We’re witnessing a strategic shift away from coal towards gas at the moment, but unless urgent action is taken, the climate benefits of choosing this cleaner fuel will be lost. Following the climate change discussions in Paris in December it has emerged that the developed world has, by and large, signalled the intent to move away from carbon dioxide emitting coal-fired power stations, using natural gas as a ‘bridging fuel’ towards more carbon-neutral forms of energy including wind and solar power.
In the UK, the government has ordered all coal-fired power plants closed by 2025 and alongside the opening of the Shetland gas terminal last month and Shell’s megamerger with BG Group in a bid to become the world’s leading LNG player, we’re already seeing changes take place.
When generating electricity, on a furnace-to-furnace comparison, natural gas consisting primarily of methane produces about half the carbon dioxide per unit of energy compared with coal. However, few realise that the picture looks less rosy when the current state of the gas production and supply system is taken into account. A host of recent studies show that accidental and intentional leaks of methane from production and transportation threaten to cause more net climate change damage than coal.
Methane is 20 times worse a GHG than CO, and the level of escape from engineered systems is significant.
A study published last year by engineers at the University of Colorado Denver (//doi.org/bcv8) found that in terms of greenhouse gas emissions, just 4% of gas leakage during production and supply would eliminate any advantage over coal. This may sound impossibly high but a review by the authors of leakage estimates from other studies found estimates as high as 10%.
Clearly, our natural gas production systems are not sealed tight. There are some areas where methane is allowed to leak intentionally in the interests of safety but there are also a lot of leaky valves and cracked pipes allowing gas to escape.
Estimates do vary wildly but it looks safe to assume that the “official” estimates are low.
So if there is to be any benefit from closing coal-fired power stations and building the gas fired units, the impact of methane leakage is a big challenge for the natural gas–methane supply chain. It must eliminate these incidental losses. This clearly represents both an economic opportunity to improve, but most importantly, eliminating both the intended and unintended leaks of natural gas is the only way that it is possible to have a positive impact on the carbon footprint of the world when using it as fuel to make electricity.
This will very much depend on improved gas production and supply systems, system maintenance, new operating procedures plus an improvement in the gas industry’s approach to emission prevention.
The Union of Concerned Scientists suggests that “Technologies are available to reduce much of the leaking methane, but deploying such technology would require new policies and investment.”
Writing for Scientific American in 2014, Claimet Central – an independent group of scientists and journalists – wrote that for President Obama’s Clean Power Plan to work, “the amount of methane leaking from the nation’s natural gas infrastructure must be capped.”
I suspect the call for action would be better served and accelerated if we had a better handle on the nature and scale of the problem. Chemical engineers with their expertise in systems engineering and focus on operational envelopes could play an important role in helping to better map and quantify the problem, including for emerging (and divisive) gas extraction methods such as fracking and underground coal gasification.
– Stan Higgins, CEO of North East Process Industry Cluster (NEPIC)
Published by The Chemical Engineer via www.thechemicalengineer.com