Ten different microalgal species were screened for their antioxidant activity using 2,2 ́-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, both total phenolic and carotenoid contents were determined. The ethanolic extract ofOscillatoriasp. showed the highest antioxidant activity (69.1 %), while the greenChlorellasp. showed higher phenolic content (39.1 mg GAE g-1dry wt.) andScenedesmus obliquusrecorded higher carotenoid content (3.73 mg L-1), than cyanobacterial species Microalgal biomass plays a great role as a potential source of natural antioxidants, not only due to the carotenoids but also the phenolic compounds.

Limited information is available about the thermodynamic evaluation for biomass gasification process using updraft gasifier. Therefore, to minimize errors, the gasification of dry refinery sludge (DRS) is carried out in adiabatic system at atmospheric pressure under ambient air conditions. The objectives of this paper are to investigate the physical and chemical energy and exergy of product gas at different equivalent ratios (ER). It will also be used to determine whether the cold gas, exergy, and energy efficiencies of gases may be maximized by using secondary air injected to gasification zone under various ratios (0, 0.5, 1, and 1.5) at optimum ER of 0.195. From the results obtained, it is indicated that the chemical energy and exergy of producer gas are magnified by 5 and 10 times higher than their corresponding physical values, respectively. The cold gas, energy, and exergy efficiencies of DRS gasification are in the ranges of 22.9–55.5%, 43.7–72.4%, and 42.5–50.4%, respectively. Initially, all 3 efficiencies increase until they reach a maximum at the optimum ER of 0.195; thereafter, they decline with further increase in ER values. The injection of secondary air to gasification zone is also found to increase the cold gas, energy, and exergy efficiencies. A ratio of secondary air to primary air of 0.5 is found to be the optimum ratio for all 3 efficiencies to reach the maximum values.

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Considerable amount of oily waste is generated from petroleum refinery in Malaysia. A typical refinery produces about 40 tons of sludge per month. Disposing via land filling (common method) is becoming less accepted and more expensive. As a result, refineries and other facilities have accumulated large volumes of this waste in makeshift landfills or other storage areas. For this reason solvent extraction method has been selected for oil recovery and to minimize the solid waste. Three solvents (chloroform, MEK, and n-hexane) and two extraction methods (sludge–solvent mixing method , and Soxhlet apparatus) were applied to recover the oil from the refinery sludge. Soxhlet extraction method has shown higher efficiency in extraction than sludge-solvent mixing method. Soxhlet extraction method using MEK solvent can recover about 48.3 % of oil, as compared to mixing method which accounts to only about 32.5 % of recovered oil. It has an added recovery of about 7.1 %, 15.8 % and 5.7 % for n-hexane, MEK and chloroform solvents respectively. FTIR results confirmed that MEK has the highest capability to extract hydrocarbon from refinery waste.

Many papers have been published about the gasification of different biomass fuels in fixed bed reactor. To date, no experimental analysis is available in the open literature on gasification of refinery sludge. Therefore the descriptions of dynamic temperature in an updraft reactor for a dry refinery sludge gasification are investigated in details. The rate of the temperature change with operation time and the temperature profiles inside the reactor are taken for various equivalent ratios. The dynamic results show that increasing the ER from 0.195 to 0.244 shift the combustion zone peak temperature from 858 °C to 986 °C and cause turbulence behavior in reduction zone temperature. With an ER of 0.195, the rate change of temperatures zones was found to be in the ± 50 OC min-1 indicating stable gasification process. The axial temperature for starting of a steady state gasification process was found to be between 20 to 60 min operation time in process.