It is increasingly likely that we will not reach the 2030 targets for reducing CO₂ emissions, nor those set for 2050. As a result, many people are now arguing that we should instead focus our efforts on adapting to climate change, rather than obsessively trying to get it under control.
However, the Intergovernmental Panel on Climate Change (IPCC) has singled out an interesting, though complex, way to improve mitigation numbers: capturing, absorbing or removing CO₂ and storing it. But what exactly does this technique consist of, and is it feasible on a large scale?
The history of carbon capture
CO₂ was first stored, though unintentionally, underground in 1972 in Texas, USA, in order to “pump” oil and encourage its extraction, a technique that is still often used today.
A similar but much more advanced system led to the first major full-scale project of this sort in 1996: the Sleipner gas field in Norway. This facility aimed to reduce the impact of emissions by storing CO₂ extracted from natural gas at the bottom of the North Sea.
This technology is part of what is known as carbon capture and storage (CCS). At the time of the 1997 Kyoto Protocol it was already being proposed as a way to reduce emissions in localised sources – in the chimneys of coal or gas-fired power plants, for instance. Since then, many companies and researchers have been developing carbon capture processes and looking for geological storage locations for CO₂.
Spain, for example, was home to one of the world’s largest CCS programmes until the arrival of the 2008 financial crisis. The initiative was somewhat scandalously halted a few years ago, though several experts are now trying to revive it.
‘Negative emissions’: from carbon capture to removal
CCS technology has many detractors, with reasons ranging from its high costs to its alleged complicity in maintaining the use of fossil fuels. It therefore seems that this technology’s future is linked to industries that are very difficult to decarbonise, such as the cement industry, where even production with “clean” energy generates large amounts of CO₂.
In addition, a new concept called carbon dioxide removal (CDR) has emerged on a global level in the last few years. It is based on the simple principle that, when it comes to avoiding emissions, a draw is better than a loss, but a win is better than a draw. If CCS is a draw, then CDR technology can provide a win by achieving “negative emissions”.
The two most common variants of CDR today build on CCS technology. BECCS (bioenergy with carbon capture and storage), captures carbon after burning biomass in thermal power plants, while DACCS (direct air capture and carbon storage), captures CO₂ directly from the atmosphere.
Both technologies are currently under development and so far their potential seems modest (0.1 % of annual emissions). In parallel, finding a use for CO₂ instead of burying it is also being considered for various applications, such as manufacturing soft drinks.
Nature lends a hand
Within CDR, a number of nature-inspired possibilities emerge. The most traditional is reforestation, but other options such as the restoration and enhancement of wetlands and peatlands, as well as the enormous potential of soil as a carbon sink, also stand out.
Significant carbon sequestration figures are already attributed to all of them, but they are somewhat uncertain for a number of reasons, including climate change itself, the possible generation of methane emissions, potential instability of carbon capture, or the interaction between vegetation and soil carbon.
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Sometimes complications arise in procedures as simple as preparing soil for tree planting (by ploughing or removing existing vegetation). This can release some of the CO₂ stored in the soil, especially in carbon-rich ecosystems such as grasslands.
Other “natural” CDR solutions include the use of charcoal known as biochar, CO₂-consuming micro-organisms, crushed rocks rich in magnesium and calcium, or even the design of artificial soils from waste.
All these options are being researched and trialled by initiatives such as the C-SINK project, of which the University of Oviedo is a member. These alternatives are already regulated at the European level.
A complex problem demands complex solutions
Both historical experience and our current situation demonstrate that energy transitions are slow, uneven and incremental processes. Replacing the base of the production and consumption system represents a huge challenge, full of uncertainties and accompanied by a growing, widespread fear that we are not reducing emissions in time.
Carbon capture and removal could be an essential component in achieving global temperature moderation goals. However, its currently limited deployment, and the inherent unknowns of lengthy research and development processes, raise many doubts.
Nevertheless, uncertainty should not deter us from pursuing these solutions. As global emissions spiral out of control, it is imperative that we reduce them immediately, and at the same time capture as much CO₂ as possible in all sectors, everywhere, at the same time.
This article was written in collaboration with the Cátedra Cambio Climático de la Universidad de Oviedo.
