Start‐up and recovery of a biogas‐reactor using a hierarchical neural network‐based control tool

Due to its intricate internal biological structure the process of anaerobic digestion is difficult to control. The aim of any applied process control is to maximize methane production and minimize the chemical oxygen demand of the effluent and surplus sludge production. Of special interest is the start‐up and adaptation phase of the bioreactor and the recovery of the biocoenose after a toxic event. It is shown that the anaerobic digestion of surplus sludge can be effectively modeled by means of a hierarchical system of neural networks and a prediction of biogas production and composition can be made several time‐steps in advance. Thus it was possible to optimally control the loading rate during the start‐up of a non‐adapted system and to recover an anaerobic reactor after a period of heavy organic overload. During the controlled period an optimal feeding profile that allowed a minimum loading rate of 6 kg COD m^?3 d^?1 to be maintained was found. Maximum loading rates higher than 12 kg COD m^?3 d^?1 were often reached without destabilizing the system. The control strategy resulted simultaneously in a high level of gas production of about 3 m³_biogas m^?3_reactor and a methane content in the biogas of about 70%. To visualize the effects of the control strategy on the reactor's operational space the data were processed using a data‐mining program based on Kohonen Self‐Organizing Maps. Copyright © 2003 Society of Chemical Industry     

Specific energy dissipation rate for super‐high‐rate anaerobic bioreactor

BACKGROUND: Specific energy dissipation rate (?) is an important performance parameter of the super‐high‐rate anaerobic bioreactor (SAB) and is closely linked with power matching and operation optimization. The ? value was investigated for a SAB using anaerobic granular sludge and simulating gas production. The ? models for separation, reaction and water distribution units were established. RESULTS: Experimental results showed that the model predictions agreed well with the experimental data and, thus, they may be used for power matching and operation optimization of similar high‐rate anaerobic bioreactors. The ? value for the separation unit was so low as to be neglected. The maximum ? values for the reaction unit during nonfluidization, granular sludge agglomeration, liquid‐solid two‐phase fluidization and gas‐liquid‐solid three‐phase fluidization states were 0.143 W m^?3, 4.449 W m^?3, 2.173 W m^?3 and 11.132 W m^?3, respectively. The maximum ? value for the water distribution unit was 8.37 W m^?3. ? for the reaction unit was significantly influenced by ρ_p, u_l and V_p, u_g and d_p. CONCLUSION: The maximum ? value of 11.132 W m^?3 was the basic parameter for power matching for the SAB. Some measures were introduced to reduce the ? values based on parametric sensitivity analyses. The present investigation will further assist in optimizing the operation and design of SABs. Copyright © 2011 Society of Chemical Industry     

The dynamics of anaerobic phenol biodegradation in lower greensand

The anaerobic biodegradation of phenol in the unsaturated zone beneath landfill sites has been simulated by percolating an artificial landfill leachate containing phenol through columns of disturbed Lower Greensand. The columns were inoculated with microbes from a laboratory-scale landfill simulator. Phenol degradation was observed at concentrations up to 8.2 g dm^?3 but decomposition was increasingly inhibited above 3.0 g dm^?3. Maximum rates of decomposition were observed at concentrations between 1.5 and 3.0 g dm^?3. The V_max value at a flow rate of 0.5 cm³ h^?1 was 1.05 g dm^?3h^?1 and the K_m value was 450 mg phenol dm_?3. Zero- (r₀) and first-order (r₁) rate constants increased with increasing flow rate. The data are used to calculate the rates of phenol degradation which might be obtained in real landfill.     

