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frequently asked questions

 

 

 

What does resource recovery mean?

Resource recovery is the capture or removal of substances, materials or energy out of discarded materials or waste. Resource recovery typically takes place at a point in time after the discarded items are placed together in one waste pile or container.

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What happens to your garbage at a Waste-to-Energy Facility?

What happens to your waste at a Waste-to-Energy Facility?After your hauler picks up your garbage, the hauler delivers it to a waste-to-energy facility where it is dumped on the floor or in a pit and either processed into fuel or fed directly into combustors and burned to create electricity or steam. Emissions are carefully controlled and monitored to limit air pollution. Ash from the combustion of the garbage is managed in a landfill. Only 10% of the volume of your original garbage becomes ash, the rest becomes energy.

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What are the environmental benefits of Waste-to-Energy?
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What are the environmental impacts from Waste-to-Energy? Physical and Mechanical Separation

The physical and mechanical separation of materials creates noise and dust. There is a residue whose composition depends upon the product the process is making. Biological Treatment and Composting The biological treatment or composting of waste may result in odors. These facilities have special filters that are used to remove odors from the air before discharge. The facilities require the collection and treatment of any liquid running off of the compost piles. The biological process itself results in the production of carbon dioxide and waste from the microorganisms and vapors of other gasses from biological activity. There is a residue from compost facilities that consists mainly of stones, bits of broken glass, small metal pieces, plastic, and other non-biodegradable items. Chemical Treatment and Combustion The chemical treatment or combustion of waste produces carbon dioxide and a number of other compounds such as sulfur dioxide, carbon monoxide, nitrogen oxides, hydrogen chloride, dust, dioxins, and metals. The combustion gases typically flow through a "scrubber" which cleans the acid gases (sulfur dioxide and hydrogen chloride) and ammonia and carbon is may be added to remove metals and nitrogen oxides. The temperature of the boiler is monitored to ensure the destruction of any dioxins that are formed, and all particulates are removed by filters in the "baghouse". Equipment on the smokestack known as the continuous emission monitoring system or CEMS constantly monitors the flue gases to ensure compliance with the air permit issued by the federal and state authorities. The remaining "fly ash" from the baghouse and the "bottom ash" from the boiler is collected and then disposed of into a landfill for ash only. Testing has confirmed that the ash is not a hazardous waste. The leachate, or water passing through the ash, almost meets drinking water standards but is recycled or cleaned at a waste water treatment facility.

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What are the other advantages and benefits of resource recovery?

 

What are the other advantages and benefits of resource recovery?

 


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How much landfill space do we save and how much electricity do we generate?

Sending garbage to a waste-to-energy facility saves valuable landfill space. These facilities take in the equivalent of four Metrodomes full of garbage each year. And they put your garbage to work, burning it to make enough electricity to meet the needs of 111,000 homes.

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How Does Waste-To-Energy reduce greenhouse gases?

When solid waste decomposes, it creates methane which is 23 times more potent than C02 in term of its impact on greenhouse gas  production and global warming. Waste to energy facilities eliminate that production of methane and reduce greenhouse gases. In 2005, the MRRA voluntarily reported to the EPA a reduction of carbon dioxide and methane gases equivalent to removing 89,736 cars with their emissions from our roads.


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Is Municipal Solid Waste a renewable source of energy?

Is Municipal Solid waste a renewable source of energy?

  • Minnesota defines waste-to-energy (WTE) as a renewable energy source for meeting the state's renewable goal of 25% by 2025.
  • Waste-to-energy is sustainable.
  • Waste-to-energy is indigenous.
  • Waste-to-energy reduces methane emissions from landfills and, thus, greenhouse gases.
  • Waste-to-energy offsets the use of fossil fuels such as coal and natural gas to create electricity.
  • Waste-to-energy contributes to healthy fuel diversity.

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How does burning garbage in a waste-to-energy facility compare to using a burn barrel?

How does burning garbage in a waste-to-energy facility compare to using a burn barrel?
Burn barrels burn trash at low temperatures and are extremely polluting. They are estimated to be the largest source of dioxins, a very toxic and carcinogenic group of pollutants.
  • Just one family using a backyard burn barrel will emit more dioxins per year than a 200-ton-per-day waste-to-energy facility.


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Do Waste-to-Energy facilities emit Mercury?

Do Waste-to-Energy facilities emit Mercury?

Mercury moves through the environment as a result of both natural (volcano eruptions) and human activities. Human activities that are most responsible for causing mercury to enter the environment involve the use and consumption of products containing mercury and disposal into the waste stream or wastewater system. Waste-to-Energy facilities in Minnesota have been working hard to reduce mercury air emissions. Since 1990, Minnesota's Waste-to-Energy facilities have decreased their mercury emissions by over 90%. Counties have assisted in this effort by implementing mercury recycling and reduction programs.

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  What are the different methods of recovering resources?
  • Physical or mechanical separation
  • Biological treatment or composting
  • Chemical treatment or combustion  

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What does physical or mechanical separation mean?

Physical or mechanical separation uses a variety of equipment or manual labor to prepare, divide, and sort waste into items of similar size, nature, or quality. Physical or mechanical separation of waste is often an essential part of composting and combustion facilities. For example, the mechanical separation of the non-combustible fraction of the waste results in the production of refuse derived fuel, or RDF. Similarly, the mechanical separation of biodegradable materials could be use to make compost.

 
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  How does physical or mechanical separation work?
  1. Screens separate waste items by size
  2. Shredders prepare items for sorting and division
  3. Blowers separate lighter items from heavier ones
  4. Magnets remove ferrous items
  5. Slow moving conveyor belts allow workers to remove recyclables


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What is a MRF?

A MRF is a materials removal facility that manually and mechanically removes problem materials from the incomingwaste stream prior to combustion in a waste-to-energy facility. Sometimes referred to as fuel cleaning facilities, they aredesigned to reduce maintenance costsand downtime for waste-to-energy facilities. The majority of the materials removed at a MRF can be recycled or used as alternate daily cover at a landfill.

Other MRFs, or materials recovery facilities, are designed to sort out co-mingled recyclables for use in recycling applications. These systems targetall recyclable materials while MRFs used for waste-to-energy facilities are limited to a few items.


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What does chemical treatment or combustion mean?

 

Chemical treatment or combustion is the controlled burning of waste materials to create heat that destroys the waste and produces heat energy ash. The volume of waste is reduced in size by 90%. The ash is often taken to an ash landfill for disposal; sometimes it is used in road construction. Metals are removed from the ash with a magnet and delivered to a recycler. The heat produced by the combustion process is used to boil water, which produces steam. The steam is used to heat or cool buildings, generate electricity, or power a manufacturing process such as food processing, papermaking, or leather tanning. Some combustion facilities use mechanical separation of municipal waste to reduce the amount of non-burnable items entering the furnace. When this is done, the remaining burnable fraction is commonly referred to as refuse-derived fuel, or RDF.

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What kinds of waste can be handled by these resource recovery processes?

All three methods can handle municipal solid waste.The physical or mechanical process is especially effective in removing items that are recyclable, not biodegradable, or are not combustible.The composting method is most effective in handling items that are biodegradable such as food waste and yard and garden wastes.The combustion method is most adaptable to handling combustible items such as wood, paper, plastics, tires, oily waste, and when a use for steam or electricity is needed.In both the composting and combustion methods, the non-compostable or non-burnable fractions pass through the process and can be recovered or recycled at the end. For example, the non-biodegradable plastics, which pass through a composting facility, can be recovered and delivered to an combustor facility.

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Can combustor ash be utilized?

Yes, however it is not widely practiced in the United States at this time.  In Europe, combustor ash is not allowed to be deposited in landfills, therefore it is widely utilized. Bottom ash is primarily used in asphalt mix, but also in road base and bermapplications. Fly ash is treated and reused in building materials or deposited safely in old salt mines.

In Minnesota, Polk County has performed two demonstration research projects substituting waste combustor ashas a partial replacement for natural aggregate in road paving projects. Both projects havebeen very successful at demonstrating superior structural performance and showing no negative environmental impacts. Two additional projects are planned for the summer of 2007.

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What are the economic impacts of these processes?

These processes tend to be capital intensive and the operations are usually 24 hours a day, 7 days a week. Costs depend on the size of the operation but generally, the unit costs decrease as size increases. The facilities require few but highly skilled laborers to operate and maintain the equipment. The operations are highly automated and monitored and controlled by computers. The facilities produce products such as compost, fuel, steam or electricity, which are sold. The value of these products offset some, but not all of the debt and operating costs of the facility.

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What are the behavioral impacts of these processes?

Households or businesses typically do not need to change their behavior for the disposal of normal trash. With the exception of hazardous waste, resource recovery facilities can easily accommodate the broad spectrum of products present in trash discarded by households and businesses.

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