Waste to Energy
The enormous increase in the quantum and diversity of waste materials generated by human activity and their potentially harmful effects on the general environment and public health, have led to an increasing awareness about an urgent need to adopt scientific methods for safe disposal of wastes. While there is an obvious need to minimize the generation of wastes and to reuse and recycle them, the technologies for recovery of energy from wastes can play a vital role in mitigating the problems. Besides recovery of substantial energy, these
technologies can lead to a substantial reduction in the overall waste quantities requiring final disposal, which can be better managed for safe disposal in a controlled manner while meeting the pollution control standards.
Waste generation rates are affected by socio-economic development, degree of industrialization, and climate. Generally, the greater the economic prosperity and the higher percentage of urban population, the greater the amount of solid waste produced. Reduction in the volume and mass of solid waste is a crucial issue especially in the light of limited availability of final disposal sites in many parts of the world. Although numerous waste and by product recovery processes have been introduced, anaerobic digestion has unique and integrative potential, simultaneously acting as a waste treatment and recovery process.
GARBAGE energy
TO BURN OR NOT TO BURN?
Some critics of waste-to-energy plants are afraid that burning waste will hamper recycling programs. If everyone sends their trash to a waste-to-energy plant, they say, there will be little incentive to recycle. Several states have considered or are considering banning waste-to-energy plants unless recycling programs are in place. Massachusetts, New Jersey, and New York City have delayed new waste-to-energy plants, hoping to increase the level of recycling first.
So, what’s the real story? Can recycling and burning waste coexist? At first glance, recycling and waste-to-energy seem to be at odds, but they can actually complement each other. That’s because it makes good sense to recycle some materials, and better sense to burn others.
Let’s look at aluminium, for example. Aluminium ore is so expensive to mine that recycling aluminium more than pays for itself. Burning it produces no energy. Also, because aluminium melts at a low temperature, it can clog up the works in a waste-to-energy plant. So clearly, aluminium is valuable to recycle and not useful to burn.
Paper, on the other hand, can either be burned or recycled—it all depends on the price the used paper will bring. A few years ago, the East Coast experienced a glut of old newspapers. Some East Coast communities were paid almost nothing for the paper they collected. And some communities couldn’t find anyone who wanted to buy their old newspapers, so they ended up paying a trucking company to haul the newspapers to a landfill!
In these cases, burning the newspapers for their energy value would have been a good alternative. Other types of paper, such as those using coloured inks and glossy finishes, are not easily recycled and usually should be burned for their energy content.
Plastics are another matter. Because plastics are made from petroleum and natural gas, they are excellent sources of energy for waste-to-energy plants. This is especially true since plastics are not as easy to recycle as steel, aluminium or paper. Plastics almost always have to be hand sorted and making a product from recycled plastics may cost more than making it from new materials.
To burn or not to burn is not really the question. We should use both recycling and waste-to-energy as alternatives to land filling.
AIR EMISSIONS
The Environmental Protection Agency (EPA)—an agency of the federal government—applies strict environmental rules to waste-to-energy plants. The EPA requires waste-to-energy plants to use anti-pollution devices, including scrubbers, fabric filters, and electrostatic precipitators. The EPA wants to make sure those harmful gases and particles are not going out the smokestack into the air. Scrubbers clean chemical gas emissions by spraying a liquid into the gas stream to neutralize the acids. Fabric filters and electrostatic precipitators remove particles from the emissions. The particles are then mixed with the ash that is removed from the bottom of the waste-to-energy plant’s furnace when it is cleaned. Waste-to-energy plants also have a kind of built-in anti-pollution device. A waste-to-energy furnace burns at such high temperatures (1,800 to 2,000 degrees Fahrenheit) that many complex chemicals naturally break down into simpler, less harmful compounds.
ASH DISPOSAL
Another challenge is the disposal of the ash after combustion. Ash can contain high concentrations of various metals that were present in the original waste. Textile dyes, printing inks, and ceramics, for example, contain the metals lead and cadmium. Separating waste before combustion can solve part of the problem. For instance, because batteries are the largest source of lead and cadmium in the solid waste stream, they should be taken out of the mix and not burned.
