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ABOUT DMGA

The DeKalb Master Gardener Association is just that — an  association of about 40 Master Gardeners and friends in DeKalb County, Georgia.  The organization was formed to foster more extensive educational, community service, and social events for interested Master Gardeners. 

DMGA is classified as a "Master Gardener volunteer organization outside the UGA university structure" and receives no support or public funds through the Cooperative Extension Service.  For information about the DeKalb County Cooperative Extension Service, please visit the following website:  www.ugaextension.com/dekalb/

 

 

 


 
Tuesday, 02 September 2014
 
 
 
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DeKalb County Landfill Produces Compost — and Electricity

The reason that a vanload of DMGA members took a January 2009 field trip to the Seminole Road Landfill in south DeKalb County was to find out where our "County Compost" comes from and how it's made.  As Master Gardeners, we love county compost.  We recommend it to other gardeners.  We have even raffled off delivery of a truckload of the wonderful black stuff at past plant sales.

Besides seeing the composting operation firsthand, we learned three other important functions of this 1100-acre facility:

(1) the residential convenience center, where customers can dispose of large items and recyclables,
(2) the landfill operation, which accepts nearly 2000 tons of residential waste material every day, and
(3) the "Green Energy" plant, where methane gas naturally produced from the landfill is turned into electricity.
 
Did you know that the Seminole Road Landfill is the first certified green energy producer for Georgia Power?
 
DeKalb County is the first government in Georgia to harness landfill gas this way.  For the past 2 years, the green energy project has generated 3.2 Megawatts of electricity an hour and generated over $2 million in revenue for DeKalb County by selling it to Georgia Power, which puts it into the power grid as part of the green energy program.

Composting Operations

Every day the composting section of the Seminole Road Landfill takes in from 200 to 400 tons of leaves, branches, trees, and grass clippings.  It's a busy 27-acre area with bulldozers and dump trucks constantly in motion. 

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Tub grinder
The first processing station is a monstrous tub grinder that can accommodate tree trunks up to 48" in diameter and turn them into pieces no bigger than 4" across.  Some of the ground-up material is sold to commercial facilities for boiler fuel.
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Windrow turner

The rest is placed into long triangular-shaped windrows 8 feet tall and 16 feet wide.  They are turned every 2 weeks using a windrow turner which has an auger that aerates the windrow by turning it inside out. 

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Screen trommel
After composting at temperatures of 130° to 160° F. for about 26 weeks, the final processing stage is a huge screen trommel that eliminates any pieces larger than 1".  The compost is then ready to truck to one of the DeKalb County Sanitation transfer stations where you see a green "FREE COMPOST" sign.

That's how the current composting process works.  At the same time, the composting crew is still trying to clear out about 75,000 cubic yards of older debris.  Some of it dates back to the the tornado that struck the Fountainebleau neighborhood in 1999, which might explain the occasional presence of a piece of plastic in your compost.

There's also the risk of fire spreading through the highly combustible material and compromising the quality of the compost, but worse, damaging the equipment.  A large fire in January 2008, for example, left a lot of burned and scorched material that ended up in the compost.  Steps have been taken to assure that this type of compost does not leave the facility in the future, and new safety precautions have been put in place to reduce the likelihood of fire.

Residential Convenience Center

Close to the entrance of the Seminole Road Landfill is a residential convenience center where DeKalb residents can drop off recyclable goods in carefully marked separate areas for "white goods" (refrigerators, washers, driers), scrap metal, cardboard, newspapers, plastics, electronics, and glass.  For a reasonable fee, residents can also dispose of building materials, tires, and even sofas.

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Recycling bins
Recyclables are sold to recycling companies like S&P Recycling in Forest Park.  S&P hauls recycled paper to a facility in Dublin, Georgia (the largest paper recycling facility in the U.S.) which makes new paper products out of it.  Whenever possible, materials like cardboard and newspaper are separated.  A recycling company will pay more for cardboard separated from newspapers ("single source") than for mixed materials ("single stream").  The motto here is "Everything you recycle doesn't take up space in the landfill." 

