Abstract:In this research work, eight different samples of substrates with varying percentage total solid (TS) and volatile solid (VS) were used. The samples which comprises mainly of water hyacinth, waste water (i.e., from ice fish cold room, septic tanks, and abattoir), pig dung, cow dung, corn cobs, potato peels, pineapple peels, rice left over, yam peels, cassava peels, orange peels, sweet potato peels, garri left over, plantain peels, beans waste, banana peels and vegetables, etc., were codigested. In each of the samples, 10kg of substrates were used and the experiment was conducted within mesophilic temperature range of 36°C-37°C, pH range of 6.9-7.4 and hydraulic retention time (HRT) of thirty-three (33) days. It was observed that the quantity of biogas yield from these substrates increase with increasing percentage volatile solid and decrease with decreasing percentage volatile solid concentration below and above the optimum value of 91.1% (2.88kg) volatile solids which gave the maximum amount of biogas yield for the samples of substrates to be 1.01kg (23.6%), 2.01kg (60.75%), 2.55kg (84.72%), 2.41kg (68.0%), 2.35kg (67.67%), 1.85kg (59.23%), 1.45kg (25.39%). Furthermore, the results obtained reveal that bio-digesters should be run at 10.16% total solids, since optimum cumulative biogas generation is achieved at this %TS concentration.

Nigeria just likes every other country in sub-Sahara Africa is faced with solid waste generation and management. Solid waste is dump indiscriminately and seen in huge heaps on any piece of unused land, around buildings, drainage system, institutions, playing ground, roads side, and in the open market places in major cities and towns. Living with solid wastes littered around seems to be an acceptable way of life among the people in this part of the world. This research work reported intensive review on solid wastes generation and management in this region using Nigeria as a case study. The application of knowledge of solid waste generation and management approach is crucial for inculcating a change of attitude towards improving the management of generated solid waste in this region. From the review, it was observed that biodegradable solid waste that can be managed via the biogas technology and landfill technology have the highest percentage fraction while the remaining fraction that comprised of non-biodegradable and combustible solid waste can be managed via other technology such incineration, gasification, pyrolysis, etc. Besides, the inefficient management of generated solid waste by individuals, households, institution, consumers and waste management companies can be attributed to inadequate information on waste management benefits, insufficient academic research and industry linkages, financial constraint, economic constraint, cultural constraint, lack of planning and projection, social constraint, lack of producers' involvement in waste management as well as poor implementation of government policies and lack of comprehensive legal framework.

The rate at which feedstock is added to the anaerobic digester (AD) reactor has to be adjusted for the growth rate of methanogens bacteria. Increase in biogas yield is as a result of improved mathanogens forming bacteria. Under loading and over loading of feedstock in the AD reactor has effect on methanogens forming bacteria. If more feedstock is added than the bacteria are able to degrade, the process will become acidic. Feedstock has to been fed to the reactor at a uniform rate and volume. If feeding pattern has to change, this must be done gradually so that bacteria can adapt to the new conditions. For optimum biogas yield, required amount of feedstock must be added to the AD reactor. The aim of this research work is to determine the effect of organic loading rate (OLR) on biogas yield from food waste, water hyacinth, cow dung, waste water from abattoir, poultry dropping and pig dung. The experimental set up comprises of single stage and three-stage continuous AD reactors. The same quantity and composition of feedstock were used and this was subjected to a variation of OLR 0.5 kg/m3(1.5 kg/m3, 2 kg/m3, 2.5 kg/m3, and 3 kg/m3). The experiment was conducted within a mesophilic temperature range of 36°C-37°C, percentage total solid (%TS) of 9.98% and percentage volatile solid (%VS) of 78%. pH meter was used to monitored the daily pH reading of the slurry. It was observed that the quantity of biogas yield from the feedstock increases with increasing organic load rate to the optimum value of 1.5 kg/m3and started decreasing above the optimum value for a single stage AD reactor but this was not the case for the three-stages continuous AD reactors that experienced continuous increase in biogas yield with a successive increase in OLR from 1-5 kg/m3-3.0 kg/m3.

Biogas purification which is the removal of impurities so as to improve the efficiency of gas produced, ensure the safety of end users and prolong the life of the equipment cannot be neglected. This paper is focused on the design and performance evaluation of AD system biogas purification filter. Three different conceptual designs were generated from possible design consideration, feasibility study and preliminary test and with the help of decision matrix; the best conceptual design was selected from which the purification filter was fabricated. The selected concept for detail design was a transparent polyethene cylindrical purification filter fitted with local iron sponge containing activated charcoal and local potash. The reagents were arranged in this order; local potash for the removal of water vapour and carbon dioxide followed by activated charcoal which serves as a purifying agent for hydrogen sulphide. The results obtained showed reduction in percentage composition of hydrogen sulphide (H2S), carbon dioxide, and water vapour. On the other hand, there was an increase in percentage composition of methane (CH4) which is an indication of improvement in methane production after purification. The outcomes of the results obtained were satisfactory and the combination of local potash and activated charcoal was adequate for biogas purification.

