Volatile Fatty Acid Production Research Articles

Nanoparticle-mediated advancements in volatile fatty acids production through anaerobic fermentation: a comprehensive review

Nanoparticle-mediated advancements in volatile fatty acids production through anaerobic fermentation: a comprehensive review

Enhancing volatile fatty acid production in batch test reactors by modulating microbial communities with potassium permanganate

The shift from conventional wastewater treatment plants to biorefineries is one of the most environmentally and economically sustainable pathways for extracting valuable compounds from waste. Besides chemical-physical processes, microorganisms within sewage sludge utilize organic and inorganic pollutants in the wastewater as nutrients, leading to effective water purification. However, the remaining solid sludge residue, typically destined for specific landfills or incineration, could undergo microbial fermentation to produce volatile fatty acids (VFA), metabolic precursors for biopolymers. Increasing attention has been directed towards optimizing operational parameters to enhance VFA production during sewage sludge fermentation. This study examined the impact of potassium permanganate (PP) on microbial communities during the sewage sludge's acidogenic fermentation. The results highlighted the positive effect of PP treatment, which increased COD production and VFA yield up to 1263.5 mg/L and 664.2 mg COD/L, respectively. The presence of PP significantly enhances VFA yield promoting bacteria positively linked to VFA production.

Rumen fluid pretreatment promotes anaerobic methane production: revealing microbial dynamics driving increased acid yield from different concentrations of corn straw.

In this work, the corn straw (CS) with concentrations of 3%, 6%, and 9% (w/v) were pretreated by rumen fluid (RF) and then used for batched mesophilic biogas production. The results showed that after a 6-day pretreatment, volatile fatty acid (VFAs) production of 3.78, 8.27, and 10.4 g/L could be found in 3%, 6%, and 9%, respectively. When concerning with biogas production, the highest accumulative methane production of 149.1 mL CH4/g volatile solid was achieved by 6% pretreated CS, which was 22% and 45% higher than 3% and 9%, respectively. Also, it was 3.6 times higher than the same concentration of unpretreated CS. The results of the microbial community structure analysis revealed that the 6% CS pretreatment not only maintained a microbial community with the highest richness and diversity, but also exhibited the highest relative abundance of Firmicutes (45%) and Euryarchaeota (3.9%). This high abundance was conducive to its elevated production of VFAs and methane. These findings provide scientific reference for the utilization of CS and support the development of agricultural waste resource utilization and environmental protection.

Rumen fermentation and nutrient utilization of growing Yankasa rams fed a mixed ration containing tiger nut (Cyperus esculentus) residue and cowpea husk (Vigna unguiculata L. Walp)

Thirty (30) Yankasa growing rams were used to investigate the effect of feeding cowpea husk and tiger nut residue in a mixed ration on the rumen ecology, nutrient intake, nutrient digestibility, and nitrogen balance of Yankasa rams. Significant differences (p < 0.05) were observed in the rumen ecology, nutrient intake, nutrient digestibility, and nitrogen balance between the treatments. Rumen ecology was influenced by the diet, with variations in rumen pH, temperature, and volatile fatty acid production. The results indicated that the highest rumen pH and temperature were observed in Treatment 2, while acetate, butyrate, and propionate levels varied among treatments. Nutrient intake and digestibility were significantly affected by the diet. Dry matter intake, crude protein intake, nitrogen detergent fiber (NDF), and acid detergent fiber (ADF) intake varied among treatments. Treatment 3 showed the highest dry matter intake, while Treatment 5 had the highest NDF intake. Crude protein intake was highest in Treatment 3, and the highest values for most nutrients were observed from the same treatment. The results for nitrogen balance in Yankasa rams indicate a positive nitrogen balance, suggesting that the rams received adequate amounts of nitrogen from the diets fed. Feeding 20% cowpea husk and 20% tiger nut residue provides optimum performance for rams in terms of rumen fermentation, and nutrient utilisation.

Enhancing biomethanation performance through co-digestion of diverse organic wastes: a comprehensive study on substrate optimization, inoculum selection, and microbial community analysis.