Kinetics of syntrophic acetogenesis in a saline medium

BACKGROUND: The anaerobic degradation kinetics of volatile fatty acids (VFA) in a saline (24 g NaCl dm^?3) and mesophilic (37 °C) medium was studied under batch test conditions. The acetate production kinetics without inhibition by propionic, butyric and valeric acids was determined. The inhibition of acetate production during syntrophic acetogenesis by VFA and pH was studied. The acetogenesis without inhibition was modelled using a Monod equation. The pH inhibition was represented by a Michaelis pH function, while the inhibition by acetic acid (HAc) was represented by a non‐competitive model. RESULTS: The specific maximum degradation rate and saturation constant (k_{max, VFA}, K_{S, max}) values were (5.89, 15.95), (7.97, 25.99) and (7.75 g VFA g^?1 volatile suspended solids day^?1, 11.52 mg VFA dm^?3) for propionic, butyric and valeric acids respectively, with maximum velocity at pH 7. The inhibition constants (K_{I, HAc}) were 1295, 671 and 572 mg HAc dm^?3 for propionic, butyric and valeric acids respectively. CONCLUSION: VFA and pH can be inhibitory for acetogenesis under these conditions. Copyright © 2008 Society of Chemical Industry     

Start-up and Operation of Laboratory-Scale Thermophilic Upflow Anaerobic Sludge Blanket Reactors Treating Vegetable Processing Wastewaters

Thermophilic anaerobic treatment of hot vegetable processing wastewaters was studied in laboratory-scale UASB reactors at 55°C. The high-strength wastewater streams, deriving from steam peeling and blanching of carrot, potato and swede were used. The reactors were inoculated with mesophilic granular sludge. Stable thermophilic methanogenesis with about 60% COD removal was reached within 28 days. During the 134 day study period the loading rate was increased up to 24 kg COD m⁻³ day⁻¹. High treatment efficiency of more than 90% COD removal and concomitant methane production of 7·3 m³ CH₄ m⁻³ day⁻¹ were achieved. The anaerobic process performance was not affected by the changes in the wastewater due to the different processed vegetables. The results demonstrated the feasibility of thermophilic anaerobic treatment of vegetable processing wastewaters in UASB reactors. © 1997 SCI.     

Dependence of initial cluster aggregation kinetics on shear rate for particles of different sizes under turbulence

Initial aggregation kinetics for three particle sizes and broad range of Péclet numbers were investigated under turbulent conditions in stirred tank. This allowed us to observe the transition from diffusion‐controlled to purely shear‐induced aggregation. The evolution of the root‐mean‐square radius of gyration, zero‐angle intensity of scattered light, and obscuration was obtained by small‐angle static light scattering. For a given particle size the measured evolution of all integral quantities obtained for various volume average shear rates 〈G〉, scales with a dimensionless time, τ_exp = α_exp × 〈G〉 × ? × t. The experimentally obtained aggregation efficiency α_exp, follows the power law α_exp = Pe^?n, where Pe is the primary particle Péclet number. With increasing particle size a decrease in n is observed in accordance with theory and literature data. As previously predicted by population balance equation simulations three aggregation regimes were observed experimentally. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Influence of molecular weight distribution on the linear viscoelastic properties of polymer blends

Literature data for the dynamic viscoelastic properties of binary blends of nearly monodisperse polybutadienes, polystyrenes, and poly(methyl methacrylate)s was analyzed using logarithmic plots of dynamic storage modulus G′ versus loss modulus G″, based on a recent theoretical study by Han and John.²⁸ It has been found that for binary blends of monodisperse polymers with molecular weights M much greater than the entanglement molecular weight M_e, the value of G′ in log G′ ? log G″ plots becomes independent of molecular weight, increases sharply as small amounts of a high-molecular-weight component are added to a low-molecular-weight component, and passes through a maximum G′_max at a critical blend composition (?₂)_max, and that G′_max becomes larger and (?₂)_max becomes smaller as the ratio of component molecular weights increases. However, as the molecular weight distribution of the constituent components becomes broader, the effect of blend composition on G′ in log G′ ? log G″ plots becomes less pronounced. This observation has enabled us to explain why log G′ ? log G″ plots of binary blends of commercial polymers, namely, blends of two low-density polyethylenes, blends of poly(?-caprolactone) and poly(styrene-co-acrylonitrile), and blends of poly(methyl methacrylate) and poly(vinylidene fluoride), all having broad molecular weight distributions, give rise to values of G′ between those of the constituent components. When one of the constituent components has molecular weight smaller than M_e, while the other has molecular weight larger, and as small amounts of the high-molecular-weight component are added to the low-molecular-weight component, log G′ ? log G″ plots of binary blends give rise to values of G′ larger than those of the constituent components at low values of G″, but approaches the value of G′ for the low-molecular-weight component as the value of G″ is increased. However as the amount of the high-molecular-weight component is increased above a certain critical composition, binary blends give rise to values of G′ close to that of the high-molecular-weight component at all values of G″. The experimentally observed dependence of G′ on blend composition in log G′ ? log G″ plots is favorably compared to the theoretical prediction of a blending law proposed by Montfort and co-workers.^14,15     

