Novel Insights into Anaerobic Digestion of Rice Straw Using Combined Pretreatment with CaO and the Liquid Fraction of Digestate: Anaerobic Digestion Performance and Kinetic Analysis

Abstract

Combined pretreatment using CaO and the liquid fraction of digestate (LFD) was proposed as an eco-friendly pretreatment method for high-quality anaerobic digestion (AD). In this study, rice straw was pretreated by CaO–LFD at three pretreatment temperatures (5, 20, and 35 °C) and four pretreatment times (1, 2, 3, and 4 days). The results showed that the optimum pretreatment condition for rice straw was 35 °C for 2 days. In this case, the maximum biomethane yield reached 308 mL g–1 of VS, 77.4% higher than that of the control. The Fitzhugh and Cone models were demonstrated to be more suitable for CaO–LFD pretreated rice straw in the AD process. AD of pretreated rice straw had a shorter effective biomethane production period and lag phase time, exhibiting high AD efficiency. This study enhances the knowledge about CaO–LFD pretreatment from multiple angles, in addition to demonstrating promising possibilities for practical application.

Intervention Strategies for the “Inhibited Steady State” Dry Thermophilic Anaerobic Digesters: The Mitigation Mechanisms of Tailored Biochar

“…Alternatively, it was obviously observed that the CH 4 production of T0 (372 ± 24 mL/gVS) was even higher than that of MBL (331 ± 33 mL/gVS). It would probably indicate that all of the reactors were started with the mesophilic inoculum taken from a mesophilic AD plant, without prior thermophilic acclimation for M0, MBL, MBS, and MAB, which limited the abundance of thermophiles . Simultaneously, it also indicated that 2 cm biochar and <5 μm biochar addition was insufficient to overcome the temperature shock from mesophilic to thermophilic on the reactors that inoculated the mesophilic inoculum during the inhibited steady state.…”

Microbial and Functional Succession during Anaerobic Digestion along a Fine-Scale Temperature Gradient of 26–65 °C

“…First, our experimental inoculum seed was acclimated with mesophilic anaerobic sludge, which limited the abundance of thermophiles. 24 Second, 59 °C was the key to the reconstruction of methanogenic from thermophilic to hyperthermophilic temperatures, potentially leading to prolonged reconstruction to hyperthermophilic temperatures. Overall, our results indicate that a mesophilic reactor would be able to maintain stability (or high performance at 32−41 °C) at a temperature below the 47 °C threshold, with no obvious process perturbation induced by changing from mesophilic to thermophilic temperatures.…”

“…At 59 °C, this can be explained by two phenomena. First, our experimental inoculum seed was acclimated with mesophilic anaerobic sludge, which limited the abundance of thermophiles . Second, 59 °C was the key to the reconstruction of methanogenic from thermophilic to hyperthermophilic temperatures, potentially leading to prolonged reconstruction to hyperthermophilic temperatures.…”

Second International Symposium on Biomass/Wastes Energy and Environment (BEE 2019), Tianjin, China, May 23–26, 2019

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