There are about 10,000 old municipal landfills in the United States that have reached capacity, and now their waste is sealed underground.  These landfills are taking up space across the country, and are often in areas close to dense populations were land is valuable.  A developing trend has been to utilize this land and construct a solar photovoltaic (PV) array on the surface.  These solar landfill caps are in New Jersey, New York, Massachusetts, Texas, California, and Georgia.

When landfills reach capacity, they are normally capped carefully with a polyethylene material, which makes sure hazardous waste cannot leak into the soil and also help the trapped material degrade.  On top of the cap is usually a couple feet of soil and grass, to make it more visually appealing, but still not safe for public use, or development of any commercial or residential buildings, or even roads.  It is essentially useless land, but placing a solar PV cover on top, can generate revenue through energy production.  Proximity to the grid is paramount for many solar projects, and landfills are useful because they are close to populated areas.    

A key part of this development is the use of an exposed geo-membrane solar cover (EGSC) system that caps the landfill.  This technology combines an enhanced final cover anchoring system and then thin film photovoltaic solar panel attached to a geo-membrane.  The EGSC and solar panels are designed for both long-term outdoor exposure and to withstand specific weather events, giving it an advantage over typical soil or vegetation covers that require maintenance.  There are still high costs associated with installing the solar panels, but it can be regained as the energy is sold to a local utility. 

Underneath these solar arrays can be 10 million plus cubic yards of garbage.  Until the country has a better control over our waste steam, and encourages greater reuse and recycle, systems like this will become increasingly important. 

Below is a short list of landfill sites with or developing solar arrays over old landfills. 

  • A landfill site on the outskirts of Atlanta, Georgia has covered 10 acres of land with solar panels and the underground also collects methane gas, which is used for power production.
  • A six megawatt solar array went up in 2010 on a Superfund site in Sacramento County, California, with the energy powering the cleanup of the site.
  • A 10 megawatt solar installation in 2010 was constructed on a brownfield site in Chicago.
  • The Pennsauken Sanitary Landfill in New Jersey is a 2.6 megawatt site powers the daily operation of Aluminum Shapes.
  • A project underway in Madison County, New York will generate energy from the eight acres of panels and that energy will be used to run the recycling center next door.

However, there are still issues with developing solar on top of landfills.   The ground can sink as the material in the landfill settles and the site can also generate gases from the decomposing wastes.  Additionally, if the cap is old (15-20 years) there could be requirements for a third-party environmental assessment that could make the process longer and more expensive. 

The U.S. Environmental Protection Agency and U.S. Department of Energy are conducting feasibility studies to determine which sites should be developed.   The math goes something like this: by installing solar power arrays on just one quarter of the possible 10,000 landfills, we could produce a potential 212 gigawatts of clean energy, almost 500 times the solar energy produced in the U.S. in 2009 (425 megawatts).  There is widespread application and opportunity for solar array landfill caps across the country.  If the U.S. plans to shift to more sustainable economy with a decreased reliance on fossil fuels, utility scale renewable systems like this will have to be part of the process.

Author: Nora Prevoznak

Image Courtesy: http://i2.cdn.turner.com/cnn/dam/assets/111130040356-landfill-overview-horizontal-gallery.jpg