Mass transfer performance and correlations for CO2 absorption into aqueous blended of DEEA/MEA in a random packed column

The mass transfer performance of CO₂ absorption into blended N,N‐diethylethanolamine (DEEA)/ethanolamine (MEA) solutions was investigated using a lab‐scale absorber (H = 1.28 m, D = 28 mm) packed with Dixon ring random packing. The mass transfer coefficient K_Ga_v, the unit volume absorption rate Φ, outlet concentration of CO₂ (y_CO2), and the bottom temperature T_bot of CO₂ in aqueous DEEA/MEA solutions were determined over the feed temperature range of 298.15–323.15 K, lean CO₂ loading of 0.15–0.31 mol/mol, over a wide range of liquid flow rate of 3.90–9.75 m³/m²‐h, by using inert gas flow rate of 26.11–39.17 kmol/m²‐h and 6–18 kPa CO₂ partial pressure. The results show that liquid feed temperature, lean CO₂ loading, liquid flow rate, and CO₂ partial pressure had significant effect on those parameters. However, the inert gas flow rate had little effect. To allow the mass transfer data to be really utilized, K_Ga_v and y_out correlations for the prediction of mass transfer performance were proposed and discussed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3048–3057, 2017     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.     

Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP). RESULTS: Batch cultivations carried out at different initial levels of glucose (G₀) in the presence of 10 g L^?1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G₀≤10 g L^?1 (B_max = 104–110 mg L^?1). The recombinant strain exhibited slightly lower levels of biosurfactants (B_max = 90–104 mg L^?1) but only at higher glucose concentrations (G₀ ≥ 20 g L^?1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase. CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry     

Synthesis of hybrid magnetic molecularly imprinted polymers for the selective adsorption of volatile fatty acids from anaerobic effluents

A novel magnetic, structured (with ordered pores) and hybrid imprinted polymer (HMMIP) was synthesized to selectively adsorb volatile fatty acids (VFAs) from aqueous matrices. Usual characterization techniques showed that a mesoporous adsorbent was obtained with relatively low specific areas but that could selectively (imprinting factor of 1.64) remove isovaleric acid (used as template) from aqueous solutions and effluents containing VFAs with a good capacity (Q_e ~ 50 mg g^?1). From kinetic studies a pseudo‐nth‐order model showed the best fit to the experimental data and resulted in k _{n = 3} equal to 8 × 10^?4 g mg^?1 min^?1 whereas thermodynamic studies indicated that the adsorption of isovaleric acid onto HMMIP was endothermic and entropically driven. Reuse studies indicated that HMMIP loaded with VFA could be efficiently regenerated with acetone–water solution which led to an adsorption loss of ca 10% after three regeneration/reuse cycles and that the magnetic and specific adsorbent could be removed from complex matrices with an efficiency of ca 77%. Biochemical methane production assays showed that the addition of HMMIP to anaerobic batch reactors increased by four times the methane production due to the selective adsorption of VFAs. © 2020 Society of Chemical Industry     

Prediction of The Kolmogorov Entropy Derived from CT Data in a Bubble Column Operated under The Transition Regime and Ambient Pressure

