Anaerobic Digestion Reactor Research Articles

Tetracycline, sulfadimethoxine, and antibiotic resistance gene dynamics during anaerobic digestion of dairy manure.

Antibiotic use in animal husbandry is a potential entryway for antibiotics and antibiotic resistance genes (ARGs) to enter the environment through manure fertilizer application. The potential of anaerobic digestion (AD) to remove antibiotics and ARGs was investigated through tetracycline (TC) and sulfadimethoxine (SDM) additions into dairy manure digested for 44 d. This was the first study to evaluate antibiotics at concentrations quantified on-farm and relevant to field applications of manure. Triplicate treatments included a 1mg L-1 TC spike, a 10mg L-1 TC spike, a 1mg L-1 SDM spike (SDM 1), a 10mg L-1 SDM spike, a mixture of TC and SDM at 1mg L-1 each (TC+SDM 1), and a manure-only treatment. The SDM spikes were reduced by>99% reduction during the AD processing, but TC additions had variable reductions (0-96%). Molecular analyses showed that decreases in tetM gene copies correlated with declines in TC; however, reductions in SDM concentration did not correlate with decreases in sul1 gene copy concentrations. The AD reactors containing 10mg L-1 of TC and 10mg L-1 of SDM both had CH4 production reductions of 7.8%, whereas no CH4 reduction was observed in other treatments (1mg L-1 treatments). The study results were the first to confirm that AD can remove SDM when adding at concentrations observed in on-farm manure(<1mg L-1 ) without compromising energy production. Because TC adsorbs to the solid particles and transforms into isomers, the decreases in TC concentrations were more variable and should be closely monitored.

Demand-Driven Biogas Production from Anaerobic Digestion of Sewage Sludge: Application in Demonstration Scale

The power system needs flexible electricity generators. Whilst electricity generation from anaerobic digestion (AD) of sewage sludge has traditionally been baseload, transforming the generation capacity into a modern flexible operator is an opportunity to further valorise the resource. This work aims to demonstrate that AD of sewage sludge can support flexible generation and be operated dynamically in a relevant operational environment, to promote full scale implementation. A demonstration scale plant (20 m3 conventional AD reactors) was used to test several feeding regimes designed to return a biogas production rate that matches the demand. Two demand profiles are defined, either by common corporate power purchase agreements or by the main balancing mechanism used by the grid operator in UK. Demand-driven biogas production is demonstrated in this relevant operational environment, and the flexibilisation performance is positive in all scenarios. The value of the biogas increases by up to 2%, which outperforms the results obtained at pilot scale. Additionally, an increase in biogas yield is observed. Whilst transitional imbalances are recorded, they last for few hours and the overall stability is not affected. In conclusion, these trials demonstrate demand-driven biogas production is a feasible operational solution and full-scale implementation is possible.Graphical

UTILIZATION OF TOFU LIQUID WASTE INTO BIOGAS: REVIEW

Tofu production produces by-products in the form of liquid waste and solid waste. Tofu liquid waste which contains organic compounds has not been able to be managed properly. Industry owners only disposed of wastes into the environment. It causes water pollution and unpleasant odors around the tofu industry. One of the solutions to reduce environmental pollution is to utilize tofu liquid waste as alternative energy, namely biogas. The management of tofu liquid waste into biogas for the household scale tofu industry can use a fixed bed reactor, batch scale anaerobic reactor, and anaerobic sludge blanket (UASB) up-flow reactor. The UASB reactor is the best reactor for processing tofu liquid waste into biogas on a household scale. The volume of biogas produced by the UASB reactor was 11.115 liters, while the volume of biogas produced by the fixed bed reactor and batch scale anaerobic digester reactor was 3.5 liters and 1.525 liters, respectively.

Symbiotic Bacteroides and Clostridium-rich methanogenic consortium enhanced biogas production of high-solid anaerobic digestion systems

The high-solid anaerobic digestion (AD) for anaerobic co-digestion of palm oil mill effluent (POME) and oil palm empty fruit bunches (EFB) has low degradation efficiency. The enhancement of biogas production and EFB degradation efficiency by Bacteroides and Clostridium-rich methanogenic consortium was investigated. A Bacteroides and Clostridium-rich methanogenic consortium have xylanase, FPase, endo-glucanase, and exo-glucanase activity of 9.2, 1.3, 2.1, and 1.5 IU·mL−1, respectively with EFB degradation efficiency of 57.5%. Methane production (79 m3-CH4·tonne−1-EFB) by Bacteroides and Clostridium-rich methanogenic consortium augmentation was increased by 67.2%. The real application of bioaugmentation in the feedstock mixing tank before a feed to the AD reactor significantly increased methane yield (376.7 mL-CH4·g-1-VS−) by 85.5%. Bioaugmentation of Bacteroides and Clostridium-rich methanogenic consortium increased the number of hydrolytic bacteria and strengthened symbiotic relationships with indigenous microorganisms resulting in high biogas production, accelerated hydrolysis, and reduced solids accumulation of the high-solid AD process.

