The types of low emission technologies (LETs)
There are a number of technologies available and in development that can significantly reduce greenhouse gas emissions.
1. Capturing carbon
We all know that trees and plants capture CO2, helping reduce emissions. But fewer people know that another type of plant – one that produces power and manufactures products – can also capture carbon through the use of low emission technologies (LETs).
One of the main types of low emission technology is carbon capture utilisation and storage (CCUS) – which is also often called carbon capture and storage or CCS.
CCUS uses technology proven over decades to capture over 90% of CO2 from industrial plants, then safely and permanently store it in porous rock located kilometres under the earth’s surface.
But captured CO2 can also be useful. CCUS technology removes carbon dioxide but, as well as locking it away, can repurpose it for use in manufacturing processes. Products like cement, plastics, methanol, memory foam, pharmaceuticals and even fizzy drinks all have the potential to be made from captured carbon.
CCUS allows the world to keep producing energy and making the things we need while lowering carbon emissions.
Globally there are 26 operational, large-scale CCUS facilities, with three more under construction and another 34 in development. That equals the capacity to lock-up 127 million tonnes of CO2 each year. And the International Energy Agency says a further 2,000 plants are needed to meet international climate goals.
There are four main CCUS projects currently running in Australia: the Gorgon CO2 Injection Project off the coast of Western Australia, the CarbonNet multi-user storage facility in Gippsland, the Otway carbon storage research facility in Victoria, and Glencore’s CTSCo Project in Queensland.
Carbon capture is like taking a car that produces polluting fumes, fitting it with technology on its exhaust pipe to capture those fumes, and then storing them away safely. The benefit is that we can keep driving the car, just in a more environmentally sustainable way.
There are three links in the chain: capturing the carbon, transporting the carbon, and then storing or using the carbon.
During the capture process, CO2 is separated out from other gases and particles in the exhaust stream. The remaining pure CO2 is then compressed into a liquid-like state called supercritical carbon.
After capture, the liquid carbon can then be transported by road tanker, ship or pipeline, which is most common. Transporting carbon is similar to other fluids such as gas and oil. And carbon has been transported safely this way for more than three decades.
CCUS is flexible technology. All it depends on is a source of carbon. It doesn’t matter where that comes from – industry or energy production. The most obvious use is at power plants that run on fossil fuels. But around the world, projects are underway to incorporate CCUS technology for other high emissions industries including steel, chemicals, fertiliser and cement production.
When captured, we can do two things with carbon dioxide.
It can firstly be used in industries that require pure CO2. That includes something as simple as making carbonated or ‘fizzy’ drinks, all the way through to producing chemicals (such as urea, used in fertiliser), jet fuel, fire extinguishers, food packaging and refrigeration.
Another use is to increase the amount of oil that can be recovered from depleted oil fields, helping Australia’s fuel security.
Carbon dioxide can be stored safely and permanently deep underground where it is trapped, preventing it from escaping into the atmosphere and contributing to emissions.
To store carbon dioxide, it is injected more than a kilometre below the earth’s surface into reservoirs. These are in sites of ‘porous’ rocks containing small holes that can hold the carbon dioxide.
There are two types of suitable storage sites. The first is former oil and gas fields, where CO2 fills the pores in the rock that held the oil and gas for millions of years.
The second is found in deep ‘saline’ formations, where the porous rocks are filled with typically brine (salty water). The CO2 reacts with the water to stably bind into the rock.
Above all, carbon storage underground is a safe, long term solution. This practice is highly regulated and has been used by the oil and gas industry for more than 40 years.
Carbon dioxide can be stored permanently, due to a number of factors that mean it is locked away and can’t escape from within its storage location.
The CO2 is injected beneath a thick layer of rock known as ‘caprock’. Here, the CO2 is trapped in the pore spaces of the reservoir rocks. It can also dissolve into the water (solubility trapping), and over time become bound to the rock and create a solid carbonate mineral (mineral trapping).
CCUS storage sites are sealed by geological formations above, constantly monitored – both underground and at the surface – to confirm the CO2 is safely contained and that there is no leakage.
The CO2CRC Otway Project, located in south-west Victoria, is one of the most comprehensive monitoring and verification programs for CO2 storage in the world. The project is being run by Australia’s leading CCUS research organisation CO2CRC and the CSIRO – and is funded in part by LETA.
The project, which has been operating since 2003, has confirmed that “storage in depleted gas fields and saline aquifers can be safe and effective and that these structures could store globally significant amounts of CO2”.
