Carbon dioxide graveyard… between solutions and fears

Carbon dioxide cemetery… solutions and concerns

The goal of controlling climate change has become inevitable in light of the worsening global warming – and the related phenomena and natural disasters – to the point of holding periodic international conferences to discuss the situation, and how can these negative effects be reduced? Perhaps the most prominent of these summits is the “Conference of the Parties (COP),” which was recently held in Sharm El-Sheikh.
These major challenges – posed by climate change – have created a parallel climate of creativity, thinking and scientific research. To find innovative solutions to address the problem of Greenhouse Gases (GHGs), the most famous of which is carbon dioxide. Perhaps the most prominent of these solutions that have recently emerged on the scene are carbon capture and storage technologies, or what is known for short as “CCS.” In this article, we will shed light on the nature of this technologytechnology, the most prominent concerns related to it, and how it can contribute to reducing the phenomenon of global warming.

What is the purpose of this technology?

This technology works to capture and separate carbon dioxide gas from different generation sources, and then collect and transport it. Until it is buried in the ground to reduce the load and carbon footprint in various activities, thus reducing greenhouse gas emissions.
This technology is not new to scientists, as methods for capturing carbon dioxide began to appear in the late last century. Despite this, the biggest barrier to the development of this technology and increasing reliance on it is how to deal with the captured gas, how to store it, and where are the stores that will contain it? From this standpoint, it has been proposed to inject carbon dioxide into the sedimentary layers of the earth – or into any type of layer that has the appropriate specifications – to be a graveyard for this gas.
This technology has many purposes, perhaps the most important of which is achieving relative stability in climate change, and this is by contributing to supporting the achievement of the goal of the Paris Agreement, which is to limit global warming to less than two degrees above pre-industrial revolution rates, in addition to achieving net zero emissions in many energy-intensive industries, such as cement and energy production plants.
The importance of this technology also lies in reducing the carbon footprint of industries whose operations produce large amounts of carbon, and not just from burning fuel. It is also a quick solution to the problem of Greenhouse Gases (GHGs) without the need for radical changes in infrastructure, or the need for a pivotal change in energy strategies in various industries, as this technology can capture carbon dioxide gas directly from pollution sources, before it sneaks into the atmosphere.

How does CCS technology work?

The nature of the work of carbon dioxide capture and storage technology can be divided into four main stages, which we list for you as follows:

First: Capturing carbon dioxide gas

The gas capture process takes place either in the pre-combustion stage – as happens in the fertilizer industry – where carbon monoxide resulting from production processes reacts with water vapor to produce carbon dioxide, and the gas emitted can be captured during the manufacturing process, but the matter has its costs and disadvantages. Or by capturing carbon dioxide after combustion – which is the most common – where the gas is captured directly from chimney emissions in power plants or in cement or iron and steel factories. There are also ways to capture carbon dioxide from the air.
The capture process is carried out by passing the chimney exhaust through an amino solvent to absorb carbon dioxide gas, or passing it through a caustic substance such as sodium hydroxide, which reacts with carbon dioxide to precipitate sodium carbonate.

Second: Separation process

After the exhaust gas is captured, it is physically separated by pressure or heat. Sodium carbonate, for example, is heated to produce a stream of highly pure carbon dioxide, and sodium hydroxide can be recycled again in the process.
The separation process can also be completed in other ways, such as using some membranes with a special morphology, such as palladium membranes and membranes made of polymer. In this approach, the porosity and permeability of those membranes to different gases is relied upon. After completing the process of separating carbon dioxide gas, it moves to the stage of compression or liquefaction of the gas. So that it is easy to transport and store.

Third: The transportation process

Once carbon dioxide is captured and separated, it is subjected to very high pressure, to transform it into a liquid-like state, where the liquid occupies less space than gas, making it easier to transport in large quantities to a suitable site for geological storage. Transportation is usually done by pipelines, which are considered the cheapest method of transportation. It is also possible to transport by trucks – with less amounts of carbon dioxide – while some countries resort to transportation using ships, due to the final burial site of carbon dioxide, which may sometimes be at the bottom of the ocean.

Fourth: Geological storage and injection into the ground

It is common knowledge in geological fields that there are some exploratory wells that end up empty, without any trace of fossil fuels in the drilling area, and even productive wells run out of black gold after a while, and become empty awaiting final backfilling. In order to optimally exploit these expenses, carbon dioxide gas can be injected into the ground at great depths in suitable geological formations using these wells.
Carbon dioxide can be stored underground as a supercritical fluid (Supercritical CO2), and by this we mean that carbon dioxide can exist in a state between the liquid and gaseous states; It has properties that make it viscous like a liquid and dense like a gas, which makes the required storage volume much less than if it were the gas at its standard conditions. Given that Earth’s geology is characterized by a decrease in pressure and an increase in temperature – with increasing depth in the Earth’s crust – carbon dioxide injected into the depths can remain in the supercritical state that we referred to.
Carbon dioxide can also be stored underground by the sequestration method. This method involves injecting carbon dioxide into impermeable salt domes, or into basalt formations, using hydraulic fracturing technology, where these rocks are penetrated in a manner similar to gunshot wounds. These formations crack from the inside in a certain geometric shape, and carbon dioxide is injected into these formed cracks, and then the final end of those pores ends up being blocked with an impermeable concrete layer.

Concerns about relying on this technology

Although this technology is a promising solution to confront climate change immediately, there are many concerns associated with it, perhaps the most prominent of which is the leakage of carbon dioxide to the surface again, which is disastrous! The operations of transporting the captured gas will also carry many challenges, and will require more preventive measures and caution during transportation or storage.
So far, there is no evidence that storing carbon dioxide underground will completely eliminate the global warming crisis, and the Earth’s layers – in the long term – will be saturated with huge quantities of the gas. Therefore, this solution may not always be available, in addition to the fact that the geographical distribution between emission sources and injection sites may constitute another obstacle.
Injecting carbon dioxide into the Earth’s layers may lead to an increase in geothermal energy, which will constitute a danger no less than the danger of global warming. Also, when reliance on this technology increases, it may act like an anesthetic injection, as reliance on fossil fuels will continue – given the possibility of containing their emissions – instead of accelerating the transition to cheaper and cleaner renewable energy. This technology – in the eyes of many – is a temporary and emergency solution, and cannot be relied upon for a long time. How much carbon stock can the Earth bear, and for how long?!
Another thing we must not lose sight of is that carbon dioxide capture and storage may also threaten wetlands and groundwater sources. These underground gatherings constitute potential pollution hotspots in all the ecosystems around them.
Despite all these fears, the supporters of this technology explain that with continued development, this technology will become safe to use, because it is a proven method that has been working safely for more than 45 years, and all the components of the technology, including carbon capture and storage, are technologies that have received extensive areas of research and study, and have been used for decades on a wide commercial scale.
In conclusion, we have tried in this presentation to outline the broad outlines of CCS technology, between the quick solutions it can provide and the fears of relying on it too much. However, the matter requires more research and study for each case, taking into account those economic aspects and long-term climate strategies. Perhaps we will devote more space to this topic in the upcoming issues.