A study on biogas production from cassava peel and stem in anaerobic digestion reactor

Many countries are suffering from the limitation of clean energy sources. Global management nowadays is facing severe problems and challenges in supply energy without destroying the environment. Anaerobic digestion (AD) is a solution, that makes the best use of organic matter by changing it to biogas to generate of renewable heat, electricity, and fuel. Here, we demonstrate the potential of the feedstock—cassava peel (CP) and cassava stem (CS)—to produce biogas, using a continuous laboratory-scale AD reactor (2L working volumes) operated at mesophilic conditions (T = 35 °C), an organic loading rate of 0.0756 gCOD/L.day, for 25 days. Cassava peel depicted high total suspended solids (TSS = 404 mg/g), biochemical oxygen demand (BOD5 = 0.28 mg/L), and chemical oxygen demand (COD = 378 mg/L) as compared to cassava stem. Moreover, the hemicellulose and cellulose in the peel are higher than the stem. A compost tea from the vermicomposting process is using as an inoculum for the AD reactor. The highest biogas yield (~ 1000 ml) obtained from cassava peel with seeding. Polynomial trends with acceptable regression obtained for biogas generation and operating pH. The results also indicate that in the selected experimental range (25 days), the highest yield of biogas generation can be observed in the range of day 13 to day 20 to be around 56.1–54.5% (CP + S) and 54.5–50.0% (CS + S), respectively. Finally, the overall trends of cumulative biogas and cumulative methane yields in both CP + S and CS + S show linearity with almost positive slops.

Tri‐fold process integration leveraging high‐ and low‐temperature plasmas: From biomass to fertilizers with local energy and for local use

AbstractIn the present study, a series of thermochemical equilibrium modeling was conducted to assess the thermodynamic potential of biomass conversion to ammonia using thermal and nonthermal plasma at small‐ and large‐scale production. The system was designed and evaluated for five different locations in Australia including the Northern Territory, South Australia, Western Australia, and New South Wales using local biomass feedstock. The equilibrium modeling showed that the pathway of biomass to biomethane using an anaerobic digestion reactor, biomethane to hydrogen using a thermal plasma reactor, followed by conversion of hydrogen to ammonia via a nonthermal plasma reactor is a plausible route, by which the exergy efficiency of the process can be as high as ~60%. It is identified that the thermal plasma reactor required two distinct zones at 3000°C &lt; T &lt; 4000°C and 1500°C &lt; T &lt; 2500°C. The first zone aims at converting electric energy into very high temperature thermal flow while the second one enables to split methane molecules into solid carbon and hydrogen. The new ammonia process is also assessed from the viewpoint of the current industrial transformation, being accelerated by the post‐COVID economy, which moves toward local, resilient, integrated and self‐sufficient production under the umbrella of an emerging fractal economy. With respect to local production, the developed process is designed for a quick response to farm use and on‐time production in view of the demands of modern ICT‐sensor based precision agriculture. The proposed process was found to be flexible (“resilient”) against production scale, geographical location, price and type of feedstock, and source of renewable energy. The system was found to be flexible against different feedstock such as spent grape marc, mustard seed, bagasse, piggery and poultry. The system can be self‐sustained up to ~80% at T = 3500°C; with the thermal plasma reactor‐zone 2 producing the electricity requirements for the nonthermal plasma via a steam turbine power block. Finally, the system it is investigated to which degree the system is adaptable to local production, self‐sufficient, and circulatory.

