Acacia Holosericea: An Invasive Species for Bio-char, Bio-oil, and Biogas Production

To evaluate the possibilities for biofuel and bioenergy production Acacia Holosericea, which is an invasive plant available in Brunei Darussalam, was investigated. Proximate analysis of Acacia Holosericea shows that the moisture content, volatile matters, fixed carbon, and ash contents were 9.56%, 65.12%, 21.21%, and 3.91%, respectively. Ultimate analysis shows carbon, hydrogen, and nitrogen as 44.03%, 5.67%, and 0.25%, respectively. The thermogravimetric analysis (TGA) results have shown that maximum weight loss occurred for this biomass at 357 °C for pyrolysis and 287 °C for combustion conditions. Low moisture content (<10%), high hydrogen content, and higher heating value (about 18.13 MJ/kg) makes this species a potential biomass. The production of bio-char, bio-oil, and biogas from Acacia Holosericea was found 34.45%, 32.56%, 33.09% for 500 °C with a heating rate 5 °C/min and 25.81%, 37.61%, 36.58% with a heating rate 10 °C/min, respectively, in this research. From Fourier transform infrared (FTIR) spectroscopy it was shown that a strong C–H, C–O, and C=C bond exists in the bio-char of the sample.

Nutritional attributes of Hemiparasitic mistletoe Scurrula ferruginea in Brunei Darussalam

Three different associations of Scurrula ferruginea parasites on three different hosts, namely Tabebuia pallida, Acacia holosericea and Acacia auriculiformis were collected from the Brunei-Muara District, Brunei Darussalam. Moisture content and chemical analyses (ash content, total carbohydrate content, crude protein, proline and mineral content composition) were determined to explain the host-parasite physiological biochemistry. Scurrula ferruginea contained relatively higher moisture content (47 – 65%) and ash content (2.1-2.5%, dry basis) than the hosts (0.7-1.4%, dry basis). High nutrient and moisture contents in Scurrula ferruginea make it more preferred food source than its hosts for generalist herbivores in a given community. The mistletoe exhibited differential storage profile of total carbohydrate (1.9-6.4%, dry basis) and total nitrogen (1.2 – 3.0%, dry-basis) when compared to hosts (total carbohydrate 2.3 - 3.0 % dry basis; total nitrogen 1.6 - 2.1%). Meanwhile the proline content (24.9-56.0 mg/kg, dry basis) were found in Scurrula ferruginea. Among all the minerals analysed, potassium is the most abundant mineral present in all mistletoe-host associations. Data indicated that certain host desired solutes are preferentially absorbed and stored in mistletoe.

Acacia holosericea (Fabaceae) litter has allelopathic and physical effects on mission grass (Cenchrus pedicellatus and C. polystachios) (Poaceae) seedling establishment

Invasion of grass weeds is a major threat for ecosystems. Mission grass (Cenchrus pedicellatus and C. polystachios) vigorously competes with native vegetation and has become a serious problem in northern Australian savanna. A lower density of mission grass has been observed under the canopy of stands of native Acacia holosericea. We used a series of laboratory and shade house experiments to assess the potential for allelopathy and the role of litter on germination, emergence and seedling growth of these two species of mission grass. Different concentrations of aqueous leaf extract of A. holosericea were used to assess allelopathic effects on germination. Various depths and types of litter were used to investigate the allelopathic and physical effects of litter on emergence and growth of mission grass seedlings in the shade house. Results indicate that extracts did not affect germination of either species of mission grass but root growth of seedlings was affected. Emergence of seedlings in the shade house was affected by physical litter treatments but not by allelopathy. After emergence no negative effects on seedling growth were detected. Overall we found that there was no allelopathic effect on germination and that the negative effect on emergence was due to the physical properties of the litter. This effect on emergence increased with increasing depth of litter. Allelopathy slightly inhibited root growth but once seedlings emerged, litter tended to facilitate growth. This has implications for the ecological management of mission grass on disturbed lands, using strategies such as manipulation of litter cover through Acacia establishment.