Sequestration

Carbon sequestration refers to the long-term transfer of carbon from the Earth’s atmosphere into plants, soils, rocks, and oceans. As a natural process, carbon sequestration happens all the time. But, increasingly, we need to find ways to enhance it.

The Earth has been sequestering carbon for billions of years. It is drawn out of the atmosphere as carbon dioxide by plants and oceans, cycled into soils and sediments, compressed into rock, peat, coal and oil. It returns to the atmosphere through weathering, volcanic eruptions, and other biological and chemical processes.

This cycling of carbon is one of the main reasons life has flourishes on Earth.

But as concentrations of atmospheric carbon increase faster than the Earth’s ability to draw it down, primarily due to the burning of fossil fuels, our climate will begin to warm. At some point, this warming could accelerate beyond our control.

Fortunately, we know what to do.

First, we need to sharply reduce the amount of greenhouse gases we are currently emitting. This can be achieved by reducing our use of fossil fuels and investing in new energy technologies. Such measures will take time—and importantly support from governments and voters—but without them the scenarios forecasted by climate scientists are alarming.

Second, we can try to increase the amount of carbon that is already being sequestered.

Image credit: Boudhayan Bardha

Globally, forests can sequester up to 4 billion tonnes of carbon each year.

Forests draw in vast amounts of carbon from the atmosphere and lock it up in their leaves, branches, trunks and roots. Some of that carbon can make its way into deeper soils and sediments—or into wood used for buildings or other products—where it can remain for the long term.

Forests that are healthy and growing can be significant carbon sinks, and can provide many other benefits. Strategies to enhance carbon sequestration in forests include:

  • Protecting existing forests from over logging or slash-and-burn practices.
  • Replanting and restoring forests that have already been logged or lost.
  • Planting new forests in places where there have never been forests (e.g. marginal lands, rocky or arid climates, urban, suburban or industrial areas).
  • Using forest products wisely, in particular using them in permanent buildings or other long-lasting products.

Soils too have the potential to sequester carbon. Estimates suggest that soils can hold more carbon than in all of the atmosphere and all of the plants and animals on Earth. Soils that contain a high-carbon content are healthier and more productive, whether they are found in natural landscapes, gardens or agricultural fields.

Image Credit: Avi Waxman

When natural land is converted to other uses, like residential or industrial projects, it can lose up to 40% of its carbon.

When we replace natural landscapes like forests, grasslands or wetlands with cities, suburbs, factories or farms, the soils lose a significant proportion of their carbon. But there are things that we can do to slow or reverse this trend, including:

  • Conserving, protecting and/or creating new national parks or protected areas.
  • Changing urban and suburban planning to allow for a more green space.
  • Adopting innovative farming practices that increase soil carbon.
  • Adding carbon directly to soils through the use of biochar.

Other options for enhancing carbon sequestration range from carbon mineralization and ocean fertilization, to technologies that capture carbon from industrial emissions or even directly from the atmosphere.