Parametric study of single and double stage membrane configuration in methane enrichment process

Operational study of a biogas upgrading plant with cleaning and methane (CH4) enrichment has been presented in this study. Parametric study was conducted to investigate the effect of variation of process conditions for single stage without recycle (SSWR) and double stage with permeate recycle (DSPR) on product purity, CH4 recovery and compression power requirement. In the study, achieving high CH4 recovery and product purity simultaneously could not be attained in SSWR configuration. The performance of DSPR yielded a better result but with higher membrane area and compression power. DSPR configuration achieved high CH4 recovery and purity at increasing feed pressure, selectivity and feed flow. The CH4 losses increased in both configurations as %CO2 increased in the feed. DSPR configuration is considered the best configuration due to the end use of the product, as vehicular fuel, which requires high product purity

Operational study and simulation of a biogas upgrading plant

The drive for finding alternative energy to supplement fossil based fuel within the South African energy sector has led to research on waste to energy in particular biomethane as vehicular fuels. Biogas is produced from the anaerobic decomposition of organic matter with 40-70% vol. of methane. Biogas if upgraded, by removing the non-combustible component, can achieve 99% methane concentration which makes it a potent vehicle fuel and a direct substitute to natural gas. In this paper, a biogas upgrading plant operation that uses gas permeation technique for methane enrichment of biogas was studied and simulated. The effect of recycling permeate stream on methane recovery was studied. Recycling of the permeate stream improved the methane recovery of the simulated process by 18%. The overall methane recovery of the simulated process is 81.23%

Enhanced Biogas Generation from Co-Digestion of Sewage Sludge and Kitchen Bio-Waste

In this study kitchen waste and sewage sludge were co-digested anaerobically to produce biogas with the aid of engineering granules to enhance biogas production. Co-digestion was conducted for mesophilic and thermophilic conditions in a 20L bio digester for a period of 30 days. Hycura was inoculated to enhance biogas production. The co-digestion resulted in significant degrease of the total volatile solids and chemical oxygen demand of the bio-waste by >75%. Mesophilic conditions favored high quality biogas production with methane content as high as 74%. Inoculation with Hycura hindered H2S production which enhanced the quality of the biogas and makes it easier for upgradin

Environmental sustainability : multi-criteria decision analysis for resource recovery from organic fraction of municipal solid waste

Abstract: Landfills within the City of Johannesburg (CoJ) are running out of airspace. To slow down airspace consumption rate, waste discharged at these landfills must be minimised, and where possible recover useful resources. A multi-criteria decision tool, the Analytical Hierarchy Process (AHP) was employed to appropriate technologies for fruit and vegetables waste discharge at Robinson Deep landfill. The goal of the approach is environmental sustainability. Pairwise comparison of four criteria and four technology alternatives were investigated. Data used were retrieved from a research group and consultations with waste to energy experts. Of the four technology alternatives, anaerobic digestion (AD) is the most preferred. Incineration technology has 49.42% preference to AD because it is perceived to reduce the bulkiness of waste discharged at the landfill. Composting has 25.24% preference to AD and it is believed to encourage home management of waste. Consistency ratio for all pairwise comparison was less than 0.1

Municipal solid waste data quality on artificial neural network performance

Abstract: Short and long-term municipal solid waste (MSW) management requires adequate planning. Understanding the relationship among variables that affect MSW generation and predicting MSW based on them is needed for an effective planning. Methodologies to forecast MSW are numerous and have been implemented at different level of data granularity. Lack of data in many African cities and countries has hampered effective waste management plan. The lack of data has mainly been attributed to insufficient budget and lack of capacity to implement such management structure. In this study, we investigated the impact of data quality on forecasting efficiency using advanced prediction techniques. It was observed that the quality of waste related data variables determines the extent of model reliability and prediction accuracy

Non-isolated high-gain triple port DC–DC buck-boost converter with positive output voltage for photovoltaic application

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A review on factors affecting municipal solid waste generation

Abstract: Municipal solid waste (MSW) management is not a one-off planning, it is a dynamic evolution and planning has to cater for it. The quantity of MSW generated and composition form the basis for planning and management of MSW. However, for an effective MSW reduction policy to be implemented, generated quantity of MSW is not sufficient alone for policy implementation but more of the variables affecting the generation rate and composition are critical. Without an in-depth understanding of these variables, waste reduction policies may be ineffective and unsuccessful. In this study, we reviewed the impact of these factors on MSW. A case of the City of Johannesburg (CoJ) was studied. Population and gross domestic product (GDP) are the two compelling factors affecting MSW generation. The waste generation per capita is influenced by income level. High income group generate on average 1.91 kg/capita/day, middle income group generates 1.01 kg/capita/day and low income group 0.92 kg/capita/day. This put the CoJ total waste generated at an average of 1.83 million ton/year

