Development of alternative carbonaceous sources for energy production is essential to alleviate the dependence on depleting fossil fuels which led to increasing atmospheric CO 2 and thus global warming. While biomass utilization for energy and chemical production has been extensively studied in the literature, such studies on municipal solid wastes is difficult to interpret due to the heterogeneous nature of the waste. Understanding of the influence of individual components is necessary for comprehensive development of waste-to-energy pathway. One such waste that is complicated and has often been ignored in the literature is composite polymer absorbent material waste which can also be considered as a potential feedstock for thermochemical pathway of energy production. Composite polymer absorbent materials are ubiquitously used these days in the form of sanitary napkins, diapers, water blockers, fire blockers and surgical pads due to their high water-absorptive nature. Pyrolysis and CO 2 gasification is ideal for such materials due to its versatile feedstock intake and uniform product output in the form of syngas with adjustable composition. CO 2 gasification also provides the added benefit of CO 2 utilization which provides carbon offset to this process. In the present study, a mixture of cellulose, absorbent material (sodium polyacrylate), polypropylene and polystyrene in a fixed proportion, to model approximate composition of a diaper, was examined for its pyrolysis and CO 2 gasification capability for viable syngas production. The influence of individual components into the syngas yield from the composite waste gasification was also investigated. A fixed-bed, semi-batch reactor facility along with gas chromatography was employed to analyse the syngas yield and compositional evolution. Pyrolysis was done under nitrogen atmosphere and gasification was done under CO 2 atmosphere. CO 2 gasification provided net CO 2 consumption which means a net reduction in carbon emissions per joule of energy produced. The sample was tested under four isothermal conditions of 973, 1073, and 1173 K to understand the impact of operational conditions on the syngas yield. Influence of individual component of the composite absorbent waste on the syngas yield and composition was also analyzed by comparing these syngas characteristics with that of the yield from gasification of its individual components separately at 1173 K. These investigations provided us with novel results on the behavior and capabilities of these composite polymer absorbent wastes and which opens up a new avenue towards efficient utilization of solid waste resources for sustainable energy production in the form of syngas which can also be used for various chemicals production such as methanol, gasoline and other petrochemical products.

Urban solid waste generation has drastically grown around the world, requiring creative, ecologically correct and sustainable solutions to be developed. This work considers a problem of thermodynamic optimization of extracting the most energy from a stream of hot exhaust produced by urban solid waste incineration, considering a stoichiometric combustion model, when the contact heat transfer area is fixed. For that, a mathematical model is introduced to evaluate the rate of heat generation due to the waste incineration process, and the exergetic (power) rate captured by a heat recovery steam generator (heat exchanger). The numerical results show that when the (cold) receiving stream boils in the counterflow heat exchanger; the thermodynamic optimization consists of locating the optimal capacity rate of the cold current. At the optimum, the cold side of the heat transfer surface is divided into three sections: preheating of liquid, boiling and superheating of steam. Experimental results are in good qualitative and quantitative agreement with the numerically calculated mathematical model results. Microalgae cultivated in large-scale vertical tubular compact photobiorreactors are investigated to treat the emissions produced by the incineration, and to increase the efficiency of the global system via cogeneration of co-products with high aggregated commercial value.

