6 minute read 2 Mar 2022
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In the race to be net zero, how will we remove what we fail to reduce?

By Carmen Maria Sprus

Project Lead EYCarbon and Smart City | Switzerland

Develops sustainability strategies. Accompanies transformations. Connects decision-makers. Moderates conferences. Loves salsa & mountains.

6 minute read 2 Mar 2022

The fight against climate change demands technical solutions that remove CO2 from the atmosphere.

In brief:
  • Greenhouse gases are major contributors to climate change
  • Reducing CO2 emissions is no longer enough in the fight against climate change
  • Negative emissions could help us achieve our goals of being net zero by 2050

Global emissions of greenhouse gases such as CO2 have been rising continuously since the 1960s. In order to halt the associated acceleration of climate change, various efforts are under way to reduce energy requirements. Approaches include energy efficiency measures and digital technologies. In addition, renewable energy sources, biomass or even hydrogen are set to replace fossil fuels. However, these efforts alone are far from enough. Unavoidable and historical emissions need to be countered by “negative” emissions, and the technology to achieve this is becoming increasingly important. But how do negative emission technologies (NETs) work, why are they negative, and what are the challenges of these novel methods?

Everyone’s talking about net zero right now. Net zero means that the emission of CO2 into the atmosphere and the absorption of CO2 in natural or engineered reservoirs balance each other out.  Especially since the 26th UN Climate Change Conference of the Parties (COP26), there has been an exponential increase in the commitments of companies and countries to be net zero by 2050. Such ambitious targets, however, beg the question: What is the concrete roadmap for achieving net zero?

Why do we need to talk about negative emissions?

At the 21st UN Climate Change Conference (COP21), the global community voted to adopt the Paris Agreement, an international treaty on climate change. Under the agreement, 197 countries agreed to limit global warming by 2100 to well below 2, preferably to 1.5°C, compared to pre-industrial levels. According to a special report by the Intergovernmental Panel on Climate Change (IPCC), the 1.5-degree target has significant advantages over the 2-degree target.  At the current level, however, the world’s activities will lead to warming of about 2.7°C compared to pre-industrial levels. Therefore, global greenhouse gas emissions must be cut drastically – to net zero by mid-century – if we are to meet the science-based climate target by 2100.   So far, however, many of the necessary transformations have failed to materialize (see also the outcomes of COP26). To reach ambitious climate goals, we need to embrace efficiency measures and reduce our use of fossil fuels, but also to tighten climate policies and adopt new technologies. This is where negative emissions come into play.

What are negative emissions?

Another way to describe negative emissions is the term “carbon dioxide removal” (CDR). CDR, i.e., the retrieval of CO2 from the atmosphere, is the opposite of carbon emissions – hence the term “negative emissions”. Negative emission technologies (NETs) remove carbon dioxide from the atmosphere and store it permanently.  While processes that remove other greenhouse gases, such as methane, from the atmosphere are also being discussed and researched internationally, the IPCC special report on the impacts of global warming of 1.5 °C and this article focus on the removal of CO2 as the most significant and long-lived greenhouse gas.

Negative emissions go one step further than carbon credits, which have been embraced by governments all over the world as a way to limit industrial CO2 emissions. Although carbon credits and CO2 certificates help to compensate for emissions, any existing or produced CO2 remains in the atmosphere. And that’s where NETs come in to play with a major advantage: they actually eliminate the existing footprint by permanently removing CO2 from the air.   

Negative emissions are indispensable if we are to limit global warming to no more than 1.5 degrees

Oil is currently still cheaper than Coca-Cola. A barrel of oil contains 159 liters; in 2021, the average price was about USD 68 per barrel, which translates into about USD 0.42 per liter. A liter of Coke retails for about USD 0.75.  

Fossil fuels are currently still too cheap

15 billion liters

of oil are consumed by the world every day.

However, there is no realistic way (yet) to achieve zero emissions simply by abandoning fuels entirely or ceasing all activities that require fuels. On average across all IPCC scenarios, a cumulative 630 billion tons of CO2 emissions will need to be removed from the atmosphere by 2100. By comparison, humanity emits about 40 billion tons of CO2 equivalent each year.  Reducing emissions by less than 100 percent would not stop the rise in temperature – and climate change – but merely slow it down, at most.  To prevent the worst-case climate scenarios and achieve the goals of the Paris Agreement, we will need to recapture emitted gases as well as pursue all the other reduction measures.

Current negative emission methods are based on technical, geochemical, or biological approaches.