The project builds on international CCUS work, such as Boundary Dam in Canada, which monitors carbon dioxide movement in the subsurface, shallower geological levels and surface levels.
2. The Allam Cycle
Low emission technologies don’t just capture emissions already produced. They can also be used to change how we produce energy in the first place.
The Allam-Fetvedt Cycle (or Allam Cycle) is a new way to generate clean, low-cost power by using carbon dioxide as the power source that drives turbines to produce electricity.
With traditional power plants, hot steam generated by burning fossil fuels is used to spin turbines that generate power. The Allam Cycle uses high-pressure CO2 to spin the turbine. It produces low-cost power while capturing 100% of CO2.
There are a number of benefits of the Allam Cycle. As with CCUS, pipeline-ready CO2 can be transported for use in industry or stored underground. And the CO2 from the Allam Cycle can also be reused over again to generate power, preventing the energy wastage of traditional plants.
Another major plus of the Allam Cycle is that it can meet the modern requirements of the grid. It can deliver power when the market needs it. The existing steam method is like boiling a kettle: it takes time to boil, so it is slow to react to the grid. The Allam Cycle is like a jet engine: it can ramp up and down with the load. Because the Allam Cycle can match the grid, it is an excellent technology to sit alongside weather-dependent wind and solar power generation.
A final benefit of the Allam Cycle is that it can be used to create hydrogen – which can be used as a clean energy source – and other valuable products.
For example, hydrogen produced by the Allam Cycle can also be used to produce the urea used in fertiliser. Australia currently imports fertiliser, which has a significant carbon footprint, but the Allam Cycle could see a new domestic industry producing zero-emissions fertiliser.
The technology was invented by British chemical engineer and Nobel Peace Prize Laureate Rodney Allam and was successfully demonstrated at a new plant in La Porte, Texas.
With Australia’s abundant natural resources, the Allam Cycle has the potential to unlock new, clean industries of the future, while also helping reduce the emissions from industrial sectors we rely on today.
3. Clean hydrogen
Hydrogen is an extremely versatile source of energy that can be used for grid electricity, heating, as a key ingredient for chemicals such as methanol and ammonia, and to fuel transport.
Clean hydrogen – produced with little or no carbon emissions – will be a major player alongside renewable energy in the move to a low-emissions economy.
In ‘hard-to-abate’ sectors – such as heavy transport including aviation, shipping and long-distance road transport; and heavy industry such as cement, steel and chemical manufacturing – clean hydrogen has a strong role to play. It is difficult to lower emissions in these sectors, yet the International Energy Association estimates 40% of global energy is used by emissions-intensive industries.
There are a number of ways to produce clean hydrogen. It can be produced using fossil fuels such as gas (steam methane reforming) or coal (gasification) in combination with technology that can capture and store the carbon, leaving the clean hydrogen.
It can also be produced from renewable electricity. This process involves ‘electrolysis’, where electricity is used to extract hydrogen from water. When renewables are used to power electrolysis no carbon emissions are produced.
Demand for hydrogen is growing here and internationally. Hydrogen is set to become an important trade export for Australia.
- We are already one of the top three exporters of hydrogen to Asian markets.
- According to Australia’s National Hydrogen Strategy produced by the COAG Energy Council, by 2050 Australia’s hydrogen industry could generate about 7,600 jobs and $11 billion in GDP.
- If global hydrogen markets develop faster, those estimates could jump to 17,000 jobs and $26 billion in GDP.
4. Soil carbon
Another method to offset greenhouse gas emissions, and complement technology such as CCUS, is the use of soil. A large amount of carbon is stored in soil, mostly as soil organic matter. Scientists say there is significantly more carbon in soil than in the atmosphere.
As soils are cultivated the carbon that was once bound in the soil gets released into the atmosphere.
But that process can be reversed through ‘soil carbon sequestration’, where the amount of carbon stored in soil is increased. The idea is to maintain soil as a major carbon ‘sink’, for example by farming methods such as reducing over cropping and grazing, and offsetting some of the carbon emitted into the atmosphere.
 Mineral carbonation and industrial uses of carbon dioxide. IPCC Special Report on Carbon Dioxide Capture and Storage. https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapter7-1.pdf
 Carbon capture and storage FAQs. Earth Resources Victoria. https://earthresources.vic.gov.au/projects/carbonnet-project/faqs-and-reports
 Energy Transition Commission. https://www.energy-transitions.org/publications/mission-possible/
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