The ash must be disposed of carefully. Like regular garbage, it is not a good idea to place ash in an unprotected landfill because water trickling through the landfill, called leach ate will pick up the chemicals and metals in the ash and could contaminate the ground and surface waters nearby. Ash is now used in some places for building roads, making concrete stronger and as artificial reefs for marine animals.
You can think of garbage as a mixture of energy-rich fuels. In 100 pounds of typical garbage, more than 80 pounds can be burned as fuel to generate electricity at a power plant. Those fuels include paper, plastics, and yard waste. A ton of garbage generates about 525 kilowatt-hours (kWh) of electricity, enough energy to heat a typical office building for one day.
The high-temperature incinerator in a waste-to-energy plant burns most of the waste. All that is left is a substance called ash. Ash is the solid residue left over when something is burned. It’s like the ash left over from a wood fire in the bottom of a fireplace. In a waste-to-energy plant, 2,000 pounds (one ton) of garbage is reduced to 300–600 pounds of ash.
RASH BURNED IN WASTE-TO-ENERGY PLANTS
More Info...
http://ewh.ieee.org/sb/bangalore/nitk/Fazer/Fazer-September.pdf
To watch video..
http://www.youtube.com/watch?v=UjZgtmd1kko
Written by M.Ajmal Khan.
The enormous increase in the quantum and diversity of waste materials generated by human activity and their potentially harmful effects on the general environment and public health, have led to an increasing awareness about an urgent need to adopt scientific methods for safe disposal of wastes. While there is an obvious need to minimize the generation of wastes and to reuse and recycle them, the technologies for recovery of energy from wastes can play a vital role in mitigating the problems. Besides recovery of substantial energy, these
technologies can lead to a substantial reduction in the overall waste quantities requiring final disposal, which can be better managed for safe disposal in a controlled manner while meeting the pollution control standards.Waste generation rates are affected by socio-economic development, degree of industrialization, and climate. Generally, the greater the economic prosperity and the higher percentage of urban population, the greater the amount of solid waste produced. Reduction in the volume and mass of solid waste is a crucial issue especially in the light of limited availability of final disposal sites in many parts of the world. Although numerous waste and by product recovery processes have been introduced, anaerobic digestion has unique and integrative potential, simultaneously acting as a waste treatment and recovery process.
The average Indian person throws away 2 Kg( 4.4 pounds) of trash every day! What are we going to do with all that trash?
One solution is to burn it. (Burning is sometimes called combustion.) All organic waste contains energy. Organic waste is waste that is made from plant or animal products. People have burned one type of organic material for millions of years. Can you guess what that material is? It’s wood. Ancient people burned wood to keep them warm and to cook their food. In many parts of the world, wood is still the number one source of energy.
Today, we can burn garbage in special plants and use its heat energy to make steam to heat buildings or to generate electricity. This may sound amazing, but it is really nothing new. More than half of electric power companies already burn another type of solid material to make electricity.
It takes 2,000 pounds of garbage to equal the heat energy in 500 pounds of coal.
That material is coal. Coal is a mineral that was formed from the remains of plants that died millions of years ago. Power companies use the heat energy in coal to make electricity.
Garbage does not contain as much heat energy as coal, though. It takes one ton (2,000 pounds) of garbage to equal the heat energy in 500 pounds of coal. Today, there are 103 waste-to-energy plants in the United States. Plus, there are another 26 old-style solid waste incinerators. These old-style incinerators simply burn trash to get rid of it. They do not use the heat energy to make steam or electricity.
Some critics of waste-to-energy plants are afraid that burning waste will hamper recycling programs. If everyone sends their trash to a waste-to-energy plant, they say, there will be little incentive to recycle. Several states have considered or are considering banning waste-to-energy plants unless recycling programs are in place. Massachusetts, New Jersey, and New York City have delayed new waste-to-energy plants, hoping to increase the level of recycling first.
So, what’s the real story? Can recycling and burning waste coexist? At first glance, recycling and waste-to-energy seem to be at odds, but they can actually complement each other. That’s because it makes good sense to recycle some materials, and better sense to burn others.