  • Technical approach

    Technical approaches include “direct air capture” and “Bio oil injection. In direct air capture, large machines filter CO2 directly out of the air. The CO2 recovered in this way can then be injected underground, for example, where it forms carbonate minerals and is stored long term. Bio oil injection technology sees waste biomass first converted into bio oil through fast pyrolysis and then pumped into deep underground rock formations. There it can be stored like crude oil for hundreds of millions of years. The process is a way of allowing excess biomass such as sawdust and wood, sugarcane bagasse, corn straw, rice straw or almond shells to be stored in bio oil, thus removing CO2 from the atmosphere rather than allowing the excess to rot, which would release stored CO₂.

  • Geochemical approach

    One example of a geochemical process is “enhanced weathering” – the acceleration of natural weathering. By enhancing natural weathering with rock dust, for example, carbon dioxide emissions can be better captured from the atmosphere. According to studies by Columbia University in the USA, this method has the potential to filter 2 billion tons of CO2 annually if farmers applied it to their fields.

  • Biological approach

    Reforestation, sustainable forestry and the restoration of coastal wetlands and peatlands are examples of biological methods that also have the potential to absorb CO2. For example, although peatlands cover only three percent of the earth’s surface, they store about 30 percent of the earth’s carbon.

What are the challenges to overcome?

One issue is that many of the technologies are still in their infancy and cannot yet be scaled. Many approaches have not yet been adequately tested or are not mature enough. This is due, among other things, to a lack of financial resources or excessive high technology costs, coupled with sluggish progress in establishing supportive frameworks.

Negative emissions can only have a positive impact on the climate if the CO2 is permanently removed from the atmosphere. The moment it is released back into the atmosphere, the effect is nullified.
Carmen Sprus
Project Lead EYCarbon and Smart City | Switzerland

This makes research and development of these technologies all the more important if they are to make a valuable contribution and support other climate measures. Because one thing is certain: reducing CO2 alone is not enough in the fight against climate change. To get to net zero, we need to capture and store any emissions that cannot be avoided.


The climate crisis demands a rethink and more stringent climate policy. The Paris Agreement – reached jointly by the global community – provides for a permanent reduction in CO2 emissions. However, reducing CO2 emissions alone is not enough in the fight against climate change as too many greenhouse gases are already in the atmosphere today. Negative emission technologies address this issue by absorbing CO2 from the air and storing it permanently. At the same time, technological approaches are currently under-tested and not yet ready for large-scale use. The situation is compounded by a lack of financial resources and supportive frameworks for scaling up the technologies we present.

  • Article references

    1. Schweizer Bundesrat (2020): Von welcher Bedeutung könnten negative CO2-Emissionen für die künftigen klimapolitischen Massnahmen der Schweiz sein? 62745.pdf (admin.ch)
    2. The Paris Agreement | UNFCCC
    3. Sonderbericht 1,5 °C globale Erwärmung – SR1.5 - de-IPCC
    4. Temperatures | Climate Action Tracker
    5. The Net-Zero Standard - Science Based Targets
    6. COP26 Outcomes - UN Climate Change Conference (COP26) at the SEC - Glasgow 2021 (ukcop26.org).
    7. Minx, J.C. et al. (2018) Negative emissions-Part 1: Research landscape and synthesis - IOPscience.
    8. Bill Gates (2021): How to avoid a climate disaster
    9. Die Welt verbraucht jeden Tag ein 76’000 km hohes Fass Erdöl – Energie-Umwelt.ch
    10. The Role of Atmospheric Carbon Dioxide Removal in Swiss Climate Policy - Texts (admin.ch)
    11. What Is Carbon Capture and Storage (CCS)? The Vacuum the Climate May Depend On – Bloomberg
    12. Steele, P., Yu, F. and Gajjela, S. (2009): Past, Present, and Future Production of Bio-oil 1079592 (osti.gov).
    13. Climate change: Stone dust in the field could bind billions of tons of CO2 - DER SPIEGEL
    14. Applying rock dust to croplands could absorb up to 2 billion tonnes of CO2 from the atmosphere, research shows | Energy Institute | The University of Sheffield
    15. Klimaschutz: Moore sind effektive CO2-Speicher | NDR.de – Ratgeber

About this article

By Carmen Maria Sprus

Project Lead EYCarbon and Smart City | Switzerland

Develops sustainability strategies. Accompanies transformations. Connects decision-makers. Moderates conferences. Loves salsa & mountains.