Green Grab Bag

Published on October 20th, 2014 | by GrowWNY Intern

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Energy-from-Waste: Utter rubbish, or potential clean energy?

BY: AMBER POTTER, GROWWNY INTERN

According to the Environmental Protection Agency, the average American produces about 4.4 pounds of garbage a day.  This adds up quickly, with a total of 29 pounds per week, and 1,600 pounds a year.  That’s a lot of waste!  While a lot of that waste ends up in landfills across the country, there are also certain methods by which we might be able to make use of it.  One such method is called Energy-from-Waste and is practiced by the Covanta Niagara facility in Niagara Falls.  Covanta Niagara processes 2,250 tons of waste per day and sells the resulting steam and electricity to nearby facilities, as well as the New York State power grid.

According to its website, Covanta is an Energy-from-Waste facility, which helps to “offer a safe, technologically advanced means of waste disposal while also generating clean, renewable energy, reducing greenhouse gas emissions and supporting recycling through the recovery of metals.”  While that may sound great, there are many things to consider, including the potential negative impacts associated with the Energy-from-Waste process.

I was able to go on a tour of the Covanta facility recently, so I wanted to share a behind the scenes look at this site and process. Before we begin our tour, we will first need an understanding of how the energy-from-waste process works:

Covanta Diagram

Covanta, “How EfW Works” (see chart)
  • Municipal waste is delivered to the facility and stored in a large bunker, or pit (1).
  • The waste is transferred from the bunker to a combustion chamber, which burns the trash at extremely high temperatures (2).
  • The heat from the combustion of the waste boils water (3).
  • The resulting steam from the boiled water is used directly for different purposes (4).
  • In some cases, the steam drives a turbine that generates electricity, which is distributed to the local electrical grid (5, 6).
  • The ash left over from the combustion is put under a magnet, which extracts any metals that did not burn (7).
  • In the meantime, all resulting gases are carefully filtered and cleaned using fabric filter bags (9, 10).
  • After passing through the filters, the air is emitted (11).
  • The ash is combined with the residue extracted from the air pollution control process.
  • The ash and extracted air pollution are disposed of in a variety of ways, including being used as cover material at landfills (8).

With this information in mind, let’s begin our tour!

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The first room we visited was the room where the waste is initially brought into the facility. Visible in the back of the pictures is the large pit where the waste is stored – The pit goes 40 feet both ways, and contains 12 thousand tons of garbage on average.

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Pictured above is one of the natural gas boilers, visible behind the sacks used to capture pollution before it reaches the smokestack. The boiler goes up nine stories.

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We then entered the control room, where the facility is closely monitored to ensure everything is going smoothly.

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The complicated controls you see here are used to control and monitor everything, including the boilers used to burn the trash.

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Above are some of the turbines used to generate electricity.  It was very hot in this room!

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Above, another view of the turbine room.

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In the above picture you see an outside view of the facility, with one of Covanta Niagara’s new boilers visible.  This boiler is much more efficient than the older ones, which we visited earlier.

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In this room, ash is sifted and shaken by the conveyor, before being placed under a large magnet to extract all remaining metal pieces.

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A view of the outside of one of the boilers, where trash is burned.  This is on the 5th floor, but the boilers go all the way to the 14th floor.

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In the photos above, we see a different view of the room in which we began our tour.  Visible are the large pit in which the trash is stored, as well as a crane that is used to move trash to be burned.

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The trash is placed into this hole, where it is moved toward the boilers by the conveyor pictured below.

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Above, the conveyor which the waste travels down on its final journey to the boilers.

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This small window can be used to see the waste being burned inside the boiler. (Spoilers! To get a good image of what it looks like inside the boiler, picture the infamous scene from Toy Story 3.)

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We then stepped back outside to view the smokestack, which goes up 430 feet.  In the room below it are thousands of hanging vacuum bags that remove particulates from the air.

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Finally, we visited the rooms where the ash is stored. Pictured above are the metals that were not burned – The metal that is left is used or sold for scrap metal.

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If you look closely, you can see what used to be a chair and shovel!  What other metal remains can you find?

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This is where the ash resulting from the burned waste is stored until it is loaded onto a truck to be taken away.

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We conclude our tour with a close-up view of what remains of the waste that is brought into the facility.  The ash is non-hazardous, and may even have useful applications in construction.

This tour gave a great, informative behind-the-scenes look at the Energy-from-Waste Process. Understanding a bit more about how it works will help in researching the effects of this process. For more information on the effects of burning waste, check out our blog “To Burn or Not to Burn?”

To learn more about Energy-from-Waste, visit Covanta’s website.

Tell us what you think about Energy-from-Waste in the comment section below.

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2 Responses to Energy-from-Waste: Utter rubbish, or potential clean energy?

  1. Robert says:

    Think it’s a great idea. As long as there are no toxic emissions released into the air. What happens to the ash after incinerating, is it stored somewhere?

    • GrowWNY Intern says:

      Robert,

      According to Covanta’s website, the combined ash is disposed of in a variety of ways, including being “disposed of in a monofill (where only ash is stored) that receives only that waste, used as cover material at a conventional landfill, or landfilled with other waste.”

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