Scrapping the Local Loop, by the Numbers [Hackaday]

View Article on Hackaday

A few years back I wrote an “Ask Hackaday” article inviting speculation on the future of the physical plant of landline telephone companies. It started innocently enough; an open telco cabinet spotted during my morning walk gave me a glimpse into the complexity of the network buried beneath my feet and strung along poles around town. That in turn begged the question of what to do with all that wire, now that wireless communications have made landline phones so déclassé.

At the time, I had a sneaking suspicion that I knew what the answer would be, but I spent a good bit of virtual ink trying to convince myself that there was still some constructive purpose for the network. After all, hundreds of thousands of technicians and engineers spent lifetimes building, maintaining, and improving these networks; surely there must be a way to repurpose all that infrastructure in a way that pays at least a bit of homage to them. The idea of just ripping out all that wire and scrapping it seemed unpalatable.

With the decreasing need for copper voice and data networks and the increasing demand for infrastructure to power everything from AI data centers to decarbonized transportation, the economic forces arrayed against these carefully constructed networks seem irresistible. But what do the numbers actually look like? Are these artificial copper mines as rich as they appear? Or is the idea of pulling all that copper out of the ground and off the poles and retasking it just a pipe dream?

Phones To Cars

There are a lot of contenders for the title of “Largest Machine Ever Built,” but it’s a pretty safe bet that the public switched telephone network (PSTN) is in the top five. From its earliest days, the PSTN was centered around copper, with each and every subscriber getting at least one pair of copper wires connected from their home or business. These pairs, referred to collectively and somewhat loosely as the “local loop,” were gathered together into increasingly larger bundles on their way to a central office (CO) housing the switchgear needed to connect one copper pair to another. For local calls, it could all be done within the CO or by connecting to a nearby CO over copper lines dedicated to the task; long-distance calls were accomplished by multiplexing calls together, sometimes over microwave links but often over thick coaxial cables.

Fiber optic cables and wireless technologies have played a large part in making all the copper in the local loops and beyond redundant, but the fact remains that something like 800,000 metric tons of copper is currently locked up in the PSTN. And judging by the anti-theft efforts that Home Depot and other retailers are making, not to mention the increase in copper thefts from construction sites and other soft targets, that material is incredibly valuable. Current estimates are that PSTNs are sitting on something like $7 billion worth of copper.

That sure sounds like a lot, but what does it really mean? Assuming that the goal of harvesting all that largely redundant PSTN copper is to support decarbonization, $7 billion worth of copper isn’t really that much. Take EVs for example. The typical EV on the road today has about 132 pounds (60 kg) of copper, or about 2.5 times the amount in the typical ICE vehicle. Most of that copper is locked up in motor windings, but there’s a lot in the bus bars and wires needed to connect the batteries to the motors, plus all the wires needed to connect all the data systems, sensors, and accessories. If you pulled all the copper out of the PSTN and used it to do nothing but build new EVs, you’d be able to build about 13.3 million cars. That’s a lot, but considering that 80 million cars were put on the road globally in 2021, it wouldn’t have that much of an impact.

Farming the Wind

What about on the generation side? Thirteen million new EVs are going to need a lot of extra generation and transmission capacity, and with the goal of decarbonization, that probably means a lot of wind power. Wind turbines take a lot of copper; currently, bringing a megawatt of on-shore wind capacity online takes about 3 metric tons of copper. A lot of that goes into the windings in the generator, but that also takes into account the wire needed to get the power from the nacelle down to the ground, plus the wires needed to connect the turbines together and the transformers and switchgear needed to boost the voltage for transmission. So, if all of the 800,000 metric tons of copper currently locked up in the PSTN were recycled into wind turbines, they’d bring a total of 267,000 megawatts of capacity online.

To put that into perspective, the total power capacity in the United States is about 1.6 million megawatts, so converting the PSTN to wind turbines would increase US grid capacity by about 16% — assuming no losses, of course. Not too shabby; that’s over ten times the capacity of the world’s largest wind farm, the Gansu Wind Farm in the Gobi Desert in China.

There’s one more way to look at the problem, one that I think puts a fine point of things. It’s estimated that to reach global decarbonization goals, in the next 25 years we’ll need to mine at least twice the amount of copper that has ever been mined in human history. That’s quite a lot; we’ve taken 700 million metric tons of copper in the last 11,000 years. Doubling that means we’ve got to come up with 1.4 billion metric tons in the next quarter century. The 800,000 metric tons of obsolete PSTN copper is therefore only about 0.05% of what’s needed — not even a drop in the bucket.

Accepting the Inevitable

These are just a few examples of what could be done with the “Buried Fortune” of PSTN copper, as Bloomberg somewhat breathlessly refers to it in the article linked above. It goes without saying that this is just back-of-the-envelope math, and that a real analysis of what it would take to recycle the old PSTN copper and what the results would be would require a lot more engineering and financial chops than I have. Even if it is just a drop in the bucket, I think we’ll probably end up doing it, if for no other reason than it takes something like two decades to bring a new copper mine into production. Until those mines come online and drive the price of copper down, all that refined and (relatively) easily recycled copper just sitting there is a tempting target for investors. So it’ll probably happen, which is sad in a way, but maybe it’s a more fitting end to the PSTN than just letting it sit there and corrode.