Let’s look at aluminium, for example. Aluminium ore is so expensive to mine that recycling aluminium more than pays for itself. Burning it produces no energy. Also, because aluminium melts at a low temperature, it can clog up the works in a waste-to-energy plant. So clearly, aluminium is valuable to recycle and not useful to burn.
Paper, on the other hand, can either be burned or recycled—it all depends on the price the used paper will bring. A few years ago, the East Coast experienced a glut of old newspapers. Some East Coast communities were paid almost nothing for the paper they collected. And some communities couldn’t find anyone who wanted to buy their old newspapers, so they ended up paying a trucking company to haul the newspapers to a landfill!
In these cases, burning the newspapers for their energy value would have been a good alternative. Other types of paper, such as those using coloured inks and glossy finishes, are not easily recycled and usually should be burned for their energy content.
Plastics are another matter. Because plastics are made from petroleum and natural gas, they are excellent sources of energy for waste-to-energy plants. This is especially true since plastics are not as easy to recycle as steel, aluminium or paper. Plastics almost always have to be hand sorted and making a product from recycled plastics may cost more than making it from new materials.
To burn or not to burn is not really the question. We should use both recycling and waste-to-energy as alternatives to land filling.
AIR EMISSIONS
The Environmental Protection Agency (EPA)—an agency of the federal government—applies strict environmental rules to waste-to-energy plants. The EPA requires waste-to-energy plants to use anti-pollution devices, including scrubbers, fabric filters, and electrostatic precipitators. The EPA wants to make sure those harmful gases and particles are not going out the smokestack into the air. Scrubbers clean chemical gas emissions by spraying a liquid into the gas stream to neutralize the acids. Fabric filters and electrostatic precipitators remove particles from the emissions. The particles are then mixed with the ash that is removed from the bottom of the waste-to-energy plant’s furnace when it is cleaned. Waste-to-energy plants also have a kind of built-in anti-pollution device. A waste-to-energy furnace burns at such high temperatures (1,800 to 2,000 degrees Fahrenheit) that many complex chemicals naturally break down into simpler, less harmful compounds.
ASH DISPOSAL
Another challenge is the disposal of the ash after combustion. Ash can contain high concentrations of various metals that were present in the original waste. Textile dyes, printing inks, and ceramics, for example, contain the metals lead and cadmium. Separating waste before combustion can solve part of the problem. For instance, because batteries are the largest source of lead and cadmium in the solid waste stream, they should be taken out of the mix and not burned.
The ash must be disposed of carefully. Like regular garbage, it is not a good idea to place ash in an unprotected landfill because water trickling through the landfill, called leach ate will pick up the chemicals and metals in the ash and could contaminate the ground and surface waters nearby. Ash is now used in some places for building roads, making concrete stronger and as artificial reefs for marine animals.
You can think of garbage as a mixture of energy-rich fuels. In 100 pounds of typical garbage, more than 80 pounds can be burned as fuel to generate electricity at a power plant. Those fuels include paper, plastics, and yard waste. A ton of garbage generates about 525 kilowatt-hours (kWh) of electricity, enough energy to heat a typical office building for one day.
The high-temperature incinerator in a waste-to-energy plant burns most of the waste. All that is left is a substance called ash. Ash is the solid residue left over when something is burned. It’s like the ash left over from a wood fire in the bottom of a fireplace. In a waste-to-energy plant, 2,000 pounds (one ton) of garbage is reduced to 300–600 pounds of ash.
RASH BURNED IN WASTE-TO-ENERGY PLANTS
Many countries have built waste-to-energy plants to capture the energy in their trash. The graph shows the top five countries that burn their trash to recover the energy in it.
Japan burns 62 percent of its trash, in part because it has little open space and very few energy resources.
The U.S. ranks fourth in the world, burning 16 percent of its trash in waste-to-energy plants.
In India Our Tamilnadu state government has announced the project for 60 municipality and 6 city municipal Corporation .
More Info...
http://ewh.ieee.org/sb/bangalore/nitk/Fazer/Fazer-September.pdf
To watch video..
http://www.youtube.com/watch?v=UjZgtmd1kko
Written by M.Ajmal Khan.
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