Australia's water supply is coming under immense demand from all sectors.
Water shows its worth
New research is helping the minerals industry better inform future debate about its water-use credentials.
30 January 2007 | Updated 14 October 2011
Life cycle assessment
Through life cycle assessment (LCA) methodology, CSIRO Minerals found that the economic value of water consumed by the minerals industry exceeds that of the agricultural and industrial sectors, supporting the view that allocating water to the minerals industry has a strong underlying economic basis.
At an average value of A$80 per cubic metre (m³), the economic value of water used by the minerals industry is higher than that of the industrial sector (about A$40 m³) and the agricultural industry (A$5 m³) (see graph).
The economic comparisons were calculated using LCA, a method of analysing environmental impacts of a process of product from 'the cradle to the grave' to optimise environmental performance.
Value of water by production and processing type
By using LCA methodology, CSIRO Minerals researcher Mr Terry Norgate was able to:
'This is how we were able to compare various industries and the value gained from water consumption,' he says.
The LCA work found that water consumption for producing various metals ranged from three cubic metres of water per tonne of steel up to about 250,000 m³/ tonne for gold, with results largely reflecting the grade of the initial ore (see graph).
Mr Norgate explains that the minerals sector uses relatively little water during mining, with the majority used in processing and refining.
'Operations such as grinding, flotation, gravity concentration, dense medium separation and hydrometallurgical processes all consume substantial amounts of water. Indirect consumption, in particular that due to electricity generation, can also make a significant contribution to the embodied water value,' he says.
Water usage within the minerals industry
The minerals industry uses about 80 per cent groundwater, 15 per cent surface water and five per cent mains infrastructure water, with the majority sourced from:
The minerals industry uses water extensively in processing as it is:
an efficient, low-energy and low-cost way of transporting and mixing particles and supplying reagents
a suitable medium for distributed force fields such as centrifugal force
an essential chemical ingredient of some processes.
The search for alternatives
The minerals industry is already researching alternative processes and water sources to deal with any changes to water allocations.
Mr Norgate says this is where LCA work is also crucial. 'Without knowing how much water is used at each step of a process, the industry has no way of understanding and minimising that use.'
He says using 'fit for purpose' and recycled water and dry processing are areas being researched by the minerals industry and CSIRO.
'Water recycling is an obvious candidate to help reduce water consumption but issues such as organic and inorganic molecule build-up, microbial species and collectors will influence the extent to which this will be achieved.'
Mr Norgate says that although many operations already use water that is unfit for agricultural use, a flexible fit for purpose' water strategy that accounts for local conditions and synergies needs to more broadly adopted by the mining, mineral processing and metal production operations.
Water minimisation - through techniques such as pinch analysis to establish minimum water requirements - and dry processing techniques will also be important.
'Although dry processing, where little or no water is used, may be a more radical solution, it is possible that this could bring other problems such as dust.'
“By showing the value in water consumption, we can discuss the demands all industries have for water and the ability to meet these demands.”
Mr Terry Norgate, Researcher, CSIRO Minerals.
Mr Norgate says that any assessment of alternative metal production processes must take into consideration other impacts - such as greenhouse gases, community capacity and economics - and not just water consumption.
'Only by looking at the whole picture can any decisions about energy use or water consumption be made and this is where LCA can make a significant contribution,' he says.
Competition for water
Although CSIRO Minerals has used LCA to assess energy consumption and greenhouse gas emissions, this is the first study to assess water use and associated economic values.
'With increasing competition for water, the minerals industry, along with others, can be expected to come under increasing pressure to reduce fresh or raw water use and integrate water from across sectors,' says Mr Norgate.
He says the LCA work shows it is worthwhile to allocate water to the minerals industry. 'By showing the value in water consumption, we can discuss the demands all industries have for water and the ability to meet these demands.'
Using LCA to discuss water reform
He says water reforms taking place in Australia aim to address issues such as:
competition for access
security of supply
increases in cost.
LCA work will help the minerals industry contribute to this debate.
'LCAs can drive the environmental debate by replacing emotion with objectivity and information, allowing groups with different objectives to find common ground in approaching a problem like increasing demand for water,' Mr Norgate says.
The University of Queensland's Professor Chris Moran, Founding Director of the Centre for Water in the Minerals Industry, agrees, saying LCA is important in helping the industry better understand its environmental footprint.
'Because LCA considers direct and indirect implications, you gain a much broader understanding of issues such as water use and greenhouse gas emissions.'
Challenges using LCA
However, Professor Moran believes there are challenges in terms of overall sustainability. 'Just because a producer reduces their energy consumption in a bid to take better account of the upstream water used in energy generation, for example, does not mean the energy is being saved overall.'
'Only if this results in less energy being generated is the water actually saved. Most institutions would not consider that their responsibility goes beyond their operation but one thing LCA teaches us is that this is not true.'
The second issue is to understand which audiences can use the LCA information in a constructive way, he says. 'The same information is not useful to all readers. For example, the owner of two steel mills may be very interested in the differences between these operations so that they can take action to improve. However, comparing alumina smelting and coal mining, for example, carries little operational content for taking action to save water.'
Broader applications for LCA
LCA approaches to environmental impacts are gaining momentum nationally and internationally, with Mr Norgate presenting his water findings at the Green Processing Conference in June 2006 and the Water in Mining Conference in Brisbane in November 2006. 'Our approach has generated significant interest,' says Mr Norgate.
Find out more about LCA by reading Sustainable products, sustainable futures.