Carbon capture, a possible solution to a worldwide problem?
Introduction
In 2019, 36.44 billion tons of positive CO2 emissions were produced. To combat this, an equal amount of negative emissions must be created to achieve net-zero. What is net-zero? Net zero means positive emission will be at zero or negative emissions (carbon capture) will balance out positive emissions. This goal must be achieved by 2050 to avoid irreversible damage to our planet.
With various carbon capture methods (both natural and manmade), we can remove CO2 from our atmosphere and store it. Natural carbon capture methods were first used over 350-420 million years ago in the form of trees, and manmade methods were first used in the 1920s and popularized in the 1970s. This was because a gas processing facility Texas began using Enhanced Recovery (EOR), a process involving piping both natural and industrial CO2 to oil fields. Today, the revolutionary technology is used to capture and store carbon emitted by factories, remove carbon from the atmosphere, and transform carbon into environmentally friendly fuel.
Carbon Capture Methods
Trees naturally store carbon through a process called photosynthesis. They capture carbon, create sugar for energy, and release oxygen. If the trees are cut down the carbon is released into the atmosphere. There are three main types of manmade carbon capture methods.
Post-combustion involves removing the CO2 from the flue gas emitted by factories and power plants. Flue gas is the exhaust gas produced by facotries and power plants. First, the chemicals are passed through a column known as an absorber. The absorber will concentrate the chemicals with a liquid solvent such as ammonia. The concentrated chemicals are then passed through a stripper filled with very hot steam, separating the CO2.
Pre-combustion can separate the carbon from the hydrogen to be stored, and the hydrogen for hydrogen-cell vehicles. First gaseous fuel is passed through a gasifier and converted into a mixture of both hydrogen and CO2. The hydrogen is then removed with a pump to produce energy or power hydrogen-cell vehicles and only CO2 remains.
When a fuel source is burned, CO2 is produced and oxy-fuel can be used to capture it. The process involves burning a fuel source such as coal in an environment filled with pure oxygen. All the CO2 from the fuel source can then be captured.
There are currently 21 carbon capture operations running, five are currently being developed, and 40 are planned.
Carbon Engineering
Carbon Engineering’s unconventional approach to carbon capture, Direct Air Capture (DAC) technology, starts with an air contractor. What is an air contractor? It is a massive fan that pulls air through thin sheets of plastic. The sheets of plastic are flowing with potassium hydroxide. The CO2 gets caught in the solution but the rest flows through. The non-toxic solution is then purified and compressed into small pellets through a series of chemical processes. The pellets can then be stored and transformed into a gas for soda companies to carbonate sodas, or used for Carbon Engineering’s AIR TO FUEL’S technology to produce renewable fuel. First water is electrolyzed with the help of clean energy (solar PV) which separates the hydrogen and oxygen. The hydrogen and CO2 react with each other to produce a fuel compatible with existing petroleum infrastructures.
Advantages
- More affordable than post-combustion at $100/ton of CO2 instead of US$600.
- The location of DAC Plants are not as limited as post-combustion, because they do not need to be beside a factory. This allows the plants to be placed even on non-fertile land.
Carbon Storage
Biological
With the help of photosynthesis, the soil can store CO2. When plants absorb CO2 from our atmosphere, a portion is added to the soil when the plants decompose. The carbon is stored as Soil Organic Matter (SOM) which is a mixture consisting of carbon compounds and soil minerals containing carbon. The soil can hold carbon for millenniums or days to be released into our atmosphere. The time the carbon is stored depends on many variables including the climate, soil texture, and drainage.
Plants on the ocean floor capture around 25% of the CO2 we emit. The cooler oceans are, the more CO2 they can collect. This is because, the warmer the CO2 molecules are, the more they agitate. Consequently, as they move around they have a tendency to bump each other up tot he surface. Therefore, arctic oceans often have carbon lakes at the bottom. Because seaweed stores CO2 through photosynthesis, washed-up seaweed can be harvested as it still contains carbon. The carbon and seaweed can then be used for methane-reducing animal feed, biofuel, and soil amendment. By restoring coastal blue ecosystems (consisting of salt marshes, mangroves and seagrass), coastal sediments will be able to absorb roughly 300 million tons of CO2 annually by 2050.
Geological
The surfaces of rocks naturally absorb CO2. To accelerate this process, we use a process known as enhanced rock weathering (ERW) where rocks are ground up to have a larger surface area. The rock granulate is also spread on farmland to remove greenhouse gases formed due to agricultural activity. If China, India, and the United States were to put this into practice 1.44 gigatonnes of CO2 could be removed from our atmosphere.
Technological
Traditional carbon storage methods involve storing CO2 in previously depleted oil drilling sites or deep rock reservoirs beneath the sea. When the CO2 is deep underground, it is unlikely to leak. However, it is estimated to take around 1 thousand years to leak about 1% and 10 thousand years to leak majorly. An estimated 12 billion tonnes of CO2 should be stored to meet the EU’s 2050 net-zero ambition. CO2 could leak at the injection well, communicating oil wells and natural faults in the land.
Who is using carbon capture
Even Though DAC costs six times less than post-combustion at $100/ton of CO2. Capturing the 36.44 billion tons of CO2 produced in 2019 would cost US$3,644 billion. This means we cannot simply deploy DAC plants as that would not be cost-effective. Bill Gates has invested in Iceland-based startup Carbfix. Carbfix is storing CO2 by first capturing it from factory emissions or power plants burning fossil fuels. Then they dissolve the CO2 in water and the carbonated water is then stored in underground rock formations where it is naturally transformed into rock. Carbfix’s solution costs US$48.55/ton of CO2. That could theoretically cut our cost from US$3,644 billion down to US$1,769 billion.
“I have put more than $1 billion into approaches that I hope will help the world get to zero, including affordable and reliable clean energy and low-emissions cement, steel, meat and more,” Bill Gates