The Kolmogorov entropy (KE) algorithm was successfully applied to single source γ‐ray Computed Tomography (CT) data measured by three scintillation detectors in a 0.162 m‐ID bubble column equipped with a perforated plate distributor (163 holes × ?? 1.32 · 10^–3 m). The aerated liquid height was set at 1.8 m. Dried air was used as a gas phase, while Therminol LT (ρ_L = 886 kg m^–3, μ_L = 0.88 · 10^–3 Pa s, σ = 17 · 10^–3 N m^–1) was used as a liquid phase. At ambient pressure, the superficial gas velocity, u_G, was increased stepwise with an increment of 0.01 m s^–1 up to 0.2 m s^–1. Based on the sudden changes in the KE values, the boundaries of the following five regimes were successfully identified: dispersed bubble regime (u_G < 0.02 m s^–1), first transition regime (0.02 ≤ u_G < 0.08 m s^–1), second transition regime (0.08 ≤ u_G < 0.1 m s^–1), coalesced bubble regime consisting of four regions (called 4‐region flow; 0.1 ≤ u_G < 0.12 m s^–1), and coalesced bubble regime consisting of three regions (called 3‐region flow; u_G > 0.12 m s^–1). The KE values derived from three scintillation detectors in the first transition regime were successfully correlated to both bubble frequency and bubble impact. The latter was found to be inversely proportional to the bubble Froude number. The KE model implies that the bubble size in this particular flow regime is a weak function of the orifice Reynolds number (d_b = 7.1 · 10^–3Re₀^–0.05).     

Changes to bacterial community make‐up in a two‐phase anaerobic digestion system

Changes to microbial populations in a two‐phase anaerobic digestion system were studied over 34 weeks. Numbers of autofluorescent methanogenic and non‐methanogenic bacteria decreased significantly during start‐up, but did not change markedly either in the acid reactor or the upflow anaerobic filter for the remainder of the study. Although the proportion of autofluorescent methanogens increased in the acid reactor, the numbers of viable methanogens decreased 590‐fold. The numbers of viable methanogens increased 10‐fold in the port, decreased 10‐fold in the effluent and there was almost no change in the drain of the upflow anaerobic filter. The data indicated that bacterial attachment in the upflow anaerobic filter gave a 90% COD removal and a methane yield of 0.33 m³ CH₄ kg⁻¹ COD removed at an organic loading rate of 7 kg COD m⁻³day⁻¹. Epifluorescence microscopy of the seed sludge revealed a diverse methanogenic population of equally dominant groups of medium rods and filaments with Methanococcus, short rods, long rods and Methanosarcina also present. The medium rod‐shaped species remained the most dominant group in the acid reactor. As the volatile fatty acid concentration increased in the acid reactor the number of Methanosarcina and filament species decreased, becoming the least dominant groups. At the end of the operation, Methanococcus species were the dominant group in the upflow anaerobic filter having been washed from the biofilm. © 2000 Society of Chemical Industry     

Synthesis and hydrothermal stability of U doped zirconolite–sphene composite materials

Two series of U doped zirconolite–sphene composite materials were prepared by solid state reaction method: CaZr_(1?m)U_mTi₂O₇?(1?m) Ca_(1?x)U_xAl_2xTi_(1?2x)SiO₅ (m?=?7x) and Ca_(1?n)U_6nZr_(1?5n)Al_2nTi_(2?2n)O₇?(1?5n) Ca_(1?y)U_yAl_2yTi_(1?2y)SiO₅ (n?=?5y/6). The effects of U content on the phase structure of the composite materials were mainly investigated. The results show that the optimal synthesis temperature of the composite material is ～1230°C. In comparison with the incorporation of U in the Zr site of zirconolite, U incorporation in the Ca site of zirconolite using Al as charge compensating ions was not very efficient. Hydrothermal stability of the U doped zirconolite–sphene composite material was examined by modified product consistency test method at 90°C in deionised water (pH 7). The normalised U leach rate is fairly constant in a low value below 10^?5 g m^?2 day^?1 after 28 days.     

