Negative CO2: Bio-CCS is non-optional, but not a silver bullet
CO2 emissions must be reduced drastically now, not just from energy, but also from transport, industry and agriculture. The requirement for technologies that remove CO2 from the atmosphere at some…
Now, more than ever, we need to cut the amount of CO2 we emit in order to prevent a further escalation of climate change. To reach the goals of the Paris Agreement, the deployment of renewable energy sources, energy efficiency, electric mobility, and new industrial processes must be accelerated.
As a global community, we have been very slow in implementing such measures, and emissions have risen year on year for decades, at best they will likely flatten. A slow motion climate car crash is currently the most likely outcome as the concrete intended actions of the parties of the Paris Agreement are not at all ambitious enough. This is why negative emissions, along with drastic emissions cuts, are required to reach the 2°C goal.
CO2 emissions must be reduced drastically now, not just from energy, but also from transport, industry and agriculture. The requirement for technologies that remove CO2 from the atmosphere at some scale is non-optional, but negative emissions will never be a safety net for reduced or delayed climate action now.
Negative emissions, although a necessary technology that will provide us with the possibility to avoid a rise of global temperature that will cause climatic disasters, are limited by geography, land use, and deployment time. Some of the primary technologies that remove CO2 from the atmosphere are: air capture in combination with CCS, afforestation, and Bio-CCS.
The technology that naturally comes to mind when discussing the removal of CO2 from the atmosphere is the direct capture thereof from the ambient air. This technology is referred to as “air capture”. Although this option sounds appealing, there are technical, financial, and structural limitations.
Air capture can achieve “negative CO2 emissions” on the condition that the captured CO2 is stored permanently, requiring CO2 transport and geological storage infrastructure. However, the process of capturing CO2 from the air is highly energy demanding. In an age where valuable low carbon energy is already in short supply, there are more benefits to the direct usage thereof to decarbonise, for instance, the steel production, transport, and home heating.
The high-energy demand, the technical challenges, and the lack of additional benefits make air capture a less desirable technology for the removal of atmospheric CO2. A more advantageous measure is afforestation.
Planting trees where there were none before, afforestation, and planting trees where forests previously stood, reforestation, have the potential to lower the level of CO2 in the air, while providing additional environmental benefits to the ecosystem. If a substantial area of trees is planted globally, CO2 from the ambient air is locked in the biological material of the trees during its life cycle, and the overall level of CO2 in the atmosphere is reduced. If the trees are planted in large enough area, and are protected from further usage, such as logging or burning to create agricultural opportunities, this can be considered a carbon sink or carbon storage.
Not only does afforestation have a positive effect on the level of CO2 in the atmosphere, larger forests also have a positive impact on other aspects of the environment. Examples of such benefits are the prevention of erosion of the soil, and the advantages such forests provide to the biodiversity in such areas.
There might, however, be resistance to the planting of large forests from those, who are competing for the same land areas for the purposes of agriculture or other economic activities. Such forests might thus be threatened, making this method a potentially more insecure climate measure.
While the impacts of afforestation and reforestation on the climate and on the environment are positive, this method of achieving negative emissions is limited. Afforestation would have to be supplemented with other, more large-scale and effective methods to remove CO2 from the atmosphere. The combination of the usage of truly sustainable biomass, which does not compete with afforestation, with CCS would provide these desperately needed large-scale negative emissions.
As is the case with afforestation, other types of biomass also absorb CO2 from the atmosphere. Examples of advanced, truly sustainable biomass, which can be used to produce decarbonisation pathways for difficult sectors such as the aviation sector, include those based on municipal sewage, agricultural waste or algae produced in sea water.
The production of these types of biomass does not present competition with regards to land use or food production, yet it has a minimal effect on the environment. When the CO2, which is produced during the production of biofuel with this biomass, is captured and stored permanently in geological formations, the CO2 is removed from the atmosphere. A major advantage of Bio-CCS is that it is the only carbon negative method that can both provide energy and at the same time remove CO2 from the atmosphere.
Limits to Bio-CCS
The emission of CO2 must be drastically curtailed without delay. Parallel to significant cuts in the emission of CO2, which can be achieved through measures like the uptake of renewable energy, improved energy efficiency, and CCS, it is essential to invest in the development and deployment of carbon negative solutions. Of these carbon negative solutions, Bio-CCS has the potential to be deployed on the biggest scale with advantages in energy supply and decarbonisation of other sectors.
There are limits to the amount of negative emissions we can achieve. Carbon negative technologies can be the key to curbing out of control climate change, but there is an upper limit of atmospheric CO2 beyond which even carbon negative solutions cannot rescue us.
For these reasons, it is of immense importance that we implement all deep decarbonisation technologies such as industrial CCS now, reducing our reliance on carbon negative solutions in the future. We must not delay the development of technologies enabling the full-scale deployment of Bio-CCS. Any such delay will also rob future generations of the tools to clean the atmosphere, which past generations have polluted.