Technical Market Support » Future Technologies
Life cycle analysis confirms that coal-based technologies do not necessarily have significantly greater emissions than gas-based technologies.
The Australian economy relies heavily on coal for electricity generation and resource processing. While coal is expected to remain a major, low-cost energy source over the long term, some environmental concerns are now leading to political, community and economic pressure to reduce its use in some countries.
Coal is a significant source of carbon dioxide emissions. Further, uncontrolled emissions from some high sulphur coals, particularly in developing countries, may pose a major threat to air quality, forests and the ecology at large.
Alternatives to coal, such as natural gas, oil, nuclear, biomass and renewables, are at varying stages of development. All have environmental, social and economic issues. Renewable energy (other than hydro) is not expected to significantly impact on electricity production until 2030-2050. Despite this, many world-wide organisations and community groups are urging governments to support the wide-scale use of renewables in the short term.
Promoters of other energy sources are unduly disadvantaging coal by quoting only the emissions at the point of conversion, while underestimating or not counting other significant emissions. This situation may be resolved by a cradle to grave comparison of impacts, otherwise known as life cycle analysis (LCA).
Project Objectives
While economic models exist for coal mining, transportation and coal-based processes, no equivalent models are readily available to make responsible and informed environmental decisions. This project provides a comprehensive environmental model for the coal industry, coal utilisation industries and competing energy industries using life cycle analysis techniques.
The specific objectives of the project are to:
- Identify and quantify the environmental credentials of coal compared with alternative energy/reductant sources
- Quantify the impact of alternative/new technologies for coal mining, combustion, ironmaking/smelting and waste utilisation
- Develop new approaches to better compare the environmental performance of coal with other energy/reductant sources
- Recommend strategies to improve the overall perception of coal to stakeholders - customers, environmentalists, government and community groups - based on quality data and analysis
The "life cycle" for purposes of this project is defined as the system to produce either 1 tonne of cast steel or 1 GJ of electricity. The subsequent use of the electricity, or fabrication of steel into manufactured products, is excluded.
Findings
The study focuses on obtaining realistic inventory values and, as the methodology for impact assessment is still in its infancy, only limited examination of the environmental effects was undertaken. Researchers aggregated each stressor (eg Co2, SOx and resource consumption) into an impact category (eg greenhouse gas emissions, acidification and resource depletion).
The production of steel and electricity produces co-products, by-products or, if no commercial application can be found, wastes. When a co-product or by-product from one process route is used to replace some other product, environmental burdens for the production of the replaced product are avoided. These system or 'earth' credits have been assigned to the functional unit in the analysis.
Steelmaking
The results show that while conventional coal-based steel production emits about 20 percent more emissions than for all-gas production, this difference can be reduced to around 10 percent by using slags and off-gases. Slag utilisation is an important product stewardship issue for the coal industry and can significantly improve the economics of steel production and the environmental image of coal.
The new and emerging coal-based technologies can match or exceed the performance of gas-based technologies. However, the rate of commercialisation of these technologies remains relatively slow. Most growth uses distributed EAF technology, with gas-based DRI providing the virgin iron units. There is, therefore, a need for the coal industry to be proactive in supporting the development of clean coal technologies for steel production, for example with studies aimed at understanding and controlling the effects of coal properties on process fundamentals and the slags produced. The benefits will be a reduction in steel production costs (especially with CEP) and an improved image for coal.
Electricity Production
While it is well established that conventional coal-based generation has higher environmental impacts than gas-based generation, the study has shown that the relative difference is less than generally reported and that there are technologies and strategies which can significantly improve the position of coal. These include displacement credits, synergies with renewables and integration with other industries.
Where To From Here
Future LCA work will be mostly confined to electricity production and will aim to further develop the findings of the present study, including:
- Providing more extensive LCA data for additional case studies for power generation
- Consideration of temporal aspects of biomass and natural gas production (eg the dynamics of the forest carbon cycle, or the variation in CO2 of wellhead gas with time) and nuclear (eg waste storage)
- Consideration of the synergies between the different technologies
- Expanding and improving the criteria used for environmental impact assessment and socio-economics
- Developing practical strategies for maximising displacement credits for coal ashes/slags from both electricity and steel production
- Consideration of the utilisation of Australian coals in other countries
- A more comprehensive analysis of nuclear generation
- Quantifying options for improving existing coal-based electricity generation