Influence of Hydroxyvalerate Content on the Crystallization Kinetics of Poly(hydroxybutyrate-co-hydroxyvalerate)

Influence of hydroxyvalerate (HV) content on the crystallization kinetics of hydroxybutyrate (HB) units in random poly(hydroxybutyrate-co-hydroxyvalerate) (P(HB-co-HV)) copolymers has been studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that the crystallization kinetics of HB units was strongly affected by the presence of the ethyl side chain of HV units whether under the non-isothermal or isothermal crystallization conditions. The spherulitic growth rate (G) and overallall crystallization rate (k _n ) of HB units decreased with increasing HV content. Both G and k _n exhibited the maxima, G ^max and k _n ^max, which showed a gradual shift toward lower temperatures with increasing HV content, which may be attributed to the depression in the equilibrium melting point (T _m ⁰) and nucleation factor (K _g). The temperature corresponding k _n ^max was different from G ^max due to the depression of nucleation rate with the degree of undercooling was more susceptible than that of the growth rate. According to the Lauritzen–Hoffman theory of secondary nucleation, the crystallization of HB units in P(HB-co-HV) copolymers was similar to that of neat PHB as regime III and n=4 growth process.     

Analysis of methane production inhibition for treatment of sewage sludge containing sulfate using an anaerobic continuous degradation process

The inhibition of methane production in the continuous anaerobic degradation process for the treatment of sewage sludge containing sulfate was investigated. Also, the competition between sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) with COD/sulfate ratio was explained in terms of electron flow. The methane production rate was 0.07, 0.13, 0.24, 0.31 and 0.33 l-CH₄ g-COD⁻¹ when the initial COD/sulfate ratio was 3.3, 5.0, 6.7, 10 and 20, respectively. The numbers of SRB and MPB were counted after the continuous reactor reached steady state and the two bacteria showed opposite growth behaviors with COD/sulfate ratio. The inhibition by sulfate compounds was found to follow the uncompetitive model and inhibition constants were 24.57 and 87.99 mg l ⁻¹ for SRB and MPB, respectively. These results can be useful data for the efficient treatment of sewage sludge in a continuous anaerobic degradation process.     

Effect of a chemical synthesis‐based pharmaceutical wastewater on performance,acetoclastic methanogenic activity and microbial population in an upflow anaerobic filter

The performance of an upflow anaerobic filter (UAF) treating a chemical synthesis‐based pharmaceutical wastewater was evaluated under various operating conditions. During start‐up, the UAF was initially fed by glucose till an organic loading rate (OLR) of approximately 7.5 kg COD m^?3 day^?1 with a hydraulic retention time of 2.3 days. A soluble COD removal efficiency of 98% was achieved before the addition of the wastewater. Initially, the filter inertia was acclimatized to the wastewater by sequential feeding of 10% (w/v), 30% (w/v) and 70% (w/v) of the pre‐aerated wastewater mixed with glucose followed by a 100% (w/v) pre‐aerated wastewater. During the operation, the COD removal efficiency and methane yield decreased to 75% and 0.30 m³ CH₄ kg^?1 COD_removed respectively. As the UAF became accustomed to the pre‐aerated wastewater, raw wastewater was fed in increasing ratios of 20% (w/v), 60% (w/v) and 80% (w/v) with the pre‐aerated wastewater as the remaining part. During this stage of the operation, a COD removal efficiency in a range of 77–86% was achieved and the methane yield decreased to 0.24 m³ CH₄ kg^?1 COD_removed. Finally, 100% (w/v) raw wastewater was fed and a COD removal efficiency of 65% was achieved with a methane yield of 0.20 m³ CH₄ kg^?1 COD_removed. At the end of the operation, acetoclastic methanogenic activity was only measured in the bottom section of the UAF, this showed a 90% reduction in comparison with activity of inoculation sludge. Microscopic examinations revealed that rod‐shaped methanogens remained as the dominant species whereas Methanosarcina‐like species and filaments were present only in insignificant numbers along the UAF. © 2002 Society of Chemical Industry     

Determination of potential methane production capacity of a granular sludge from a pilot‐scale upflow anaerobic sludge blanket reactor using a specific methanogenic activity test

