Engineering Ethics Blog: Externalities On the Roof: Solar Panels and Recycling

 A recent article by Maddie Stone at warns that in the next decade or three, the world will face a novel but entirely predictable problem:  what to do with millions of square feet of worn-out solar panels.  This problem is especially ironic because solar energy has been sold as one of the most appealing “sustainable” technologies.  But when you widen your vision to see the larger picture, you run up against a familiar problem that economists call an externality.

While less than 2% of U. S. electricity is generated by solar panels that convert sunlight directly into electric power, it tends to be one of the more visible types of renewable energy, covering the roofs of businesses and residences and whole acres of ground in sunny parts of the country.  It takes a lot of area to generate appreciable power from even the most efficient solar panels, so a lot of silicon, glass, aluminum, and copper is tied up in every installation.  And no solar panel lasts forever.  Leaks, deteriorating materials, and other age-related problems mean that the design life of the typical solar panel is about 25 years or less.  The big question is, what happens after that?


Stone says that conventional electronics recycling can’t handle solar panels, which pose unique problems. For one thing, a huge amount of stuff is involved—one estimate says there will be about 80 million metric tons of worn-out solar panels to be disposed of by 2050.  From a recycling point of view, the only easily recoverable materials in used solar panels are the metals, mainly copper and aluminum.  The rest is mostly glass, and not pure enough glass to be diverted to many ordinary glass-recycling streams.  The net result is that, in the U. S., anyway, a typical panel offers about $3 worth of recyclable metal.  But it costs $10 to $12 to recover it.  In other words, recycling solar panels is a money-losing proposition.  Consequently, most defunct solar panels today end up in landfills, where harmful materials such as lead and even gallium arsenide could conceivably leach into the soil. 


Now for the economics.  An externality is something that happens in a transaction which affects a third party not involved in the transaction.  In the case of worn-out solar panels, the parties immediately involved are the solar-panel makers and the solar-panel users.  The makers make money selling the panels, the users make (or save) money getting electricity, and both parties get that warm glow that comes to some people from promoting sustainable energy sources. 


But when it comes time to replace the panels, and the old ones get thrown away into a landfill, everybody from now on who might be affected by whatever’s in that landfill has a negative externality thrown on them.  And if you want to look at it this way, there are also missed-opportunity costs associated with throwing away something that, with clever enough recycling technology, might become the starting point for a useful product. 


Stone points out that in Europe, rigorous life-cycle laws require manufacturers of any electronics to take full responsibility for the recycling of their products.  This is somewhat idealistic in that it requires manufacturers to stay in business at least until the end of a 25-year life cycle, but I suppose the lawyers have figured that one out too, and it may be one reason that people don’t start a lot of new high-tech companies in Europe these days.  However, such a law fixes the externality problem right away, because the manufacturers have to build the cost of recycling into the cost of the new product. 


In the U. S., however, we have no such laws that apply to solar panels, except for the State of Washington, so it’s up to the solar-panel owners to do the right thing with their used solar panels.  A lot of the used panels are apparently finding their way overseas to less fussy consumers, but that just throws the externality burden onto those countries. 


Stone cites a few research projects that have attempted more sophisticated recycling to extract usable low-purity silicon from the panels.  Anybody who knows much about the semiconductor industry knows that it’s a long and arduous road from beach sand to the ultra-high-purity silicon that is used in computer chips, involving energy-intensive and complex chemical purifying steps.  It’s a shame to throw all that effort into a landfill, and so if someone could salvage the already-purified silicon from the huge number of outdated solar panels we’ll be dealing with in the coming decades, we would be ahead of the game silicon-wise.


But current supply chains simply are not set up to deal with a lot of medium-purity silicon, and so governments or other entities may need to set up incentive programs to encourage innovative ideas such as these.  The one consistent mistake that many ecological doom-criers often make is to neglect the power of human ingenuity.


A good example (good in the sense that it makes the point, not that it has no downsides whatever) is the case of hydraulic-fracturing oil production (fracking).  For decades, forecasters have been saying that we were about to reach “peak oil,” meaning that at some point, we will have found all the easy places to get oil from, and after that production will go into an inevitable decline and we’d all better get used to obtaining our energy from someplace else, like solar panels.  I’m sure some people forecast that peak oil was going to happen in the early 2000s.


Then along came George P. Mitchell, the son of a Greek immigrant who, after thirty years in the oil and gas production business, developed a set of methods in the 1990s that manage to extract fossil fuels from places that were either regarded as played out, or were not considered productive enough to develop.  Thus ensued the fracking boom that enabled the U. S. to regain its place as the world’s leading oil-producing country, where it has been since 2014. 


Maybe there’s another George Mitchell type out there who will say to himself or herself, “there’s gold in them thar used solar panels!” and fix this problem without excessive government intervention or subsidies.  Or maybe not, but let’s not discount the possibility.


Sources:  Maddie Stone’s article “Sun Kissed” appeared on Aug. 14, 2020 on Slate’s website at  I referred to the U. S. Energy Information Administration for statistics on the percentage of U. S. energy coming from solar panels, and the Wikipedia article on George P. Mitchell as well. 

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