No abstract

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.

An experiment was conducted at Suwanvajokkasikit Research Station, Pakchong, Nakornratchasima, Thailand, to determine the yield and quality of three different grass cultivars intercropped with leucaena (Leucaena leucocephala). The treatments consisted of three grass cultivars (ruzi, dwarf napier and Taiwan A25) as the main plots, planted between leucaena at three row spacings (1, 2 and 4 m width) as the sub plots and leucaena cutting height (10 and 25 cm above ground levels) as sub-sub-plots. Dwarf napier consistently produced more dry matter than Taiwan A25 or ruzi and Taiwan A25 outyielded ruzi. Leucaena yield was highest in the ruzi plot and lowest in the dwarf napier plot. However, yields of grass plus leucaena were highest in the dwarf napier plot and were lowest in the ruzi plots. The difference was due mainly to the grass components. Increasing the spacing between rows of leucaena resulted in a lower leucaena yield but the reverse was true for the grasses. Cutting of leucaena at 10 cm above ground levels depressed yields of leucaena but did not affect the associated grasses. In terms of herbage quality, it was found that the crude protein of leaves and stems of the dwarf napier and Taiwan A25 were higher than that of the ruzi grass. Leucaena gave higher levels of crude protein than all grasses. The phosphorus and potassium levels of all grasses were higher than leucaena. ADF levels were higher in the grasses than in the legumes. Nutrient contents in the leaves and stems of grasses and leucaena were not affected by leucaena spacing and cutting height.

The effect of compost and vegetation on methane (CH4) oxidation was investigated during wet and dry conditions in a tropical region. A laboratory-scale experiment was conducted to examine the performance of nonvegetated and vegetated landfill cover systems in terms of CH4 oxidation efficiency. Two types of landfill cover materials (compost and sandy loam) and two species of tropical grasses (Sporobolus virginicus and Panicum repens) were studied for their effect on the CH4 oxidation reaction. It was found that the use of compost as cover material could maintain a high methane oxidation rate (MOR) of 12 mol CH4/m3 x day over a 250-day period. Leachate application showed a positive effect on promoting methanotrophic activity and increasing MOR. A high MOR of 12 mol CH4/m3 x day was achieved when using compost cover with P. repens during wet and dry seasons when leachate irrigation was practiced. In dry conditions, a lower MOR of 8 mol CH4/m3 x day was observed for 80 days.