Energy from Waste Sources

ABSTRACT:

The term "waste to energy" has traditionally referred to the practice of incineration of garbage. Today, a new generation of waste-to-energy technologies is emerging which hold the potential to create renewable energy from waste matter, including municipal solid waste, industrial waste, agricultural waste, and waste byproducts. The main categories of waste-to-energy technologies are physical technologies, which process waste to make it more useful as fuel; thermal technologies, which can yield heat, fuel oil, or syngas from both organic and inorganic wastes; and biological technologies, in which bacterial fermentation is used to digest organic wastes to yield fuel.

Waste-to-energy technologies convert waste matter into various forms of fuel that can be used to supply energy. Waste feedstocks can include municipal solid waste (MSW); construction and demolition (C&D) debris; agricultural waste, such as crop silage and livestock manure; industrial waste from coal mining, lumber mills, or other facilities; and even the gases that are naturally produced within landfills. Energy can be derived from waste that has been treated and pressed into solid fuel, waste that has been converted into biogas or syngas, or heat and steam from waste that has been incinerated. Waste-to-energy technologies that produce fuels are referred to as waste-to-fuel technologies. Advanced waste-to-energy technologies can be used to produce biogas (methane and carbon dioxide), syngas (hydrogen and carbon monoxide), liquid biofuels (ethanol and biodiesel), or pure hydrogen; these fuels can then be converted into electricity. (For further information on the conversion of waste biomass into biofuels like ethanol and biodiesel, please see Technology Profile 3.1.2, "Biofuels.") The primary categories of technology used for waste-to-energy conversion are physical methods, thermal Methods, and biological methods.

This paper is the second in a series of two on the slagging and fouling behavior of rice husk when fired alone or in combination with other fuels in a fluidized-bed boiler. The first paper involved the fuel properties of rice husk, as investigated by a variety of laboratory methods. In this second paper, we report the results of fireside fouling measurements when burning rice husk alone and together with eucalyptus bark in various ratios. This study is based on short-term (3−10 h) deposit samples taken with air-cooled deposit probes in the super heater region of a large-scale (157 MWth) bubbling fluidized-bed (BFB) boiler burning rice husk and eucalyptus bark. Using an entrained-flow type of pilot furnace, we further made more, systematic measurements of the influence of the fuel mixture ratio on the fouling tendency of the fly ash formed. Burning of rice husk alone did not result in any detectable fouling, neither in the pilot furnace nor on the deposit probes in the super heater area of the fluidized-bed boiler. After deposit samplings with durations of up to 10 h during 100% rice husk firing, the deposit sampling probe had not collected more than 95 mg (app) of deposit material. The combustion of eucalyptus bark alone caused significant fouling. Here, the corresponding amount of deposit was approximately 90 mg after 10 h of sampling. The fouling tendency of mixtures of rice husk and bark showed a nonlinear dependence on the fuel mixture ratio. The results suggest that the rice husk ash acted as an erosive, cleaning agent in the fly ash mix.

INTRODUCTION:

RENEWABLE ENERGY:

"From everyday collection to environmental protection,

Think Green. Think Waste Management."

Governments, businesses and the public are increasingly concerned about the security of supply. The sustainability and the environmental impact of our energy sources. Is responding to the demand for alternatives to fossil fuels through the development of waste based energy from the waste we all generate.

About Waste Management:

As the leading provider of comprehensive waste management and environmental services in North America, Waste Management serves municipal, commercial, industrial and residential customers throughout the United States, Canada and Puerto Rico. Headquartered in Houston, Texas, the company serves more than 20 million residential and two million commercial customers through its network of collection operations, transfer stations, landfill disposal sites, waste-to-energy plants, recycling plants, landfill gas to energy projects and other related services.

Waste-to-energy (WtE) :

Energy-from-waste (EfW) is the process of creating energy in the form of electricity or heat from the incineration of waste source. WtE is a form of energy recovery. Most WtE processes produce electricity directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels.

OVERVIEW:

Traditionally, waste is viewed as an unnecessary element arising from the activities of any industry. In reality, waste is a misplaced resource, existing at a wrong place at a wrong time. Waste is also the inefficient use of utilities such as electricity, water, and fuel, which are often considered unavoidable overheads. The costs of these wastes are generally underestimated by managers. It is important to realise that the cost of waste is not only the cost of waste disposal, but also other costs such as:

_ Disposal cost

_ Inefficient energy use cost

_ Purchase cost of wasted raw material

_ Production cost for the waste material

_ Management time spent on waste material

_ Lost revenue for what could have been a product instead of waste

_ Potential liabilities due to waste.

What is waste minimisation?

Waste minimisation can be defined as "systematically reducing waste at source". It means:

* Prevention and reduction of waste generated

* Efficient use of raw materials and packaging

* Efficient use of fuel, electricity and water

* Improving the quality of waste generated to facilitate recycling and/or reduce hazard

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