Ellen Phiddian
Cosmos science journalist
Human-made materials – the “technosphere” – are a deep store of fossil carbon – and possibly a ticking time bomb.
That’s according to a fascinating new study published in Cell Reports Sustainability.
“We have no idea of how much carbon has been accumulated in the technosphere, how long it stays and what might happen to it once it is released,” says co-author Professor Klaus Hubaeck, a researcher at the University of Groningen, the Netherlands.
The researchers found that the technosphere accumulated 8.4 billion tonnes of fossil carbon from 1995-2019.
Were all this carbon to be burned and sent into the atmosphere, it would be equivalent to 30 billion tonnes of CO2. The world’s annual greenhouse gas emissions into the atmosphere over that period were roughly 770 billion tonnes.
“Carbon is used as a feedstock everywhere in our daily items, even the laptop I type on, and we were wondering if there is a potential time bomb of all that carbon contributing further to climate heating as it gets released to the atmosphere,” Hubaeck tells Cosmos over email.
Human-made materials are often made from fossil carbon sources like oil and gas. Plastics, for instance, are 74% fossil carbon on average. When these items reach end of life, the carbon makes its way back into the environment via dumping – or into the atmosphere via combustion.
The researchers calculated the amount of fossil carbon stored in the technosphere in the year 2011, using economic data to judge how much was flowing in and out of various industries.
They found that most of this carbon was going into rubber and plastic (30%), while 24% was put in bitumen, and 16% in machinery and equipment.
They found that 9% of extracted fossil carbon was stored in the technosphere in 2011, or about 0.4 billion tonnes of fossil carbon.
The team extrapolated these findings to a 25-year time period (1995-2019), which told them that 8.4 billion tonnes of fossil carbon had been accumulated.
Hubaeck says that the technosphere is nearing the stage where it stores more carbon than the natural world.
“We are not far from that turning point. Indeed, the accumulated fossil carbon is in the same order of magnitude, and indeed already higher than that stored in animals.”
What happens to all of this carbon? The researchers estimate that 3.7 billion tonnes of fossil carbon was disposed of over this time period: 1.2 billion tonnes sent to landfill, 1.2 billion tonnes incinerated and sent into the atmosphere, 1.1 billion tonnes recycled, and the rest littered.
“On the one hand, you can consider it as a form of carbon sequestration if this fossil carbon ends up sequestered in landfill, but on the other hand, it poses an environmental hazard, and if you burn it, you increase carbon emissions,” says co-author Dr Franco Ruzzenenti, also from the University of Groningen.
This means it is very important to make sure the waste is being processed properly, according to the researchers. They say that product lifetimes and recycling rates need to increase, and landfill and waste discharges need to be minimised.
“It’s best to avoid or reduce the throughput in the first place,” says Hubaeck.
“Certainly in rich countries, we have too much stuff (whereas the Global South still needs to catch up), we should question the amount of durable products and (inefficient) infrastructure we produce.
“Shifting to bio-based carbon also has environmental impacts, land requirements, biodiversity, and impacts on food prices.”
The researchers say that circular economy strategies are important for reducing the amount of waste as well, alongside managing waste better after disposal.
