Renewables are vaunted for their ability to reduce greenhouse gas emissions as part of the push to address climate change in the United States and elsewhere, but that doesn’t mean they have zero environmental impact.
Projections from the Energy Information Administration (EIA) show the share of renewable generation increasing from 18% in 2018 to to 31% in the U.S. by 2050. As their capacity grows, so does the scale of their effects — along with industry and public awareness of the challenges.
Some of the environmental issues getting the most scrutiny have been toxic substances and wastewater generated in the production of some solar photovoltaic (PV) cells; changed land use and disrupted wildlife habitat from both solar and wind projects; and significant recycling and disposal challenges for both solar panels and wind turbine rotor blades.
Renewables do have some environmental impacts, and they're not perfect, according to Dustin Mulvaney, an environmental studies professor at San Jose State University who has researched and consulted around solar environmental standards. But he believes they're still better for the environment overall than other forms of generation — and not just from the emissions generation perspective, but regarding other parts of the lifecycle.
Even so, solar and wind shouldn’t benefit from a free pass or "green halo," Mulvaney said. "There’s a thread that basically says the industry’s emissions don’t matter [because] they’re so small compared to other energies — that’s always been frustrating," he said. "If we don’t pay attention, these problems will emerge as we scale."
"We don’t want to take trees down that produce fruit or crops to put solar up, but we have to look at what the value and use of the land is, and how you account for that."
Vasilis Fthenakis
Director, Center for Life Cycle Analysis in the Department of Earth & Environmental Engineering, Columbia University
But the renewable energy sector is increasing efforts to clean up production and recycle its materials, as researchers and third-party certifiers work to hold it to account. The Green Electronics Council (GEC) and NSF International, for instance, announced new eco-standards for solar within the past year that evaluate areas like recycled content, not only for the PV panels themselves, but also for solar inverters. More recently, they added solar panels and inverters to their EPEAT ecolabel registry, which gives manufacturers guidelines to strive for, and can point purchasers to the most sustainable PV panels and inverters.
"I do think we’ve made strides [over the past five years]," said Evelyn Butler, senior director of codes and standards for the Solar Energy Industries Association (SEIA), which is encouraging its 1,000 members to meet the standards that went into the new EPEAT criteria. "I don’t think we shy away from answering those questions."
Here’s a deeper look at some of the challenges that solar and wind stakeholders are trying to face head-on — and some potential solutions.
Manufacturing byproducts
Depending on the vintage of manufacturing machinery and technologies used, PV production has been known to produce hazardous material byproducts, including silicon tetrachloride, silane, hydrofluoric acid and large quantities of acidic and alkaline wastewater needing treatment.
Vasilis Fthenakis, founder and director of the Center for Life Cycle Analysis in the Department of Earth and Environmental Engineering at Columbia University, examined those issues early on. In 2003, he began heading the new National Photovoltaic Environmental, Health and Safety Center at Brookhaven National Laboratory. The center was praised for early studies that created the gold standard for environmental health and safety in solar production facilities.
The manufacturing issues have improved over time, both with increased awareness and more advanced technologies, Fthenakis said. First Solar, which annually produces 5.7 GW of solar module capacity among plants in Ohio, Malaysia and Vietnam, is one example of advancing technologies. Rather than using multicrystalline silicon, First Solar now produces its PV panels with CdTe, or cadmium telluride, a waste byproduct coming out of copper mining, according to Andreas Wade, the company's global sustainability director.
"The waste materials coming out of that are extremely limited," he said. In the thin-film CdTe technology (copper indium gallium selenide, or CIGS, is another), semiconductor material deposited on the glass is 3 microns thick, he said, compared to a more industry-typical thickness of 160 microns. Additionally, wastewater is reused throughout First Solar’s manufacturing process, Wade said. What is finally disposed of is first treated by a combination of ion exchange — used to remove the heavy metals inherent to its process — and reverse osmosis for further cleaning and purification.
