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%

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

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

Enrichment of biogas for use as vehicular fuel: a review of the upgrading techniques

Biogas, a renewable energy, can be captured, upgraded and used to fuel a vehicle as an alternative to fossil fuel, thus, reducing greenhouse gas emission. Biogas is environmentally hazardous if emitted directly into the environment. Increasing demand for bio-methane to be used as vehicular fuel has called for efficient use of waste and technology that is optimal yet economical. Biogas in its raw state contains impurities that reduce its heating value to be used directly as fuel, hence, a need to enhance it by upgrading to bio-methane. Several techniques exist for upgrading biogas to bio-methane. This paper present four upgrading techniques; absorption, adsorption, membrane and cryogenic techniques, a brief theoretical background, advantages and operational issues associated with each technique

Economic analysis of biogas upgrading and utilization as vehicular fuel in South Africa

Abstract: Economic and sensitivity analysis of a simulated biogas upgrading plant using a gas permeation software has been presented in this study. The effect of three process conditions on gas processing cost (GPC) were simulated. An increase in CO2 increased the GPC from $0.73 to$1.39/m3 of biomethane while an increase in feed pressure increased GPC from $0.65 to$1.16/m3 of biomethane. As the feed flow rate increased from 80-140 m3/h, the product flow rate increased from 46-100 m3/h while the GPC decreases from $0.79 to$0.39/m3 of biomethane. At optimized condition, the calculated GPC was $0.46/m3 of biomethane. The 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. Using CBG over gasoline, the end user saves 34% of annual fuel cost which is approximately R47,255 with a payback period of one year and three months for vehicle retrofitting. The fuel prices differential between gasoline and CBG as well as the overall savings, makes CBG attractive to the producer and end user

Renewable energy: deployment and the roles of energy storage

Abstract: Hydro energy still remains the highest RE contributor to electricity generation globally, nevertheless, trends in solar and wind energy has shown increasing investment in RE. Though a decline in investment was observed between 2012 and 2013, yet investment in RE exceeded that of non-RE in the excess of $80 billion dollar. In 2014, investment increased by 16%. As developed countries get saturated with RE technologies, developing countries are now the focus for investment. Wistfully, path dependency problem, lack of adequate infrastructure and policy framework have been highlighted as the major barrier to RE deployment in developing countries. Also, lack of harmonised government agency for RE implementation, incentives and educational gap are the institutional and social barriers. Energy Storage (ES) is being promoted as the “game changer” with capability of smoothening the variability associated with the two RE technologies, wind and solar, with the highest deployment rate. Recent developments are indicative of cost reduction for ES. This paper therefore presents a concise and holistic review of renewable energy (RE) technologies for electricity generation and assess the roles of ES in mitigating intermittency associated with their generation profile