Biomass from microalgae is a potential feedstock for biofuels production. It poses no threat to food security as it does not compete with agricultural crops for arable land. Scenedesmus acutus was used as feedstock to produce bio-oil in a large liquefaction reactor. The influence of reaction temperature (280-360ºC), reaction atmosphere (N2 or CO2) and solvent on bio-oil yield, C-16 fatty acid yield and oil properties were investigated. Oils were characterised using gas chromatography, Fourier transform infrared (FTIR) spectroscopy and ultimate analysis. Higher bio-oil yields were obtained in a CO2 atmosphere (250 g.kg-1 dry microalgae) than in a N2 atmosphere (210g.kg-1 dry microalgae) whilst higher C16 fatty acid concentrations (600g.kg-1 bio-oil) were recorded in N2 atmosphere compared to oil prepared in a CO2 atmosphere (500 g.kg-¹ bio-oil). The oil yield increased to a maximum at 320°C, after which there were no significant changes. Highest bio-oil yields (425 g.kg-1 dry microalgae) were obtained in ethanol as solvent. FTIR spectroscopy and ultimate analysis showed that proteins present in the feedstock were degraded by breakage of peptide linkages, and nitrogen present in the oils is peptide fragments from protein degradation. The carbon content of all produced oils was high, but the hydrogen content was low, leading to low hydrogen/carbon ratios. Energy consumption and energy efficiency calculations showed that liquefaction in both reaction atmospheres results in a net energy gain, and a CO2 atmosphere is best for high energy efficiency.Highlights • Higher bio-oil yields obtained in a CO2 atmosphere than N2. • N2 atmosphere resulted in a higher C-16 content of the oil than in a CO2 atmosphere. • Significantly higher bio-oil yields were obtained in ethanol as solvent. • There was a lower energy consumption rate value for oils prepared in a CO2 atmosphere.

A novel 'green coal' product formulation has recently been developed and the utilization concept tested at the North-West University coal research laboratories. Hydrothermal liquefaction was used to produce bio-oil and biomass char from sweet sorghum bagasse at operating temperatures ranging between 280 and 300°C, and the resultant char was mixed in various ratios (0, 0.25, 0.50, 0.75, and 1) with fine medium-rank C bituminous discard coal (<212 μm) and CaCO3 (1-5 wt%). The mixtures were pressed into 12 χ 12 mm pellets using an LRX press at a pressure of 4 bar and gasified using CO2 at atmospheric pressure and temperatures ranging between 800 and 1000°C. Kinetic parameters obtained from the experimental data showed that the reaction rate of the biochar was an order of magnitude higher than that of raw coal, with the blend containing 3 wt% CaCO3 having the fastest reaction rate. In order to study the effect of temperature and catalyst on the retention of elemental sulphur during combustion of the various pellets, a combustion set-up consisting of a furnace, glass bayonet-type reactor, Liebig cooler, liquid traps, and an SO2 gas analyser was used, with experiments conducted at temperatures between 500 and 800°C. As expected, sulphur retention was low for the raw coal and biochar blends, but increased significantly to between 56 and 86%, decreasing with increasing temperature, in the runs with added metal catalyst/sorbent. A simulation using FactSageTM predicted that >50% of the pyritic sulphur entering the fixed-bed gasifier would be removed from the gaseous phase as insoluble CaSO4 when operated in a catalytic gasification mode at a temperature of 800°C, which is in good agreement with the experimental findings.

Abstract Two bacteria, namely Bacillus subtilis and Pseudomonas aeruginosa were exposed to different concentrations of diesel to increase their adaptation to the fossil fuel, and were used for the degradation of diesel-biodiesel blends. The biodegradation rate was evaluated using the redox indicator 2,6-dichlorophenol indophenol (DCPIP) test and gravimetric analysis. The preliminary exposure of cells to diesel proved to improve their biodegradation capacities, and exposure to a higher concentration (70%) of diesel resulted in maximum biodegradation of up to 58.38 g and 1.78 g of degraded oil per CFU/mL (1010) for P. aeruginosa and B. subtilis respectively. It was found that the adapted cells preferably used diesel in the blend. P. aeruginosa and B. subtilis exhibited different adaptation capabilities and biodegradation behaviour. Biodiesel stimulated the biodegradation of the diesel-biodiesel blends by non-adapted cells only; the adapted cells exhibited a different behaviour.

All over the world an increase in the use of renewable energy sources is being sought, and here the utilisation of wind energy plays an important role. Germany currently represents one of the world's largest markets for wind energy. At the end of 2013, nearly 24 000 onshore wind turbines with a total output of approximately 34 000 MW had been installed in Germany. Hub heights of up to 140 m and outputs of 3 to 4 MW are now no longer unusual features of new onshore wind turbines. The focus of this paper is on concrete support structures for wind turbines. Different concrete tower concepts are presented, and the influence of the construction method on the design and verification processes is described. In particular, the text deals with the eigenfrequency analysis, as well as the bearing, shear and torsional resistances of concrete towers. The differences between cast-in-place and precast towers are listed.