Goodbye to heavy metals

Although solar modules produce “green” electricity, they make use of dangerous substances. How “chemically green” does the PV industry have to be? And what happens to old equipment after it’s taken out of use? Discussion of these two questions is intensifying in Europe, because two environmental guidelines dating back to 2003 are being revised in Brussels. These are:

• The Directive on Waste Electrical and Electronic Equipment, known in the jargon of the European Union (EU) as the WEEE Directive, and
• The Directive on the Restriction of the use of certain Hazardous Substances in Electrical and Electronic Equipment (RoHS Directive).

With these directives, the EU wants to achieve two goals: to collect electrical and electronic devices like shavers, washing machines, television sets and mobile phones, reuse their raw materials, and protect people and the environment against dangerous substances.
The photovoltaics industry is undecided on whether its products should come under these directives. “It would be absurd to exclude solar arrays,” says Milan Nitzschke, Spokesman for Solar world in Bonn. Jan Kallmorgen, Managing Director of the Bohnen, Kallmorgen & Partner consultancy bureau, agrees that, for the sake of its green image, the solar industry should set a good example and do without toxic substances. Kallmorgen is a member of the Non Toxic Solar Alliance (NTSA), which calls for a solar future that is non-toxic.
On the other hand, Brandon Mitchener, Spokesman for First Solar of the U.S., asks why solar arrays should fall within the purview of two directives on consumer goods. “Modules are installed and maintained by specialists and can also be collected again and recycled by specialists.” He sees this as a closed cycle as the modules don’t end up in rubbish dumps. He fears that the objectives of the solar industry – to combat climate change and construct a safe, sustainable energy market – could suffer under the directive.
The main objective of the WEEE Directive, which came in force in January 2003, was that each EU state should collect and recycle at least four kilograms of old electrical and electronic equipment per capita, starting at the end of 2006. The devices to be collected are listed in ten product categories, such as large and small domestic appliances, IT and telecommunications devices, and lighting fixtures.
With the RoHS Directive, on the other hand, the EU sets limits on the use of dangerous substances in the ten product categories of the WEEE Directive. No toaster or stereo system may contain more than 0.1 percent lead, mercury or hexavalent chromium by weight. The same limit applies to polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE), used as fire retardants. The EU has imposed a tighter limit on cadmium – a maximum of 0.01 percent by weight per article.
Both directives are now being revised. In 2008, the EU Commission presented two preliminary versions with the aim of simplifying and standardizing implementation throughout the EU. The European Parliament’s Environment Committee is currently examining these preliminary versions, discussing fundamental changes to both laws that make them applicable to all electrical and electronic devices, not just those in the ten product categories mentioned earlier. This unrestricted area of applicability will ensure clarity in the law, says Karl-Heinz Florenz, member of the European Parliament and rapporteur for the WEEE Directive. Courts have often had to decide in recent years which articles come under the Directive and which don’t.

