It’s easy to recycle a glass bottle or a piece of aluminum foil. They’re made of single materials. But a solar panel or battery is much more difficult; they’re made of numerous substances mashed tightly together in different ways. So it’s a real technical challenge to extract components and refine constituent materials at high enough purity that they can be reused. To get a feel for just how hard recycling them can be, let’s take a closer look at the main materials and configurations commonly used in a lithium-ion battery, a solar panel and a wind turbine.
Illustration: Binh Nguyen
Inside electric vehicles and battery storage connected to a home solar array, a lithium-ion battery resides, often contained in a pouch. (Here, the battery cells are shown flat, though they can also be rolled up like a not-so-delectable jellyroll.)
Several features of batteries make recycling hard. They come in vastly different shapes and sizes, they can explode or catch fire, and their chemistries (especially in the cathode) vary and so require different kinds of chemical processing to extract useful elements. Yet another hurdle is that the materials are tightly stuck together: powdered graphite is glued to copper foil on the battery cell’s anode side, and powdered lithium metal oxides are glommed onto aluminum foil on the cathode side. Trying to separate all of these components often leads to contamination — for example, bits of aluminum can get mixed in with the lithium metal oxides. Even successfully detaching the materials from each other yields fine particles and thin strips of metal that are difficult for recyclers to handle.
What’s most valuable to recover from a lithium-ion battery? In particular, cobalt, but also nickel, lithium, copper, manganese, aluminum and iron, which are found in different formulations of the cathode.
For more on battery recycling, see Julian Spector’s pieces on five innovative battery-recycling startups and the best ways to develop smart recycling policy. And for more on lithium-ion batteries in general, see David Roberts’ batteries and clean energy series.
Illustration: Binh Nguyen
Over 90 percent of solar panels sold today are silicon photovoltaic panels. (Secondary to those are thin-film solar panels that use semiconductors other than silicon — for example, cadmium telluride or copper indium gallium diselenide.)
Structurally, a silicon photovoltaic panel is like a sandwich: The solar panel’s glass cover, frame and polymer backing are like the bread around a more exotic electronic filling of solar cells. The solar cells are made of chemically doped silicon combined with a grid of metals to conduct the electricity produced.
Solar panel recyclers typically prioritize collecting the easily accessible bulk materials — the aluminum frame, external copper wires and low-iron glass — which make up most of the weight of the panel.
But the most valuable materials are tougher to tease out of the sandwich: the silver, copper and silicon in the solar cells. It doesn’t help that they’re only present in very small amounts.
For more on recycling solar panels, see Eric Wesoff’s piece on a startup that aims to recycle 95 percent of a solar panel’s high-value metals.
Illustration: Binh Nguyen
Much of a wind turbine is actually relatively easy to reuse or recycle, including the steel tower, copper wires, and machinery and metals in the body of the capsule-like pod on top of the tower called the nacelle (derived from French for “small boat”).
But the blades, built to withstand tremendous stresses, are harder to break down.
To manufacture a blade, dry fiberglass and carbon fiber, along with very lightweight core materials of balsa wood or foam, are laid down in a mold. Then a liquid resin is drawn into these materials under vacuum pressure and allowed to solidify into a hard plastic, melding everything together to form a composite. Engineers typically use resins that can’t melt so they won’t separate from the materials they’re bound to. That spells trouble for recycling the blades and extracting resalable materials, like the carbon fibers.
For more on recycling and repurposing wind turbine blades, see Maria Gallucci’s piece on how to keep wind turbine blades out of landfills.
Batteries: Lighting Global’s 2019 Technical Notes report, Lithium-ion batteries part I: General overview and 2019 update | A. Vanderbruggen et al. (2021) Automated mineralogy as a novel approach for the compositional and textural characterization of spent lithium-ion batteries. Minerals Engineering | Rodrigo Serna-Guerrero, minerals processing and recycling engineer at Aalto University
Wind: E-V Năstase. (2017) Influence of the material used to build the blades of a wind turbine on their starting conditions. MATEC Web of Conferences. | M Gkantou et al. (2020) Life cycle assessment of tall onshore hybrid steel wind turbine towers. Energies | Olympus | Derek Berry, wind technology engineer at the National Renewable Energy Laboratory
Solar: G. A. Heath et al. (2020) Research and development priorities for silicon photovoltaic module recycling to support a circular economy. Nature Energy
Solarcycle is proud to support Canary Media’s Recycling Renewables series. Solarcycle offers solar asset owners a low-cost, eco-friendly, comprehensive process for retiring solar systems. We pull out valuable metals such as silver, silicon and aluminum and have the technology to recycle 95% of panels currently in use. Follow Solarcycle on LinkedIn as we ramp up to meet this pivotally important challenge at giga-factory scale.
Alison F. Takemura is staff writer at Canary Media. She reports on home electrification, building decarbonization strategies and the clean energy workforce.