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In China, there is an urgent need for an efficient anaerobic digester to sustainably treat rice straw. In this study, a downward plug-flow anaerobic digester (DPAD) was designed in which the total working core is separated into three sections: an upper liquid zone, a lower liquid zone, and a solid-state bed (SSB) in the middle. A solid/liquid separation mechanism was designed to recirculate liquor and the discharged solid residue after complete digestion. The 70-L DPAD was run indoors for 100 d, time in which chopped rice straw (30 to 50 mm in length) was fed every 20 d. The digestion performance and biogas production were analysed to assess the feasibility for practice application. The results showed that the DPAD can control scum formation and offers a methane yield of 162.60 L/kg volatile solids, 21.1% higher than that of the control test. It was also found that straw was continuously and efficiently digested by the DPAD in 3 experimental stages. Methane production rates increased by 76.30%, 57.37%, and 13.33% on the second day compared to the first day, respectively, and then, all decreased as the substrate was gradually exhausted. Based on the results, it is clear that the DPAD is a promising solution for chopped straw digestion.

Li + -ion and Na + -ion transfer at interfaces composed of inorganic solid electrolytes and polymer or organic liquid electrolytes were compared. La 0.55 Li 0.35 TiO 3 and Na 3 Zr 1.88 Y 0.12 Si 2 PO 12 , which are conductive for Li + and Na + , were selected for use as inorganic solid electrolytes. PC solution and PEO-based polymer electrolytes were added to Li salt or Na salt to give ionic conductivity. Using these electrolytes, solid electrolyte/liquid electrolyte or solid electrolyte/polymer electrolyte interfaces were constructed. The resistivities of Li + or Na + transfer through these interfaces were estimated based on the results of ac impedance measurements. In both solid/liquid and solid/polymer systems, the activation energies of Na + -ion transfer at the interface were smaller than those of Li + -ion. The Lewis acidity of both ions, Li + and Na + , clearly explains this difference and supports the idea that the interaction between ion and solvents plays a major role in interfacial ion-transfer processes.