Civil Engineering

Global energy demand is on the rise due to continuous increases in population, economic growth, and energy usage. Several studies have been done on biogas, but in South Africa, these are biased towards industrial wastewater. Therefore, there is need to explore other alternatives for biogas generation, for example energy crops such as fodder beets and cassava, on which studies are limited. Cassava has several advantages compared to other crops, including the ability to grow on degraded land and where soil fertility is low. It also has the highest yield of carbohydrate per hectare (4.742 kg/carb) apart from sugarcane and sugar beet, which makes it suitable for bioenergy (biogas) generation. This study was designed to determine the performance of co-digestion of cassava peel (CP) with cattle manure (CM) at different ratios, as well as to study the effect of the mixed ratios on methane yield through batch anaerobic digestion. All digesters were run simultaneously under mesophilic temperatures of 35 ± 1 °C. The digestion was carried out in 600 mL SCHOTT DURAN® glass laboratory bottles. The results showed that co-digestion influenced biogas production and methane yield. The final cumulative methane yields by the co-digestion of CM and CP at the CM:CP mixing ratios of 80:20 and 20:80 were 738.76 mL and 838.70 mL, respectively. The corresponding average daily methane yields were 18.42 mL/day and 20.97 mL/day. This indicates that CP enhanced the production of methane in the co-digestion process with the 20:80 CM:CP ratio.

High energy prices, rising energy imports, concerns about petroleum supplies and greater recognition of the environmental consequences of fossil fuels have driven interest in renewable transportation biofuels. To assuage the depleting fossil reserves, environmental concerns and the rising cost of fuels in the world market, there is a spurring demand to look for sustainable, greener fuels that are economically competitive with substantial environmental benefits. At this juncture, the positive attributes of biodiesel makes it a viable alternative to the conventional, petrodiesel. As the emphasis switched to production of natural oils for biodiesel, microalgae became the exclusive focus of the research. There is a need to develop and deploy microalgae technology as it provides an exciting option for the recycling of fossil fuel emissions. Algal biodiesel opens up a promising avenue for producing several " quads " of biodiesel because microalgae generally produce more of the right kind of high density natural oils needed for the production of biodiesel. Though, a nascent field today, microalgae seem to present the only bio-solution to replace fossil fuels completely. This paper reviews the production processes of biodiesel from microalgae, procedures involved in the microalgal propagation, harvesting and extraction of oil, microalgal strain improvement and importance of manipulation of microalgal lipid composition via metabolic engineering.

Sustainability in the construction industry is a global concern, and one way of handling this is the idea of recycling old concrete rubbles in the production of fresh concrete. Recycled aggregate concrete is normally classified as light weight concrete and recommended for use in production of low-grade non-structural elements. This study examined the properties of crushed old concrete cubes as replacement for natural aggregate. Five specimens 150x150mm concrete cubes with varying percentages of coarse recycled aggregate of 0 %(control), 25, 50, 75 and 100% were prepared. All the mixes were proportioned using the absolute volume method with a targeted compressive strength of 30N/mm 2 and varying w/c ratio. The result shows that with up to 75% replacement of natural aggregate with recycled aggregate, the 28 days compressive strength of concrete is in close proximity with that of normal concrete. While the strength of exclusive recycled aggregate concrete is about 15% lesser than that of exclusive natural aggregate. The result of this research confirms that crushed old concrete cubes can be safely used in the production of high grade concrete.

Owode, a sprawling water catchment area better known for its commercial activities in metal and iron casting and fabrication, is located off the Lagos Lagoon and the Ajuwon River, in Lagos State. The extensive iron and steel work along with seasonal flooding of the area and the habits of the people in this area is considered a threat to its groundwater integrity. Samples designated SW1, SW2, and SW3 for stream water WW1, WW2, and WW3 for well water and BH1, BH2, and BH3 for samples collected from boreholes were collected and analyzed to determine the presence of certain physicochemical elements and heavy metals. Including pH, EC, TDS, DO, SO 4 2-, Cl, NO 3-, and PO 4 3-. Heavy metals analyzed include Fe, Pb, Zn, Cu, Cr, Cd, and Mn. The findings showed that while a number of parameters when compared with the WHO and NADWQ stipulated maximum acceptable concentration fell within acceptable limits, others especially the heavy metals had trace elevations above the maximum acceptable levels which if not checked could have serious future groundwater contamination implications.

Sustainability in the construction industry is a global concern, and one way of handling this is the idea of recycling old concrete rubbles in the production of fresh concrete. Recycled aggregate concrete is normally classified as light weight concrete and recommended for use in production of low-grade non-structural elements. This study examined the properties of crushed old concrete cubes as replacement for natural aggregate. Five specimens 150x150mm concrete cubes with varying percentages of coarse recycled aggregate of 0 %(control), 25, 50, 75 and 100% were prepared. All the mixes were proportioned using the absolute volume method with a targeted compressive strength of 30N/mm 2 and varying w/c ratio. The result shows that with up to 75% replacement of natural aggregate with recycled aggregate, the 28 days compressive strength of concrete is in close proximity with that of normal concrete. While the strength of exclusive recycled aggregate concrete is about 15% lesser than that of exclusive natural aggregate. The result of this research confirms that crushed old concrete cubes can be safely used in the production of high grade concrete.