A blend of organic municipal solid waste, slaughterhouse waste, fecal sludge, and landfill leachate was selected in different mixing ratios to formulate the best substrate mixture for biomethanation. Individual substrates were characterized, and the mixing ratio was optimized with the help of a response surface methodology tool to a value of 1:1:1:1 (with a C/N ratio of 28±0.769 and total volatile fatty acid (VFA) concentration of 2500±10.53 mg/L) to improve the overall biomethanation. The optimized blend (C/N ratio: 28.6, VFA: 2538 mg/L) was characterized for physicochemical, biological, and microbial properties and subjected to anaerobic digestion in lab-scale reactors of 1000 mL capacity with and without the addition of inoculum. The biogas yield of individual substrates and blends was ascertained separately. The observed cumulative biogas yield over 21 days from the non-inoculated substrates varied between 142±1.95 mL (24.6±0.3 ml/gVS) and 1974.5±21.72 mL (270.4±3.1 ml/gVS). In comparison, the addition of external inoculation at a 5% rate (w/w) of the substrate uplifted the minimum and maximum cumulative gas yield values to 203±9.9 mL (35.0±1.6 mL/gVS) and 3394±13.4 mL (315.3±1.2 mL/gVS), respectively. The inoculum procured from the Defence Research and Development Organisation (DRDO) was screened in advance, considering factors such as maximizing VFA production and consumption rate, biogas yield, and digestate quality. A similar outcome regarding biogas yield and digestate quality was observed for the equivalent blend. The cumulative gas yield increased from 2673±14.5 mL (373.7±2.2 mL/gVS) to 4284±111.02 mL (391.47±20.02 mL/gVS) over 21 days post-application of a similar dosage of DRDO inoculum. The 16S rRNA genomic analysis revealed that the predominant bacterial population belonged to the phylum Firmicutes, with the majority falling within the orders Clostridiales and Lactobacillales. Ultimately, the study advocates the potential of the blend mentioned above for biomethanation and concomitant enrichment of both biogas yield and digestate quality.

Non-targeted facilitation of primary sludge anaerobic fermentation by micro-aeration and the simultaneous nutrients transformations

Anaerobic fermentation is a widely used technology for resource recovery from municipal sludge (e.g., primary sludge). Micro-aeration is an emerging strategy which can be incorporated into this technology. However, the effect of micro-aeration on the anaerobic fermentation performance and the nutrients transformations are not well known. This study investigated the impact of micro-aeration on the production of volatile fatty acids (VFAs) from primary sludge as well as the simultaneous nitrogen (N) and phosphorus (P) transformations in the system. The obtained results indicated that application of micro-aeration improved the microbial activities and facilitated all the hydrolysis, acetogenesis and methanogenesis processes. Hydrogenotrophic methanogen was enriched by micro-aeration while the acetoclastic methanogenesis was still the dominant CH4 production pathway at gene level. The concentration of VFAs was lower with micro-aeration than in the control system, which could be attributed to the enhanced consumption of VFAs. The simultaneous transformations of N and P were observed with different patterns. Micro-aeration led to removal of up to 131.6 mg/L of N, with occurrence of nitrification and denitrification found to be responsible for the N removal. In contrast, the total P content remained unchanged in the reactor. However, micro-aeration was found to inhibit both extracellular organic-P mineralization and intracellular poly-P degradation, resulting in lower soluble PO43−-P and more P distributed in the organic-P fraction in solid phase. This study provides novel insights into the microscopic mechanisms of the micro-aeration on anaerobic fermentation and the simultaneous regulation of N and P release.

171 Current limitations to implement fiber in U.S. sow and nursery diets, and nutritional strategies to support ideal fiber profile

Abstract The importance of fiber in swine nutrition is increasingly recognized, and the consequences of insufficient dietary fiber can be significant. Consequently, U.S. production nutritionists have begun exploring the incorporation of fiber into their nutrition programs. However, incorporating fiber into diets is not without challenges. Analytical capabilities for assessing fiber content have improved, yet accessing accurate data remains a hurdle. Furthermore, the cost of analysis limits the ability of nutritionists to utilize these advanced methods for ingredient analysis. The lack of information around fiber requirements in the diet may be due to the insufficient methodology that has historically been available to measure the indigestible fraction of the diet. In the nursery phase, research findings on the effects of fiber have been mixed, likely influenced by the health status of the animals. Short-term growth performance trials may not fully capture the benefits of fiber, and more comprehensive, long-term studies focusing on health-related parameters are lacking. Similarly, research on sow nutrition faces challenges due to the limitations of barn structures and feed lines. Sow trials typically involve only a small number of treatments, often requiring before- and after- assessments. Moreover, the benefits of fiber are more apparent in later reproductive cycles, necessitating prolonged research efforts. Given the limited phases in sow diets, primarily lactation and gestation, conducting sow research is both challenging and costly. Evidence from European literature and recent U.S. studies suggests that the total dietary fiber and the level of soluble, fermentable fiber have a crucial role in swine diets, particularly for sows and piglets. However, the availability and affordability of such fiber types in the U.S. are limited. The majority of fiber-rich ingredients in the U.S. consist mostly of insoluble fiber. To address this limitation, technological advancements will be needed to transform available fiber sources into the desired fiber constructs, rather than relying solely on fiber-rich ingredients. A stimbiotic, which encourages fiber fermentation, may be key to achieving the desired fiber profile. The addition of a stimbiotic has been shown to increase the digestibility of fiber. It also increases the capacity of the beneficial microbiome to break down and ferment fiber, which leads to an increase in the production of volatile fatty acids (acetic, propionic and butyric). In conclusion, U.S. swine nutritionist must explore alternative dietary strategies to capturing the ideal fiber composition. Key word: fiber, nursery, sow

