Introduction
A long time ago, we were gifted a pristine planet, a planet which was habitable and where all life
forms could co-exist. The presence of greenhouse gases was proportionate enough to maintain
temperatures that ensured emergence of life forms as we know them, including humans. Earth’s
climate has changed throughout history. About 12,000 years ago marked the end of the ice age and
the beginning of the modern climate era. We had a habitable atmosphere and planet. However,
during the 18th century, societies started getting more urban and industrialized which led to the
beginning of the Industrial Revolution. Anthropogenic activities led to emissions of greenhouse
gases at rates never seen before. Anthropogenic emissions mean emissions due to human activities.
As the proportion of carbon dioxide rises in the atmosphere, it traps more heat resulting in
increased temperatures and warming of the planet.
The concentration of Carbon Dioxide in the atmosphere is measured as molecules of CO2 per
million molecules. Before industrialization, there were 280 parts per million. We began burning
fossil fuels, chopping off trees and emitting more carbon and other greenhouse gases in the
atmosphere. The inhabitants became the conquerors who were consuming beyond their needs.
Because of this phenomenon, in 1960 itself, we had reached 315 parts per million CO2 molecules
and as per the recent data in 2019, we are at 410 parts per million.
We are already experiencing frequent cases of extreme weather events all over the world. Weather
events are becoming unpredictable. From wildfires in California and Australia, storms in UK to
flooding in China and Germany. This results in loss of life on earth, imbalances in growth of crops
for food, infrastructure collapse, etc.
It is evident that we need to reduce our emissions and get to net zero. The coming decades need to
be spent in building technologies and systems that will help reverse the existing impacts and can
create a sustainable planet for the coming generations of humans and protection of all life forms.
Extensive discussions are taking place throughout the world in all forms of media on the subjects
of global warming and climate change. The world is largely becoming aware of climate change
and its negative impacts. People are understanding the reasons for global warming.
The purpose of this paper is to discuss the concept of Carbon Emissions and other connected terms
namely Carbon Sinks, Carbon Capture and Sequestration and Carbon Capture and Utilization. It
will consist of providing the meaning and background of each of the terms, statistical data and the
worldwide efforts that are being made in each sector.
Carbon Sinks
Carbon sinks are natural (Oceans and Forests) and artificial (certain technologies and chemicals)
deposits or reservoirs that absorb and capture carbon dioxide (CO2) from the atmosphere and
reduce its concentration in the air. They absorb more carbon dioxide than they release. Oceans,
forests and soils are the main natural carbon sinks.
1) Oceans – Oceans are the main carbon sinks as they are capable of absorbing about 50%
of the carbon emitted into the atmosphere. In particular, plankton, corals, fish, algae
and other photosynthetic bacteria are responsible for this capture. While the ability of
the ocean to capture and store carbon has helped slow the accumulation of atmospheric
CO2 – and hence the pace of global warming, it comes at a cost. Increasing CO2 in the
ocean alters the chemistry of seawater- an effect known as ocean acidification, which
has negative impacts on marine life.
2) Forests – As plants and trees grow, they need carbon dioxide, water and sunlight for photosynthesis. During this process, the leaves can absorb carbon dioxide from the atmosphere. This carbon then becomes part of the plant, which maintains it and releases oxygen. In this way large quantities of carbon dioxide are taken in by forests and they act as natural carbon sinks. According to a report published in January 2021, forests absorb twice as much as carbon as they release each year, absorbing a net 7.6 billion metric ton of carbon dioxide annually. The most critical of all forest types are primary forests. These are forests that have achieved great age with mature canopy trees and complex understories. As the world’s largest and best known tropical rainforest, the Amazon accounts for just over a third of tree covers across the tropics and is one of the most important carbon sinks in the world, their role is more important than ever especially as the world’s carbon emissions exponentially increase over the last few decades. According to the World Resources Institute (WRI), 30% of the world’s forestland has been cleared completely. Another 20% has been degraded. One of the dominant storylines of nineteenth and twentieth centuries was the vast loss of forestland. Its restoration and re-wilding could be the twenty-first century story.
