When Scituate, Mass., placed solar on its landfill to power the town, it took somewhat of a leap of faith that this would be a good value proposition. It was one of the first towns to pursue solar on a landfill in a state that now has about 70 such projects, comprising more than half of solar landfill projects in the U.S., according to a list maintained by the U.S. Environmental Protection Agency (EPA).
The boon was fueled largely by a governor’s initiatives and robust renewable energy program.
“We wanted to buy inexpensive, renewable energy and leased the land to the project developer for one dollar a year to get the best price,” says Al Bangert, special projects director for the town of Scituate. “We own and are responsible for the land but let them have rights to use it for 20 years at this price.”
Scituate was already generating energy from wind turbines and wanted to lower the town’s footprint further but had limited places for more turbines without disturbing residents.
“Meanwhile, we had this big [closed] landfill that was empty. Putting a second wind turbine there was not feasible because we would have to dig a large hole, but with solar, you can put concrete blocks on top of the surface and mount solar arrays on them. So, nothing goes through the surface of the landfill,” he says. Now, 100 percent of the town’s electricity is renewable.
Today, the town nets about $250,000 a year on wind turbine and about $350,000 a year on solar. The returns are a result of savings on this renewable energy over traditional electricity. Wind and solar cost 9.5 cents per kW hour, while traditional electricity runs 17 to 25 cents, depending on the season.
In recent years, solar projects have popped up at landfills around the country—RE-Powering America’s Land, an EPA renewable energy initiative, lists about 123 of these installations on municipal solid waste landfills and another 18 on landfills exclusively for special uses.
BQ Energy is now constructing a 16.8 MW solar array over an 80-acre landfill in Annapolis, Md. With more than 50,000 solar panels, it will reportedly be the largest solar array built on a covered landfill in this country. Annapolis, Anne Arundel County and the Anne Arundel County Board of Education all committed to buy power generated from the site.
Solar renewable energy credits are a vital part of what makes these projects economical for third-party solar developers, utilities and landfill owners. But there have also been technology developments to make these projects more efficient and economical, says Mark Roberts, vice president of HDR.
One is geosynthetic caps, which eliminate the need to mow around panels, and there are no erosion issues under the panels when rain falls.
Another approach that’s cutting costs and boosting efficiency is making use of side slope versus the top of the landfill.
“The greatest areas of the landfill are the side slopes. You can get more panels on the sides,” says Roberts.
One fairly new method enabling panels to be erected on side slopes is to connect them to closure turf. Conversely, with a grass-covered landfill, panels are typically installed on the flat part of the site’s crown and require ballasted panels with racks.
The ballasts are to avoid penetration of the cap, but the industry is trying to make ballast systems cheaper and more efficient, says Bill Pedersen, an associate at Brightfields Development, a solar energy project developer headquartered in Wellesley, Mass.
“[For instance,] some companies are starting to use trucks to pour concrete in the field, eliminating the need to transport fully formed ballast blocks, though not all states allow this,” he says.
Still, it’s more expensive to build solar on a landfill with a ballast system than a system basically involving driving a pole in the ground. And there are other site-specific cost considerations to protect the landfill’s integrity—not to mention permits may have to be reworked.
So, forward-thinking states have created differentiated incentives with higher payment to build on landfills, versus on other sites like agriculture, to offset costs, says Pederson.
While Scituate was initially expecting little to no savings, it’s been happily surprised with what’s materialized from its investment.
“We now have five years of good performance,” says Bangert. “We have stable prices for all our electrical needs [contractually established for 15 to 20 years], which is good because we as a municipality are not a risk-taking entity. So, we have taken ourselves out of the game of yo-yoing energy prices.”