giving emphasis on the fermentation challenges for the efficient implementation of the bioprocess and how they were addressed. These challenges were addressed through a research project funded by the European Commission under the Horizon 2020 programme entitled 'VOLATILE-Biowaste derived volatile fatty acid platform for biopolymers, bioactive compounds and chemical building blocks'.

Toward net-zero sustainable aviation fuel with wet waste–derived volatile fatty acids

With the increasing demand for net-zero sustainable aviation fuels (SAF), new conversion technologies are needed to process waste feedstocks and meet carbon reduction and cost targets. Wet waste is a low-cost, prevalent feedstock with the energy potential to displace over 20% of US jet fuel consumption; however, its complexity and high moisture typically relegates its use to methane production from anaerobic digestion. To overcome this, methanogenesis can be arrested during fermentation to instead produce C2 to C8 volatile fatty acids (VFA) for catalytic upgrading to SAF. Here, we evaluate the catalytic conversion of food waste-derived VFAs to produce n-paraffin SAF for near-term use as a 10 vol% blend for ASTM "Fast Track" qualification and produce a highly branched, isoparaffin VFA-SAF to increase the renewable blend limit. VFA ketonization models assessed the carbon chain length distributions suitable for each VFA-SAF conversion pathway, and food waste-derived VFA ketonization was demonstrated for >100 h of time on stream at approximately theoretical yield. Fuel property blending models and experimental testing determined normal paraffin VFA-SAF meets 10 vol% fuel specifications for "Fast Track." Synergistic blending with isoparaffin VFA-SAF increased the blend limit to 70 vol% by addressing flashpoint and viscosity constraints, with sooting 34% lower than fossil jet. Techno-economic analysis evaluated the major catalytic process cost-drivers, determining the minimum fuel selling price as a function of VFA production costs. Life cycle analysis determined that if food waste is diverted from landfills to avoid methane emissions, VFA-SAF could enable up to 165% reduction in greenhouse gas emissions relative to fossil jet.

Single Cell Oil Production by Oleaginous Yeasts Grown in Synthetic and Waste-Derived Volatile Fatty Acids.

Four yeast isolates from the species—Apiotrichum brassicae, Candida tropicalis, Metschnikowia pulcherrima, and Pichia kudriavzevii—previously selected by their oleaginous character and growth flexibility in different carbon sources, were tested for their capacity to convert volatile fatty acids into lipids, in the form of single cell oils. Growth, lipid yields, volatile fatty acids consumption, and long-chain fatty acid profiles were evaluated in media supplemented with seven different volatile fatty acids (acetic, butyric, propionic, isobutyric, valeric, isovaleric, and caproic), and also in a dark fermentation effluent filtrate. Yeasts A. brassicae and P. kudriavzevii attained lipid productivities of more than 40% (w/w), mainly composed of oleic (>40%), palmitic (20%), and stearic (20%) acids, both in synthetic media and in the waste-derived effluent filtrate. These isolates may be potential candidates for single cell oil production in larger scale applications by using alternative carbon sources, combining economic and environmental benefits.

Utilization of food waste-derived volatile fatty acids for production of edible Rhizopus oligosporus fungal biomass

Rhizopus oligosporus is an edible filamentous fungus that can contribute to meet the growing demand for single-cell protein. Volatile fatty acids (VFAs) are favorable potential substrates for producing R. oligosporus biomass due to their capacity to be synthesized from a wide range of low-value organic solid wastes via anaerobic digestion. The goal of this work was to cultivate R. oligosporus using food waste-derived VFAs as the sole carbon source. To maintain the requisite low substrate concentrations, the fed-batch cultivation technique was applied. This resulted in a four-fold improvement in biomass production relative to standard batch cultivation. Maximum biomass yield of 0.21 ± 0.01 g dry biomass/g VFAs COD eq. consumed, containing 39.28 ± 1.54% crude protein, was obtained. In the bubble-column bioreactors, the complete uptake of acetic acid was observed, while the consumptions of caproic and butyric acids reached up to 97.64% and 26.13%, respectively.

Effect of synthetic and food waste-derived volatile fatty acids on lipid accumulation in Rhodococcus sp. YHY01 and the properties of produced biodiesel

Abstract Food waste-derived volatile fatty acids (VFAs) can act as a renewable feedstock for biodiesel production. In synthetic media, Rhodococcus sp. YHY01 was able to utilize various organic acids (acetate, butyrate, lactate, and propionate) as a carbon source. Butyrate was the optimal carbon source, having a minimum inhibitory effect on growth, and a maximum growth yield coefficient (Yx/s 0.288 g dcw/g butyrate) and fatty acid yield coefficient (Yf/s 0.206 g/g butyrate), compared to other organic acids (lactate, propionate, and acetate). Acetate, butyrate, and lactate mostly supported the production of fatty acids with an even number of carbons, whereas propionate enhanced the content of odd-numbered fatty acids. Response surface methodology (RSM) design study resulted in maximum biomass (2.8 g/L) and fatty acid yield (1.9 g/g) with acetate:butyrate:lactate (0.333:0.333:0.333) as a carbon source. Culture of Rhodococcus sp. YHY01 in media containing food waste-derived VFAs as the carbon source had a biomass (3.2 g dcw/L), fatty acid yield (2.2 g/L), and fatty acid accumulation (69% w/w) under nitrogen-limited condition. Biodiesel produced from food waste had an iodine value (IV, 37), cetane number (CN, 63), high heating value (HHV, 39), density (υ, 3.9), and viscosity (ρ, 0.868) that meet international standards.

