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Background: To prevent the interruption of the carbon cycle by the disposal of waste to landfills, organic kitchen waste requires proper treatment such as composting to reduce its uncontrolled degradation on disposal sites and subsequent greenhouse gases, odour emissions and nutrient losses. This study investigated the effects of bulking agent, newspaper and onion peels, composting waste load sizes of 2 and 6 kg, or the use of starter culture on kitchen-waste composting consisting of nitrogen-riched substrates, vegetable scraps and fish processing waste in an in-vessel system. The optimised formulation of kitchen waste mixture was used for a 30-day composting study, where the temperature profiles were recorded and the carbon-to-nitrogen ratios were measured as an indication of compost maturity. The kitchen-waste composting process was conducted in parallel in two fabricated kitchen waste composters. Results: It was found that the onion peels were more suitable in producing matured compost where the carbon-to -nitrogen ratio reduced to 10 within 16 days of composting. A smaller kitchen waste load size of 2 kg gave a shorter composting time by half when compared to the 6 kg. The use of a microbial cocktail consisting seven types of bacteria and eight types of fungi isolated from soils as a starter culture for this kitchen-waste composting did not show advantages in accelerating the composting process. Conclusions: The results suggest that the in-vessel kitchen-waste composting can be efficient with a minimal load of about 2 kg using onion peels without additional starter culture.

Various applications of oil palm empty fruit bunches (OPEFB) would be hindered by the presence of residual oil. This study aimed to remove and recover the residual oil from OPEFB using an integrated system, high pressure water spray system (HPWSS). The performance of the HPWSS was evaluated at different temperatures and water pressures, and the residual oil collected was recovered through water shaking method and tested for biodiesel application. A maximum of 84.9% of residual oil was removed by HPWSS at 60 °C and 8960 kPa and the highest residual oil recovery of 58.8% was observed at 95 °C, using power shaking 5 and 90% of dilution. The following ranges of deterioration of bleachability index (DOBI), free fatty acid (FFA), and peroxide value (PV) for the residual oil were 1.21 to 2.67, 7.11 to 10.4%, and 4.85 to 7.56, respectively. Biodiesel with different blends of recovered residual oil (5%, 10%, and 15%) showed lower values (9.87, 9.57, and 9.56 Nm) of brake torque as compared with diesel (10.89 Nm). Overall, this study showed the potential of HPWSS to obtain an acceptable quality of residual oil from OPEFB to be used in any value-added product generation.

This paper presents the isolation of kenaf bast fiber to produce cellulose nanofiber (CNF) using chemical-physical treatment (e.g. delignification, bleaching and ultrasonication). Raw bast fiber was bleached and then subjected to high-intensity ultrasonication at four different output powers (100 W, 200 W, 400 W and 700 W). SEM and TEM analysis of treated bast fiber revealed that the morphological structure of CNF with diameter distribution in the range less than 100 nm (100 W) to 10 nm (700 W). Hemicellulose and lignin content were successfully reduced by chemical treatments, as there was increment of the cellulose content in the fiber more than 90% recorded. Higher ultrasonication output power attributes to the decreasing diameter size of CNF. This finding reflected that smaller CNF fibrils provide larger surface area per volume ratio. Larger stretching vibration of – OH group is detected as the higher composition of cellulose in CNF. CNF produced also had higher thermal stability than raw bast fiber after undergoes the chemical-physical treatment. Therefore, chemical-physical treatment did not only to attribute the success of deposition of lignin and hemicellulose, but also to increase the nano-sized fiber distribution in CNF suspension.