Developing Landfill Energy Systems | Case Study

Using the Unusable: More Landfills Becoming Sources of Renewable Energy

The EPA’s RE-Powering America’s Land Initiative is picking up steam. The effort, launched in 2008, encourages the reuse of contaminated lands, landfills and mine sites for renewable energy generation. The agency’s Action Plan 2.0, released last fall, details how far the program has come and what is being done to expand it.

“The cleanup and revitalization of contaminated properties is integral to EPA’s mission to ensure the protection of human health and the environment,” the plan notes. “The RE-Powering America’s Land Initiative brings together the benefits of cleaning up sites and promoting renewable energy. In its first five years, the Initiative has helped highlight and address environmental issues at sites while propelling renewable energy development on contaminated lands from merely an interesting idea to an ever-increasing portfolio of projects.”

After noting its work has been recognized by Harvard University as a Top 25 Innovation in American Government, the EPA said, “As the Initiative moves forward, the Agency expects to refine its activities to meet emerging needs of stakeholders involved in site cleanup and reuse. This action plan articulates the continuation of activities that have been impactful and suggests areas of new emphasis.” Its three goals:

  • Provide technical and programmatic assistance
  • Promote policies and best practices that encourage renewable energy on contaminated lands
  • Partner with stakeholders and leverage agency efforts.

Those efforts have already led to the installation of more than 130 renewable energy projects on 128 contaminated lands, landfills and mine sites in 34 states and territories from coast to coast. Massachusetts alone has 49 installations, and New Jersey 11. More than 100 of the projects to date have employed photovoltaic solar arrays to turn an environmental liability into a revenue-producing asset. Most often that asset is wholesale electricity; and the most-often-used location is the landfill or landfill buffer.

Among the landfill sites now producing electricity is the Hartford Landfill in Hartford, Connecticut. In 2007, an agency now known as the Materials Innovation and Recycling Authority began the process of capping and closing the 96-acre facility. By 2011, the landfill’s operators identified potentially viable options for capping the remaining uncapped area and allowing for the development of a solar array on top of the cap.

Landfill sites can be challenging locations to locate solar arrays. After all, under the landfill cap is a mound of decomposing waste that is constantly changing in content type and shape due to the natural process of decomposition.

The Hartford site is unique in that its photovoltaic system was made possible by implementing an innovative alternative final cover system approach to achieve the most economical and risk-adverse solution available for supporting landfill energy systems. The geosynthetic membrane landfill cap provides durable, stable surfaces that are easily maintained, can support vehicular traffic, prevent erosion, and reduce dust.

The latest advancement in geosynthetics is the Engineered Synthetic Turf (EST) System, which meets or exceeds regulatory requirements mandated by the EPA and can be less costly to construct and maintain for site owners over time. Additional EST System advantages include superior erosion and wind resistance, long-term geomembrane integrity and ease of accessibility. The system offers several economical benefits throughout its life cycle, even in applications that involve placement of energy systems at landfills.

In 2013, MIRA approved the installation of EST System technology – ClosureTurf® marketed by Agru America – as the final landfill closure system and solar development platform for the landfill energy system at the Hartford facility, making it the first in the industry to incorporate the innovative final capping system and the deployment of a solar array on a landfill.

The EST System combines six functional layers of the traditional Subtitle D cover into three components:

  • A 50-mil-thick structured geomembrane called AGRU Super Gripnet®
  • A tufted geotextile referred to as engineered synthetic turf
  • Approximately 0.5 in of infill placed into the engineered turf, which can be either sand or a cementious infill.

The EST System is essentially soilless, but provides for coverage of the underlying geomembrane. It has the look and feel of natural grass because of its geosynthetic erosion layer created by engineered turf infilled with sand. This geosynthetic erosion layer also serves to protect the underlying geomembrane from wind uplift and UV exposure from the sun.

By June 2014, the closure at the Hartford Landfill was substantially complete and the solar array was generating up to one megawatt of electricity, enough to power about 1,000 homes. The five-acre solar field sits atop ClosureTurf®, while the remainder is covered with soil and appropriate vegetation.

The EST system, used in conjunction with solar electric-energy generation technologies, should serve as a catalyst for further validating the effectiveness of ClosureTurf®, the EPA’s Re-Powering America’s Lands Initiative and other efforts that promote sustainability and energy independence.