Around half of the CO2 emitted since 1750 has been in the last 40 years. In fact, atmospheric carbon dioxide levels are the highest they’ve been in over 400 thousand years. Unless you have been living under a rock, we all know the implications this has on our environment. The world is heating up. And it’s heating up fast.
Thanks to the burning of fossil fuels, our natural atmospheric balance is being tainted by extremely large amounts of carbon, which would otherwise be stored in the geosphere (primarily rocks and sediment). In order to prevent impending climate chaos, experts are now looking not only to limit the release of new carbon, but also to collect previously released carbon from our atmosphere. This process is known as Carbon Sequestration, and it is the next big solution to our climate catastrophe.
Carbon Sequestration is the broad term used for the process by which carbon dioxide is extracted from the atmosphere and stored. This can be done through both natural and man-made means. In the natural world carbon sequestration occurs when carbon dioxide is removed by plants and trees from the atmosphere through photosynthesis. This carbon is then stored as biomass and soils. For example, the Amazon forest holds something like 90 billion tons of carbon alone . Looking at this figure, recent angst from scientists and climate campaigners over the record rate of fires burning in the Amazon Rainforest is not surprising. The sudden release of carbon into the atmosphere is set to have grave implications on our already warming earth.
Aside from on land, the ocean also has its own carbon extracting ecosystem. In fact, the ocean is home to over a quarter of the world’s carbon, which is collected in two primary ways. Various species such as phytoplankton and algae, which intake carbon through photosynthesis, as well as through simple chemistry: carbon dioxide dissolving in water. This reaction creates carbonic acid. Carbonic acid then releases hydrogen ions, which combine with carbonate in seawater to form bicarbonate, a form of carbon that doesn’t escape the ocean easily. It is worth noting that this process takes place at an extremely slow rate, measured in hundreds to thousands of years. However, once a carbon atom has dissolved it will stay there on average more than 500 years.
One hundred years ago, the earth’s very own built-in carbon filtration system would have been enough to equally balance the amount of carbon dioxide and other greenhouse gases in our atmosphere. Now, the post industrial natural world is struggling to keep up with human enterprise and our ecological system is suffering because of it. Since the Industrial Revolution, the oceans pH has become 30 per cent more acidic, a tell tale sign that it is being heavily impacted by the increase in carbon it is intaking. This type of change can have significant implications for marine life. For this reason, as the natural world can no longer keep pace, artificial ways to sequester carbon are growing in popularity.
So far, scientists have found two places to store CO2 on a large scale- underground and underwater. In fact, estimates project that the planet can store up to 10 trillion tons of carbon dioxide in this way. This would allow 100 years of human created emissions. In some countries, this process has already taken place. Sleipner, Gudrun and Snøhvit petroleum fields run by Norwegian Petroleum have been using CSS technology from as early as 1996 in order to contain the amount of emissions they are releasing into the atmosphere.
Underwater, scientists push the carbon 3,500 meters beneath the ocean’s surface, where it forms a slush like formation that will sink to the sea floor. Critics of this process voice concerns on what this could mean for marine life and the uncertainty of the safety of the process. E.g. Could the carbon eventually make it back into the environment and if so what impact would a huge bubble of released carbon have on global warming?
Other forms of carbon capture can also happen on land. Post Combustion at the effluent combustion site, namely, power plants is considered a promising approach to collect carbon dioxide before it even enters into the atmosphere. Technologies to achieve this are heavily researched due in large part to the intuitive nature of removing CO2 from the stack gas and the ease of retrofitting existing CO2 sources with these technologies. Notable among CO2 capture technologies are amine-based technologies. Amines are known for their reversible reactions with CO2, which make them ideally suited to separate CO2 from other flue gases which are a by-product of industrial manufacturing.
When analysing this sequestration method it should be noted that this type of carbon capture and storage systems also require fossil fuels for energy, initially releasing even more carbon into the atmosphere. Nonetheless, in return for the initial increase in usage of carbon, the United Nations’ Intergovernmental Panel on Climate Change estimates that a power plant fitted with self- contained CCS systems could successfully reduce net CO2 emissions by 85 to 95 per cent.
Post Combustion carbon collection also has the added benefit of opening up carbon as a marketable resource, which can then be used in less traditional methods, to produce other practical and in demand goods such as concrete, biofuels and even fish food.
Startups such as CO2Concrete based at the University of California, Los Angeles have made great headway in this field. CO2Concrete turns carbon dioxide emissions into products that can replace traditional concrete, with a much lower carbon footprint. The technology is based on the concept of CO2 mineralization — the conversion of gaseous CO2 into solid mineral carbonates e.g.CaCO3. In this way, CO2Concrete cuts down on the use of traditional cement, which the production of currently results in more than 8% of annual man-made carbon dioxide emissions, according to the Netherlands Environmental Assessment Agency.
Another route to tackle two birds with one stone is the advancement of carbon negative biofuels through algae cultivation as a method of carbon capture, tackling both future car emissions and industrial carbon production in one fell swoop. Helios-NRG, their objective is to produce 35 grams of algae per square meter of area per day and to capture more than 70 percent of carbon dioxide emissions from a concentrated source. The company has made significant progress toward those goals, using special photobioreactors and inventing new processes to achieve high algal growth and CO2 capture rates says Benjamin Lam, Helios-NRG senior research engineer. Once harvested, microalgae can be used in biofuel, feed for animals and nutraceuticals for humans.
As the world’s resources deplete and we look for new methods of creating sustainable food, using carbon as a source of animal feed is another innovative concept being looked into. Deep Branch, a start up founded in the University of Nottingham in the UK are using similar microbial processes to take CO2 directly from the industrial source and combine it with hydrogen, by bubbling through a liquid medium. According to Pete Rowe, CEO the process is “ just kind of like brewing beer but rather than producing ethanol we produce protein — and that protein is used as an animal feed.”
While it’s not the ideal situation, these startups give us a glimmer of hope that with a stroke of human innovation and brilliance, something good can come out of the exorbitant amount of carbon in our atmosphere.To keep global warming at 2 degrees, the internationally recognised level to prevent the most dangerous impacts, we will need negative emissions, not just carbon neutrality. We have already released too much carbon into the atmosphere that just reducing our carbon emissions is not going to be enough. Therefore, offsetting current carbon stored is essential if we want to maintain our current ecosystem. Whether it’s through natural means, small startups with big ideas or the multinational oil industry.
Sally Benson, executive director of the Global Climate and Energy Project (GCEP) and professor of energy resources engineering, had this to say on carbon sequestration:
‘’The notion is that the sooner we wean ourselves off fossil fuels, the sooner we’ll be able to tackle the climate problem,’’ said ‘’But the idea that we can take fossil fuels out of the mix very quickly is unrealistic. We’re reliant on fossil fuels, and a good pathway is to find ways to use them that don’t create a problem for the climate.’’
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Dutcher, Bryce & Fan, Maohong & Russell, Armistead. (2015). Amine-Based CO 2 Capture Technology Development from the Beginning of 2013 — A Review. ACS applied materials & interfaces. 7. 10.1021/am507465f.
DOE, NETL, “Carbon Capture Program,” fact sheet, June 2016, at https://www.netl.doe.gov/File%20Library/ Research/Coal/carbon%20capture/Carbon-Capture-Factsheet-June-2016.pdf.
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