This paper is focused on B-pillar design and reinforcement with certain criteria that the final reinforcement design weight does not exceed 6Kg and the maximum displacement must be less than 40mm on the application of 140KN load. Surface welding method was applied on the first and second design while spot welding was used for the third design, whereas, seam welding was applied on the fourth design which happened to have the least maximum displacement, least maximum stress and weight compared to the other designs. The welding methods applied in each of the design gave different displacement values with the fourth design showing the least maximum displacement of 13.8mm and the third design showing highest maximum displacement of 31.9mm, while there was proximity in displacement values obtained for the first design (15.2mm) and second design (16.4mm). Hence, for the purpose of design against unforeseen damages during side collision, auto manufacturers may consider employing seam welding techniques when manufacturing a B-Pillar for occupant safety.

The rate of MSW generation is increasing and at present, there is no single engineered landfill designed to address the challenges posed by MSW generation in Nigeria. Unmanaged open dump sites and uncontrolled MSW disposal is currently practiced in Nigeria, thus this research work which is focused on the effects of landfill gas flow trajectories at three distinct temperature phases on the stress-strain-displacement properties of a gas extraction. Conservation mass equation was derived for solid, liquid, and gaseous phase. A PVC plastic with a linear elastic isotropic property was used. Von Mises Stress was used as the default failure criterion. The material yield and tensile strength were 52 N/mm^2 and 30 N/mm^2. Other properties of the material include; elastic modulus of 3000 N/mm^2, poisson's ratio of 0.394, mass density of 1020 g/cm^3, shear modulus of 318.9 N/mm^2, and thermal expansion coefficient of 79/K. The results obtained reveal that the rate of gas generation in a landfill is dependent on the increase in temperature and pressure within the landfill system, usually causing subsurface pressures in the landfill to be higher than either the atmospheric pressure or indoor air pressure.

Melon fruits are usually depodded in Nigeria using traditional/manual method which is not only curbersome, but equally time consuming, and poor quality of finished products obtained. In other to curb these problems, a continuous melon fruit depodding machine was designed and simulated for failure. The Melon fruit depodding machine was made up of the following main units; hopper, depodding chamber, electric motor, chain, sprocket, bearings, and frame which act as supporting base. The depodding machine has a maximum capacity of 0.185m 3 , and this volume can take melon fruit of 28.25 kg powered by 2.5 hp, 1440 rpm electric motor. The following parameters were design for; depodding force, torque, power, shaft diameter, bearing, density, basic dynamic load on bearing, basic dynamic life of bearing, velocity ratio, etc. The results obtained from the detail design show that a depodding force of 277.13 N and torque of 27.713 Nm was required for the operation of the machine. SolidWorks CAD was used for the simulation of the machine. The Von Mises stress obtained was less than the yield stress, thus the design is safe. The mass of melon fruit and depodded melon fruit were used to calculate the efficiency. The results obtained showed that an average efficiency of 73.55% was obtained.

Briquetting is a mechanical compaction process for increasing the density of bulky materials. Nigeria’s current energy requirements for industrial, commercial and domestic needs cannot be met by our national electric grid which at present can only generate 5000MW for Nigeria growing population. In this research work, an improved low cost biomass briquetting machine was successfully designed and fabricated for local use in Nigeria. Preliminary tests were carried out to determine the compression ratio required (compression pressure) and the type of mould to be used. Design considerations that guided in the generation of a conceptual design that satisfy the functional requirements were established. The briquette machine design was based on mechanical (hydraulic or piston) compression principle. The machine is operated manually by a hydraulic system to generate pressure required for compression. The results obtained from the design calculation reveal that force exerted on plunger (F1) is 490.5N, total compaction force of 355.03N, total compaction pressure of 2MPa, maximum bending stress of 456MPa, projected area of 0.015m2, total force acting upward exerted by the spring is 654N and a pressure of 4.34MPa is exerted on the compression piston. Analysis carried out on the produced briquette from the biomass (elephant grass) by the fabricated machine reveals that the machine performance is satisfactory. The biomass (elephant grass) had calorific values of 14011.2KJ/kg before briquetting. The calorific value increased to 15013.9KJ/Kg after formation of briquette. This increase is partly attributed to the moisture content of the biomass.