Carbon Capture and Storage - Frequently Asked Questions
Carbon capture and storage (CCS) involves capturing carbon dioxide (CO2) that would otherwise be emitted into the atmosphere from sources such as power stations and industrial processes, and transporting it to a suitable storage site for safe, long-term storage deep underground. Carbon capture and storage technologies are being investigated around the world, because they have the potential to significantly reduce greenhouse gas emissions.
Victoria offers world-class potential for CCS - the Bass Strait’s geology provides potential to safely store large quantities of CO2 while also being located close to the Latrobe Valley.
A fully established CCS chain usually consists of four actions:
- The CO2 is captured (usually separated from coal or oil, such as within a power station or oil or gas refinery).
- The CO2 gas is then compressed into a liquid-like form.
- The CO2 is transported along a pipeline to a suitable injection site.
- The CO2 is injected deep below the ground (at a depth of greater than 800 metres) into a secure geological formation for long-term storage. Typical storage formations are areas of porous rock underlying thick layers of impermeable rock, similar to oil and gas reservoirs.
CCS – The basics
Is CCS safe?
Carbon capture and storage (CCS) involves storing CO2 at depths of greater than 800 meters, securely trapped in geological storage formations.
Naturally occurring underground rock formations have stored large quantities of oil and gas (hydrocarbons), as well as other gases including CO2, for millions of years.
The CO2 is initially trapped by structural mechanisms involving a ‘cap rock’ – thick layers of impermeable rock overlying the storage area. However over time, the CO2 is further secured as it mineralises or is dissolved into saline water contained within the storage reservoir. Analysing and managing risk is a crucial element of a CCS project. In Australia, CCS projects must comply with relevant laws and strict regulatory requirements that include the long-term monitoring of the sequestered CO2.
Is CCS being used or investigated elsewhere?
Yes, right here in Victoria - the CO2CRC Otway Project has injected and stored over 65,000 tonnes of CO2 - and it has also been used in many other places around the world by the oil and gas industry. The Global CCS Institute lists around 43 CCS projects at various stages worldwide. The Gorgon Project in WA will sequester and store CO2 in a sandstone reservoir 2.5 kilometres below Barrow Island. In the US there are thousands of miles of CO2 pipelines. The oil and gas industry uses CO2 in the process of enhance oil recovery. Visit the Global CSS Institute website for annual global status reports of CSS.
What role can carbon capture and storage play in a low emissions future?
Capturing and safely storing CO2 will significantly contribute to our move to a low emissions future. Leading scientists and international authorities such as the Intergovernmental Panel on Climate Change (IPCC) have identified CCS as having the potential to safely and effectively help reduce our greenhouse gas emissions.
There is overwhelming scientific agreement that man-made global warming will have a significant impact on our planet. CO2 is recognised as the chief greenhouse gas, increasing the amount of the sun’s radiation, which is trapped within the earth’s troposphere (lower atmosphere) and causing temperatures to rise.
If not addressed, the increase in temperatures is predicted to exceed 2°C this century, with widespread impacts on climate and human habitats.
CCS can play a valuable role during the transition to a low carbon economy as investment continues in developing renewable energy technologies. CCS does not replace the need to increase energy efficiency or develop renewable energy technologies. Rather, CCS is part of a portfolio approach to addressing the issue of greenhouse gas emissions and climate change.
Fossil fuels still account for approximately 80 percent of global energy production, and energy demand is forecast to increase significantly.
Analysis from the International Energy Agency suggests CCS will contribute around one fifth of required global emissions cuts by 2050.
The EU Commissioner for Energy and Climate Action (2015) Miguel Arias Cañete has commented that: "Carbon capture and storage will together with other innovative low-carbon technologies play an essential role in reaching greenhouse gas emission reduction targets around the globe".
What are the costs?The relative costs of capture, transport and storage will depend on the site and industry. Transport costs are related to distance and pipeline capacity, while storage costs are related to the geological characteristics of sites. However the capture component of CCS will be the most costly part of the process.
Carbon capture and storage is not a new technology and many of the technologies involved in CCS are already well developed and have been demonstrated. Capturing emissions from power plants at a large scale on a commercially viable basis is now occurring in several places around the world.
Victoria’s largest emission sources in the Latrobe Valley are close to prospective storage areas. This means costs for pipelines and transportation are likely to be lower than in many other places.
How is CO2 captured?
There are a variety of technologies that have potential to capture CO2. These technologies are not new. They have been used in the oil and gas sector and commercially applied for decades. The challenge is to apply these technologies to the power station industry and integrate them with existing and new infrastructure.
Capture technologies include:
- Pre-combustion capture refers to taking the primary fuel (e.g. coal) and converting it into gas. The gas produced is then processed and separated to CO2 and hydrogen. The hydrogen is used as the fuel to generate electricity.
- Post-combustion capture occurs after the primary fuel is burned and the CO2 is contained in the exhaust gas. The exhaust gas is captured, the CO2 is then separated from the other gases.
- Oxyfiring, or oxyfuels, involves burning fuels in pure oxygen rather than in air. This creates a flue gas with a high CO2concentration, simplifying the capture process.
After the capture process, the CO2 gas is compressed for transport and injection into suitable underground storage sites.
How is the CO2 injected?After capture, CO2 is compressed to a dense, liquid form, then transported and injected with sufficient pressure to displace any water currently stored within the porous rock.
At depths of greater than 800 metres, where the CO2 is injected, it will remain in a compressed, dense form, allowing each reservoir to store vast quantities of CO2.
Industries such as those in the energy sector have extensive experience related to the injection and storage of CO2. The injection of CO2 has been used by oil companies for decades to increase oil recovery from deep geological formations.