RETRACTED: Prospects of Bioenergy Production From Organic Waste Using Anaerobic Digestion Technology: A Mini Review

Anaerobic digestion (AD) from organic waste has gained worldwide attention because it offers significant environmental and economic benefits. It can reduce the local waste through recycling which will conserve resources, reduce greenhouse gas emissions, and build economic resilience in the face of an uncertain future for energy production and waste disposal. The productive use of local waste through recycling conserves resources by reducing landfill space, the whole of life impacts of landfilling, and post-closure maintenance of landfills. Turning waste into a renewable energy source will assist the decarbonisation of the economy by reducing harmful emissions and pollutants. Therefore, this mini-review aims to summarise key factors and present valuable evidence for an efficient AD process. It also presents the pros and cons of different AD process to convert organic waste along with the reactor technologies. Besides, this paper highlights the challenges and the future perspective of the AD process. However, it is highlighted that for an effective and efficient AD process, appropriate temperature, pH, a strong inoculum to substrate ratio, good mixing and small particle sizes are important factors. The selection of suitable AD process and reactor is important because not all types of processes and reactors are not effective for processing organic waste. This study is of great importance for ongoing work on renewable energy generation from waste and provides important knowledge of innovative waste processing. Finally, it is recommended that the government should increase their support towards the AD technology and consider the unutilized significant potential of gaseous biofuel production.

Can the addition of biochar improve the performance of biogas digesters operated at 45°C?

Biogas from anaerobic digestion (AD) may contribute towards a green energy scene in the future. Despite many benefits, AD plant operators are still challenged by limitations of the technology. This study aimed at evaluating the effect of biochar addition to AD reactors operated at 45°C to optimize productivity, efficiency and stability of the process. Biochar is characterized by a large surface area and may therefore facilitate the creation of biofilms on the one hand and remove environmental contaminants on the other hand. Moreover, biochar may serve as pH control agent due to its alkaline properties, counteracting reactor acidification. Our results showed that the addition of biochar reduced efficiently the amount of H2S that initially occurred in the headspace during reactor start-up. Nevertheless, no impact on biogas- and methane yields was observed. This might be explained with an already well-working AD system without any severe disturbances, where the balancing nature of biochar did hardly count. Future studies, however, need to evaluate the effect on stressed systems. The microbiome analysis provided a detailed view of the microbial dynamics during the start-up phase, revealing Methanosarcina as dominant methanogen in the end. The addition of biochar did not alter the microbial community composition.

Innovative air-cathode bioelectrochemical sensor for monitoring of total volatile fatty acids during anaerobic digestion

Bioelectrochemical sensors have proven attractive as simple and low-cost methods with high potential for online monitoring of volatile fatty acids (VFA) in the anaerobic digestion (AD) process. Herein, an innovative dual-chamber air-cathode microbial fuel cell was developed as biosensor for VFA monitoring. The response of the biosensor was nonlinear and increased along with the concentration of VFA mixture increase (2.8–112 mM). Meanwhile, the relationship was linear with low VFA levels (<14 mM) within 2–5 h reaction. High concentrations of bicarbonate decreased the voltage. Stirring speeded up the response and amplified the signal but reduced the saturation concentration (approximately 30 mM) and therefore narrowed the detection range. The applicability of the biosensor was further validated with the effluents from an AD reactor during a start-up period. The VFA concentrations measured by the biosensor were well correlated with the gas chromatographic measurement. The results demonstrate that this biosensor with a novel design could be used for VFA monitoring during the AD process. Based on the 16S rRNA gene sequencing, the dominant microbiomes in the biofilm were identified as Geobacter, Hydrogenophaga, Pelobacter, Chryseobacterium, Oryzomicrobium, and Dysgonomonas.

Comparative life cycle assessment of three alternative techniques for increasing potable water supply in cities in the Global South

Abstract Clean water is becoming an increasingly scarce resource, and its availability is already compromised in many cities. Several techniques for increasing urban water availability are under consideration, but how their life cycle environmental impacts compare amongst one other remain largely unknown. For cities in developing countries, which are more susceptive to water shortages, this is particularly true. Furthermore, to directly compare these technologies, they must be evaluated using the same methodological framework. This paper compares, for the first time, the life cycle environmental impacts of the following three techniques: i) seawater desalination by reverse osmosis (SWRO); ii) indirect potable wastewater reuse (IPR) through an upflow anaerobic sludge blanket digestion reactor, oxidation ditch, ozonation, and managed aquifer recharge; and iii) rainwater harvesting (RWH) to substitute drinking water from the local distribution network. These techniques were evaluated in the Brazilian southern city of Florianopolis. Life cycle assessment (LCA) was used to calculate 15 environmental impact categories with the ReCiPe methodology. Variations in electricity consumption according to technical developments, effluent quality, and pumping efficiency were taken into consideration with parametric analysis. Furthermore, a sensitivity analysis was carried out regarding the direct emissions of methane and nitrous oxide during IPR, and the electricity mix. SWRO indicates the highest results for 12 out of the 15 impact categories, and IPR indicates the lowest values in nine categories. Electricity consumption is the main contributor to most impact categories during SWRO and IPR. Out of six categories (including climate change and human toxicity), RWH is the preferable option whilst comparatively also presenting the worst results for water depletion and marine eutrophication, with glass fibre produced for storage tanks being the main contributor. In the climate change potential category, for instance, SWRO, IPR and RWH have mean results of 751, 998, and 591 kg CO2 eq./1000 m3, respectively. However, the sensitivity analysis showed that if direct emissions of CH4 and N2O in IPR are low, then the IPR technique will have better results than the SWRO method, resulting in 710 kg CO2 eq./1000 m3. Additionally, the country electricity mix was found to be highly influential in the environmental impacts, especially for SWRO and IPR. The results obtained from this research will inform stakeholders, particularly those in developing countries, about possibilities of adopting new techniques for increasing water supplies, without comprising the environmental sustainability of these systems.

