Carbon is responsible for all forms of life on Earth, as it is the principal structural element of their molecules and DNA and it contributes to the regulation of the atmosphere’s temperature, creating ideal conditions for the development of life. It is also a principal element of the food chain and energy supply and is assumed as one of the foundations of human society and the global economy. Carbon is present in our atmosphere in the form of carbon dioxide, and it has its own cycle, the “Carbon Cycle”. It is so called because, although the total amount of carbon that exists on the planet remains unchanged, the Earth and its atmosphere form a closed loop, in which carbon travels, without interruption.
Atmosphere, rocks, oceans, and living organisms are where carbon is found. On the one hand, it is released in the air by natural sources, such as volcanos, forest fires, respiration and in vast extend by human processes, such as the extraction and burning of fossil fuels, agricultural activities, and deforestation. On the other hand, carbon returns to its origins only through natural processes, mainly photosynthesis, which is carried out by land plants, sea algae and cyanobacteria (microscopic organisms found in all types of water); all of them, absorb carbon dioxide, water, and sunlight energy to synthesize carbohydrates and the most vital by-product, oxygen. Since the beginning of the Industrial Revolution (approx. 1750), human activities interfere with carbon cycle’s equilibrium and have contributed substantially to climate change, by releasing CO2 and other greenhouse gases to the planet’s atmosphere, in such rate, that the natural processes cannot counterbalance it. As a result, the amount of carbon dioxide in the atmosphere is rapidly rising and it is already considerably greater than at any time in the last 800,000 years (NOAA, 2022).
Therefore, if carbon has its own cycle in Earths’ atmosphere and humans are disturbing this cycle by artificially adding more and more CO2 to it, then why not imitate carbon’s natural cycle and capture it before or after it is released in the atmosphere and then re-use it or return it to the source, which it came from? And that’s how the idea of Carbon Capture, Storage and Utilization was born.
Today, roughly 80% of all global energy sources are fossil fuel based. Thus, fossil fuels are likely to continue to play an important role in the short and medium term. As many countries benefit from fossil fuel energy and coal, oil and gas remain vital for their energy security and economic well-being. Therefore, although the most effective way to reduce CO2 emissions is to reduce fossil fuel consumption, carbon neutrality will require rapid deployment of carbon capture, usage, and storage (CCUS) technologies, to act as a steppingstone towards decarbonization, until next generation fuels, i.e., zero-carbon fuels, are commercially available, in the required amounts and at a reasonable cost.
Carbon capture can be very efficient and cost-effective when applied at large scale, land-based infrastructures, and facilities, which use fossil fuels for activities, such as energy production, and emit major carbon dioxide quantities. Extracting carbon dioxide from air is possible, although far more complicated and expensive since its concentration in the atmosphere is much lower compared to typical combustion flu gases. Broadly, four different technologies exist: post-combustion, pre-combustion, oxyfuel combustion and direct air capture.
The vessel has LNG as primary fuel and is equipped with 4- stroke engines capable of burning LNG mixed with a percentage of hydrogen, steam-methane reformer units, fuel cell units, LNG tanks and CO2 tanks. Part of the LNG is directed to the reformer, where hydrogen and CO2 is produced; hydrogen is used for powering the fuel cells and for mixing with LNG for the engines fuel. Accordingly, the CO2 stream, after the reformer, passes through a heat exchanger, where the cooler LNG stream cools it down and then the carbon dioxide is stored in the relevant tanks as a liquid.
Once the CO2 has been captured, can either be permanently stored or utilized for various processes. Different approaches have been conceived for permanent storage. One of them is the possibility of injecting the captured carbon dioxide back into geological formations and store it deep underground. Some options for storage are:
At the same time, captured carbon may as well replace the artificially created CO2 for the purpose of many industries such as food, oil, chemical and for other various commercial purposes and activities; the two possible directions, that carbon dioxide may follow after it’s captured.
Some significant examples of industries that will rely on carbon capture and utilization technologies are referred below: