Could We Build a Carbon-Zero Internet?

Sub-sea fibre optic cables connect us to the world. But are they sustainable?
Anastasia Beasley
Anastasia Beasley
Freelance Writer
Could We Build a Carbon-Zero Internet?
Image credit:   Photo by Brett Sayles:

Every time you go swimming at City Beach, you’re floating right on top of the internet. The popular paddling spot is the landing for five undersea cables, each packed with fibre optics that carry data between cities. Together, these cables link Perth to the World Wide Web.

But our hunger for data is increasing. According to Dr Bill Corcoran, an ARC Future Fellow and Senior Research Fellow at the Centre of Excellence in Optical Microcombs for Breakthrough Science (COMBS), the internet is growing exponentially at about 25% every year. “Our data demands aren’t going down, they’re only going up,” he says.

To meet this demand, SUBCO is starting construction on a sixth cable this year. It’s called SMAP (Sydney-Melbourne-Adelaide-Perth), and when it’s finished, it will deliver 300 terabytes per second – that’s like carrying 75,000 movies from Sydney to Perth at 18 million km/h.


Our growing internet use has seen the digital sector grow its emissions by 6% every year, so its impact is on par with all the heavy goods vehicles in the world. 

According to Bill, reducing the energy we use to support AI, machine learning and large language models is becoming a priority for tech companies as our computing needs exceed our capacity.

“All of that’s currently coming at a cost where, you know, the projections look ridiculous and we’re going to hit barriers in terms of being able to power these things and get any further growth in those sorts of applications,” he says.

SMAP claims to be the world’s first carbon-zero submarine cable system. But are these claims all they’re cracked up to be?


Bill points out that the claim to be building a zero-carbon cable is about the energy consumption while it’s running – it probably doesn’t include the manufacturing process.

SUBCO’s press release says it will build renewable energy farms at each terminal to supply power to the cable. Bill calculated that they only need to generate the equivalent of a few houses worth of rooftop solar to power each section of SMAP.

SUBCO doesn’t report its own emissions and didn’t participate in the industry-wide Report on Best Practices in Subsea Telecommunications Sustainability.


Manufacturing fibre optics is far more energy and resource intensive than powering them. SUBCO’s cable partners ASN and OMS do not publish sustainability reports, though ASN has taken steps to reduce its climate impact by installing solar panels and hot water recycling at its manufacturing facility in France. 

Despite these measures, making kilometres of pure glass is always going to have an environmental impact – from the damage caused by sand mining to the energy-intensive melting process.

The best practices report suggests that green fibre optics aren’t impossible, saying “if customers were to ask for different cable compositions—including less carbon-intensive designs—[cable manufacturers] would be interested in meeting this demand”.


One of the industry leaders in sustainability is Hexatronics, a Swedish cable manufacturer. In notable contrast to SUBCO, its annual report goes into great detail about exactly what it’s doing to reduce the footprint of its fibre optic cables.

It already transitioned three factories to use 100% renewable energy, started making its ducts with recycled plastic and optimised its packaging and transport to reduce its carbon footprint. It invested in reducing energy consumption in its production lines and introduced programs to reclaim excess ducts and empty drums.

Despite this, its Scope 1 and 2 emissions in 2023 were higher than in 2022. This illustrates just how difficult it is to reduce emissions while keeping up with demand, even with a whole-of-company approach to sustainability.


The environmental impact of SMAP itself might be relatively low, especially once it’s complete, but the way we use the internet continues to exponentially demand more infrastructure – even when we build a cable with room to grow.

The best practices report shows that conversations about sustainability are taking place in the fibre optics industry, but instead of improving the infrastructure, the focus is on reducing the energy cost of running it.

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Microcomb chip on a $2 coin

Image credit: Monash
Microcomb chip on a $2 coin

This is one of the reasons Bill, in collaboration with a Perth-based optic fibre company Terra 15, is researching optical microcombs. They’re smaller and more efficient than the lasers we currently use to send information, and in 2020, they were used to break the internet speed record on obsolete fibre optic cables in Melbourne.

If we’re able to use this technology at a commercial level, we could significantly increase the capacity of existing cables and reduce the need to keep laying new ones.

SMAP is scheduled for completion in 2026, but you can see its progress in real time here.

Anastasia Beasley
About the author
Anastasia Beasley
Anastasia is a scientist and artist who cultivates curiosity through workshops in science, art, sustainability and technology in schools. In 2018, they co-founded science art collective Snart Club, which continues to produce fun, informative discussions around how and why we do science.
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Anastasia is a scientist and artist who cultivates curiosity through workshops in science, art, sustainability and technology in schools. In 2018, they co-founded science art collective Snart Club, which continues to produce fun, informative discussions around how and why we do science.
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