Treatment of Fracturing Wastewater by Anaerobic Granular Sludge: The Effect of Salinity and its Mechanism

The effects of salinity on the anaerobic treatment of fracturing wastewater regarding COD removal performance, sludge characteristics and microbial community were investigated. Results showed COD removal efficiency decreased from 76.0% to 69.1%, 65.6%, 33.7% and 21.9% with increasing salinity from control group (2.5 g/L) to 10, 15, 25 and 45 g/L, respectively. The cumulative biogas production decreased by 13.8%–81.1% when the salinity increased to 15–85 g/L. The increase of salinity led to the decline in the particle size of granular sludge, and the activity of granular sludge, including SMA, coenzyme F420 and dehydrogenase, was inhibited significantly. The results from flow cytometry indicated the percentage of damaged cells in granular sludge gradually increased with increase of salinity. Sequence analysis illustrated the microbial community structure in anaerobic digestion reactor was affected by the salinity, high salinity reduced the diversity of microbial community and decreased the abundance of methanogens, especially Methanosaeta.

A Model for Organic Matter of Fields Fertilized with Anaerobic Digestion Reactor Effluent

Soil fertility in agriculture is maintained by recalcitrant organic matter in manures and crop residues that are recycled to the fields. In some countries crop residues are burned in the field and in others these are collected and burned in furnaces as a source of renewable energy. These practices reduce the organic matter of the soils which is essential for their fertility. Anaerobic digestion installations convert manures and crop residues (mainly straw) into carbon dioxide, methane and other components. There remains a residue of recalcitrant organic material. The methane is is used as a source of renewable energy. The objective of this study is to determine the reduction in soil organic matter due to the anaerobic digestion of straw and cattle manure. The dynamics of the decay process of straw in the soil has been applied to the anaerobic digestion of these substrates. The decay of the organic material in the effluent of anaerobic digestion installations recycled to the fields has been modelled and compared to the decay of the substrates in the soil, without anaerobic digestion. The few field data on the effect of the effluent of anaerobic digestion reactor show no or little variation, compared to those when the substrates are directly applied to the fields. Around 45% of the energy content of straw and manures can be used as a source of renewable energy. The contribution to the soil organic matter of recycled effluent is 85% of that of the substrates directly applied to the soil.

Evaluation of the recirculation process of aerobic sludge from a percolating biological filter in an upflow anaerobic sludge blanket digestion reactor, with characterization of sludge solids

Evaluation of the recirculation process of aerobic sludge from a percolating biological filter in an upflow anaerobic sludge blanket digestion reactor, with characterization of sludge solids

Effect of total solids contents on the performance of anaerobic digester treating food waste and kinetics evaluation

The effects of total solids (TS) content on the performance of anaerobic digestion (AD) treating food waste (FW) and kinetic characteristics were investigated in mesophilic batch reactors. The results showed that FW could be digested normally in the AD system within the TS of 3%-30%. The volume methane yield of dry-AD increased by 5.2-10.6 times than that of wet-AD and the degradation time of unit substrate was shortened by 35%-71%. The system stability indicators of dry-AD, such as pH, VFA/TA, TAN and salt remain within the suppression threshold after digestion. dry-AD had obvious advantages. The kinetic analysis showed that ADM1 could be used to simulate the anaerobic digestion reactor of FW, and accurately simulated the methane production in different TS systems after calibrating. With the increase of TS, the hydrolysis and methane production showed a tendency to increase first and then decrease, but the decrease rate of hydrolysis was higher than that of methanogene. Increasing TS simultaneously weaken the hydrolysis rate and methanation rate, but the effect on the hydrolysis and acidification phase weaker. The ratio of the hydrolysis rate constant to the methanogenic Monod maximum specific absorption rate (khy/km_ac) was a new perspective to used to evaluate the balance between the hydrolysis stage and the methane production stage. The results show that the khy/km_ac ratio of the 15% TS and 20% TS experimental groups was close to 1. It can be speculated that the system TS between 15%-20% can be used as recommended value in anaerobic digestion engineering design to treat FW. Within this TS range, hydrolysis and methane production dynamics matching, the accumulation of inhibitors is also in a relatively moderate state in the threshold.

