What are negative emissions?

We investigate some of the ways nature and technology can enable us to remove more CO2 from the atmosphere than we emit. The 6th post in our series ‘Powering to net zero’.

Negative emissions are what we call the process when more CO2 or greenhouse gases are taken out of the atmosphere than are being emitted.

There are a number of ways to achieve negative emissions. Some are based on nature, whilst others are a result of innovative technology developed to remove CO2 at scale.

How can we remove CO2 from the atmosphere with nature-based solutions?

Perhaps the most obvious way to achieve negative emissions is forests. As they grow, trees absorb carbon, which they either convert into energy — releasing oxygen in the process — or store throughout their lifetimes. The country of Bhutan is carbon negative thanks to its incredibly dense forests.

Forests have a huge role to play in reducing atmospheric CO2 levels, with forestation and afforestation having a very positive effect on the health of our planet.

And it’s not only forests that could help us reach negative emissions. Seven tenths of the world’s surface is covered by water, and the vegetation that grows beneath that water can also absorb and store CO2.

Some seagrasses actually have the capacity to store double the amount of carbon as forests on land. This has led to the development of a method of contributing to negative emissions known as ‘blue carbon’.

How can we use man-made technology to deliver negative emissions?

Bionergy with carbon capture and storage (BECCS) is one approach that many experts believe could help bring about negative emissions. It generates electricity using biomass from sustainably sourced forests. Therefore, because the forests where the biomass is sourced from absorb CO2 as they grow, any CO2 released in generation is already accounted for.

BECCS then captures this CO2, making the process of electricity generation carbon negative, because a greater amount of carbon has been removed from the atmosphere during the process than has been emitted.

Direct air carbon capture and storage (DACCS) offers another way to achieve negative emissions. DACCS captures CO2directly from the air, which can then be safely stored or used. Although the technology shows promise, it will require greater investment to develop at scale.

How much negative emissions do we need?

The Intergovernmental Panel on Climate Change, has stated that if we are to avoid catastrophic climate change between now and 2050, nature-based and negative emissions solutions will need to capture 20 billion tonnes of carbon every year.

Negative emissions — the facts

• Sufficient sustainable biomass is available to the UK to enable BECCS to remove 51 megatonnes of CO2 annually by 2050, according to the Committee on Climate Change.
• Greater numbers of the world’s leading corporations are now investing in negative emissions technologies, with Apple conserving mangroves, Stripe allocating $1 million annually to buy sequestered carbon, and Microsoft declaring it will be carbon negative by 2030.