3) Soil – The world’s soils hold a significant amount of carbon. Healthy soils with more organic matter can store carbon while providing agricultural and environmental benefits. Soil carbon storage directly benefits farmers by improving soil fertility, reducing erosion and increasing resilience to droughts and floods. Methods that significantly enhance carbon storage in soil include no-till farming, reside mulching, cover cropping and crop rotation, all of which are more widely used in organic farming than in conventional farming. Soil carbon is present in two forms: inorganic and organic.
Forests soils constitute a large pool of carbon. Anthropogenic activities such as deforestation causes release of carbon from this pool, which may significantly increase the concentration of greenhouse gases in the atmosphere. The balance of soil carbon is held in peat and wetlands. The peatland ecosystem covers 3.7 million square kilometers and is the most efficient carbon sink on the planet. Peatlands are another example of carbon storehouses. Though these unique ecosystems cover just 3% of the earth’s land area, they are second only to oceans in the amount of carbon they store – twice that held by world’s forests. Wetlands store approximately 44.6 million tonnes of carbon per year globally. The ability of many tidal wetlands to store carbon and minimize methane flux from tidal sediments has led to sponsorship of blue carbon initiatives that are intended to enhance those processes.
4) Artificial carbon sinks – In addition to natural carbon sinks, technological advances have helped produce artificial techniques that extract carbon from the atmosphere. For instance, upon harvesting, wood (carbon – rich material) is immediately burned or otherwise used as fuel, returning its carbon to the atmosphere, or it can be incorporated into construction or a range of other durable products, thus sequestering its carbon over years or even centuries.
Projects
| Indonesia | In Sumatra, Indonesia, mangrove forests are a key part of its ecosystem, as they absorb vast amounts of carbon. But mangroves are being felled to make way for shrimp farms and palm oil plantations, or for cities, turning pristine carbon sinks into emitters. Reforest’Action’s team is fighting back. First, local teams collect propagules – Long tubers that naturally fall from adult mangroves, transplanting them to nurseries where they are watered and protected from pests. After a few weeks hundreds of local people help to replant them, rebuilding their local ecosystem while generating an income. During the 2020-2021 planting season, the project planted 500,000 trees. |
| Netherlands | The Netherlands has a clever scheme to create new forests fast. Its relocating unwanted saplings from existing forests to be replanted where they are needed. This initiative is called Meer Bomen Nu. It means More Trees Now in English. The Netherlands plans to create 37,000 hectares of new forests by 2030. Every year trees produce hundreds of offsprings, the vast majority will not survive into maturity. This project harvests indigenous saplings that would otherwise die or be cut down. It gives them away for free to be replanted among diverse mixture of species. In 2020, the campaign gave away 250,000 saplings, 80% of them survived. |
Carbon capture and Sequestration
Carbon capture and storage (CCS) refers to a collection of technologies that can combat climate change by reducing carbon dioxide (CO2) emissions.
The idea behind CCS is to capture the CO2 generated by burning fossil fuels before it is released to the atmosphere. The question is then: What to do with the captured CO2? Most current CCS strategies call for the injection of CO2 deep underground. This forms a “closed loop”, where the carbon is extracted from the Earth as fossil fuels and then is returned to the Earth as CO2. Today, CCS projects are storing over 30 million tons of CO2 every year, which is about the amount of CO2 emissions created by 6.5 million passenger cars.
Capturing CO2 is most cost-effective at point sources, such as large carbon-based energy facilities, industries with major CO2 emissions (eg. cement production, steelmaking), natural gas processing, synthetic fuel plants and fossil fuel-based hydrogen production plants. Extracting CO2 from air is possible, although the lower concentration of CO2 in air compared to combustion sources complicates the engineering and makes the process therefore more expensive.
According to the IPCC, carbon capture will need to be part of any climate solution that keeps warming under 1.5 °C. Even the most optimistic projections predict that expected carbon dioxide emissions will lead to over 2 °C of warming. Some carbon capture will be necessary to stop climate change.
Now the more difficult question — how do we remove carbon dioxide from the atmosphere? More specifically, how do we sequester it in a manner that is scalable, cheap, and safe?
