03/02/2015

Natural Gas: As Squeaky Clean as its Name?

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Natural gas has enjoyed a fortunate PR run in the green sphere with well-meaning advocates praising it as a ‘cleaner’ alternative to the common evils of the coal and mining industries. But as a range of environmental complications arise from fracking, the global warming potential of natural gas is also under scrutiny from environmentalists and its status as the benign power source of a post-coal economy is on shaky ground.

Unfortunately, comparison between coal and natural gas is not a matter of simple maths. Balancing which resource emits more carbon dioxide per energy unit generated is a complicated story.

When you compare the two only at the point of combustion, gas wins out, but the impact of gas should take into account all the emissions associated with it, from extraction to processing to combustion.

Gas vs Coal

Natural gas loses its green cred as soon as ‘unconventional’ extraction methods enter the equation. ‘Unconventional’ refers to accessing gas from coal seams mining or shale deposits, rather than natural (i.e. ‘conventional’) deposits. As economies scale and gas rises in popularity – ironically, in part due to the appetite for greener energy sources – natural deposits cannot keep up with demand.

Beyond Zero Emissions, the research and education organisation working towards a zero emissions economy for Australia, puts natural gas on a par with coal energy. They are supported by several studies from the US – notably, a 2011 National Center for Atmospheric Research study which examined the hypothetical scenario of cutting worldwide coal burning by half and using natural gas instead. The study found that global temperatures would in fact increase above those predicted with continued reliance on coal.

This supports Beyond Zero Emissions’ statement that, “Gas as a fuel in buildings is outmoded, hazardous and unnecessary, and deserves to go the way of the once-ubiquitous gas light.” The Alternative Technology Association (ATA) agrees.

Hidden Emissions

Natural gas is predominantly made up of methane, which seeps into the atmosphere when the resource is extracted, especially coal seam gas and shale gas.

To source hidden gas resources trapped in shale deposits, hydraulic-fracturing, aka ‘fracking’, where huge volumes of highly pressured water are injected into the earth, is used to shatter the shale. This releases the gas particles, which we want, and the methane which we don’t.

Fracking produces at least 30 per cent more methane than mining conventional gas. The unintentional release in the process of fracking to obtain the ‘cleaner’ energy source of natural gas may be more harmful than burning coal or oil in the first place.

Methane traps heat within the atmosphere more effectively than carbon dioxide – much more effectively.

A curious fact that isn’t often considered in ordinary discussions about global warming is that the atmospheric warming potential of gases should be looked at over a period of time, rather than given a flat rate of comparison, because as gases have different life cycles. So for example, methane, which oxidises over time in the atmosphere, turning into carbon dioxide and water, has a global warming potential of 72 times that of CO2 when averaged over 20 years, but only 25 times that of CO2 when averaged over 100 years (these figures come from the IPCC’s Third Assessment Report; other reports have found even higher rations).

Whether you choose to look at the next 20 years or the next century, natural gas and it the methane emissions that come with it still looks like a poor option.

So Where to From Here?

The short answer is: avoid natural gas.Of course that’s easier said than done if you have a stove or hot water heater that runs on gas. But it is something to consider when given the choice.

It is important to spread awareness of the pitfalls of buying into the idea that natural gas is a viable alternative to coal. Where great organisations and programs like the Green Table accreditation still promote using gas in cooking as an environmentally friendly initiative, there is a need to update public awareness the reality of renewable and non-renewable resources.

Natural gas should be put in the same box as coal, as a non-renewable resource that must be phased out and replaced with renewable energy sources.

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