The use of organic waste-derived volatile fatty acids as raw materials of C4-C5 bioalcohols

This study highlights a novel method for the production of bioalcohols, like 1-butanol, from organic waste-derived volatile fatty acids (VFAs) via non-biological pathways. A strategic two-step process was conducted to afford the bioalcohols. The process consists of esterification of VFAs to form VFA methyl esters (VFAMEs) followed by hydrogenation to bioalcohols. In the first step, carbon nanotubes was determined to be an effective carbon material to convert VFA to VFAME with high yields (>90%). In the second step, various metals (Pt, Pd, Rh, Ru, Ni, Co, and Cu) were tested and the inexpensive cobalt was the most active metal for hydrogenation of VFAMEs to their corresponding alcohols. The final yield of 1-butanol via the two-step process was 19 wt.%, which is comparable to that of conventional fermentation processes. Given the massive generation of organic waste, the two-step process to produce biobutanol has excellent potential for being developed in large scale.

Oleaginous yeast Yarrowia lipolytica culture with synthetic and food waste-derived volatile fatty acids for lipid production

BackgroundThe sustainability of microbial lipids production from traditional carbon sources, such as glucose or glycerol, is problematic given the high price of raw materials. Considerable efforts have been directed to minimize the cost and find new alternative carbon sources. Volatile fatty acids (VFAs) are especially attractive raw materials, because they can be produced from a variety of organic wastes fermentation. Therefore, the use of volatile fatty acids as carbon sources seems to be a feasible strategy for cost-effective microbial lipid production.ResultsLipid accumulation in Y. lipolytica using synthetic and food waste-derived VFAs as substrates was systematically compared and evaluated in batch cultures. The highest lipid content obtained with acetic, butyric, and propionic acids reached 31.62 ± 0.91, 28.36 ± 0.74, and 28.91 ± 0.66%, respectively. High concentrations of VFA inhibited cell growth in the following order: butyric acid > propionic acid > acetic acid. Within a 30-day experimental period, Y. lipolytica could adapt up to 20 g/L acetic acid, whereas the corresponding concentration of propionic acid and butyric acid were 10 and 5 g/L, respectively. Cultures on a VFA mixture showed that the utilization of different types of VFA by Y. lipolytica was not synchronized but rather performed in a step-wise manner. Although yeast fermentation is an exothermic process, and the addition of VFA will directly affect the pH of the system by increasing environmental acidity, cultures at a cultivation temperature of 38 °C and uncontrolled pH demonstrated that Y. lipolytica had high tolerance in the high temperature and acidic environment when a low concentration (2.5 g/L) of either synthetic or food waste-derived VFA was used. However, batch cultures fed with food fermentate yielded lower lipid content (18.23 ± 1.12%) and lipid productivity (0.12 ± 0.02 g/L/day). The lipid composition obtained with synthetic and food waste-derived VFA was similar to commercial biodiesel feedstock.ConclusionsThis work demonstrated the feasibility of utilizing synthetic and food waste-derived VFA for lipid production by Y. lipolytica. The good adaptability of Y. lipolytica to the high temperature and acidic environment further illustrated its considerable potential for practical application.

Culture strategies for lipid production using acetic acid as sole carbon source by Rhodosporidium toruloides

Rhodosporidium toruloides AS 2.1389 was tested using different concentrations of acetic acid as a low-cost carbon source for the production of microbial lipids, which are good raw materials for biodiesel production. It grew and had higher lipid contents in media containing 4–20g/L acetic acid as the sole carbon source, compared with that in glucose-containing media under the same culture conditions. At acetic acid concentrations as high as 20g/L and the optimal carbon-to-nitrogen ratio (C/N) of 200 in a batch culture, the highest biomass production was 4.35g/L, with a lipid content of 48.2%. At acetic acid concentrations as low as 4g/L, a sequencing batch culture (SBC) with a C/N of 100 increased biomass production to 4.21g/L, with a lipid content of 38.6%. These results provide usable culture strategies for lipid production by R. toruloides AS 2.1389 when using diverse waste-derived volatile fatty acids.

Bioelectrochemical recovery of waste-derived volatile fatty acids and production of hydrogen and alkali

Volatile fatty acids (VFA) are organic compounds of great importance for various industries and environmental processes. Fermentation and anaerobic digestion of organic wastes are promising alternative technologies for VFA production. However, one of the major challenges is development of sustainable downstream technologies for VFA recovery. In this study, an innovative microbial bipolar electrodialysis cell (MBEDC) was developed to meet the challenge of waste-derived VFA recovery, produce hydrogen and alkali, and potentially treat wastewater. The MBEDC was operated in fed-batch mode. At an applied voltage of 1.2 V, a VFA recovery efficiency of 98.3%, H2 of 18.4 mL and alkali production presented as pH of 12.64 were obtained using synthetic fermentation broth. The applied voltage, initial VFA concentrations and composition were affecting the VFA recovery. The energy balance revealed that net energy (5.20–6.86 kWh/kg-VFA recovered) was produced at all the applied voltages (0.8–1.4 V). The coexistence of other anionic species had no negative effect on VFA transportation. The VFA concentration was increased 2.96 times after three consecutive batches. Furthermore, the applicability of MBEDC was successfully verified with digestate. These results demonstrate for the first time the possibility of a new method for waste-derived VFA recovery and valuable products production that uses wastewater as fuel and bacteria as catalyst.