15 Effects of post-MSC DDGS inclusion in gestation diets compared with other fiber sources on in vitro gas and volatile fatty acid production

Abstract In vitro fermentation has been used to characterize hindgut fermentation of fibrous ingredients fed to grower pigs. However, there is little to no work investigating hindgut fermentation of fibrous feedtuffs in gestating sows, who have greater fermentative capacity compared with grower pigs. The objective of this study was to characterize hindgut gas production and volatile fatty acids (VFA) following in vitro fermentation using fecal inoculum collected from the sows when fed either post-protein separation dried-distiller’s grains with solubles (post-MSC DDGS), soyhulls, or sugar beet pulp. Pregnant sows (n = 22; parity 0 to 1; body weigh = 190 ± 10 kg) were allocated to 1 of 6 dietary treatments in a crossover design with two collection periods (period 1 from d 40-59 of gestation and period 2 from d 60-79 of gestation) to attain at least 7 observations per treatment. Two of the six diets were practical corn-soybean meal-based gestation diets with either soyhulls (17.5% inclusion) or post-MSC DDGS (15% inclusion). The remaining four diets included a corn-basal diet and the basal diet plus 30% inclusion of post-MSC DDGS, soyhulls, or sugar beet pulp. Sows were fed experimental diets (2.2 kg/d in a single feeding) in two 20 d collection periods. For in vitro fermentation, fresh fecal samples were collected on d 16 of each collection period, prepared as inoculum, and subjected to the gas production measurement technique through in vitro fermentation. Supernatant residue from the in vitro fermentation was subjected to VFA analysis by gas chromatography. Data were analyzed with ANOVA and fixed to a mixed linear model using treatment as the main effect and collection period as a random variable. Total gas production of the practical diet containing post-MSC DDGS diet was 132 ml/g less (P = 0.03) than the practical soyhull diet. While the total concentration of total VFA did not differ between practical diets, the concentration of isovalerate tended to be greater for the post-MSC DDGS diet compared with the soyhull diet (P = 0.09). Total gas production was 140 and 375 mg/L less for the post-MSC DDGS than soyhulls and sugar beet pulp, respectively (P < 0.01). The concentrations of butyrate and isovalerate (relative to total VFA) were approximately 7 and 2%, respectively, greater for the post-MSC DDGS than in the soyhulls or sugar beet pulp fermentation residues (P < 0.05). Concentrations of other VFA relative to total VFA did not differ between fiber sources. In conclusion, post-MSC DDGS can contribute to sustainable swine production when fed to gestating by lowering total gas production and being a source of volatile fatty acids.

Biosurfactant induced microwave disintegration of macroalgae for fermentative biohydrogen production

Biosurfactant-induced microwave disintegration (BSMD), an energy and cost effective pretreatment method, has been proposed to increase biohydrogen production from marine macroalgae (Chaetomorpha antennina). Microwave disintegration (MD) was performed for microwave powers from 90 to 540 Watts in varied periods from 0 to 60 mins. During this MD process, a disintegration time of 25 mins and microwave power of 360 W were obtained as optimum conditions, resulting in the dissolvable organics release (DOR) of 1860 mg/L and a disintegration efficiency (DE) of 14.3%. BSMD was implemented by adding the biosurfactant dosages from 0.005 to 0.05 g/g TS with the optimum power of MD at various intervals of time of 0–30 min. The optimum biosurfactant dosage for efficient disintegration in BSMD was 0.03 g/g TS, resulting in 19.55% DE and 2542 mg/L of DOR in 10 mins. BSMD sample showed increased volatile fatty acid (VFA) production of about 1393 mg/L than MD (1000 mg/L). In addition, BSMD consumed less input energy (IE) of (480 kWh / kg of solids) than MD (1200kWh / kg of solids). The highest amount of biohydrogen was produced by BSMD (120 mL H2/g COD) than MD (78 mL H2/g COD). The results showed BSMD method was energy-efficient for producing biohydrogen with an energy ratio of 1.96, and economical with a net profit of 74.78 $.

