Abstract
Mesophilic and thermophilic anaerobic digestion reactors (MR and TR) for the organic fraction of municipal solid waste (OFMSW) were tested to reveal the differential microbial responses to increasing organic loading rate (OLR). MR exhibited faster adaptation and better performance at an OLR range of 1.0–2.5 g VS·L−1·d−1, with average profiles of a biogas yield of 0.38 L/gVSadded*d at 0.5 g/L*d OLR and 0.69 L/gVSadded*d at 2.5 g/L*d OLR, whereas TR had a biogas yield of 0.07 L/gVSadded*d at 0.5 g/L*d OLR and 0.44 L/gVSadded*d at 2.5 g/L*d OLR. The pyrosequencing results of amplicons revealed the microbial mechanisms of OFMSW anaerobic digestion. Larger shifts in the bacteria composition were observed in the TR with OLR elevation. For methanogens in both reactors, Methanothrix dominated in the MR while Methanosarcina was favored in the TR. Moreover, analysis of the mode and efficiency of metabolism between the MR and TR demonstrated different performances with more efficiency related to the limiting hydrolytic acid step.
Highlights
The treatment and disposal of the organic fraction of municipal solid waste (OFMSW) represent major challenges worldwide owing to growing production levels [1]
Profiles of the biogas yield (SBY) of the added organic loading rate (OLR), methane production and concentration, intermediate alkalinity to partial alkalinity ratio (IA:PA), and pH of the two reactors are shown in exhibited a much better ability for biogas and methane production, implying that a normal atmospheric temperature seed biomass allows for stronger adaptability of mesophilic Anaerobic digestion (AD)
The results of the present study suggest that that mesophilic AD of OFMSW showed better performance than thermophilic AD during both the adaptive phase and the OLR increasing phase
Summary
The treatment and disposal of the organic fraction of municipal solid waste (OFMSW) represent major challenges worldwide owing to growing production levels [1]. Anaerobic digestion (AD) is an efficient and eco-friendly treatment to transform OFMSW into energy. Mesophilic (30–40 ◦ C) and thermophilic (50–60 ◦ C) AD systems are the most commonly used. Several methods for increasing biogas production have been proposed, including raw material pretreatment and optimizing the fermenting digester [4,5]. According to the Arrhenius equation, chemical reaction rates could be doubled with a 10 ◦ C temperature increase. Thermophilic AD is a possible strategy to improve the process efficiency owing to a higher reaction rates. Thermophilic AD shows several advantages such as higher loading rates of organic feedstock and a smaller pathogen degree [6].
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