Carbon reduction: In the fight against climate change – is it enough?
The climate continued to make headlines in 2024 – for all the wrong reasons. Last year was the warmest since records began in 1850, with global surface temperatures averaging 1.6°C above pre-industrial levels. This surpassed the threshold of 1.5°C set in the 2015 Paris Agreement for the first time. Ocean warming in particular has been unprecedented, with 2024 beating records set only the year before.
Although emissions reduction remains the most critical first step in addressing global warming, it is unlikely to be sufficient on its own. The Intergovernmental Panel on Climate Change (IPCC) consider carbon removal to be essential to meeting global and national global emissions and global warming targets – and it plays a role in all of their modelling scenarios that limit global warming to 2°C or lower by 2100.
What is Carbon Dioxide Removal (CDR)?
Simply defined, CDR is technologies, practices and approaches that remove CO₂ from the atmosphere and durably store it away. It only refers to human actions that intentionally achieve this aim – natural CO₂ removal, such as the growth of natural woodland, would not be considered CDR.
There are many different CDR methods which can be broadly grouped into either nature-based solutions or technological solutions.
Nature-based solutions:
Afforestation / Reforestation – planting trees or restoring forest captures CO2 from the atmosphere and stores it in biomass or the soil.
Agroforestry – combining trees with crops and livestock on the same land can maintain agricultural productivity and improve soil health whilst also increasing carbon storage.
Wetland restoration – marshes and peatlands act as carbon sinks, storing carbon in sediments and vegetation for long periods of time.
Biochar – pyrolysis offers the opportunity to convert waste organic material into a stable form of carbon that can then be spread on the land, locking it away for the long term. Biochar offers the co-benefits of improving soil health and producing bio-oil and syngas as by-products that can make it an energy-positive process.
Soil carbon sequestration – healthy soils can store large amounts of carbon, and sustainable agricultural practices such as over cropping and rotational grazing can improve soil health to increase the amounts of carbon stored there.
Technological solutions:
Direct Air Capture (DAC) – the extraction of CO₂ from the atmosphere and its conversion into a concentrated form that can then be stored in geological formations (such as aquifers or disused oil and gas fields) or used to produce materials such as concrete.
Bioenergy with Carbon Capture and Storage (BECCS) – biomass such as crops or trees is used for energy production, but the resultant CO₂ emissions are then captured before they can enter the atmosphere and placed into long-term storage.
Ocean Fertilization – stimulating the growth of phytoplankton by adding nutrients to the ocean, which absorb CO₂ during their lifetimes, but then sink to the ocean floor when they die, sequestering the carbon for extended periods.
Enhanced weathering – applying silicate minerals to the land or ocean to accelerate natural chemical reactions that absorb CO₂ from the atmosphere or water and convert it to stable solid carbonates.
Nature-based approaches are often lower cost and require less technical expertise, making them easier to implement at a local level and become widely adopted at relatively little expense. Many nature-based initiatives also offer co-benefits such as improved soil quality, habitat restoration, enhanced biodiversity and in the case of wetland restoration, increasing resilience to extreme weather events such as flooding and storm surges.
The downside is that these options have more limited carbon removal potential than large-scale technological options. There is also some uncertainty around the long-term stability of carbon storage in natural systems. Forests can be threated by fire, disease and land-use changes, all of which can release the captured carbon back to the atmosphere, and carbon captured in soil may be vulnerable to changing management practices or even global warming itself.
Technological solutions have a much higher carbon removal potential. They can offer the security of storing carbon deep underground, or in the case of enhanced weathering – in the oceans as solid bicarbonate, where it will not be released back to the atmosphere for thousands or even millions of years. They can also be scaled rapidly, however this requires significant financial investment, not only in the CDR technology itself, but also in the infrastructure required to store and transport the CO₂.
Why is carbon removal important?
Quicker impact – even scenarios that consider the most aggressive cuts in emissions do not reduce atmospheric CO₂ quickly enough to prevent dangerous levels of warming. Adding CDR to the mix can help limit warming more quickly
Tackles hard-to-abate sectors – certain sectors are more difficult to decarbonise than others. Heavy industrial processes, aviation and shipping pose particular challenges as they are energy-intensive and difficult to electrify. CDR is a way of tackling emissions from these hard-to-abate sectors.
Offers the opportunity for reversal in atmospheric CO₂ – over the longer term, CDR offers the opportunity to reverse the damage that has already been done. By removing the excess CO₂ that is already in the atmosphere and potentially reducing the warming effects, carbon removal can give long-term climate stability.
Climate Targets Require Negative Emissions – to meet global climate goals, such as keeping warming below 2°C, we need to remove CO₂ from the atmosphere in addition to reducing ongoing emissions.
Whilst CDR is not a substitute for deep emissions reductions, it is an essential component in the overall mix of mitigation methods and should be viewed as a complementary solution. CDR can play an important role in reducing net greenhouse gas emissions in the near term and help achieve and sustain net negative emissions in the longer term. Mitigation scenarios assume much larger-scale CDR deployment than what is currently taking place, which will require rapid and sustained investment in CDR initiatives. The potential for CDR to make a real difference is clear – let’s take on the challenge!