Development of alternative, clean and renewable energy production from different hydrocarbon materials helps to partially replace the limited resources of fossil fuels and also help reduce carbon emissions from fossil fuels that drives global warming. Biomass and bio-wastes are renewable and sustainable hydrocarbon resources, which can be used for energy and fuels production along with permanent disposal of plastic wastes. Landfills of wastes is unsustainable with additional problems of non-degradability and growing burden to the environment and society. Co-pyrolysis and co-gasification of biomass with different types of plastic wastes has shown to provide enhanced product yields and quality for syngas and liquid fuel production. To date, limited information is available on the understanding of chars produced from co-pyrolysis. The effect of co-pyrolysis on the type, quality and yield of chars produced is essential for efficient utilization of a wide variety of biomass, bio-waste and plastic waste resources. This paper provides information on the effect of plastic addition to the pyrolysis of biomass as well as the quality and quantity of char produced with different amounts of plastic waste added at different pyrolysis temperatures. TGA reactor was used for all these investigations and the quality of char produced was examined from the perspective of char combustion for energy production. Char is commonly produced as a by-product from pyrolysis and gasification reactors. Carbonization temperatures investigated were in the range of 573–773 K for 30 min using pinewood biomass, while recycled polyethylene terephthalate was used as plastic waste. The investigations revealed that chars produced from co-pyrolysis especially for carbonization temperature (T c ) of 673 K and above behaved completely differently than the chars produced from separate pyrolysis of biomass and plastic waste under the same pyrolysis conditions. These chars produced from co-pyrolysis were more uniform in their behavior in oxidation environment, with higher heat flow for almost similar quantities of chars during oxidation. This was conjectured to be from enhanced quality of chars produced having increased C content (from increased heavy aromatics and efficient loss of volatiles) during co-pyrolysis without any loss of char yield. The char yield was found to be equal or higher during co-pyrolysis compared to the weighted aggregate of individual pyrolysis. These investigations provided novel results on the behavior and capabilities of chars produced from co-pyrolysis of biomass and plastic wastes to provide a new avenue for the quality enhancement of bio-chars and efficient utilization of carbonaceous solid waste resources.

Gasification is a technologically advanced and environmentally friendly process for solid waste treatment. The chemical reactions in the gasification process highly depend on the agents’ flow rates which, due to fluid dynamics and thermodynamics, are in fact functions of particle size and structure. Therefore, in order to obtain a better prediction model, it is important to determine the effect of particle size on the operation of a gasification system. The purpose of this research is to investigate the effect of particle size of some common solid waste on the gasification process. Specimens including starch and polyethylene of different sizes are investigated experimentally. To achieve the aim, the gasification processes are monitored by a thermal gravimetric analysis system. The mass change and the heat flow are measured in real time during the reaction. Comparison between the experimental results and different gasification models are made. Based on the experimental results, the effect of particle size was studied and the importance of the porous structure was revealed. The relationship between particle size and porous structure during gasification was developed.

The total installed electric power capacity of Pakistan is about 20,000 MW. Pakistan is currently facing a power deficit of about 4,000 MW. This deficit is creating huge difficulties for the consumers as electrical power load shedding has become a norm in all over the country. Currently only about 33% of the total power is being produced by hydro sources and major electric power is still produced by burning oil and gas. The hydro potential of Pakistan is estimated to be about 41 GW, out of which 1,290 MW can be generated by micro-hydro systems. These potential off grid micro-hydro systems are very essential for the consumers living in the remote areas of Pakistan and may be installed on canals and water falls which are abundant in the remote areas. This paper discusses the potential and the status of installed of hydro power systems in Pakistan. Cross flow turbines are being manufactured in Pakistan and are usually quite successful for micro-hydro systems. However, cross flow turbines are not suitable for majority of the prospective site conditions. Furthermore, custom made conventional turbines are not mass produced and for the micro-hydro systems, standard centrifugal pumps may be used as turbines. These centrifugal pumps are easily available in the market at comparatively much lower cost and shorter delivery periods. A pump was installed at a suitable site for generation of electricity, while running in turbine mode. It was initially estimated that the Pump as Turbine, PaT would be able to generate about 70 kW of power based on the available flow rate and head parameters at the site. Currently only half of that power is being generated by the PaT, under study. Efforts are underway to rectify the problems being faced and improve the power generation capacity of the installed unit. This paper discusses the problems associated with the use of PaT and measures being undertaken to make it feasible for the use of micro-hydro systems. Two major issues; draft tube design and presence of trash in the canal water, responsible for performance deterioration have been discussed in this paper.

The increase of waste and the dryness of natural resources including fossil fuels have become serious problems for the sustainable development of industrial activities and our daily living. A great deal of human effort has been put into the careful use of finite resources and environmental impact reduction. The appropriate processing and the effective use of waste are really in demand in light of our social responsibility for manufacturing and energy development. In addition, the construction of a new recycle system for production is also important from the standpoint of the manufacturer’s responsibility. A procedure is being developed to process industrial and municipal wet wastes to solid fuel, called Refuse paper & plastic fuel (RPF), using superheated steam. A drying system using superheated steam is drawing much attention for use with drying high water content materials due to its high thermal efficiency. A material recycle system for processing high water content waste to solid fuel will be introduced in the present study using a demonstration system, and the optimum conditions for the system operation will be examined. The temperature and the quantity of superheated steam required for material drying are evaluated, and the energy consumption and emissions from the system are theoretically estimated and compared. The purpose of this paper is to test-operate a practical waste recycle system, and the results of this new system are compared with the results from a waste incinerator. The effectiveness of a drying system using superheated steam is shown from the standpoint of the reduction of CO 2 emissions and energy consumption for the waste processing.

