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Increasing the feed total solids to anaerobic digester improves the process economics and decreases the volume of liquid effluent from current wet anaerobic digestion. The objective of this study was to develop a novel psychrophilic (20 °C) anaerobic digestion technology of undiluted cow feces (total solids of 11%-16%). Two sets of duplicate laboratory-scale sequence batch bioreactors have been operated at organic loading rates (OLR) of 6.0 to 8.0 g total chemical oxygen demand (TCOD) kg-1 inoculum day-1 (d-1) during 210 days. The results demonstrated that the process is feasible at treatment cycle length (TCL) of 21 days; however, the quality of cow feces rather than the OLR had a direct influence on the specific methane yield (SMY). The SMY ranged between 124.5 ± 1.4 and 227.9 ± 4.8 normalized liter (NL) CH4 kg-1 volatile solids (VS) fed d-1. Substrate-to-inoculum mass ratio (SIR) was 0.63 ± 0.05, 0.90 ± 0.09, and 1.06 ± 0.07 at OLR of 6.0, 7.0, and 8.0 g TCOD kg-1 inoculum d-1, respectively. No volatile fatty acids (VFAs) accumulation has been observed which indicated that hydrolysis was the rate limiting step and VFAs have been consumed immediately. Bioreactors performance consistency in terms of the level of SMYs, VFAs concentrations at end of the TCL, pH stability and volatile solids reduction indicates a stable and reproducible process during the entire operation. [ABSTRACT FROM AUTHOR]

This paper reports experimental results which demonstrate psychrophilic dry anaerobic digestion of cow feces during long-term operation in sequence batch reactor. Cow feces (13–16% total solids) has been anaerobically digested in 12 successive cycles (252 days) at 21 days treatment cycle length (TCL) and temperature of 20 °C using psychrotrophic anaerobic mixed culture. An average specific methane yield (SMY) of 184.9 ± 24.0, 189.9 ± 27.3, and 222 ± 27.7 N L CH 4 kg −1 of VS fed has been achieved at an organic loading rate of 3.0, 4.0, and 5.0 g TCOD kg −1 inoculum d −1 and TCL of 21 days, respectively. The corresponding substrate to inoculum ratio (SIR) was 0.39 ± 0.06, 0.48 ± .02, 0.53 ± 0.05, respectively. Average methane production rate of 10 ± 1.4 N L CH 4 kg −1 VS fed d −1 has been obtained. The low concentration of volatile fatty acids indicated that hydrolysis was the reaction limiting step. [ABSTRACT FROM AUTHOR]

Degrading antibiotics discharged in the livestock manure in a well-controlled bioprocess contributes to a more sustainable and environment-friendly livestock breeding. Although most antibiotics remain stable during manure storage, anaerobic digestion can degrade and remove them to various extents depending on the concentration and class of antibiotic, bioreactor operating conditions, type of feedstock and inoculum sources. Generally, antibiotics are degraded during composting > anaerobic digestion > manure storage > soil. Manure matrix variation influences extraction, quantification, and degradation of antibiotics, but it has not been well investigated. Fractioning of manure-laden antibiotics into liquid and solid phases and its effects on their anaerobic degradation and the contribution of abiotic (physical and chemical) versus biotic degradation mechanisms need to be quantified for various manures, antibiotics types, reactor designs and temperature of operations. More research is required to determine the kinetics of antibiotics' metabolites degradation during anaerobic digestion. Further investigations are required to assess the degradation of antibiotics during psychrophilic anaerobic digestion. [ABSTRACT FROM AUTHOR]

This review article compiles the various advances made since 2008 in sustainable high-rate anaerobic technologies with emphasis on their performance enhancement when treating agro-food industrial wastewater. The review explores the generation and characteristics of different agro-food industrial wastewaters; the need for and the performance of high rate anaerobic reactors, such as an upflow anaerobic fixed bed reactor, an upflow anaerobic sludge blanket (UASB) reactor, hybrid systems etc.; operational challenges, mass transfer considerations, energy production estimation, toxicity, modeling, technology assessment and recommendations for successful operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A kinetic model is developed for low-temperature anaerobic digestion (AD) process. • The AD is integrated with dry methane reforming process to produce renewable H 2. • 194.64 kg/day hydrogen could be produced from 1153.68 kg/day of biogas. • The proposed process shows an energy efficiency of 78.85% at optimal conditions. • 398,736 tonnes/year CO 2 emissions can be avoided using the proposed process. Hydrogen is a clean fuel for heat and power generation and can serve as a feedstock for chemical synthesis. This study assesses the hydrogen production from biomass (e.g., cow manure) through integrating psychrophilic anaerobic digestion and dry methane reforming. For the first time, a rigorous model is developed for the low-temperature anaerobic digestion process by implementing the complex kinetics of the fermentation bioreactions. The produced biogas from the anaerobic digestion process is fed to the reforming process for hydrogen production. The kinetics of the dry methane reforming and water gas shift reactions over Co-Ni-Al 2 O 3 catalyst are incorporated into the model. Validating the results of the proposed process using experimental data shows <5% relative deviation. The effects of total solids content, organic loading rate, hydraulic retention time, and digestate recirculation fraction on biogas and CH 4 yield are investigated. The optimum values of operating parameters in the anaerobic digestion process as well as the dry methane reforming process are obtained. The process is designed to achieve the highest CH 4 -to-H 2 conversion and the lowest energy consumption. A 48.07 kg/h biogas could produce 8.11 kg/h H 2. The biomass-to-H 2 process offers an energetic efficiency of 72.85%, revealing its superiority to similar processes, such as steam and auto-thermal reforming. The proposed process highlights a high potential for CO 2 emission reduction (e.g., 398,736 t/y), compared to the direct biogas combustion for electricity production. Economic analysis shows that the cost of biogas-to-H 2 production is 1.39 USD/kg H 2 for a plant capacity of 45.5 kg/h H 2. [ABSTRACT FROM AUTHOR]