Mixing Assessment of an Industrial Anaerobic Digestion Reactor Using CFD

Mixing Assessment of an Industrial Anaerobic Digestion Reactor Using CFD

가축분뇨의 저장 방법에 따른 유기물 변화 및 바이오가스 생산 비교

In this study, the characteristics of pig manure according to the storage period were analyzed after storage for 60 days under different conditions of pH (4.0~6.0) and temperature (10,20,35oC) using sulfuric acid for pig manure among livestock manure and Optimal storage conditions was derived through the BMP test. In addition, the derived optimal storage conditions were applied to the anaerobic digestion reactor and biogas production was compared through continuous operation. frist, as a result the lowest decrease in organic matter was observed under the conditions of pH 4.0 and temperature of 10oC. In addition, as a result of evaluating the potential of biogasification, the lowest biogas was produced even though the amount of organic matter was preserved at the pH 4.0 condition in the result of the change of properties, while the higest produced of 332.5 mL was at pH 5.0 condition. through this, under conditions of pH 5.0 or less, biogas production is affected, which is considered to be the influence of sulfur components. secondly, storage method through temperature change, in proportion to the property change result, the maximum generation value of 395.2 mL was shown under 10oC condition where the most amount of organic matter was preserved. finally, the optimal temperature 10oC condition and the control group derived from the previous study were compared with the continuous operation based on the hydraulic residence time of 50 days. As a result, the methane yield per 1g VS was 0.26 and 0.22 L CH4, respectively. The biogasification rate was higher when the stored substrate was used through temperature control. Through the above results, it is thought that a higher amount of methane generation can be obtained when anaerobic digestion, a subsequent process, is applied as a storage method through temperature control.

Performance prediction of ZVI-based anaerobic digestion reactor using machine learning algorithms

The use of zero-valent iron (ZVI) to enhance anaerobic digestion (AD) systems is widely advocated as it improves methane production and system stability. Accurate modeling of ZVI-based AD reactor is conducive to predicting methane production potential, optimizing operational strategy, and gathering reference information for industrial design in place of time-consuming and laborious tests. In this study, three machine learning (ML) algorithms, namely random forest (RF), extreme gradient boosting (XGBoost), and deep learning (DL), were evaluated for their feasibility of predicting the performance of ZVI-based AD reactors based on the operating parameters collected in 9 published articles. XGBoost demonstrated the highest accuracy in predicting total methane production, with a root mean squared error (RMSE) of 21.09, compared to 26.03 and 27.35 of RF and DL, respectively. The accuracy represented by mean absolute percentage error also showed the same trend, with 14.26%, 15.14% and 17.82% for XGBoost, RF and DL, respectively. Through the feature importance generated by XGBoost, the parameters of total solid of feedstock (TSf), sCOD, ZVI dosage and particle size were identified as the dominant parameters that affect the methane production, with feature importance weights of 0.339, 0.238, 0.158, and 0.116, respectively. The digestion time was further introduced into the above-established model to predict the cumulative methane production. With the expansion of training dataset, DL outperformed XGBoost and RF to show the lowest RMSEs of 11.83 and 5.82 in the control and ZVI-added reactors, respectively. This study demonstrates the potential of using ML algorithms to model ZVI-based AD reactors.