A small-scale power generation system including a process of producing low-BTU gas by gasification of wastes has been developed. This system is called as the Micro STAR-MEET. Because the size of this system is small, on-site waste treatment is possible. Wastes are continuously fed into the gasifier and, high temperature air and steam are introduced into the gasifier and reformer to gasify and reform wastes. A pilot plant was constructed in order to investigate the performance of the Micro STAR-MEET system, and experiments using wood chips and plastics as fuels were conducted. Sufficient amount of gas that has 4.0 MJ/m 3 N HHV was evolved so that the dual-fueled diesel engine could be driven. The main components of the evolved gas were CO and H 2 . In this study, the gas that could be used as a fuel for the engine was evolved constantly, which indicates that the Micro STAR-MEET system is technically feasible.

Aiming to obtain an optimum balance between economical profit and environmental protection, a cost-profit model based on heat balance is built up for urban refuse incineration power system, in which the air preheat temperature and oil consumption are taken as parameters, while the maximization of the incomes of the station is taken as the objective. Considering the steady burning as constraint, the influence of the varieties of throwing oil, as well as the electric price adjusting on optimum operation parameters and profits are analyzed according to the running process of urban refuse burning power plant. Three different government’s subsidy and punishments mode are introduced into the model due to the emission of trace organic matter to analyze the influence on the power station’s best running parameters and on the behavior of the power plants. Results reveal that the government’s subsidy to garbage treatment can restrain the function ways of rubbish power station effectively.

The conversion of coal, biomass and RDF (refuse-derived fuel) etc, by means of gasification into a fuel suitable for a high temperature fuel cell has recently received more attention as a potential substitute for fossil fuels in electric power production. However, combining the gasification with a high temperature fuel cell (Molten Carbonate Fuel Cell) raises many questions with regard to gas quality and impurities. We have paid attention to H 2 S impurity contained in fuel gas and investigated the effect of H 2 S on MCFC performance by operating a 10kW-class stack. The experimental results show the H 2 S tolerable concentration to MCFC performance decreases with the decrease of H 2 concentration in fuel gas. A reason for this H 2 S tolerance is due to the inhibition for shift reaction (H 2 O + CO → H 2 + CO 2 ) by H 2 S adsorption to anode. This inhibition by H 2 S adsorption decreases the capability of high temperature fuel cell to utilize CO as a fuel.

The most popular method of controlling sulfur dioxide (SO 2 ) emissions in a steam turbine power plant is a flue gas desulfurization (FGD) process that uses lime/limestone scrubbing. Another relatively newer FGD technology is to use seawater as a scrubbing medium to absorb SO 2 by utilizing the alkalinity present in seawater. This seawater scrubbing FGD process is viable and attractive when a sufficient quantity of seawater is available as a spent cooling water within reasonable proximity to the FGD scrubber. In this process the SO 2 gas in the flue gas is absorbed by seawater in an absorber and subsequently oxidized to sulfate by additional seawater. The benefits of the seawater FGD process over the lime/limestone process and other processes are; 1) The process does not require reagents for scrubbing as only seawater and air are needed, thereby reducing the plant operating cost significantly, and 2) No solid waste and sludge are generated, eliminating waste disposal, resulting in substantial cost savings and increasing plant operating reliability. This paper reviews the thermodynamic aspects of the SO 2 and seawater system, basic process principles and chemistry, major unit operations consisting of absorption, oxidation and neutralization, plant operation and performance, cost estimates for a typical seawater FGD plant, and pertinent environmental issues and impacts. In addition, the paper presents the major design features of a seawater FGD scrubber for the 130 MW oil fired steam turbine power plant that is under construction in Madinat Yanbu Al-Sinaiyah, Saudi Arabia. The scrubber with the power plant designed for burning heavy fuel oil containing 4% sulfur by weight, is designed to reduce the SO 2 level in flue gas to 425 ng/J from 1,957 ng/J.