Advanced Materials Research Vols. 18-19

Abstract: This devise addresses the inadequacies of providing a quick means of holding jobs of irregular shapes such as are encountered in small scale fabrication workshops. The conventional bench vise often does not provide the adequate grip for such shapes so that attachments in the form of V blocks are usually provided to enhance the grip before drilling operations are carried out. This versatile work holding device enables fabricators to perform drilling and other production operations on a work piece. This device produced from mild steel plates uses the toggle principle to provide rapid grip. Comparative tests on time span in the use of this device and the bench vice for job set up, production operation and then disassembly showed that time is gained with use of the device.

Abstract: The distribution of heavy metals in leachates from a waste dumpsite was investigated. Soil samples were taken from a major dumpsite in Edo State located at Oluku near the National Institute for Oil Palm Research (NIFOR) and analyzed. The heavy metals considered were Iron, Lead, Zinc, Mercury, Chromium, Cadmium, Arsenic, Nickel, and Copper. The concentrations, in mg/l, of these heavy metals in the leachates from the soil samples over a distance of 80 meters were determined using the Atomic Absorption Spectrophotometer (AAS). The following results were obtained, the concentration of Iron ranged between 1.25-1.85 mg/l, Chromium: 0.01-0.07 mg/l, Zinc: 0.45-3.45 mg/l, Copper: 0.01-0.03 mg/l, Lead, Mercury, Cadmium, Arsenic, and Nickel had negligible values, i.e. less than 0.01 mg/l. From the results the concentrations of iron and zinc fell within Federal Environmental Protection Agency (FEPA) limits.

Abstract: Plastic carrier bags have gained popularity with Zimbabwean shoppers since they provide convenient carriage of groceries and related goods. However most of these have a short useful life and are often disposed into landfills or littered. This research was aimed at assessing the interaction between the High Density Polyethylene (HDPE) plastic carrier bag life cycle and the environment, hence identifying specific life cycle stages that pose significant threats to the environment. The study was conducted in accordance with the ISO 14040 based Life Cycle Assessment (LCA) methodology. The life cycle stages assessed include the extraction of HDPE, transportation of HDPE pellets, production of the bags, transportation of the finished goods to retailers and disposal scenarios. Improvement strategies were then identified to optimise the environmental performance of the plastic carrier bags.

Abstract: Estimates of weight of general refuse generated in this country’s major cities vary, but in Harare it is estimated at above 823 000 tonnes, which is mostly land-filled. This paper proposes the incineration of combustible municipal waste to produce 40 MW of electricity and considers its feasibility. This can give a waste reduction to as low as one tenth of the initial volume and is quite effective in killing pathogens. The work involved use of questionnaires, interviews and access to primary data at the Harare City Council. The positive and negative environmental and health impacts, particularly relating to dioxins are discussed and solutions to pollution proposed.

Abstract: In this work, a comparative study of biogas production from poultry droppings, cattle dung, kitchen waste, fruit waste and vegetable waste was done under the same operating conditions. 3kg of each waste was mixed with 9kg of water and loaded into the 5 constructed digesters. Biogas production was measured using water displacement method for a period of 40 days and at an average temperature of 30.5oC. Results indicated that poultry droppings produced 0.0332dm3/day, cow dung produced 0.0238dm3/day, Kitchen waste produced 0.0080dm3/day, vegetable waste produced 0.0066dm3/day and fruit waste with 0.0022dm3/day. It is concluded that poultry droppings produced more biogas because it contains more nutrients and nitrogen compared with plant and other animal waste

Abstract: The search for alternative sources of energy from organic waste has been on in Nigeria. This report focuses on a simple design, fabrication and performance test of a prototype biogas digester. The volume of the digester was 340dm3 and that of the absorber/adsorber was 12.5dm3. The digester was fabricated using mild and stainless steels, styrofoam, polythene sheets and other materials. The digester can be moved about and agitated manually. In the performance test, 8.134L of biogas was generated within 14 days of anaerobic digestion of palm oil mill effluent (POME). The optimum pH and temperature for biogas production were 6.2 and 29oC respectively.