Agricultural Wastes and Their By-Products for the Energy Market

The conversion of lignocellulosic agricultural waste into biofuels and other economically valuable compounds can reduce dependence on fossil fuels, reduce harmful gas emissions, support the sustainability of natural resources, including water, and minimize the amount of waste in landfills, thus reducing environmental degradation. In this paper, the conversion of agricultural wastes into biomethane, biohydrogen, biodiesel, bioethanol, biobutanol, and bio-oil is reviewed, with special emphasis on primary and secondary agricultural residues as substrates. Some novel approaches are mentioned that offer opportunities to increase the efficiency of waste valorization, e.g., hybrid systems. In addition to physical, chemical, and biological pretreatment of waste, some combined methods to mitigate the negative effects of various recalcitrant compounds on waste processing (alkali-assisted thermal pretreatment, thermal hydrolysis pretreatment, and alkali pretreatment combined with bioaugmentation) are evaluated. In addition, the production of volatile fatty acids, polyhydroxyalkanoates, biochar, hydrochar, cellulosic nanomaterials, and selected platform chemicals from lignocellulosic waste is described. Finally, the potential uses of biofuels and other recovered products are discussed.

Sustainable Aviation Fuel from High-Strength Wastewater via Membrane-Assisted Volatile Fatty Acid Production: Experimental Evaluation, Techno-economic, and Life-Cycle Analyses

Sustainable Aviation Fuel from High-Strength Wastewater via Membrane-Assisted Volatile Fatty Acid Production: Experimental Evaluation, Techno-economic, and Life-Cycle Analyses

Competitive partitioning of denitrification pathways during arrested methanogenesis: Implications in ammonium recovery, N2O emission, and volatile fatty acid production

The complex interaction between nitrate (NO3−) reduction and fermentation is poorly understood when high levels of NO3− are introduced into anaerobic systems. This study investigated the competitive distribution between conventional denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA) during simultaneous denitrification and fermentation in arrested methanogenesis. Up to 62% of initial NO3− (200 mg-N/L) was retained as ammonium through DNRA at a chemical oxygen demand (COD)/N ratio of 25. Significant N2O emission occurred (1.7 – 8.0% of the initial NO3−) with limited carbon supply (≤1600 mg COD/L) and sludge concentration (≤3000 mg COD/L). VFA composition shifted predominantly towards acetic acid (>50%) in the presence of nitrate. A novel kinetic model was developed to predict DNRA vs. DEN partitioning and NO2− accumulation. Overall, NO3− input, organic loading, and carbon source characteristics independently and collectively controlled competitive DNRA vs. DEN partitioning.

Biohydrogen, Volatile Fatty Acids, and Biomethane from Mezcal Vinasses—A Dark Fermentation Process Evaluation

Mezcal is a drink made in Mexico, the production of which generates vinasses with a high content of organic matter (OM) that is not utilized. However, these residues have the potential to be drawn upon in dark fermentation (DF) processes to obtain biogas rich in biohydrogen, biomethane, and volatile fatty acids (VFAs) with the potential to become biofuels. In the present work, the effect of reaction time (RT) and organic load (OL) was assessed based on the efficiency of removing OM, the production of VFAs, and the generation and composition of biogas in a process of DF fed with mezcal vinasses. The results show that increasing the RT and decreasing the OL increases COD removal but decreases biohydrogen production. The maximum production of H2 (64 ± 21 NmL H2/Lreactor) was obtained with the lowest RT (1 d) and the highest OL (13.5 gCODm3d−1), while the highest accumulation of VFAs (2007 ± 327 mg VFA/L) was obtained with an RT of 3 d. It was determined that RT and OL are key parameters in DF processes for biohydrogen and VFA production.

