Anaerobic digestion challenges and resource recovery opportunities from land-based aquaculture waste and seafood processing byproducts: A review.

The unprecedented demand for seafood has resulted in land-based recirculating aquaculture systems (RAS), a highly intensive but sustainable fish farming method. However, intensification also results in concentrated waste streams of fecal matter and uneaten feed. Harvesting and processing vast quantities of fish also leads to the production of byproducts, further creating disposal challenges for fish farms. Recent research indicates that anaerobic digestion (AD), often used for waste treatment in agricultural and wastewater industries, may provide a viable solution. Limited research on AD of freshwater, brackish, and saline wastewater from RAS facilities and co-digestion of seafood byproducts has shown promising results but with considerable operational and process stability issues. This review discusses challenges to AD due to low solid concentrations, salinity, low carbon/nitrogen ratio, and high lipid content in the waste streams. Opportunities for recovering valuable biomolecules and nutrients through microbial treatment, aquaponics, microalgae, and polyhydroxyalkanoate production are also discussed.

Clarifying configurations of reaction rate constant for first-order and Monod-type kinetics: A comparative manner and a pursuit of parametric definition.

The mechanisms of first-order and Monod-type kinetics describes degradation in distinct manner and yet too little attention is paid on the fact that first-order kinetic was derived from pure elementary reaction while Monod-type degradation was based on microbial uptake. Both mechanisms are basic theories in developing sophisticated degradation models and there are needs to give more guidance on selection of kinetics. The objective of this study was to compare the two kinetics when used for modeling degradation and biodegradability during composting. With both experimental data, from reactor composting of swine manure/wheat straw, and simulated results, it was found that Monod-type kinetic was more capable of modeling the lag phase, while first-order kinetic could explain the fast oxygen uptake rate for the oxidation of soluble substrate. Comparison of growth rate constants, based on Monod-type equation, with maximum degradation rate constants, based on first-order kinetic, showed that the former was generally one magnitude greater, which could be explained with the fact that part of growth of cell weight was from water consumption.

Incubation of innovative methanogenic communities to seed anaerobic digesters.

The methanogenic communities in alternative inocula and their potential to increase CH4 production in mesophilic and psychrophilic dairy manure-based anaerobic digesters were examined. Quantitative-PCR and terminal restriction fragment length polymorphism (T-RFLP) profiles were used to determine archaeal and methanogenic community changes when three inocula (wetland sediment (WS), landfill leachate (LL), and mesophilic digestate (MD)) were incubated at 15, 25, and 35 °C for 91 and 196 days. After each incubation period, the inocula were used in biochemical methane potential (BMP) tests at the incubation temperatures. There was no significant correlation between inoculum mcrA gene copy numbers and CH4 produced in BMP tests, suggesting that population size was not a distinguishing characteristic for predicting CH4 production. Archaeal composition in LL and WS reactors generally converged with MD reactors after incubation at 25 and 35 °C for 196 days. These MD reactors had high relative abundance of TRF 302, likely Methanosaetaceae, and low acetic acid (0.62-1.61 mM). At 15 °C incubation, most reactors were associated with high acetic acid (1.61-133.6 mM) and dominated by TRF 199, likely Methanosarcinaceae. The LL reactor incubated at 25 °C for 91 days had higher relative abundance of TRF 199 and produced significantly higher CH4 than WS and MD reactors in BMP test. In the future, it may be possible to create enrichment cultures that favor particular methanogens and use them as inoculum to benefit digesters at low mesophilic temperatures. Our data provides evidence that tailoring the archaeal community could benefit digesters operating under different conditions.

Application of Contois, Tessier, and first-order kinetics for modeling and simulation of a composting decomposition process.

An integrated model was developed by associating separate degradation kinetics for an array of degradations during a decomposition process, which was considered as a novelty of this study. The raw composting material was divided into soluble, hemi-/cellulose, lignin, NBVS, ash, water, and free air-space. Considering their specific capabilities of expressing certain degradation phenomenon, Contois, Tessier (an extension to Monod kinetic), and first-order kinetics were employed to calculate the biochemical rates. It was found that the degradation of soluble substrate was relatively faster which could reach a maximum rate of about 0.4perhour. The hydrolysis of lignin was rate-limiting with a maximum rate of about 0.04perhour. The dry-based peak concentrations of soluble, hemi-/cellulose and lignin degraders were about 0.9, 0.2 and 0.3kgm(-3), respectively. Model developed, as a platform, allows degradation simulation of composting material that could be separated into the different components used in this study.