Carbon is the essence of life but nowadays, we are hearing only negative things about it. Why the world’s perspective for this friendly element has changed? What has gone wrong? Well, nothing has changed in poor carbon. Instead, humans have changed and have been over exploiting the long-preserved carbon treasures since decades. Now, we are paying the price; global warming, Climate Change, and polluted ecosystems are some of unwanted outcomes of our endless wants. Time demands us to come out with biological and technological ways to utilize the potential of carbon and reverse the wrath of its over-exploitation. Carbon Capture is a promising technology to balance the concentration of carbon on our planet.
Why carbon capture is needed?
Burning of fossil fuels emit carbon-dioxide and since the advent of Industrial Revolution, we are constantly emitting it. Many natural processes are also responsible for emission of carbon-dioxide but nature has a perfect balance to absorb it. Natural carbon sequestration occurs with the help of carbon sinks such as forests, oceans, and soil. But the imbalance created by humans has exceeded the natural capacity of these natural carbon reservoirs. The world is aiming to limit the temperature to 1.50C above pre-industrial levels and IPCC 9 Intergovernmental panel on climate change) reports claim that it is not possible without carbon-dioxide removal technologies. Capturing the carbon from the industrial emissions will help in decarbonization: an important dimension to reach the net zero emissions target by 2050.
What is Carbon Capture and Storage?
Carbon capture and storage (CCS) involves different technologies to extract carbon-dioxide from industrial or power point emissions before its escape into the atmosphere. The captured carbon is compressed into liquid form and transported for storage in coalbeds, saline aquifers, or depleted coal and oil reservoirs. As per the IPCC report (2005), carbon capture and storage has the potential to capture 85-95% of the total CO2 released.
How it is done?
Three conventional processes employed for carbon capture are :pre-combustion capture, post- combustion capture, and oxy-fuel combustion capture. In Pre combustion capture (used in Integrated Gasification combined cycle power plants), coal is partially oxidized in the presence of air/oxygen and steam to produce synthetic gas (Syngas) – a mixture of CO2, CO, H2 and a small proportion of CH4. The obtained Syngas is treated to produce CO2 and H2 ; CO2 (15-50%) is captured and H2 can be used as fuel. The post-combustion capture is removal of CO2 from flue gas mixture after combustion but it has low efficiency due to low concentration of CO2 ( 7-14%) in flue gas. In oxyfuel combustion capture, fuel is burned in the presence of pure oxygen (around 98%) and the resulting flue gas contains only H2O and CO2. Water is removed by condensation and remaining is CO2 captured.
Boon for hard to abate industries
Some of the industries such as cement, chemicals’, and iron and steel cannot evade the production of carbon-dioxide. These industries for which decarbonization is challenging are known as hard to abate industries. If they cannot avoid the CO2 emissions; the best they can do is capturing the carbon-dioxide from the emissions before its release into environment. There is one amine-based carbon capture plant operating in the Emirates Steel facility, Abu Dhabi with capacity of 8,00,000 tonnes of annual carbon- dioxide capture.
CCS plants across the globe
United States of America and Europe are the leading players in deployment of Carbon Capture and Storage projects. Other regions are following the footsteps to establish CCS plants to decrease their carbon footprints. Till September 2022, there were 196 carbon capture facilities with capacity of 243.9 million tonnes per annum. Europe has leverage of North sea due to its substantial storage and capture capacity. Endurance is United Kingdom’s CCS project in North sea that aims to decarbonize the Industrial Clusters. World’s largest Direct Air Capture Plant will be developed in Wyoming (United States) in 2023.
Advanced technologies
There are two advanced carbon dioxide removal technologies: Direct air carbon capture and storage(DACCS) and Bioenergy with carbon capture and storage (BECCS). DACCS is a nascent stage technology which extracts CO2 directly from air while BECCS captures carbon-dioxide from bioenergy combustion. DACCS is expensive technology and its large scale deployment will depend on cost reduction. Global CCS ( carbon capture and storage) institute estimated that DACCS of one ton of carbon-dioxide costs from 137 US$ to 412 US$. On the other hand, BECCS is a better option as it provides both carbon-dioxide removal and usable energy. But the unavailability of ample biomass for energy is a drawback.
Insecurities about storage of captured carbon
In 1972, carbon captured from a gas processing facility was injected into Sharron Ridge Oilfield in Texas to boost the oil recovery. With time, the purpose has changed, pace has increased, and doubts about storage of carbon have emerged. The current storage does not focus to enhance oil recovery but to decarbonise the planet. But the fear about sustainability of injecting and storing carbon-dioxide in geological formations does not have a solid ground. First of all, it is happening for decades without any evidence of leakage. Secondly, carbon-dioxide slowly diffuses into rocks under storage sites and becomes a part of strata in that geology over time. Thirdly, the inspiration behind injecting and storing the carbon is taken from nature as it is naturally happening since centuries. But in spite of all the positive reasons in defence, monitoring of geological sites in use is equally important.
What is the way forward?
The potential of carbon-dioxide removal technologies is known but still there are few projects in operation. Why? The truth is that CCS projects requires high capital infrastructure that can be developed with the support of government along with financial backing. It requires capture equipment, transport system, permissions and maintenance of on-shore and off-shore geological storage. Governments of developed countries are taking the lead: The Inflation Reduction Act of United nations provides tax credits to support BECCS. United Kingdom has launched BECCS Innovation programme in 2022 for green hydrogen and carbon capture with funding of more than 30 million GBP. It is commendable that developed countries are paving the path for developing and underdeveloped countries to balance planet’s carbon-dioxide. Carbon-dioxide removal technologies can definitely buy us more time to remain within carbon budget of this century.