Enhancing sludge fermentation and anaerobic digestion by mechanical cutting pretreatment

A new sludge pretreatment approach was developed to disintegrate waste activated sludge by mechanical cutting in this study, and the effect of mechanical cutting pretreatment on sludge fermentation and anaerobic digestion was analysed. The study results showed that a sludge disintegration degree of 6.7 % was achieved when the sludge was mechanically cut for 8 min. Moreover, the sludge fermentation was promoted by mechanical pretreatment. After the pretreatment, the soluble COD (SCOD) production in the sludge fermentation system was as high as 3052 mg/L, which was 2.28 times higher than that of the control group. More short-chain fatty acids (SCFAs), especially acetic acid, were observed in the pretreatment group. The mechanical pretreatment accelerated the sludge digestion process and increased biogas production, resulted in a maximum yield of 539.30 mL and 3.06 times higher than that of the control group. High-throughput sequencing results indicated that the microbial community composition in the sludge fermentation system was affected by the mechanical pretreatment, and these changes were conducive to sludge fermentation. The composition of methanogens in the anaerobic digestion reactors was changed by mechanical pretreatment, the relative abundance of Methanosaeta in the control group was 52.70 %, while that in the pretreatment group was as high as 94.05 %. The methanogens in the sludge anaerobic digestion system involving and without involving pretreatment was 5.47 × 107 and 5.12 × 107 copies/g, respectively. Overall, the mechanical pretreatment was beneficial for the enrichment of methanogens, especially acetotrophic Methanosaeta, and it increased methane production.

Assessment and optimization of a decentralized food-waste-to-energy system with anaerobic digestion and CHP for energy utilization

Biogas derived from the decentralized anaerobic digestion (AD) of food waste may be used to generate electrical and thermal energy for nearby residents through combined heat and power generation technology. A mobile food-waste-to-energy system in conjunction with an anaerobic digester and biogas engine was developed for food waste (FW) treatment and energy output. The scale-up was simulated to explore the methane yield and energy flow at different ambient temperatures of 0 °C, 10 °C, 20 °C, 30 °C and different feedstock of 200 kg, 500 kg FW. Accordingly, the results demonstrated that the installed system with a 1 m3 digester had a methane yield of 0.55L CH4 /g VS when the feedstock load was 30 kg FW/d and the Organic Load Rate (OLR) was 5.4 g VS /L, while the thermal and electrical efficiencies of this system were 31% and 16%, respectively. The corresponding exhaust gas of the thermal energy from the biogas combustion was recovered by a heat exchanger in order to keep the digester at mesophilic conditions. The simulations carried out on the scale-up systems under loads of 200 kg FW/d and 500 kg FW/d achieved a thermal energy balance at different ambient temperatures of 0 °C, 10 °C, 20 °C and 30 °C. Improvements were proposed in the optimized system by optimizing pre-treatment facilities as well as the AD reactor, biogas engine and heat exchanger. The net thermal and electrical energy output of the optimized system at 500 kg FW/d were 175.93kWh and 163.90kWh, respectively. The energy generated by the FW-to-energy system illustrated by the Sankey diagrams depicts that was enough for operation without the need of extra heat and a power supply, moreover, the surplus energy may be utilized for its neighboring communities. In addition, the optimized system under the same OLR were increased by 87% and 135%, regards the thermal and electrical energy outputs, respectively in comparison with the current system.

Adjusting Organic Load as a Strategy to Direct Single-Stage Food Waste Fermentation from Anaerobic Digestion to Chain Elongation

Production of medium chain carboxylic acids (MCCA) as renewable feedstock bio-chemicals, from food waste (FW), requires complicated reactor configurations and supplementation of chemicals to achieve product selectivity. This study evaluated the manipulation of organic loading rate in an un-supplemented, single stage stirred tank reactor to steer an anaerobic digestion (AD) microbiome towards acidogenic fermentation (AF), and thence to chain elongation. Increasing substrate availability by switching to a FW feedstock with a higher COD stimulated chain elongation. The MCCA species n-caproic (10.1 ± 1.7 g L−1) and n-caprylic (2.9 ± 0.8 g L−1) acid were produced at concentrations comparable to more complex reactor set-ups. As a result, of the adjusted operating strategy, a more specialised microbiome developed containing several MCCA-producing bacteria, lactic acid-producing Olsenella spp. and hydrogenotrophic methanogens. By contrast, in an AD reactor that was operated in parallel to produce biogas, the retention times had to be doubled when fed with the high-COD FW to maintain biogas production. The AD microbiome comprised a diverse mixture of hydrolytic and acidogenic bacteria, and acetoclastic methanogens. The results suggest that manipulation of organic loading rate and food-to-microorganism ratio may be used as an operating strategy to direct an AD microbiome towards AF, and to stimulate chain elongation in FW fermentation, using a simple, un-supplemented stirred tank set-up. This outcome provides the opportunity to repurpose existing AD assets operating on food waste for biogas production, to produce potentially higher value MCCA products, via simple manipulation of the feeding strategy.