With Australia under global scrutiny over its approach to climate action and its perceived lack of priority in slowing down the warming of our atmosphere, there needs to be a broadening of the focus beyond CO2 emissions into methane reduction and utilisation, writes Jan Kwak, managing director Australia and Asia of Hatch.
The amount of methane released into the atmosphere from Australian coal mining activities makes up around 6 per cent of Australia’s national emissions, but there are a number of ways in which this methane—known as fugitive methane, in the mining context—can be treated to both reduce emissions and create valuable by-products, such as fuel.
The United Nations Environment Programme stated in a recent report that methane emissions are driving climate change. This gas has accounted for roughly 30 per cent of global warming since pre-industrial times, and is today proliferating at the most rapid rate since records began.
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A potent threat
Despite methane accounting for just 6 per cent of Australia’s total emissions, fugitive methane is 80 times more potent in warming the atmosphere than CO2 over a 20-year period. In addition, while methane is only in the atmosphere for a couple of decades (compared with around 1000 years for CO2), the impact it has on global warming over that short period is far more pronounced.
Having studied the impact of fugitive methane from coal mining, we have identified a number of highly effective options that can be taken pre-mining, during mining, and post-mining to drastically reduce the amount of fugitive methane escaping into the atmosphere.
Methane is extracted in three stages of coal mining: pre-mining, during mining, and post-mining.
Methane is often drained prior to its liberation during the mining process, mainly for safety reasons, and occasionally for economic purposes (to utilise the methane elsewhere). In terms of safety, the primary concern is that methane is explosive in concentrations as low as 5 per cent in the air.
During the mining process, further pre-drainage takes place as the mine expands, and ventilation air methane (VAM) capture occurs (in underground mining only). For both open cut and underground mining, residual methane in coal seams cannot be completely captured, resulting in fugitive emissions which currently enter the atmosphere.
Post-mining, there are techniques that are applied in underground coal mining such as goaf (where the part of the mine from which the mineral has been removed is subsequently filled with waste material and closed off), and drainage via directional drilling.
Once methane is extracted, there are three possible options for handling it:
- Flaring, or combustion: Eliminates the high GWP (Global Warming Potential) of methane by converting it to carbon dioxide. Effectively, this reduces the GWP of these emissions by a factor of 28 if the methane is 100 per cent combusted.
- Utilisation as natural gas or for power generation: This converts the methane to mobile vehicle fuel, or for heating or electricity value. Emissions are effectively converted from the mine operator’s Scope 1 to Scope 3 (Scope 1 emissions refer to fuel and gas emissions sources directly within the operating area of a site. Scope 2 refers to emissions incurred in providing electricity, steam, heat or cooling to the site. Scope 3 refers to gas emitted at either the suppliers of materials, or the downstream customers of a site’s products). Under this option, the emissions are now the responsibility of a separate end-user.
- Sequestration: The best solution from a climate change perspective is placing captured methane or carbon dioxide into long-term storage or usage.
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A more resourceful future
As an industry, the focus for future operations should be to reduce the flaring of captured methane, and switch to better uses such as energy or chemical production.
A prime example of how this can be successful is the arrangement between Arrow Energy and Anglo American, where Arrow supplies drilling and drainage services to Anglo to capture and utilise methane. The captured methane is then sold to either gas power producers like EDL or injected into domestic and LNG gas supply chains.
Although CO2 from natural gas combustion also has a climate change impact, using this fugitive methane displaces natural gas that would otherwise be extracted from other sources.
Australian coal mining companies should commit to decarbonisation by investing in more fugitive technology and the wider supply chain.