Reforestation
One of the most attractive features of carbon capture from the atmosphere is flexibility.
Do not cut the trees. Let them grow to absorb CO2. Plants can be built anywhere and can offset CO2 emissions from across the world.
Direct Air Capture
First, a large fan assembly sucks up massive amounts of air. This air passes through a specialized set of filters that captures CO2 molecules. Once these filters reach capacity, they can be removed and placed in a specialized location. The filter is then heated, releasing the CO2 bound to the filters, leaving a highly concentrated CO2 gas. The filters can then be reused.
Next, the carbon dioxide is mixed with compounds like potassium hydroxide to produce a carbonate salt. These carbonate salts allow for the easy transport of carbon dioxide, which can then be rereleased by further processing. Ultimately, carbon dioxide is stored underground, where it will form into rock over a few years. Projects
| China | As of 2019 coal accounted for around 60% of China’s energy production. The majority of CO2 emissions come from coal-fired power plants or coal-to-chemical processes (eg. the production of synthetic ammonia, methanol, fertilizer, natural gas, and CTLs). According to the IEA, around 385 out of China’s 900 gigawatts of coal-fired power capacity are near locations suitable for CCS. As of 2017 three CCS facilities are operational or in late stages of construction, drawing CO2 from natural gas processing or petrochemical production. China’s largest carbon capture and storage plant at Guohua Jinjie coal power station was completed in January 2021. The project is expected to prevent 150,000 tons of carbon dioxide emission annually at a 90% capture rate. |
| UK | A trial of bio-energy with carbon capture and storage (BECCS) at a wood-fired unit in Drax power station in the UK started in 2019. If successful this could remove one tonne per day of CO2 from the atmosphere. In the UK CCS is under consideration to help with industry and decarbonization. |
| OPEN100 | The OPEN100 project, launched in 2020 by the Energy Impact Centre (EIC), is the world’s first open-source blueprint for nuclear power plant deployment. The Energy Impact Centre and OPEN100 aim to reverse climate change by 2040 and believe that nuclear power is the |
| only feasible energy source to power CCS without the compromise of releasing new CO2. This project intends to bring together researchers, designers, scientists, engineers, think tanks, etc. to help compile research and designs that will eventually evolve into a blueprint that is available to the public and can be utilized in the development of future nuclear plants. | |
| Climeworks Direct Air Capture Plant and CarbFix2 Project | Climeworks opened the first commercial direct air capture plant in Zürich, Switzerland. Their process involves capturing CO2 directly from ambient air using a patented filter, isolating the captured CO2 at high heat, and finally transporting it to a nearby greenhouse as a fertilizer. The plant is built near a waste recovery facility that uses its excess heat to power the Climeworks plant. |
Carbon Engineering’s plant is also the most efficient in the world. Earlier studies estimated the cost of direct air capture to be at least $200 per ton of carbon. Much of this cost comes from energy usage. A 2019 study from Nature predicted that carbon capture could use one-quarter of global energy by 2100. Overall, there is room to improve the efficiency of direct air capture.
Carbon sequestration is the process of storing carbon in a carbon pool.
Carbon sequestration describes long-term storage of carbon dioxide or other forms of carbon to either mitigate or defer global warming and avoid dangerous climate change. It has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases, which are released by burning fossil fuels and industrial livestock production.
How is Carbon Sequestration done?
Carbon dioxide is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land use and agricultural practices, such as converting crop and livestock grazing land into land for non-crop fast-growing plants. Artificial processes have been devised to produce similar effects, including large-scale, artificial capture and sequestration of industrially produced carbon dioxide using subsurface saline aquifers, reservoirs, ocean water, ageing oil fields, or other carbon sinks, bio-energy direct air capture when combined with storage.
The USGS is conducting assessments on two major types of carbon sequestration: geologic and biologic.
It is the process of storing carbon dioxide (CO2) in underground geologic formations. The CO2 is usually pressurized until it becomes a liquid, and then it is injected into porous rock formations in geologic basins. This method of carbon storage is also sometimes a part of enhanced oil recovery, otherwise known as tertiary recovery, because it is typically used later in the life of a producing oil well. In enhanced oil recovery, the liquid CO2 is injected into the oil-bearing formation in order to reduce the viscosity of the oil and allow it to flow more easily to the oil well.