Bentonite as an arsenic and lead adsorbent in the bovine digestive tract: an in vitro study

Objective. To determine the recommended dose of bentonite as a chelator of arsenic (As) and lead (Pb) in the rumen, abomasal and duodenal environment by means of an in vitro system, considering the variables of ruminal fermentation and the adsorbent effect of As and Pb. Materials and Methods. Vials were prepared with 50 mL of anaerobic medium and 0.5 g of alfalfa as substrate. The culture media were added with 1.01 and 1.95 ppm of As and Pb, respectively. The treatments consisted of different levels of bentonite (B) added to the medium, B-0%, B-1.5%, B-3.0% and B-4.5%. The media were incubated for 24 h, and pH, volatile fatty acid (VFA) and N-NH3 production, in vitro DM digestibility (IVDMD) and chelating effect of bentonite were measured, simulating rumen, abomasum and duodenum conditions. A completely randomised design and orthogonal contrasts were used. Results. Bentonite did not modify the pH (p > 0.05) and the molar proportion of VFAs, but the total VFA concentration presented a negative linear effect with increasing bentonite levels. Likewise, the N-NH3 level decreased (p < 0.05) with increasing inclusion levels of bentonite. The IVDMD was reduced with B-3% and B-4.5% (52.36b and 49.74b%) in comparison to B-0% and B-1.5% (62.30a and 61.98a%). Treatments B-1.5% and B-4.5% improved (p < 0.05) As and Pb adsorption in the rumen, abomasal and duodenal environments. Conclusions. The recommended level of bentonite as chelator of As and Pb is 1.5%; doses of 4.5% affect IVDMD and, consequently, animal productivity.

Life cycle analysis for the production of volatile fatty acids from wastewater treatment plant sludge

Life cycle analysis for the production of volatile fatty acids from wastewater treatment plant sludge

Bioreduction of chromate in a syngas-based membrane biofilm reactor

This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis. Corresponding to the short hydraulic retention time of 0.25 days, a high chromate removal rate of 80 µmol/L/d was attained. In addition to chromate reduction, in situ production of volatile fatty acids (VFAs) by gas fermentation was observed. Three sets of in situ batch tests and two groups of ex situ batch tests jointly unravelled the mechanisms, showing that biological chromate reduction was primarily driven by VFAs produced from in situ syngas fermentation, whereas hydrogen originally present in the syngas played a minor role. 16 S rRNA gene amplicon sequencing has confirmed the enrichment of syngas-fermenting bacteria (such as Sporomusa), who performed in situ gas fermentation leading to the synthesis of VFAs, and organics-utilising bacteria (such as Aquitalea), who utilised VFAs to drive chromate reduction. These findings, combined with batch assays, elucidate the pathways orchestrating synergistic interactions between fermentative microbial cohorts and chromate-reducing microorganisms. The findings facilitate the development of cost-effective strategies for groundwater and drinking water remediation and present an alternative application scenario for syngas.

The effect of carbon source produced by modified corncob fermentation on denitrification

The advanced nitrogen removal is always limited by low carbon to nitrogen ratio (C/N), the feasibility of producing carbon source through fermenting corncob was evaluated in this study. The effect of initial pH, solid content and temperature on the production of volatile fatty acids (VFAs) by alkali pre-treated corncob were investigated, and the denitrification performance with anaerobic fermentation liquid (AFL) and sodium acetate (SA) was compared. The results showed that alkali pretreatment improved the mass transfer inside the corncob, and the solid content had a major impact on VFA production. The denitrification rate of the two systems was related to the influent NO3−-N concentration only when the C/N was 6:1 and 8:1, and the removal efficiency was bigger than 95 %. Nevertheless, the nitrite reduction of the AFL system was limited at a C/N of 4:1, and the removal efficiency of NO₃−-N was only 65.10 %. Moreover, the AFL system enriched a large number of genera involved in nitrogen removal and organic decomposition. The functional analysis showed that the denitrification activity and ability of the AFL system were slightly lower. However, the SA system enriched more pathogenic bacteria, the relative abundances of Arcobacter and Pseudomonas were 28.74 % and 11.85 %, respectively. This study provides a reference for optimizing the design and control of VFAs production by continuous fermentation from agricultural waste.