A temporary exemption

An unrestricted area of applicability would include solar arrays. The German Solar Industry Association (BSW) fears that the RoHS Directive could mean that makers of solar arrays and their associated components are excluded from the European market. The BSW says such a situation is inconsistent with the EU’s objectives of protecting the climate and securing supplies of energy.
The most controversial question is the possibility of a ban on cadmium, which would have a major effect on those manufacturers who use cadmium telluride (CdTe), a chemically stable compound, as a semiconductor. These semiconductors are in demand on the market, and every tenth module manufactured around the world is a thin film cell containing CdTe. The market leader is Arizona’s First Solar, but Calyxo of Bitterfeld-Wolfen, Germany, and two Colorado firms, Abound Solar (formerly AVA-Solar) and Primostar Solar, also use this semiconductor. A typical First Solar panel (60 by 120 centimeter) contains 14 grams of CdTe (19 gm CdTe/m²), meaning around seven grams of cadmium.
Cadmium has a bad reputation because it causes cancer in humans and animals. Brandon Mitchener of First Solar, however, sees no risks for people or the environment because, although cadmium telluride is a toxic compound, it is not carcinogenic. “Under normal circumstances, solar arrays do not release CdTe.” Even in extreme situations such as fire, he says everything is under control because the semiconductor is pressed between glass plates and, if there’s a fire, it’s encapsulated in molten glass. Mitchener moreover considers it discriminatory to regulate solar panels in the same way as toasters or mobile phones for the sake of eliminating hazardous substances, while coal-fired power plants are allowed to go on outputting harmful emissions. He quotes the German Environmental Agency as reporting that German coal-fired power plants emit up to 1.6 tons of cadmium annually. Mitchener and the BSW also point to scientific studies showing that neither the manufacture nor the use of CdTe presents an unjustifiable risk to humans or to the environment.
In contrast, the NTSA’s Jan Kallmorgen is skeptical. He holds that heavy metals on roofs and fields constitute an unnecessary hazard for humans and the environment. “In the event of fire, breakage or incorrect recycling, cadmium components can get into the environment.” He says he only knows of tests in which horizontally positioned solar panels were exposed to fire temperatures. In practice, however, panels are set up on a slant, “so breakage or the melting of the glue can make the glass plates slip, and toxic substances can escape.”
Nowhere can 100-percent certainty be ensured. The question therefore arises whether the risk from modules containing CdTe is so great that they have to be prohibited. The European Parliament is now arguing over that question. Jill Evans is leading the debate as the rapporteur. A Welshwoman and a member of the Greens in the European Parliament, she has weighed up the evidence and isn’t in favor of banning semiconductors containing CdTe. In her view, no other technology established on the market today consumes so little CO2 during manufacture, use and recycling as do thin film cells containing CdTe.
CdTe thin film cells can be manufactured at relatively low cost and have a short energy amortization period. CdTe modules installed in Germany, for example, can generate as much electricity as was required for their manufacture within 15 to 18 months, while crystalline wafers take two to three years. For First Solar, these are persuasive arguments.
But it’s only a snapshot, says Evans. She proposes a temporary exemption for CdTe that can be renewed, if required. For firms like First Solar, this exemption does have a catch, in that it’s to be checked for the first time after a few years, say in 2018. If by that time a company has established a cadmium-free alternative on the market that contains no dangerous substances, requires less energy during manufacture, and produces an equivalent amount of electricity, CdTe semiconductors could be prohibited. “That’s the logic of the directive,” says Evans.
Jan Kallmorgen thinks this transitional period is too lengthy. Since CdTe modules can be made very cheaply, he has three fears: they could be installed in the millions on roofs and fields around the world; Cd-free semiconductors like CIGS semiconductors made from copper, indium, gallium and selenium will have no chance on the market; and other manufacturers worldwide will enter into this technology. The last point is particularly important to Kallmorgen. “No one knows whether all firms will adhere to the same standards as today’s market players in Europe.” He therefore asks for a prohibition on all cadmium compounds as a precautionary measure, which he says would be a logical policy to protect consumers and the environment.
The discussion about the RoHS Directive isn’t just about cadmium; if the Directive were to apply immediately, there probably wouldn’t be any more new modules, for practically all manufacturers use lead, which is highly toxic. It can be found for example in the solder tape connecting solar cells to each other and in the silver paste used for printing on cells.
Some manufacturers are already preparing for the RoHS Directive. SolarWorld, for example, has begun to eliminate lead. It accepts a few disadvantages in return, for lead-free products are currently more costly. In addition, manufacturing the modules requires higher temperatures.

WEEE – a trial exemption

Two firms, SolarWorld of Bonn and First Solar of Arizona, have shown that the solar industry can take old equipment back and recycle it. In 2003, SolarWorld officially opened the world’s first (and so far only) recycling facility for silicon-based crystalline wafers in Freiberg, Lower Saxony. Then five years later, First Solar started up a recycling facility in Frankfurt an der Oder for thin film cells using cadmium telluride as a semiconductor.
Yet there are many more manufacturers. “They should all take steps to recover and recycle used arrays,” says Florenz. He is also ready to give the photovoltaics industry a chance, saying they should organize the recovering and recycling of old equipment themselves. It is just up to them to show they can do it. “If they can’t get it working convincingly by the end of 2014, solar arrays should automatically come under the WEEE Directive.” So this is a trial exemption from the WEEE Directive.
The photovoltaics industry is prepared. The European PV Cycle association was founded back in 2007 with the precise objective of organizing a program for taking back and recycling old equipment. The association, whose 65 member firms cover 85 percent of the market, is currently fine-tuning a statement. In this voluntary ‘Environment Agreement,’ all member firms are to agree to take old equipment back and recycle it. “We’re in the last round of voting,” says Jan Clyncke, director of PV Cycle. The Environment Agreement is to be published in June. Signing this declaration of intent is to be voluntary for each company. Florenz wants to take a close look at it to ensure that old equipment from firms not members of PV Cycle will be included: directives apply to all market participants, but a voluntary statement on the environment doesn’t.
Jan Clyncke would like to be allowed more time. He thinks it makes little sense to organize a functioning collection and recycling system for the complete industry as soon as 2014. He says the industry is still very young, and solar modules were made to supply electricity for 25 years and more. As the first large arrays were built in the early nineties, “It’ll probably take ten to fifteen years before genuinely large quantities of old equipment have to be collected at the end of their life cycle,” he points out.
It still isn’t clear whether the European Parliament will call for solar arrays to fall under the WEEE and RoHS Directives. Not all MEPs are willing to follow the proposals of Jill Evans or Karl-Heinz Florenz. A preliminary decision may be made early June. That’s when the members of the Environment Committee will vote on the proposed amendment. The first reading in a plenary session is planned for July. Almost all PV manufacturers use lead, which is highly toxic.
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