It refers to storage of atmospheric carbon in vegetation, soils, woody products, and aquatic environments. For example, by encouraging the growth of plants—particularly larger plants like trees—advocates of biologic sequestration hope to help remove CO2 from the atmosphere.
Technological Carbon Sequestration
Scientists are exploring new ways to remove and store carbon from the atmosphere using innovative technologies:
Graphene Production
The use of carbon dioxide as a raw material to produce graphene, a technological material. Graphene is used to create screens for smart phones and other tech devices.
Direct Air Capture (DAC)
While the techniques such as direct air capture can be effective, they are still too costly to implement on a mass scale.
Engineered Molecules
Scientists are engineering molecules that can change shape by creating new kinds of compounds capable of singling out and capturing carbon dioxide from the air. The engineered molecules act as a filter, only attracting the element it was engineered to seek.
Significance
According to the Paris Climate Accord, the members ratified the deal has to work towards the goal of achieving net-zero emissions, which is crucial to limit global warming. This scenario, calls for rapid scale-up of carbon capture, use and storage (CCUS). The process involves capturing CO2 emissions from coal and gas power plants, and from heavy industry, for deep underground storage or re-use.
Disadvantages
- Carbon dioxide may be stored deep underground. At depth, hydrostatic pressure acts to keep it in a liquid state. Reservoir design faults, rock fissures, and tectonic processes may act to release the gas stored into the ocean or atmosphere.
- The use of the technology would add 1–5 cents of cost per kilowatt-hour, according to an estimate made by the panels about climate change. The financial costs of modern coal technology would nearly double if the use of CCS technology were to be required by regulation. The costs tend to increase with CCS capture implementation.
Carbon Capture and Utilization
Carbon capture and utilization is the process of capturing carbon dioxide to be recycled for further usage. This paper discusses the process of carbon capture and conversion to energy. Carbon can be converted to alcohols, such as methanol, to use as biofuels and other alternative and renewable sources of energy. By converting CO2 to fuel before it is emitted into the atmosphere or by capturing it from the atmosphere, it can mitigate the effects of burning of fossil fuels.
With mounting concerns over climate change, the utilization or conversion of carbon dioxide into sustainable, synthetic fuels, most notably for transportation purposes, continues to attract worldwide interest. These offer considerable potential since, instead of consuming fossil crude oil, the fuels are produced from carbon dioxide using sustainable renewable hydrogen and energy. Carbon neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In addition to being carbon neutral, such renewable fuels can alleviate the costs and dependency issues of imported fossil fuels.
Projects
| NASA | NASA has developed a technology that can convert CO2 into fuel by using solar powered, thin filmed devices. It uses sunlight and inexpensive titanium dioxide composites to perform the reaction. The device can be used to capture carbon dioxide produced in industrial processes before it is emitted to the atmosphere and convert it to a useful fuel such as methane. These devices can be deployed to the commercial market with low manufacturing and material costs. |
| Ulsan National Institute of Science and Technology | In a study, scientists from this university have developed a system that produces electricity from CO2. A percentage of human CO2 emissions are absorbed by the ocean and turned into acid. The researchers focused on this phenomenon and came up with the idea of melting CO2 into water to induce an electrochemical reaction. If |
| acidity increases, the number of protons increases, which in turn increases the power to attract electrons. A battery system based on this phenomenon can produce electricity by removing CO2. |
Conclusion
As is understood from the paper, efforts are made to reduce the concentration of potent greenhouse gases like carbon dioxide from the atmosphere, but it is a long road and collective efforts are required.
Two effective tools that can help us accelerate our efforts and deal with climate change are Technology and Nature Based Solutions.
Technology is the biggest enabler for implementing innovative ideas in capturing carbon and sequestering for hundreds of years and for other solutions including conversion of carbon.
Nature based solutions provides the low cost but high impact approach to dealing with the issues of greenhouse gas concentration and must be implemented world over.