Relationship between predicted in vivo and observed in vivo methane production from dairy cows fed a grass-silage based diet with barley, oats, or dehulled oats as a concentrate supplement

The objectives of this study were to compare predicted in vivo methane (CH4) values based on data from an in vitro gas production experiment with observed in vivo values measured by the GreenFeed system, and to investigate the effect of the diet fed to donor animals of rumen inoculum (RI) on predicted in vivo CH4 production. For this purpose, we conducted an in vivo experiment simultaneously with an in vitro gas production experiment. The in vivo experiment (previously published) was a 4 × 4 Latin square design including 16 Nordic Red dairy cows. Cows were fed 60% grass silage and 40% concentrate which consisted of either barley, oats with hulls (hulled oats), dehulled oats, or a 50:50 mixture of hulled and dehulled oats on dry matter basis. The in vitro experiment was a 2 × 4 factorial design replicated in 4 runs. The in vitro diets were incubated for 48 h in two types of RI and formulated according to the diets fed in vivo. The RI was obtained from cows fed either barley (two cows) or hulled oats (two cows) as concentrate in the in vivo experiment. A set of models were applied to the gas and CH4 data obtained from the in vitro system to predict in vivo total gas and CH4 production. For the comparison between predicted in vivo and observed in vivo CH4, two different mean retention times (MRT of 35 and 50 h) in the rumen were used for the predictions. In the in vitro experiment, incubation residues were determined for organic matter digestibility and volatile fatty acids at 48 h of incubation. Assuming a MRT of 35 h in the rumen resulted in a significant relationship (P = 0.04) between predicted in vivo and observed in vivo CH4 yield (g/kg dry matter) with an R-square of 0.91 and a root mean square error of 0.20. Ranking of the diets in terms of their CH4 production was consistent between the in vitro and in vivo experiment. There were no significant interactions between diet and RI for any of the investigated parameters (P = 0.40). Rumen inoculum did not affect organic matter digestibility or total volatile fatty acid production. In conclusion, there was a good agreement between predicted in vivo and observed in vivo CH4 values. In addition, the diet of RI donor animal did not influence the comparison of diets in terms of CH4 production.

Integrating microbial abundance time series with fermentation dynamics of the rumen microbiome via mathematical modelling.

The rumen represents a dynamic microbial ecosystem where fermentation metabolites and microbial concentrations change over time in response to dietary changes. The integration of microbial genomic knowledge and dynamic modelling can enhance our system-level understanding of rumen ecosystem's function. However, such an integration between dynamic models and rumen microbiota data is lacking. The objective of this work was to integrate rumen microbiota time series determined by 16S rRNA gene amplicon sequencing into a dynamic modelling framework to link microbial data to the dynamics of the volatile fatty acids (VFA) production during fermentation. For that, we used the theory of state observers to develop a model that estimates the dynamics of VFA from the data of microbial functional proxies associated with the specific production of each VFA. We determined the microbial proxies using CowPi to infer the functional potential of the rumen microbiota and extrapolate their functional modules from KEGG (Kyoto Encyclopedia of Genes and Genomes). The approach was challenged using data from an in vitro RUSITEC experiment and from an in vivo experiment with four cows. The model performance was evaluated by the coefficient of variation of the root mean square error (CRMSE). For the in vitro case study, the mean CVRMSE were 9.8% for acetate, 14% for butyrate and 14.5% for propionate. For the in vivo case study, the mean CVRMSE were 16.4% for acetate, 15.8% for butyrate and 19.8% for propionate. The mean CVRMSE for the VFA molar fractions were 3.1% for acetate, 3.8% for butyrate and 8.9% for propionate. Ours results show the promising application of state observers integrated with microbiota time series data for predicting rumen microbial metabolism.

Source-Separated Industrial Wastewater Is a Candidate for Biogas Production through Anaerobic Digestion

Anaerobic digestion is a potential treatment for industrial wastewater that provides valuable end-products, including renewable energy (biogas). However, waste streams may be too variable, too dilute at high volumes, or missing key components for stable digestion; all factors that increase costs and operational difficulty, making optimisation crucial. Anaerobic digestion may benefit from process intensification, particularly the novel combination of high-strength source-separated wastewater to minimise volume, together with the use of biosolids biochar as a chemical and microbial stabiliser. This study investigates the stability, yield, and microbial community dynamics of the anaerobic digestion of source-separated industrial wastewater from a food manufacturer and a logistics company, using biosolids biochar as an additive, focusing on gas and volatile fatty acid (VFA) production, process stability, and the microbial community using bench-scale semi-continuous reactors at 30- and 45-day hydraulic retention time (HRT). While gas yields were lower than expected, stability was possible at high HRT. Methane production reached 0.24 and 0.43 L day−1 per litre reactor working volume at 30- and 45-day HRT, respectively, despite high VFA concentration, and was linked to the relative abundance of Methanosarcina in the microbial community. Interactions between substrate, VFA concentration, and the microbial community were observed. Biochar-assisted anaerobic digestion holds promise for the treatment of source-separated wastewater.