The number of active municipal solid waste landfills that accept our household waste have been on a major decline, from nearly 8,000 in the late 1980s to less than 2,000 by the mid 2000s.
All of the closed landfills around the U.S. (not to mention closed cells on still-active landfills) leave us with a big question: What to do with those brownfields of largely undevelopable land? Many cities and towns —from Massachusetts to Colorado and Georgia to Nevada, are using that unused and often unusable land to generate revenue and/or save on energy costs through solar farms.
Hickory Ridge Landfill Solar Energy Cover – Source: HDR Inc
What makes landfills such an ideal spot for solar? For one, often the disrupted or even contaminated land may not be suitable for commercial or residential development. Also, putting solar on landfill sites is often cheaper, less impactful, and raises less community concerns than an installation on a greenfield site.
Another reason why landfills make such good areas to put solar farms on is the fact that many municipalities don’t have large areas of green space. However, it’s estimated that there are over 10,000 old municipal landfills in the country, many of which are located in close proximity to an existing utility grid, making interconnection economical.
Massachusetts leading the way
Massachusetts has taken the lead in repurposing its landfills with large-scale and utility-scale solar, and much of that work has been done by PV financing and contracting company Borrego Solar. “When I look at a landfill I see a great opportunity,” Amy McDonough, senior project developer for Borrego Solar, told RMI. “Putting a solar energy generating system on land that couldn’t be used for anything else and that will save the municipality millions of dollars over the terms of the PPA is a win-win situation.”
Once a landfill’s useful life is over, it gets capped. Capping consists of putting a barrier over the landfill, the geomembrane, to separate any harmful elements from people and the environment. Then comes a layer of sand for drainage, then vegetation. The geomembrane must not be penetrated, so Borrego Solar has engineered a ballast system for the racks. Since every solar array rack has two ballasts it costs more than doing a regular foundation, adding about 25 cents per watt to the total price of the system.
Massachusetts incentivizes solar installations on brownfields, though, helping improve the economics for landfill-based solar, which despite certain addition requirements like the ballast system already benefits from economies of scale associated with utility-scale PV projects. Now Borrego Solar is working with the New York State Energy and Research Development Authority (NYSERDA) to convince that agency to put in incentives for brownfields as well.
According to McDonough, the Northeast has a lot of great landfill opportunities. “A lot of the landfills are small, often with flat tops,” McDonough explains. “A properly closed landfill offers a really great base for a solar project. If it’s been closed for 10 or 12 years you don’t have to worry about settlement. But you can’t build a building on it, so there’s not much else you can do with it.”
One success story can be seen in the Town of Ludlow in Hampden County. The Town signed a 20-year PPA with Borrego Solar to lease 17 acres of the town’s closed landfill. Ludlow now purchases the energy produced from the solar panels at a rate of 5 cents per kilowatt-hour—compared to 9 cents per kilowatt-hour charged by the local utility. The 2.6 MW system is saving the town approximately $140,000 a year on energy bills, created local construction jobs on land that had been previously written off as undevelopable, and is estimated to offset 4.3 million pounds of CO2 each year.
Other states joining the trend
Massachusetts now has dozens of solar farms on landfills generating over 78 megawatts of power, but other states in the Northeast are joining the trend. Vermont’s first solar landfill project, a 2.7 MW system, is currently being installed in Coventry, on the only active landfill in the state. Although the landfill is still active, the solar system is being built on the buffer zone, the required land that separates the landfill from other usable land. Since very little can be built on buffer zones, solar farms present a great option. The landfill in Rutland, Vermont, meanwhile is making headlines as it is including 4 MW of battery storage to shave peak electricity demand and to provide emergency backup power for Rutland High School (an emergency shelter) during outages.
New Jersey has also hopped on board as just last year the Garden State approved a proposal to turn the state’s 800 closed landfills into solar farms. And New York State is about to turn the world’s largest landfill—2,200 acres on Staten Island—into a park with a 47-acre, 10-MW solar farm.
Although the Northeast seems to be taking the lead in solar landfill development, the area is home to only 7 percent of the landfills in the U.S.—40 percent are in the western U.S. and 35 percent in the South. In fact, the largest solar energy generating facility in Georgia is a 1 MW farm on the Hickory Ridge landfill that uses a geomembrane cap covered with 7,000 thin-film PV panels.
While as of February 2013 there are 15 solar PV farms on landfills producing 30 megawatts of power, that number is growing quickly. The U.S. Environmental Protection Agency has prescreened 1,600 landfills for solar potential. One study estimates closed landfills cover hundreds of thousands of acres of solar opportunity. A 2013 NREL study estimated that municipal solid waste landfills and other contaminated sites covered an astounding 15 million acres across the United States. Once other states get on board offering incentives for brownfield development, we may see those old heaps of garbage turning into electricity generating stations across the country.
Source: Rocky Mountain Institute edited by Laurie Guevara-Stone (Writer / Editor)