Implementation of multi-criteria decision method for selection of suitable material for development of horizontal wind turbine blade for sustainable energy generation

The material selection process for producing a horizontal axis wind turbine blade for sustainable energy generation is a vital issue when using Nigeria as a case study. Due to the challenge faced with the low wind speed variations. However, this paper focuses on implementing MCDM for the material selection process for a suitable material for developing a horizontal wind turbine blade. This paper used a quantitative research approach using AHP and TOPSIS multi-criteria decision method. The study put into consideration the environmental conditions for the material selection process when designing the questionnaire. The authors extracted the data used for the selection process from the 130 research questionnaire distributed to materials engineers and renewable energy professionals. This research considered four alternatives that is, aluminum alloy, stainless steel, glass fiber, and mild steel to determine the best material for the wind turbine blade. Also, the model has four criteria and eight sub-criteria used for developing the pair-wise matrix and the performance score used for the ranking process of the alternatives. The result shows that a consistency index of 0.056 and a consistency ratio of 0.062 gotten via the AHP method is workable for material selection practice. 78%, 43%, 67%, and 25% are the performance scores for the four alternatives via the TOPSIS techniques. In conclusion, aluminum alloy is the best material, followed by glass fibre. Therefore, the decision-makers recommended aluminum alloy; hence, manufacturers should apply aluminum alloy to develop the wind turbine blade for sustainable energy generation

Review of biochar role as additive in anaerobic digestion processes

because of the urgent need to provide renewable energy sources and efficiently manage the continuously growing amount of organic waste. Biochar (BC) is an extremely versatile material, which could be produced by carbonization of organic materials, including biomass and wastes, consistently with Circular Economy principles, and “tailor-made” for specific applications. The potential BC role as additive in the control of the many wellknown critical issues of AD processes has been increasingly explored over the past few years. However, a clear and comprehensive understanding of the connections between BC and AD is still missing. This review paper analyses and discusses significant references (review articles, research papers and international databases and reports), mostly published in the last 10 years. This review is aimed at addressing three key issues related to the better understanding of the BC role in AD processes: 1. Investigation of the influence of BC properties on AD performances and of their ability to counteract its main challenges; 2. Assessment of the optimal BC production chain (i.e. feedstock-pyrolysis-activation) to achieve the desired features; 3. Evaluation of the economic and environmental advantages connected to BC use in AD processes, compared to conventional solutions applied to address AD challenges

Parametric study and economic evaluation of a simulated biogas upgrading plant

M. Tech. (Chemical Engineering)The usual target of an upgrading process using membrane is to produce a retentate stream, the product, with high CH4 concentration. This work presents a simulation of two possible membrane configurations, single stage without recycle (SSWR) and double stage with permeate recycle (DSPR), of an existing operational biogas upgrading plant. The simulation was conducted using ChemCAD and AlmeeSoft gas permeation software to investigate the performance of the configurations on product purity, recovery and required compressor power with a view to determine the optimal operational conditions for maximising the concentration of CH4 and its recovery. Thereafter, an economic assessment on the optimal configuration was conducted to determine the gas processing cost (GPC), the profitability of producing biomethane and cost-benefit of utilising biomethane as a vehicular fuel. The simulation was validated against plant data with a maximum percentage error of 2.64%. Increasing CO2 in feed reduced product recovery and purity. Increasing feed pressure and selectivity increased product recovery and purity up to the pressure limit of the membrane module. Increasing feed flow rate increased product recovery but reduces purity. In both configurations, increasing CO2 in the feed and increasing feed pressure increased the GPC. However, increasing feed flow rate reduced the GPC. The overall performance of DSPR configuration was much higher due to increased trans-membrane area available for separation. At optimal conditions, a product purity of 91% and 96% CH4 recovery was achieved from the initial plant result of 87.2% product purity and 91.16% CH4 recovery. The total compression duty was 141 kW. The GPC was $0.46/m3 of biomethane. The cumulative discounted NPV, IRR and BCR for producing biomethane was R15,240,343, 22.41% and 2.05 respectively, with a break-even in the 5th year after plant start-up considering a prime lending rate at 9%. Using CBG instead of gasoline saves 34% of annual fuel cost with a payback period of one year and three months for the cost of retrofitting the vehicle