The significance of the resources industry to the Australian economy has grown to the point where it generates about 50 per cent of exports and almost nine per cent of GDP. However, in a carbon-constrained future, will economic growth in this critical area come under threat?

Currently, the minerals industry is only a moderate contributor to greenhouse gas (GHG) emissions, but this could quickly change with the implementation of GHG reductions in the power generation and transport industries.

In addition, GHG emissions for the production of metals are likely to increase in the future because of the rapid growth in global demand for metals combined with the problem of declining ore grades and subsequent higher energy consumption.

Therefore, it is necessary to identify major opportunities to reduce the minerals industry’s energy consumption and carbon footprint, in addition to harnessing Australia’s engineering talent to develop sustainable solutions.

Major opportunities in reducing GHG emissions

Currently the minerals industry is responsible for a relatively small portion of global GHG emissions through mining, mineral processing, metal extraction and refining. CSIRO’s life cycle assessment studies have indicated that extraction and refining of metals from concentrates are the most energy-intensive steps in the mineral cycle and are thus responsible for the major portion of GHG emissions.

Taking into account the tonnage of different metals being produced in Australia and globally, it then becomes clear that the major opportunities for reducing GHG emissions in the sector are in production of steel from iron ore and aluminium from bauxite.

The technologies being investigated by CSIRO through the Centre for Sustainable Resource Processing (CSRP) and in collaboration with the steel industry, are forecast to result in a reduction of more than 500 million tonnes per annum of GHGs globally. It is interesting to note that the potential reduction in GHGs resulting from implementation of these technologies is similar to the current level of total GHG emissions by Australia.

Renewable fuels and reductants

The steel industry is almost entirely dependent on fossil carbon for fuel and reductant and contributes significantly to GHG emissions in Australia and globally. Processed biomass (for example, char) is a potential source of renewable energy and carbon for metallurgical reactors, providing an essentially GHG-neutral form of fuel/reductant. By-products (such as biodiesel or electricity) from production of char from biomass can also contribute to reduction of GHG from industry.

The supply of biomass should (and can) be managed in sustainable or even restorative ways to avoid adding stress to agricultural and forestry ecosystems. Our studies have shown that partial replacement of fossil carbon by bio-char over the next decade or two will create a demand for biomass supply of up to 10 million tonnes a year. Such volumes of biomass could be supplied in a sustainable way through use of large volumes of forestry and sawmill residues currently being produced and/or plantation of short-rotation-cycle woody biomass, such as the oil mallee, that could meet the metallurgical carbon requirements of Australia’s steel industry.

The innovative challenge is to find viable solutions that capture the inherent sustainability opportunities associated with the use of biomass char and other forms of renewable, recycled or waste carbon.

Furthermore, by using deep-rooted biomass that has been grown in salinity-prone areas we will also help to improve soil quality in those areas. It is worth noting that a plantation program of short-rotation trees (oil mallee) has already commenced in the WA wheatbelt to lower the watertable and hence address the salinity issue in this region.

Full rehabilitation of salinity-affected farmland will produce 25 million tonnes per annum of biomass. The local and overseas steel industries could potentially provide an excellent market opportunity for such volume of renewable carbon source.

In addition to the environmental benefits associated with substitution of biomass-derived charcoal for coal, there are also some economic benefits. Studies by J G Mathieson have shown the value-in-use of pyrolysied woody biomass could be up to 80 per cent higher than a reference coal used for pulverised coal injection into a modern blast furnace. This study shows that conditions used for pyrolysis of biomass could result in production of a range of chars with varying value-in-use, thus it may be possible to design and produce semi-charcoals that optimise blast furnace heat and mass balance.

These chars are aimed at replacing a significant portion of the fossil fuel and reductant used by the industry.

Integrated heat recovery and dry granulation

The second technology being developed by CSIRO, in collaboration with the Australian steel industry, aims at capturing and utilising the large quantity of heat currently being lost through by-product streams such as molten slags. Successful development and commercialisation of the technology in Australia will not only result in reduction of GHG emissions by millions of tonnes, but also reduce water consumption by thousands of millions of litres. An additional benefit is the conversion of millions of tonnes of by-product slag into cement.

Our pilot-plant work has provided insights into process design and control, and how slag atomisation can be optimised to produce fine granulates. The results have demonstrated how enhanced fast cooling can improve granulate handling and have assisted in the design of a compact unit to reduce cost and take advantage of heat recovery. Work is now progressing on optimising the scale-up of the integrated process, product evaluation and plant measurements at OneSteel and BlueScope Steel sites.

Partnership and future direction

Industry engagement is a critical success factor in development and implementation of the emerging technologies. Our current projects on use of biomass-derived charcoal in the iron and steel industry and waste-heat recovery through dry granulation of slags have attracted investment by the Australian steel industry with plans for scale up and demonstration of the technology being endorsed by collaborators (BlueScope Steel and OneSteel).

The first plant trial on use of bio-char in steel making is currently taking place. Parallel activities on sustainable supply of biomass and techno-economics of the technologies and supply chain have been commissioned through collaborative projects involving a number of stakeholders representing mineral and agri-industries, local councils and state and local governments, investors, other technology providers and steelmaking companies.

Through its actions, industry has demonstrated it agrees with CSIRO that our creative, cross-disciplinary approach to deriving benefits from biomass is paying dividends.

The International Iron & Steel Institute’s CO2 Breakthrough Program has recently acknowledged the transformational nature of the biomass and dry granulation projects and enrolled these R&D projects as part of its worldwide portfolio of projects.

This allows engagement of a broader range of collaborators and sponsors, and possibly quicker technology uptake by overseas iron and steel producers in the future.

Further reading:

T. Norgate, S, Jahanshahi, and WJ Rankin, Assessing the environmental impact of metal production processes, Journal of Cleaner Production, 15, pp.838-848, 2007

T Norgate and S Jahanshahi , Opportunities for reducing energy consumption and greenhouse gas emissions in mineral processing and metal production; In Proceedings of the Chemeca 2007 conference, Melbourne, 2007.

J G Mathieson, The Value-in-Use of Some Biomass-Derived Blast Furnace Injectants, BlueScope Steel, unrestricted report, BSR/N/2007/071, December 2007

Dr Sharif Jahanshahi studied metallurgical engineering at the Imperial College, London. He joined CSIRO Minerals in 1987 following a number of years of research at the former BHP Central Research Labs. His current role is Theme Leader – Sustainable Processing, at the CSIRO Minerals Down Under National Research Flagship. He also leads a research program at the CRC for Sustainable Resource Processing. His research interest includes process chemistry of high temperature systems and sustainability driven projects aimed at reducing waste and emissions in mineral processing and metal production. He has authored/co-authored more than 150 technical papers through international journals and conference proceedings.