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Millions of tons of municipal solid waste (MSW) are generated annually, posing dramatic threats to our environment. To reduce its environmental impact, MSW can be segregated and thermochemically converted into clean syngas (CO and H2) fuel via gasification process. The feasibility of Gasification of MSW depends on its composition and quantity. In this work, assessment of the gasification metric of MSW is conducted under steam (H2O) as gasification moderator in a pilot scale 20kW gasifier. The characteristic of local MSW are experimentally determined using Flash 2000 organic analyzer (CHNS-O), the thermo-gravimetric analyzer (TGA) and bomb calorimeter following ASTM standards and arriving to molar formula of MSW. A thermodynamic equilibrium model based on Gibbs energy minimization method is used for the steam gasification of MSW to assess the composition of syngas. Using the baseline operating condition from the thermodynamic equilibrium model, a reactive high fidelity numerical model of a downdraft gasifier is developed to gain more fidelity. Result of gasification efficiency of thermodynamic model is 64% while reactive model gives 7% additional efficiency. Nonetheless, the stipulated efficiency and the high-quality syngas produced via the steam gasification of MSW suggest the viability of the process scale up. [ABSTRACT FROM AUTHOR]

The valorisation of waste is often represented through the form of energy recovery, nutrient reclamation and other by-products. Solid Recovered Fuel (SRF) or Refuse Derived Fuel (RDF) as a solid alternative fuel has shown promising results for waste management and enhancing the energy security. The energy recovered is dependent on the quality of the solid fuel, which is evaluated by several parameters, including the calorific value, the moisture content, the density, the oxygen content and the gas emissions. The parameters varied following different types of wastes, which increase the complexity in producing high quality of solid fuel from a mixture of solid waste. This study aims to compare different mixtures of alternative fuel composed of municipal solid waste (MSW), non-hazardous industrial waste and agricultural waste. The selected wastes have high calorific value (2,601-8,657 cal/g), low moisture content (0.06 - 9.86 %), various density (63 - 910 kg/m³), high carbon (C) of 45 - 67 %, low nitrogen (N) of 0.15 - 2.22 %, low sulphur (S) of 0.01 - 0.80 %, moderate hydrogen (H) of 4.9 - 8.21 % and high oxygen (O) of 25 - 45.5 %. The high C and O content indicated high energy and combustibility, whereas low N and S concentration can reduce the emissions of unwanted gas. The selection of the optimised mixture is based on technical and economic feasibility assessment. The technical score is calculated over seven criteria, including calorific value, moisture content, density, O and gas emissions (COx, NOx, SOx). Based on the assessment on these parameters, the optimum mixture consists of 23.00 % rice straw, 19.52 % wood, 24.58% plastics, 18.43 % cotton stalks, and 14.47 % used tires. The optimum mix has a calorific value of 5,272 cal/g, density of 311 kg/m³, and moisture content of 1.94 %. The analysis demonstrated that mixture with high proportion of plastics, rice, wood and cotton stalk ranked high as preferable alternative fuel. The analysis also showed that the ranking of the alternative fuel decreases following an increase of sludge and olive pomace in the mixture. The proposed selling price of the alternative fuel produced is 135.47 USD/t covering all capital costs and operational and maintenance costs. [ABSTRACT FROM AUTHOR]

Effective management, utilisation and conversion of municipal solid waste (MSW) to useful energy (Waste-to-Energy) could be a potential means of providing a sustainable and environmentally friendly solution. There are many types of waste-to-energy technology that can be chosen for application. The aim of this paper is to propose a tool called the Quantitative Index for Waste to Energy Technology Selection with the purpose of assisting users in screening before selecting the most suitable technology for converting MSW to energy in term of safety and health parameters. There are three components developed under both safety and health parameters. In safety parameters, the components are flammability, explosiveness and toxicity while in health parameters the components are volatility, material state and occupational exposure limit (OEL). A set of scores representing the level of hazards is assigned to these components through the application of logistic function. After all components in both parameters have been scored, the scores are added together and the maximum scores produced are taken to present the safety and health parameters for each technology called the Safety Score and Health Score. Both safety and health scores are then added together to produce a single score representing the technologies called the Safety and Health Total Score (SHTS). Lower score indicates the technology as preferable in term of safety and health parameters than the technology with higher score. This technique was applied to a simple case study of four waste-to-energy technologies which are landfill gas recovery system (LFGRS), waste incineration, gasification and anaerobic digestion. According to the assessment made, anaerobic digestion is the least preferred technology while LFRGS is the most preferred technology in term of SHTS. Further analysis showed gasification scores the highest in Health Score due to the existence of carbon monoxide as the by-product which has high volatility and low OEL indicating workers will have more exposure to carbon monoxide. Anaerobic digestion scores the highest in Safety Score due to the existence of hydrogen sulfide that is highly flammable and very toxic. Additional assessment in terms of economy, energy and environmental needs also to be included for a comprehensive assessment. [ABSTRACT FROM AUTHOR]

The potential energy that algae possess has led to re-emergence of a worldwide interest in it as a biofuel feedstock. Algae derived fuel takes many pathways and challenges. Algae are enthusiastically embraced in the energy sector as the feedstock which overcomes the current market and technical hurdles. This is because of its diversity in composition, co-production and conversion pathways. The quest of finding/engineering algae strains that exhibit highest growth, production rate and a lipid content is never ending. In this work, the whole alga is considered for gasification. Due to its low energy density, it is being considered side by side to coal cofiring, thereby reducing the fossil base CO2 emission additional to its economic gain. Gasification generates syngas that is used to fuel gas turbine at higher conversion metrics than mass incineration. Starting with material characterization and inferring their unit molar formula, gasification under CO2 and H2O moderation is perused following equilibrium conditions based on Gibbs energy minimization principle. Metrics are evaluated and accordingly high fidelity reactive flow analysis for the downdraft gasifier is conducted at the optimal conditions. Systematic gasification conditions under H2O lead to higher gasification efficiency of nearly 8 points compared to CO2. Results of the two approaches are compared and 5% efficiency difference is calculated using equilibrium based versus CFD. [ABSTRACT FROM AUTHOR]

Rural areas are exposed to severe environmental pollution issues fed by industrial and agricultural activities combined with poor waste and sanitation management practices, struggling to achieve the United Nations' Sustainable Development Goals (SDGs) in line with Agenda 2030. Rural communities are examined through a "dual approach" as both contributors and receivers of plastic pollution leakage into the natural environment (through the air–water–soil–biota nexus). Despite the emerging trend of plastic pollution research, in this paper, we identify few studies investigating rural communities. Therefore, proxy analysis of peer-reviewed literature is required to outline the significant gaps related to plastic pollution and plastic waste management issues in rural regions. This work focuses on key stages such as (i) plastic pollution effects on rural communities, (ii) plastic pollution generated by rural communities, (iii) the development of a rural waste management sector in low- and middle-income countries in line with the SDGs, and (iv) circular economy opportunities to reduce plastic pollution in rural areas. We conclude that rural communities must be involved in both future plastic pollution and circular economy research to help decision makers reduce environmental and public health threats, and to catalyze circular initiatives in rural areas around the world, including less developed communities. [ABSTRACT FROM AUTHOR]