At a time marked by growing concerns about climate change and its potentially devastating consequences, decarbonisation has emerged as a key global objective. Countries around the world are striving to mitigate greenhouse gas emissions in order to meet net zero targets, which has spurred a flurry of activity as academics from diverse disciplines explore innovative approaches to facilitate the green transition.
The pressing need to curb global carbon emissions and limit warming to 1.5° Celsius as set out in the Paris Agreement has sparked a wave of collaboration and research among scholars worldwide, as countries pursue novel ways to tackle the complex challenges of decarbonisation.
In June 2022, when the Western Australian Government announced that it would start decarbonising the state, the mining industry and academics began gearing up to collaborate. In the same month, the announcement of a ‘decarbonisation roadmap’ by Federal Mines and Petroleum Minister, Bill Johnston, symbolised the first step on the state’s journey to decarbonisation.
A roadmap for decarbonisation
Spearheaded by Curtin University’s School of Mines: Minerals, Energy and Chemical Engineering and the Minerals Research Institute of Western Australia (MRIWA) the roadmap will look at decarbonising Western Australia through integrated mineral carbonation (MC).
MC is a form of carbon capture, use and storage (CCUS) that has the potential to be a versatile approach to both remove and permanently store carbon dioxide at a gigatonne scale. It also has the added potential of providing economic advantage to quickly transition Western Australia to a low carbon economy supporting global low carbon supply chains.
It is intended that the roadmap will cover not only the engineering and scientific aspects but also business case development and policy making.
To achieve this overall goal, four key objectives have been outlined for the project:
- Technology overview and mapping – an extensive review of literature for all technology for MC, which can then be mapped against potential use cases in the state
- Scientific roadmap – identifying the short, medium and long-term scientific goals that have to be achieved in order to support the large-scale application of mineral carbonation in an industrial setting
- Business case – the development of economic models for a variety of use cases particularly relevant to Western Australia, tackling sensitivity analysis and simulation
- Policy making – pinpointing the necessary guidelines and policy suggestions for embedded emissions sequestration, trading authorisations and offset credit validation
According to Curtin WA School of Mines’ Associate Professor Tejas Bhatelia, the roadmap will “provide a clear science and technology, economic assessment, social and environmental and regulatory development pathway to de-risk the prospective development of a future mineral carbonation industry in Western Australia”.
“In addition, the roadmap will also explore possibilities of activating new markets to develop novel carbon embedded products that can be produced from MC processes.”
Is mineral carbonation the answer?
In simple terms, A/Professor Bhatelia said MC is “a naturally occurring process of locking away carbon for a very, very long time”.
MC is a carbon dioxide (CO₂ ) removal method and a natural rock weathering process, where CO₂ binds to minerals in the permanently remove and store large volumes of CO₂ from the atmosphere, transforming it from a gas into solid materials.
“Around 99.8 per cent of carbon on Earth – 1.8 billion gigatonnes – is stored and fixed in the Earth’s crust, mantle, and core. Most of the carbon in the Earth’s lithosphere exists in the form of hydrocarbons and carbonated minerals such as limestone, which is formed naturally through a process known as silicate weathering, whereby silicate minerals serve as the source of alkaline and alkaline-earth metals that naturally consume atmospheric CO₂ forming solid carbonate minerals,” A/ Professor Bhatelia said.
“Weathering alkaline rocks is a geochemical process that occurs on a geological time scale. It is estimated that natural weathering removes nearly 1.1GT of carbon in the form of CO₂ from the atmosphere per annum and predominantly stores as bicarbonate ions in oceans or solid carbonate minerals.”
The natural process is slow to occur so the roadmap aims to identify how this natural process can be accelerated. According to A/Professor Bhatelia, the team behind the roadmap has been making strides towards reaching this goal.
“The team has made significant progress in narrowing down the opportunities in the accelerated mineral carbonation process that can have a significant benefit not only to the resource sectors in Western Australia but, if realised to its potential, serve as a resource for offsetting national and international emissions and removing legacy CO₂ from the atmosphere.”
Making mineral carbonation happen
The best types of materials for MC are those rich in the metals calcium, magnesium and/or iron.
According to A/Professor Bhatelia, a range of minerals can be used for mineral carbonation including:
- Mafic and ultramafic gangue and tailings resources
- Red mud (bauxite residue) resources
- Brines from salt production or desalination
- Cement kiln dust
- Legacy asbestos tailings
- Other alkaline industrial wastes
“All of these materials can be found as waste products in the mining and resources industry in Western Australia,” A/Professor Bhatelia said.
“Wastes are the feedstock for the MC process. However, it must be noted that many wastes do not contain alkali material that are key to the MC process and cannot be used.”
Western Australia is home to a collection of unique characteristics that make it especially attractive for mineral carbonation processes. One example of this is the mafic and ultramafic rocks found within Western Australia’s prolific greenstone belts. These rocks are particularly rich in magnesium and calcium-rich minerals and, as such, are particularly prospective for mineral carbonation.
“All the key ingredients required for commercial mineral carbonation process development are existing in Western Australia,” A/Professor Bhatelia said.
These key ingredients include:
- Access to mine tailings or waste streams
- Access to land
- Existing resources industry
- Access to renewable energy in form of solar and wind
- Access to skills and research capabilities in universities
Impacting the resources industry
Without doubt the industries are facing unprecedented economic and regulatory pressures to reduce Scope 1-3 emissions. Whilst Scope 1 and 2 emissions can potentially be mitigated with the advent of renewable energy, to abate Scope 3 emissions is extremely challenging from a business sense.
“Mineral carbonation when combined with direct air capture technologies offer a feasible pathway for achieving net negative emissions for existing resource industries. When scaled up, MC will have a significant impact in the way the industry operates in the future,” A/Professor Bhatelia said.
“Western Australia’s mining sector has an opportunity to convert very large legacy stockpiles of mining and processing waste into sequestration assets. In Western Australia, sequestration potential for mineral carbonation can be estimated to achieve at a gigatonne scale.”
A/Professor Bhatelia said Curtin University is committed to developing scalable solutions for decarbonisation and is working on other methods to facilitate this.
“We have developed technologies such as SpiroPak© that can reduce the energy requirement for direct air capture by about 70 per cent, potentially making it economical at large scale. We are also developing biological pathways to sequester CO₂ in the form of organic matter and finally, we are developing thermochemical ways for utilising the CO₂ from the atmosphere in forms of energy and chemicals.”
A/Professor Bhatelia said the entire process of working in the team on the decarbonisation roadmap has been humbling.
“The participation, excitement, and collaborative nature of different working groups who have contributed to the roadmap has been fantastic experience. “MRIWA and Hon. Bill Johnston has ensured that an important piece of work is carried out and sets the state on an accelerated path of decarbonisation.”
The roadmap is expected to be released later in 2023 .