Singapore-based Maxeon Solar Technologies, which was spun off in August from U.S.-based SunPower, has found another way to deal with its wastewater, according to Markus Sickmoeller, chief operating officer. Its manufacturing process uses hydrofluoric acid for surface etching. Treating for fluoride can be difficult, Sickmoeller said. "The sludge coming out of that is sold to concrete manufacturers because you can make better concrete with the fluoride residuals," he said. "We try to do that with as many things as possible."
The solar industry’s manufacturing efforts have been paying off in terms of reducing environmental impacts, according to researchers. "On the production, things have become better," Fthenakis said. "I don’t see any decline in the environmental health and safety aspects of manufacturing."
Effects on animals, land
While in use and producing energy, PV panels and wind turbines are often scrutinized for their impacts on land use and wildlife. "We don’t want to take trees down that produce fruit or crops to put solar up," Fthenakis said, "but we have to look at what the value and use of the land is, and how you account for that."
Agrivoltaics, the simultaneous use of land for both solar production and agriculture, has helped ease some land-use concerns and generate public goodwill for solar developments, especially in rural areas more accustomed to farming. The agrivoltaic setups often involve grazing sheep and cultivating pollinator habitat on solar sites, which the National Renewable Energy Laboratory (NREL) projects will cover 3 million acres in the U.S. by 2030 and 6 million by 2050.
The potential for "floating solar" to be developed on water rather than land is another route being explored to reduce concerns about land use and environmental impacts like forest clearing and wildlife habitat loss. This year the Norwegian-government-owned Statkraft AS, Europe’s largest producer of renewables, has been working to develop a $2.4 million floating solar project with a 2 MW capacity at the Banja reservoir in Albania.
As the pilot project launches, some of the main questions will be how the biology and growth of algae underneath are affected by the large membrane that will hold the floating solar panels, Statkraft Senior Environmental Adviser Bjørn Iuell said. "I think the main purpose is to see if we can use these large reservoirs to add to power production," he said. "Anything that can improve conditions or give" value-adds to the reservoirs is helpful.
"We now have billions and billions of these panels out there, and the awareness rose that at some point we’ll have to deal with these panels coming back as waste. We don’t want to get in a second e-waste crisis."
Andreas Wade
Global Sustainability Director. First Solar
Along with changing land use, renewables can also disrupt wildlife habitat. One impact that generates attention, and where Statkraft has recently seen promising research results, is around the effect of wind turbines on birds.
Rotor blade strikes were estimated in 2013 to kill 140,000 to 328,000 birds annually. While the numbers are much smaller than the hundreds of millions of deaths attributed to colliding with buildings, vehicles and high-tension lines, localized impacts on specific populations can be significant.
The area around its Smøla wind farm — one of Norway’s largest, with 68 turbines spread over 7 square miles — is home to 45-50 breeding pairs of white-tailed eagles. Fatal strikes of the eagles averaged six per year. The deaths of raptors with 8-foot wingspans fed opposition to wind power in Norway.
Statkraft has spent $4.5 million conducting R&D toward reducing bird strikes for more than 10 years, using tools from GPS to radar to video monitoring. Hoping an ultraviolet coating invisible to human eyes would be visible to raptors and keep them away from turbines, Statkraft also ran a UV pilot that Iuell called "not very successful."
A more promising study, whose results were released this year, involved painting one blade black on each studied wind turbine at Smøla, hoping to reduce "motion smear" within the birds’ visibility. Statkraft spent $75,000 on the painting, begun in 2013. Researchers found a 72% reduction in bird fatalities, and recorded no deaths of white-tailed eagles, among the contrast-painted turbines.
Although the results, published this year in the journal Ecology and Evolution, appeared positive, Iuell is not satisfied. "I should be really happy when I saw this, that we can decrease bird mortality with this simple measure. But it’s not proven," he said. "They say this study has to be replicated to see if it’s site-specific and species-specific." Developers in the Netherlands and South Africa have expressed interest in running similar experiments.
Disposal challenges
The issue getting perhaps the most scrutiny is the recycling and disposal of outmoded PV panels and — more recently, after news photos showed them in landfills — wind turbine blades. The International Renewable Energy Agency projects that there could be as much as 8 million metric tons of total solar panel waste by 2030, and 10 times that — nearly 80 million metric tons — by 2050.
