Methane emissions are one of the major concerns surrounding coal seam gas. But we should also be paying attention to other sources of methane, in particular those from coal mining. By dealing with these we could make significant progress on reducing Australia’s greenhouse gas emissions.
Some coal mines have operational power plants and pilot studies to use the vented methane and reduce emissions. But recent mapping of the concentration of methane in the atmosphere at ground level by UNSW Australia in association with Royal Holloway University of London Greenhouse Gas Laboratory shows that we need to do much better.
Methane is a colourless and odourless gas, but, like carbon dioxide, it contributes to global warming. In fact it is more potent: methane released into the atmosphere has a global warming potential 25 times greater than carbon dioxide over 100 years.
Apart from energy, major sources of methane include municipal solid waste, municipal waste water, agriculture (predominantly cattle and rice cultivation), bushfires, termites, wetlands and natural seeps from the Earth.
It may be invisible, but we can now measure and see the distribution of methane in the atmosphere. Portable laser-based gas analysers allow us to measure in real time the concentration of the methane in the atmosphere in parts per billion (ppb).
Methane is a natural part of our world, but human activities over the past two centuries have increased its concentration in the atmosphere from a base global average of 722 ppb in 1750 to a global average of 1,823 ppb in 2015.
Due to lower population densities and industrial activities, the southern hemisphere has cleaner air. Until last year the southern hemisphere had methane concentrations less than 1,800 ppb. However, Australia passed that significant benchmark in 2015.
As we can see from the internationally important Cape Grim data collected by CSIRO, methane concentration stabilised between the years 2000 and 2006. Methane concentration oscillates with the seasons (as does carbon dioxide), peaking in September.
Between the years 2000 and 2006 the annual peak was about 1,740 ppb. But since 2007 it has increased by 4-11 ppb per year, peaking at 1,803 ppb in September 2015. Since 2007, methane in the atmosphere has steadily increased worldwide. Just why it started rising again is poorly understood.
To better understand why methane is increasing in the atmosphere, over the past three years we have been undertaking extensive measurements of greenhouse gases in the ground-level atmosphere throughout New South Wales and Queensland. The focus of our research has been mapping methane in all landscape settings to determine significant sources.
We have travelled many thousands of kilometres to measure greenhouse gas emissions in urban, rural and mining landscapes using a portable greenhouse gas analyser. The methane analyser is simply placed inside a car, and air is drawn into the analyser via a tube which has an inlet mounted on the roof. We then measure the concentration of methane in the atmosphere as we drive along roads.
From the figure above you can see that Hunter Valley coal mines are a major source of methane released into the atmosphere. Most of the methane above background concentrations in the atmosphere is due to venting of methane from underground coal mines to make them a safe place to work – if the mines weren’t vented, the methane could ignite and explode.
While some mines capture vented methane to generate power or flare the methane, this image shows that a lot more work needs to be done if we are to satisfactorily reduce the greenhouse gas footprint of coal mining, even before the coal is used to produce electricity.
On some days methane concentration above 2,000 ppb extends for 50 kilometres near the coal mines. We have not encountered any other landscape with elevated readings extending for kilometres, with the exception of days when there are bushfires.
Current approximations of methane being emitted to the atmosphere are a combination of measurements and estimates. This has resulted in considerable uncertainty in the values reported to government and tallied in Australia’s greenhouse gas accounts.
Australia needs a more extensive greenhouse gas monitoring network, so that we can reduce the uncertainty in our National Greenhouse Accounts and better track progress on our international emission reduction commitments.
Our research is focused on measuring what is actually being released into the atmosphere. This is vital for properly understanding how large our greenhouse gas emissions are, and where to focus our efforts to reduce these. Clearly, further reducing emissions from coal mining is a good place to start.
This article was co-authored by Elisa Ginty, an honours candidate at UNSW.
Urban residents naturally want to stay cool. Air conditioning is the usual choice, but it can be expensive to run. Air conditioning also adds carbon pollution, creates noise and can make outdoor spaces hotter.
So what else can we do to manage increasing urban heat? And who has the ability to act?
Urban planners are increasingly involved in developing and delivering urban greening strategies. While it seems like a “no brainer” to green cities, our international research shows that planners are not always comfortable with this idea.
However, green infrastructure – including street trees, green roofs, vegetated surfaces and green walls – is emerging as a viable way to help cities adapt to increased heat. Uptake of these technologies is slowly increasing in many cities around the world.
The Australian government has recognised this trend. An agenda to green Australia’s cities is now in place. Stated aims include managing climate change impacts, reducing urban heat, improving urban well-being and increasing environmental performance.
This urban greening agenda is part of the Clean Air and Urban Landscapes hub, under the National Environmental Science Program.
The broadening appeal of green infrastructure is helped by the fact it offers multiple benefits.
For example, shading from strategically placed street trees can lower surrounding temperatures by up to 6℃, or up to 20℃ over roads. Green roofs and walls can naturally cool buildings, substantially lowering demand for air conditioning. Green infrastructure can also provide habitat for wildlife, recreational opportunities for people, better management of stormwater runoff and improved urban aesthetics.
Hard surfacing, including concrete, asphalt and stone, is common in cities. It can increase urban temperatures by absorbing heat and radiating it back into the air. Green infrastructure can minimise this difficulty as it better regulates ambient air temperatures. Foliage allows local cooling through evapotranspiration, where plants release water vapour into the surrounding atmosphere.
Our research examined urban planners’ attitudes towards green infrastructure use in Australia, England and Ireland. We found that planners are broadly aware of green infrastructure as an urban intervention. They understand its use, application and capacity to provide multiple benefits, especially in terms of managing urban heat.
The planners we interviewed, while recognising the potential value of green infrastructure, strongly cautioned that delivering the technology can be an uncertain process. The biggest barrier cited was that planning departments are not experienced with green infrastructure.
Put simply, they tend to avoid it because it has not traditionally featured on planning agendas. Like any new planning endeavour, green infrastructure can create institutional, legal, economic, social and environmental challenges.
Some of the biophysical challenges associated with green infrastructure delivery are novel. Choosing appropriate forms of vegetation, for example, may be difficult. Decisions must be made based on prevailing climactic conditions, drainage capacity and species growth patterns.
Will root systems damage buildings or underground utility networks? Might trees topple during storms and damage houses? Are roofs strong enough to support a rooftop garden? Planners may not be able to answer these questions, which creates a need for external experts to advise them.
Our findings also highlight socio-political factors as barriers. These include governance concerns such as the political context in which planning decisions are made.
Management issues also feature. Chief among these are government commitments to budget for green infrastructure delivery and management.
Planners are also wary of public involvement. They know that public sentiment about green infrastructure can be influenced by perceptions of modified access, changed use, or loss.
The urgency for providing urban green infrastructure increases as climate change makes our cities hotter. Our research suggests the principal task for planners is to overcome embedded practices and to accept green infrastructure as an emerging but permanent urban feature.
This will not be easy. For example, a decision to use a road easement for green infrastructure may require multiple meetings with other government departments, utility companies and residents. Planners will need to coordinate these, manage stakeholder expectations and ensure cost sharing where necessary.
Legal, economic, social and environmental issues will require innovative solutions.
Planners will increasingly be tasked to deliver green infrastructure in cities. They will need to be clear on its value, be prepared to lead its delivery and learn from new challenges and solutions encountered along the way.
Urban residents all over the world stand to benefit if planners can successfully meet this challenge, particularly as hotter temperatures threaten urban comfort and habitability.