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Refined Jatropha seed oil, non-edible vegetable oil is an interesting source for biodiesel production because it has low commercial value. Thus, this work aimed to develop a novel method, combined techniques between ultrasound and microwave-assisted impregnation ((UA-IP and MA-IP) for potassium (K) loaded on hierarchical NaY zeolite synthesized from rice husk silica as catalysts for transesterification of Jatropha seed oil. Hierarchical NaY zeolite was impregnated with potassium acetate in an acetic acid buffer solution with various contents (xK/NaY, where X = 6, 8, 10, and 12 wt%) by UA-IP and MA-IP. The best catalyst from the novel method was further compared to the control method, prepared by only UA-IP. Results from XRD and N2-sorption indicated the remaining NaY structure in all samples after calcination. The total surface area determined by BET method decreased with the K loading but basicity increased with K loading suggested by CO2 -TPD. The active species was mainly K2CO3 confirmed by FTIR. When tested in transesterification at a temperature of 60 °C and 3 h with methanol: oil molar ratio of 16:1, the biodiesel yield improved with the K loading and the highest biodiesel yield of 97 ± 1.4% was obtained by 12K/NaY. The 12K/NaY gave a higher yield than 12K/NaY-control (97 ± 1.4% vs 90.7 ± 1.1%), providing the high reusability of five cycles with the biodiesel yield of 88.2 ± 1.3%.

Rice straw, a common agricultural residue, is abundant in Thailand and can be converted to biogas to reduce dependence on fossil resources for energy. Biological degradation of rice straw followed by anaerobic digestion (AD) for biomethane production (BMP) was investigated. Thermophilic lignocellulolytic bacteria for biological degradation were isolated from soil samples collected from Dong Han and Kok Soong National Forest around Roi-Et Rajabhat University, Roi-Et Province, Thailand. Cellulase and ligninolytic enzymes were assayed using standard microbiological methods. Isolate(s) with high cellulolytic and ligninolytic activities were then used to degrade rice straw in basal medium at 50 ± 2 °C for 5, 10, 15, and 20 days. Total broth was anaerobically digested with rumen microorganisms in 1.2-m3 PP digester at 39 ± 0.5 °C for 30 days. A total of 106 thermophilic bacterial isolates were sampled from soil, out of which 96 (90.6%) and 16 (15.1%) isolates tested positive for cellulolytic and ligninolytic activities, respectively. Unlike laccase and manganese peroxidase (MnP), lignin peroxidase (LiP) activity was not detected. Isolate RUFR60 showed both high cellulolytic and ligninolytic activities. Highest biogas and methane (CH4) yields (318.15 and 177.93 mL/gTS, respectively) were recorded from 20 days degraded rice straw which were not significantly (p > 0.05) different from those (315.10 and 171.72 mL/gTS, respectively) recorded from 15 days degraded rice straw. Optimal degradation period of 15 days with thermophilic lignocellulolytic bacteria was efficient and economical for BMP from rice straw.