Eight cultivars of napiergrass (Pennisetum purpureum Schumach.), namely Dwarf, Muaklek, Bana, Taiwan A148, Common, Wruk wona, Tifton and Kampheng San, were grown in central Thailand in [2008][2009] and biomass yield, chemical composition and theoretical ethanol yield were measured. Harvests were made every 3 months. Biomass yield and cell wall compositions differed significantly (P < 0.05) among cultivars. Tifton produced the highest annual biomass yield at 58.3 t/ha followed by Wruk wona (52.1 t/ha), while the lowest yield of 27.1 t/ha was in Dwarf. Biomass yield varied with season with highest yields in May and lowest in February during the dry season. Cell wall concentrations were higher in the tall cultivars than in the short ones (Dwarf and Muaklek) (P < 0.05). Theoretical ethanol conversion efficiency ranged from 350 to 460 L/t DM among the cultivars following pretreatment with steam explosion. While a number of cultivars showed significant potential for use as biofuels in central Thailand, Tifton seemed to be the most promising.

The effects of inter‐cutting interval on biomass yield, growth components and chemical composition of napiergrass (Pennisetum purpureum Schumach) as a source of bioenergy was investigated over 1 year in Thailand. Five cutting intervals (1‐, 2‐, 3‐, 6‐ and 12‐monthly) were examined on three napiergrass cultivars (Bana [hybrid with pearl millet], Common [normal type] and Muaklek [dwarf type]). Peak biomass yield occurred in all cultivars with 3‐month inter‐cutting interval, with a mean of 50.2 t dry matter (DM) ha−1 year−1 averaged across cultivars, while a 6‐month interval produced 46.2 t DM ha−1 year−1. Although cellulose concentration increased as inter‐cutting interval increased, energy concentration in the harvested material also peaked with 3‐monthly cutting. Both Common and Bana were superior to Muaklek in terms of DM production. Further studies are needed to refine harvesting frequency in different seasons to maximize biomass yields while ensuring cash flow and minimizing harvesting costs.

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The present study was performed to optimize a heterogeneous calcium methoxide (Ca(OCH 3 ) 2 ) catalyzed transesterification process assisted with tetrahydrofuran (THF) as a cosolvent for biodiesel production from waste cooking oil. Response surface methodology (RSM) with a 5-level-4-factor central composite design was applied to investigate the effect of experimental factors on the percentage of fatty acid methyl ester (FAME) conversion. A quadratic model with an analysis of variance obtained from the RSM is suggested for the prediction of FAME conversion and reveals that 99.43% of the observed variation is explained by the model. The optimum conditions obtained from the RSM were 2.83 wt% of catalyst concentration, 11.6 : 1 methanol-to-oil molar ratio, 100.14 min of reaction time, and 8.65% v/v of THF in methanol concentration. Under these conditions, the properties of the produced biodiesel satisfied the standard requirement. THF as cosolvent successfully decreased the catalyst concentration, methanol-to-oil molar ratio, and reaction time when compared with biodiesel production without cosolvent. The results are encouraging for the application of Ca(OCH 3 ) 2 assisted with THF as a cosolvent for environmentally friendly and sustainable biodiesel production.

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