Humans are adding around 400 million tons of fossil carbon each year to long-lasting products like plastics, buildings, and infrastructure, new research has revealed.
When considering carbon emissions, society often focuses on the carbon dioxide released into the atmosphere from burning fossil fuels. But now, experts are considering the carbon stored in everyday items, as detailed in a new study published published in Cell Reports Sustainability.
Growing Carbon Stockpile
“We have accumulated more carbon in human-made stuff on the planet than there is carbon in the natural world, but we completely overlook it, and those stocks get bigger and bigger,” Klaus Hubacek, senior author and ecological economist at the University of Groningen said in a recent statement. “The message is to look at stocks rather than just flows.”
The “technosphere“—the collective term for all human-made artifacts, including those in use and discarded—contains billions of tons of fossil carbon, much of it stored in products like plastics, rubber, and construction materials. Using global data from 2011, researchers found that 9% of the fossil carbon extracted that year ended up in durable products. To put this in perspective, if that same amount of carbon were emitted as CO2, it would nearly equal the European Union’s emissions that year.
Where Is Fossil Carbon Stored?
The study revealed that the largest share of fossil carbon accumulation occurs in building and infrastructure construction, accounting for 34% of the total. Products like rubber and plastics made up 30%, while bitumen (used in roads and roofing) accounted for 24%, and machinery and equipment contributed 16%.
By extrapolating their findings to a 25-year span (1995–2019), the researchers estimated that 8.4 billion tons of fossil carbon were added to the technosphere—equivalent to about 93% of global CO2 emissions in 2019. Alarmingly, the amount of fossil carbon entering the technosphere has increased each year.
The Downside of Durable Carbon
What happens to all this carbon-based material when it’s no longer useful? According to the study, from 1995 to 2019, 3.7 billion tons of fossil carbon left the technosphere. About 1.2 billion tons ended up in landfills, another 1.2 billion tons were incinerated, 1.1 billion tons were recycled, and the rest became litter. This waste represents a dual challenge: while landfills can act as a form of carbon storage, incineration contributes to carbon emissions, and litter poses serious environmental hazards.
“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,” coauthor Franco Ruzzenenti, also an ecological economist at the University of Groningen explained in a recent press release.
How Can We Improve?
The researchers emphasize that increasing the lifetime of products and improving recycling rates are essential steps for reducing the amount of fossil carbon entering waste streams. Policies to minimize waste discharge from landfills could also make a significant difference.
Looking ahead, the team is planning to analyze the potential of biogenic carbon—carbon derived from plant materials—to provide more sustainable solutions.
“For the next step, we plan to investigate the long-term potential of biogenic carbon sequestration in durables,” says lead author Kaan Hidiroglu in a statement. “This will allow us to assess whether diversifying carbon sequestration strategies, such as relying on biogenic carbon in durables such as wood materials for construction, could be a viable option.”
By rethinking how we design, use, and dispose of these products, we may find opportunities to manage carbon in our increasingly industrialized world better.
Kenna Hughes-Castleberry is the Science Communicator at JILA (a world-leading physics research institute) and a science writer at The Debrief. Follow and connect with her on BlueSky or contact her via email at kenna@thedebrief.org