There is broad consensus within the scientific community that human-generated greenhouse gas (GHG) emissions are causing global warming. If we can emit them, might we capture and remove them? The answer is yes, though perhaps not as easily. But capture them we can, and we are. The real questions are, can we do it fast enough and big enough to make a difference, and can we afford it, in terms of dollars and energy?
Carbon capture refers to the process of capturing carbon dioxide (CO2) emissions from various sources, such as power plants and industrial facilities, and storing or utilizing them to prevent their release into the atmosphere. There are different methods of capture, including post-combustion capture and pre-combustion capture. Each method involves separating CO2 from other flue gases or exhaust streams.
VIDEO & TRANSCRIPT OF KEY QUESTIONS
What is Carbon Capture?
Carbon capture is one of the methodologies that is being adopted and will be adopted to control levels of carbon dioxide in the atmosphere. Other methods are to use renewable electricity, use low carbon electricity such as nuclear. But ultimately we need to either prevent carbon dioxide getting into the atmosphere by capturing it a release source or we need to absorb carbon dioxide from the atmosphere in some way.
What's the current situation?
We release about 50 gigatons of greenhouse gases per year, around about 70% of that's carbon dioxide. About 20% is methane, five 8% nitrous oxide. And then there's some flora chemicals that are of special interest to our own industry. Today, the carbon capture methodologies are all about capturing carbon dioxide. We're currently capturing around about 70 million tonnes of carbon dioxide per year.
The IEA would like us by 2030 to be capturing 800 million tonnes of carbon dioxide. The projected plans to date are only around about 200 million metric tons, so we're quite some way off. The ice targets. The main sources of carbon dioxide from an industrial viewpoint are energy generation, from fossil fuels that outstrips just about everything else. Then if you start looking at other industrial sources, the iron and steel industry generates about two and a half gigatons per year.
Concrete and cement industry generates around about 2.5 gigatons as well and then the aluminum industry also generates around about 2.5 gigatons per year. The key steps in carbon capture. First, we need to decide where the capture takes place. Is it pre combustion before you burn the fuel? Is it post combustion after you burn the fuel?
There's then a separation process where you need to separate the carbon dioxide from other gases. And once you've separated the carbon dioxide out, then there's some form of transport activity either by ship or by pipeline or by truck.
What is Pre-Combustion and Post-Combustion?
The combustion part of the process is very important. Pre combustion, It's actually one of the oldest, oldest carbon capture technologies where carbon dioxide is removed from some form of gas. Historically, that would have been coal gas, but more recently from natural gas.
For post combustion technologies we now have some form of fuel, so let's imagine we've got natural gas, the natural gas is mixed with air for burning, and then you need to separate the carbon dioxide out from the nitrogen and residual oxygen. That's quite a low concentration and the lower the concentration, the more energy, the more complicated, the more capital intensive the separation processes become.
How do we separate Carbon?
There are various forms of separation technology once you have created your carbon dioxide source. One of the methodologies involves passing through some form of wet scrubber that absorbs the carbon dioxide, another form is solid absorbers, membranes that can be used as well as cryo processes.
Can you explain the term CCUS?
CCU is carbon capture usage or storage.
Let's go with the usage, carbon dioxide can be used as a chemical feedstock for making sodium carbonate otherwise known as baking soda, it can be used for making vinegar, it can be used for making ethanol, it can actually be used for making aviation fuel.
The storage mechanisms, routinely we're going to be looking at ways of tying up the carbon dioxide for a long time, there's no point in putting it back into the environment where it then gets released quickly, that would be a complete waste of energy.
Storage mechanisms would usually include placing it into some form of geological structure, salt domes are classic ones because they're not very permeable. We would then use it as a different source of what's called a propellant to remove residual natural gas and oil from nearly exhausted oil and gas wells. You can also use it for getting methane out of coal mines.
The idea of all through these particular applications is that the carbon dioxide is basically placed into a structure where it's going to stay.
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To read more on this subject, download Chris Jones’ article ‘Carbon Capture, Utilization, and Storage (CCUS) Technologies May Play a Larger Role in Fighting Global Warming ’, below.