Waste-to-Energy From the Inside

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For some people, “waste-to-energy” is a stirring term. The process, which generally involves burning of refuse to generate steam, heat or electricity, is an often divisive issue for a community making the decision to fund the construction of a waste-to-energy plant.

Claw at waste-to-energy plant

Huge claws raise and lower waste into hoppers that feed this system, which uses steam to create energy for more than 38,000 homes in the area. Photo: Jennifer Berry, Earth911.com

“You need three things to make it successful: the community will, the political will and a client to sell [the electricity you produce] to,” says Lynn Brown, vice president of corporate communications for Waste Management.

Waste Management knows all too well about the process of getting a waste-to-energy plant off the ground. “We also have a goal to double the amount of renewable energy we make by 2020” Brown adds. “So when we think about what we’re doing, a lot of it is about energy.”

Its 17 plants around the country power more than 650,000 homes and produce enough energy to replace nearly 7 million barrels of oil.

To see what goes on inside these imposing facilities, Earth911.com visited one of Waste Management’s Wheelabrator waste-to-energy facilities in Broward County, Fla. This plant processes more than 2,250 tons of municipal solid waste per day, generating enough power to supply the electrical needs of more than 38,000 homes.

How it works

Not surprisingly, safety is a top priority in the plant. Donning hard hats, glasses and, most importantly, ear plugs, is a necessity. The noise level without them makes the environment even more daunting, as the orange light and slight tang of waste and ash permeate the air.

However, contrary to what the team expected, the smell was barely noticeable, as a negative pressure system keeps fresh air flowing into the facility and odors from escaping into the surrounding airspace and neighborhoods around the plant.

The science behind how waste-to-energy works is simple, but seeing its execution in real-life gives a deeper understanding of the complex considerations that go into the successful operation of a plant. Essentially, here’s how the process works:

  1. Waste is brought to the plant by haulers from across the area. Their loads are dropped on the tipping floor 24 hours per day, seven days per week as the plant works around the clock to create electricity.
  2. Operators in a room high above the tipping floor lower and raise giant metal claws. The claws grab, raise and drop the waste into hoppers that feed the waste into boilers at a consistent rate.
  3. The waste is incinerated. The temperature inside a boiler is incredible (exceeding 2,000 degrees Fahrenheit).
  4. Water-filled pipes line the inside of the boilers. The water is rapidly heated, creating steam which travels up through a network of pipes to create energy in the same fashion as traditional steam-powered power plants.
  5. The water is cooled and returned to be reused over and over again in the closed loop system that this particular plant employs.

The entire process greatly reduces the volume of the waste brought in to just 10 percent of its original volume.

NIMBY

Looking into a boiler

This is the only place where you can view the 2,000 degree fire within the boiler. Photo: Jennifer Berry, Earth911.com

The data supporting the use of waste-to-energy (classified as a renewable energy source by the U.S. EPA) is compelling.

In 2003, the U.S. EPA wrote that waste-to-energy produces electricity “with less environmental impact than almost any other source of electricity.”

Earlier this year, The New York Times wrote that “a 2009 study by the E.P.A. and North Carolina State University scientists came down strongly in favor of waste-to-energy plants over landfills as the most environmentally friendly destination for urban waste that cannot be recycled. Embracing the technology would not only reduce greenhouse gas emissions and local pollution, but also yield copious electricity…”

Also, according to a report by P. Ozge Kaplan, Joseph DeCarolis and Susan Thornloe, “Burning one ton of waste in a waste-to-energy unit saves between 0.5 and one ton of greenhouse gas emissions compared to landfilling the same amount of waste.”

But adoption of the technology in the U.S. remains slow, mainly because of the “NIMBY” or “not in my backyard” concept.

It’s easy to understand not wanting a huge factory with stacks in your skyline and thousands of garbage trucks dumping their refuse 24/7. Waste-to-energy is not an inherently “sexy” concept.

However, surprisingly, communities that have these plants show greater participation in other green actions.

A 2009 study conducted by Eileen Brettler Berenyi examined the recycling rates of more than 500 communities with waste-to-energy facilities. The findings of this study were that communities with waste-to-energy facilities had a higher recycling rate than the national average.

There are environmental concerns as well from the process, such as the ash and gases produced from the combustion process.

The ash created from the process is hauled off to a landfill nearby (stay tuned for our next installment where we visit this same landfill!) to provide daily cover. The metals that did not burn are sorted from the ash and brought to the local recycling facility.

Of course, a major concern for the facility (and its neighbors) is the quality of the air that is released after the trash is burned. The air, which can contain a variety of acid gases and airborne particulates blows through a “scrubber” that uses sprays a mixture of lime and water into the hot exhaust gases. The lime neutralizes acid gases and also allows for the capture of heavy metals such as mercury. The exhaust gases then move through a baghouse, which is contains heavy-duty filters to collect additional particulates in the air.

Eye-witnesses

Seeing the process first-hand brought the debate about the benefits of waste-to-energy to light. The traditional hierarchy of “reduce, reuse, recycle” still stands, and the opportunity to make energy out of trash that would have otherwise gone to waste (no pun intended) is intriguing.

“There’s also a focus around taking all of this material that passes through our hands and making the highest and best use of it,” says Brown. “So sometimes that’s recycling, and in some cases increasingly we’re investing in ways to make energy out of it.”

Whether or not waste-to-energy works well for your community is a highly localized decision, but it does seem to be one worth looking into.

In September, the Earth911.com Editorial Staff visited three facilities operated by Waste Management: a recycling center, waste-to-energy plant and landfill. This story is the first in a series analyzing the technologies and capabilities in play that create an efficient system to maximize the recovery and utilization of waste.

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