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Greenhouse gases (GHGs) are the atmospheric gases responsible for causing global warming and climate change. The major GHGs are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20). Less prevalent --but very powerful -- greenhouse gases are hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). (Source: United Nations Framework Convention on Climate Change)

 

To stabilise global temperatures, we need to achieve Net Zero – counteracting any remaining emissions of greenhouse gases into the atmosphere with an equivalent amount of Greenhouse Gas Removal (GGR). In order to cap the rise in global temperatures at 1.5°C above the pre-Industrial level it will be necessary to achieve Global Net Zero by 2050. This means that for every tonne of carbon dioxide that is emitted into the atmosphere in that year there will need to be a tonne of carbon dioxide permanently removed from the atmosphere. GGR (also known as negative emissions) encompasses a wide range of proposed techniques to remove greenhouse gases from the atmosphere. While there are some proposed methods for removing greenhouse gases other than CO2, the vast majority of GGR methods involve the removal of CO2 from the atmosphere and its long-term storage so that it doesn’t find its way back into the atmosphere. (Source: Oxford Net Zero)

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Carbon dioxide removal (CDR), is the process of removing Carbon Dioxide (CO2) from the atmosphere and storing it. Carbon has naturally circulated from the atmosphere to forests, soils and oceans for millennia as part of the carbon cycle, but CO2 concentrations have steadily increased since the Industrial Revolution. Carbon removal seeks to accelerate and augment the natural carbon cycle to reduce the level of CO2 in the atmosphere.  (Source: World Resource Institute)

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The race to reduce carbon emissions is heating up, much like the planet itself. Decreasing emissions alone will not be sufficient to stop what is happening; the climate math is becoming clear that gigatonne-scale carbon removal is needed in the coming decades to avoid the worst effects of climate change. Given limited progress on rapidly cutting global emissions – or mitigation – over the past several decades, CDR is now recognised as a critical component for achieving a global net zero economy by 2050. Paired with simultaneous deployment of mitigation measures and other carbon management practices, CDR is a tool to address emissions from hard-to-abate sectors – like agriculture and transportation – and to eventually remove legacy CO2 emissions from the atmosphere.

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There are 3 methods for CDR, Nature-based, Technology-based, and Hybrid-based. Each method coming with its own benefits and drawbacks.

• Nature-based solutions require the conserving, restoring and better managing of ecosystems to remove CO2 from the atmosphere by sequestering it in plants, soils, and sediments. Long-term benefits of this solution beyond CO2 reduction is, cleaner air and water, economic benefits, and increased biodiversity.

  • Natural solutions can be accomplished at low cost—namely, afforestation and reforestation can cost under $20 per ton of CO2, and agricultural practices can cost under $100 per ton. In addition, it improves ecosystem health and harden natural areas to the impacts of climate change.

  • However, these natural solutions take time. Trees planted through reforestation or afforestation take years to grow, and the CO2 benefits will compound over time.  Reforestation can be geographically limited. The permanence of natural solutions can also be threatened by climate change, as disasters such as wildfires can release all the carbon stored in forests and soils in a very short amount of time.

• Technology-based solutions proposes the opportunity to provide permanent removal and artificial carbon sequestration of CO2 . However, as technology-based solutions in CDR is still in its infancy, it is still very costly.

  • The advantage of technology-based solution in comparison with nature-based solution is that the captured CO2 can be utilised in industrial forms, such as bio-fuel. Being technology-based also affords ease of monitoring.

  • Technology-based solution is costly, and it has yet to be fully explored and analysed. With such technology there could be a chance of potential leaking of stored CO2 or unforseen circumstance that has to be observed.

• Hybrid-based Solution is essentially combining Technology with Nature-based soutions. The primary hybrid CDR example is called bioenergy with carbon capture and storage (BECCS). BECCS is a process where trees or plants that sequester carbon are used to generate bioenergy where the resulting CO2 emissions captured are “negative” emissions.

  • The main concern would be the impact on food systems and land used due to the heavy reliance on BECCS for energy.

       Source: World Resource Institute (WRI), Centre for Strategic and International Studies (CSIS)