Landfill Operations and Construction

The Seminole Road Landfill is the only landfill operated by DeKalb County.  It accepts about 2000 tons of refuse every day—mostly residential solid waste.  Some people mistakenly think that a landfill is a pit into which garbage is thrown.  Not at Seminole. 

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Starting a new landfill phase
This landfill is constructed on top of the ground in order to prevent seepage into the ground water supply.  The base of the landfill area is constructed of 2 feet of clay, covered with 60 mil plastic, then topped with sand.  As new waste is spread over a limited area each day, it is covered with a 6" layer of dirt to keep from attracting birds and rodents.  The old landfill phase has absorbed about 30 years of waste and is now being "closed."  It is being covered with plastic to keep dangerous gases from escaping into the atmosphere, then topped off with soil and seeded with grass.  All you will eventually see is a large park-like grassy hill (about 1160 feet above sea level) with an observation deck offering sensational views of Stone Mountain and the Atlanta skyline.

Emerging from the landfill one can see black drainage pipes.  They are temporary surface storm water collection pipes used to control soil erosion on the slopes of the landfill.

Underneath the waste, but above the plastic liner, are a series of plastic drainage pipes.  They collect liquids (known as leachate) from the deteriorating waste and transport them to a large white leachate tank which connects to the sewer system. 

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Gas well
Scattered over the hillside are also 4' high vertical pipes, approximately 80 of them, with another 52 being installed.  They are gas wells that capture the methane that is produced and keep this dangerous gas from seeping into the atmosphere, contributing to global warming, or exploding and catching fire.

Now, this is where one steps into the 21st century and discovers that the Seminole Road Landfill is not your ordinary old dump ground ...

Green Energy Facility

A few of us on the tour had noticed large power lines leading to the building marked "Green Energy Facility."  But we had no idea that they weren't just using electricity here, but producing electricity and putting it into Georgia Power's electrical power grid.

The gas wells dotting the hillside are slowly drawing the methane/carbon dioxide gas mixture that is being produced by the decomposing organic waste.  A portion of the gases are deliberately burned off in a flare. 

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Generator
About two-thirds of the methane is piped to the generator house where a pair of massive 2200 HP generators burn it and turn it into electricity.  They continuously generate 3.2 megawatts of electricity per hour—enough to power about 3000 homes.

The showcase energy facility emphasizes education and offers tours about landfill gas utilization. Visitors can view the generators and a screen showing real-time performance data.  Even those visitors who aren't "into" statistics can learn from a pictoral mural that follows trash from its collection to the landfill to gas generation, capture, and ultimately to providing electricity to the same residents and businesses from which the trash was collected.

The DeKalb County Public Works Department, Division of Sanitation has been honored with awards from the Solid Waste Association of North America (SWANA) for the county's successful construction and operation of the Green Energy Project at its Seminole Road Landfill.  The project is innovative in that it was self-developed by the County without a third-party developer and was completed on schedule by the contractor, SCS Engineers, seven months after county commissioners approved construction.

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The cost of the Seminole Green Energy Project was $5 million.  The revenue raised by selling electricity is about $100,000 per month, enough to pay for the project in 5 years.  After that, profits will go toward reducing sanitation rates for DeKalb County customers.  The Seminole Road Landfill will stop taking in garbage in 2071, and the landfill will continue to emit gases and produce electricity until the year 2101.

What is the impact of "Green Energy"?

In the early stages of the Green Energy Program, Georgia Power will use methane gas, created by the decay of landfill waste, as its primary form of biomass energy.  It is estimated that this project will offset fossil fuel greenhouse gas emissions of 17,100 metric tons of carbon dioxide equivalents per year, the equivalent to removing emissions from 3,300 vehicles on the nation’s roads, reducing oil consumption by 40,000 barrels, or planting 4,700 acres of forest.  The more electricity that is generated from sources like methane, the less needs to come from dirtier sources like coal and other fossil fuels. You can read more about this project at the U.S. EPA website.

DMGA would like to thank Mr. Charles Gill, Superintendent of Processing and Disposal, for a most informative tour.  We think that DeKalb County—and its citizens—can be proud of the job that their forward-thinking Sanitation Division is doing.

 

 

 
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