THE CSIRO is helping the minerals industry obtain a true picture of the energy use and greenhouse gas emissions of different processing techniques in a bid to improve performance.
The researchers say that they are using Life Cycle Assessment (LCA) which is a method of analysing the environmental impacts of a process or product from ‘the cradle to the grave’, which can be used to optimise environmental performance or to compare the impact of different processes.
The group says that as the world focuses on ways to reduce the use of fossil fuels and curb dangerous greenhouse gas emissions, the minerals industry is seeking ways to become more environmentally sustainable.
The LCA is a way of obtaining a true picture of the energy use and greenhouse gas emissions of different processes and identifying opportunities for improving performance can be difficult.
Terry Norgate and colleagues at CSIRO, working through the Minerals Down Under Flagship, have been using LCA to evaluate the environmental and economic impact of different processes for making metals.
Using this method, they measure the impact from the point where ore is extracted from the ground, through the metal making process, its end use and finally disposal of the product.
Norgate says LCA is an integral part of evaluating new processes or changes to existing processes, such as making various metals. He says that it allows us to see which parts of the new process make the biggest contribution to the environmental impact so we can focus our efforts on those stages and improve their performance.As well as considering the energy used and greenhouse gas emissions from the process itself, the LCA takes account of indirect emissions such as those from the generation of electricity.
Norgate says that you can’t just look at part of the life cycle in isolation. If you look at a process that uses electricity for heating, for example, you don’t see any greenhouse gas emissions, so compared with a process that uses coal for heating, the first process appears much more greenhouse friendly. An LCA will also consider the emissions from generating the electricity in the first place.
The LCA also takes account of downstream emissions.In a comparison of aluminium and steel, for example, production of aluminium generates more greenhouse gas emissions per tonne of metal than steel, but in the end-use of the metal as components for motor vehicles, the lighter aluminium can lead to improved vehicle performance in terms of fuel consumption and this also has to be considered.
In an LCA comparing a number of metals, the researchers showed that the light metals titanium and aluminium have the greatest energy requirement on a per tonne basis, followed by nickel, while steel and lead have the lowest values.
However, on a global basis, steel production consumes by far the largest amount of energy and is responsible for the greatest emission of greenhouse gases.
The results showed that the major opportunities for reducing energy consumption and greenhouse gas emissions from primary metal production lie in the metal extraction (smelting) and refining stages of steel, and to a lesser extent aluminium, production.You can read more about CSIRO’s June 2009 issue of Process.
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