PV panels have an expected lifespan of 25-30 years. Wind turbine blades can last up to two decades, but are often taken down in half that time so they can be replaced with newer, more powerful models. Tons of their waste has nowhere to go but landfills, and as more panels and blades approach the end of their lifespans, the pressure is on to find recycling solutions.
Recycling "is a crucial determining factor for the future growth of the industry," First Solar’s Wade said. "That has changed over the past five years. We now have billions and billions of these panels out there, and the awareness rose that at some point we’ll have to deal with these panels coming back as waste. We don’t want to get in a second e-waste crisis." CdTe is valuable enough that First Solar situates recycling plants alongside its manufacturing facilities, recovering up to 95% of the semiconductor material, and 90% of the glass, to reuse.
For both wind and solar, a mix of component materials complicates efforts to recycle. In 2018, Veolia Group, the North American division of Paris-based Veolia Environnement, received its first inquiry about recycling wind turbine blades. Veolia analyzed the material, finding a mix of fiberglass, carbon fiber, wood, metal, foam and plastic. "A combination pack is the most difficult to recycle of all. That was the exact challenge here," said Bob Cappadona, Veolia Group's chief operating officer and executive vice president of environmental solutions and services.
The company started breaking, cutting and grinding U.S.-placed rotor blades, evaluating their BTU value for other potential applications. Veolia found the thermal value too inconsistent to be a waste-to-energy source. Ultimately, leaders devised a mechanical process to grind the massive blades to dust. They now provide the processed material to lime kilns and the cement industry as a fuel source or material replacement. With 60-70 blades on site daily, Veolia is now handling hundreds of blades annually — expected to scale to the thousands within the next few years.
Transporting rotor blades, which can extend up to 150 feet, is a big challenge. To help, Veolia is building capacity to handle blades at "multiple locations in the central U.S." Cappadona said. "Like other commodities, there’s work that needs to be done," he said. "I don’t view it at this point as the be-all solution for everybody."
"Once everybody gets to 10% recycled glass, raise the standard to 20%, with the goal being a lower carbon footprint for solar panels and lower emissions overall. It's a big-picture circular economy."
Dustin Mulvaney
Environmental Studies Professor, San Jose State University
Longer term, researchers at NREL have recently shown that using a cheaper, lighter-weight material for wind turbine blades could also make them more sustainable. In a study published in the journal Renewable Energy, researchers demonstrated the feasibility of using thermoplastic, rather than the typical thermoset, resin. Currently, wind turbine blades are made mostly of composite materials like fiberglass infused with a thermoset resin. Thermoplastic resin can be melted back down to liquid resin and reused for new blades, making recycling more viable.
The solar industry is similarly facing end-of life issues and is gearing up to handle its coming wave of old panels. SEIA, whose Corporate Social Responsibility committee includes a recycling working group, has been partnering with EnergyBin, a 1,000-member B2B solar industry exchange network, to strengthen the reuse market for PV panels.
The association is also teaming up with recyclers in different regions, including Dynamic Lifecycle Innovations in Wisconsin, Echo Environmental in Texas, Cascade Eco Minerals in Minnesota, Cleanlites Recycling in Ohio, and Green Century in Oregon. The partners are actively recycling PV modules now and preparing to scale up their future capacity. That foresight is "not normal in the recycling industry," Butler said. "Usually recycling infrastructures are built because they’re mandated. We’re saying, 'Let’s be proactive.'"
The new EPEAT solar criteria give points for having 10% recycled glass content. That will provide an added incentive to use more recycled glass so that a company rates more highly in the EPEAT registry, Mulvaney said.
"By requiring recycled content, you create a market for those piles of materials you’ve piled up at the landfills," he said. "But how do we manufacture with fewer chemicals, less lead, less cadmium? I want the standard to ratchet up performance," he continued. "Once everybody gets to 10% recycled glass, raise the standard to 20%, with the goal being a lower carbon footprint for solar panels and lower emissions overall. It's a big-picture circular economy."