A 450 dm³ pilot‐scale upflow anaerobic sludge blanket (UASB) reactor was used for the treatment of a fermentation‐based pharmaceutical wastewater. The UASB reactor performed well up to an organic loading rate (OLR) of 10.7 kg COD m^?3 d^?1 at which point 94% COD removal efficiency was achieved. This high treatment efficiency did not continue, however and the UASB reactor was then operated at lower OLRs for the remainder of the study. Specific methanogenic activity (SMA) tests were, therefore, carried out to determine the potential loading capacity of the UASB reactor. For this purpose, the SMA tests were carried out at four different initial acetate concentrations, namely 500 mg dm^?3, 1000 mg dm^?3, 1500 mg dm^?3 and 2000 mg dm^?3 so that substrate limitation could not occur. The results showed that the sludge sample taken from the UASB reactor (OLR of 6.1 kg COD m^?3 d^?1) had a potential acetoclastic methane production (PMP) rate of 72 cm³ CH₄ g^?1 VSS d^?1. When the PMP rate was compared with the actual methane production rate (AMP) of 67 cm³ CH₄ g^?1 VSS d^?1 obtained from the UASB reactor, the AMP/PMP ratio was found to be 0.94 which ensured that the UASB reactor was operated using its maximum potential acetoclastic methanogenic capacity. In order to achieve higher OLRs with desired COD removal efficiencies it was recommended that the UASB reactor should be loaded with suitable OLRs pre‐determined by SMA tests. © 2001 Society of Chemical Industry     

Assessment of solid retention time of a temperature phased anaerobic digestion system on performance and final sludge characteristics

BACKGROUND: This paper describes the results obtained during the thermophilic/mesophilic temperature phased anaerobic digestion (TPAD) of sewage sludge on a pilot scale. The aim of this research study was not only to optimize the anaerobic digestion process, but also to obtain a digested sludge suitable for agricultural applications according to the legal requirements. RESULTS: Four TPAD assays were carried out: 5/15, 3/15, 3/12 and 3/9 (days/days of solid retention time) with a specific methane production (expressed as LCH₄ g^?1 VS_destroyed) of 0.77, 0.83, 0.66 and 0.20, respectively. TPAD 3/15 and 3/12 reached pathogen concentrations of less than 1000 MPN g^?1 TS (faecal colifoms) and 3 MPN per 4 g TS (Salmonella spp.); therefore, these digested sludges can be considered Class A biosolids, according to the US Environmental Protection Agency. Concentrations of heavy metals rose after the anaerobic digestion of mixed sludge, but the final values were always below the limits required by legal regulations. CONCLUSION: TPAD 3/15 is the best option in terms of organic matter removal, CH₄ generation, and process stability. TPAD 3/12 obtained the best final dewaterability and pathogen reduction and in general, showed much better results than those obtained by anaerobic mesophilic control (15 days of SRT). Copyright © 2012 Society of Chemical Industry     

Mesophilic anaerobic digestion of corn thin stillage: a technical and energetic assessment of the corn‐to‐ethanol industry integrated with anaerobic digestion

BACKGROUND: The purpose of this study was to reduce the VS (volatile solid) and recover energy (methane) from thin stillage through mesophilic anaerobic digestion in corn–ethanol plants. The performance of a continuously stirred tank reactor (CSTR) with different hydraulic retention times (HRTs) was evaluated in this study. RESULTS: The results show no differences in volatile solid (VS) destruction (82–83%) in the reactor with HRTs ranging from 25 to 40 days. The maximum volumetric methane production rate of 1.41 L L^?1 day^?1 was produced at 25‐day HRT, whereas the maximum methane yield of approximately 0.63 L CH₄ g^?1 VS_fed (0.77 L g^?1 VS_removed) was achieved with HRTs between 30 and 40 days. Simulation results using a kinetic model indicate that the reactor needs to be operated for longer than 23 days in order to achieve 80% of maximum methane yield. The techno‐economic potential of a corn–ethanol facility to produce an estimated 57% energy recovery using mesophilic anaerobic digestion has long been overlooked. A corn–ethanol plant integrated with mesophilic anaerobic digestion increases the net energy balance ratio from 1.26 to 1.80. CONCLUSION: Mesophilic anaerobic digestion complements the corn–ethanol business so that the sustainable energy obtained from corn recovery is made more lucrative and renewable. Copyright © 2011 Society of Chemical Industry