Technosphere: Hidden long-term carbon sinks in everyday items

Although we know a lot about how much fossil-derived carbon is released into the atmosphere, we know less about how much is stored in man-made products.

In a study published Dec. 20 in Cell Reports Sustainability, environmental economists say humans add approximately 400 million tons of fossil carbon each year to long-lasting products such as plastics, buildings, and human infrastructure. I am estimating. Although these products may be considered ‘carbon sinks’, proper waste management is essential to prevent them from posing a danger to the environment.

“We are accumulating more carbon in man-made objects on Earth than in nature, but we are completely overlooking it, and that accumulation is getting bigger and bigger.”Environmental Economics says academic and lead author Klaus Hubacek of the University of Wisconsin. Groningen. “The message is: focus on stock, not just flow.”

Little is known about the amount of fossil carbon stored in the ‘technosphere’, the sum of all man-made objects, both used and discarded. To estimate these stocks and how they change from year to year, researchers used a variety of global We used publicly available data on material inputs and outputs from economic sectors.

They then used the average carbon content of different products to calculate the amount of carbon going in and out of different fields. For example, plastics are estimated to contain an average of 74% fossil carbon. The analysis considered not only end products such as durable plastics and asphalt, but also fossil carbon-based raw materials used as intermediate products in various industries.

They found in 2011 that 9% of extracted fossil carbon is stored in long-lasting products within the technology sphere. If this same amount of carbon were emitted as CO2, it would be roughly equal to EU emissions for that year (3.7 Gt vs. 3.8 Gt). emit CO2).

Construction of buildings and infrastructure accounted for the largest accumulation of fossil carbon (34%). By product type, rubber and plastic products accounted for 30% of the fossil carbon accumulated, followed by asphalt (24%, products used in roads and roofs) and machinery and equipment (16%).

The researchers then extrapolated the 2011 findings to estimate the amount of fossil carbon that entered the technosphere between 1995 and 2019 using monetary data for that period.

Overall, it is estimated that 8.4 billion tonnes of fossil carbon was added to the technosphere between 1995 and 2019, representing approximately 93% of global CO2 emissions in 2019. The amount of carbon flowing into the technosphere increased every year from 1995 to 2019.

Many of these fossil carbon-based products end up in landfills or as trash, taking decades or even centuries to decompose. Based on the average lifespan of buildings, infrastructure, and other products, researchers estimate that 3.7 billion tons of fossil carbon were disposed of during that period. 1.2 tonnes went to landfill, 1.2 tonnes were incinerated, 1.1 tonnes were recycled and the rest ended up as garbage.

“On the one hand, if this fossil carbon ends up being sequestered in a landfill, it can be considered a form of carbon sequestration, but on the other hand, this poses a risk to the environment and burning it would emit carbon emissions. ” says co-author and environmental economist Franco Rusenenti from the University of Groningen.

Increasing product longevity and recycling rates are two ways to reduce the amount of fossil carbon entering the waste stream, researchers say. They also stress the importance of enacting policies to minimize waste emissions from landfills.

In the future, the research team plans to conduct similar analyzes for biogenic carbon (carbon derived from plant material).

“As a next step, we plan to investigate the long-term potential of biogenic carbon sequestration in durable goods,” says lead author Khan Hidiroglu from the University of Groningen.

“This will enable us to assess whether diversifying carbon sequestration strategies, such as relying on biogenic carbon in durable goods such as construction wood, could be viable options.”