As solar energy pricing drops and buyers of this renewable energy are offered incentives, more landfill owners are investing in solar projects, once all or parts of their sites close.

Solar operations are often well-suited for landfills since such facilities are typically sited near electric transmission lines, have large flat areas and are defunct spaces that provide an alternative to greenfield development for solar assets.

But while these projects offer landfill owners economic benefits, they can also present unique challenges. For example, plans to install more than 2,800 solar panels on a site in Portland, Maine, by the end of 2017 have run off course due to issues with the cover and with methane gas  accumulation.

Business models vary. Sometimes the solar facility sells power directly to a utility; sometimes corporate entities purchase it directly. 

“The policy and economic drivers behind each model can be different, but we are seeing both models continue to grow … and we expect to continue seeing a variety of business models succeed,” says Colin Smith, a solar analyst with GTM Research.

The Material Innovation and Recycling Authority (MIRA) in Connecticut, a quasi-government organization, owns and operates a solar system on the closed portion of its landfill, with 3,993 solar panels processing enough electricity to power 1,000 homes. The authority sells the power to Hartford through a 21-year agreement.

MIRA negotiated with the state department of environmental protection, committing to install a solar facility at landfill if the state approved a synthetic turf cap.

“We were interested in a synthetic turf cap that did not require soil to maximize space; therefore providing opportunity for more revenue through disposal services,” says David Bodendorf, senior environmental engineer for MIRA. “Synthetic turf also works well with this project, as there is no vegetation that would otherwise grow into panels and wiring.”

The solar project cost $3.5 million for panels, equipment and interconnection to the utility when it was built three years ago, though it would be substantially cheaper to do today, Bodendorf days.

The system generates minimal revenue considering the time required to pay off $3.5 million. But it was a way to keep the landfill open longer due to the turf.  Plus, it’s been good for community relations.

“We create energy with no emissions,” he says. “And the energy we sell to the city will save it millions of dollars … As a waste management company, we are not generally thought of well by the community, so it’s refreshing to own a project that the public supports. Plus, we get renewable energy credits in the form of cash, which we share with the city as part of our host agreement.”

The system comes with fairly minimal maintenance, mainly of inverters that convert direct current electricity from panels to alternating current electricity. MIRA contracts the work to a solar array company.

To date, the U.S. Environmental Protection Agency has identified 190 renewable energy installations on 181 contaminated lands, landfills and mine sites. These are primarily solar projects. The agency knows of more than 50 other potential renewable energy projects on contaminated sites, mainly landfills.

But, currently, low natural gas prices are impacting solar projects, which require infrastructure investment.

“I think energy prices dropped to the extent where, unless you need renewables for your portfolio, the economics are not there,” says Mark Roberts, vice president of HDR Engineering in Jacksonville, Fla. His company is seeing more interest from potential clients overseas, and has done work in Australia.

HDR is currently doing a conceptual design of a landfill closure with a large laminate solar system in Australia.

The Northern Adelaide Waste Management Authority (NAWMA), in partnership with Joule Energy, is developing a combined solar and methane power plant on an Australian landfill, reported as the first of its kind there.

Such combined solar and landfill gas energy projects may open up more opportunities believes Roberts. It’s the same grid connection for both energy sources, so the infrastructure is in place.

“A lot of coal ash disposal facilities (CCR) are closing, so we are watching that now too as a potential site for solar,” Roberts says. “As CCR disposal sites close, if they implement solar it could be a sign economics are better for solar at other waste disposal sites, whether they are CCRs or municipal solid waste sites. Some coal ash disposal facilities are looking at solar now. But they aren’t jumping at it.”

In the meantime, on domestic soil, he says, while economics may not always be the main driver, “If you have a customer that wants to buy green energy, you’re in business.”