September 28, 2022

expert reaction to Nord Stream gas leaks

There have been several news reports on the Nord Stream gas leaks following explosions. 

Prof Jeffrey Kargel, Senior Scientist, Planetary Research Institute, Tucson, Arizona, said:

“The Nordstream II leak is really disturbing. It is a real travesty, an environmental crime if it was deliberate. Although the amount of gas lost from the pipeline obviously is large, it is not the climate disaster one might think. This can be assessed very simply. The gas that was lost to the atmosphere was contained in the pressurized pipe. We know the pipe diameter and its length, therefore the volume, and we know the pressure that it was under, and the pressure drop as a result of the massive leak.

“So, from this particular massive methane leak, fear not. However, the massive roiling water due to the leak as we have seen in imagery is symbolic of the enormous amount of fossil fuel that the world is combusting. The global climate is changing drastically, with huge impacts on extreme climate mounting every year, decade after decade. It is such an extreme climate change that just about every adult age person on Earth knows it from first-hand experience. We can literally feel it on our skin.”

Prof Kargel’s calculation:

Pipeline length 1230 km, inner diameter 1.153 meters.  Volume = 1.48 million cubic meters.

Pressure drop 107 down to 5 bars reported in one source, so with an ideal gas law approximation, the depressurized volume is 151 million cubic meters. The mass of gas is about 1.08 x 10^11 g = 108 million kg = 108,000 metric tonnes.

A tonne of methane has a greenhouse gas potency of about 84 tonnes of carbon dioxide, so with that conversion, the pipeline’s leaked methane has a greenhouse potency equivalent to about 9 million metric tonnes of carbon dioxide.

That compares to annual global emissions of about 32 billion tonnes.

Hence, the methane leak is equivalent to about 0.00028 times the global annual carbon dioxide emissions, or about equivalent to 2.5 hours of global emissions.

Prof Joan Cordiner, Professor of Process Engineering at the University of Sheffield, said:

“Pipes don’t just leak catastrophically suddenly. Typically normal leaks due to corrosion start small and build up over time. Therefore such a sudden large leak can only have come from a sudden blow cutting the pipe.

“We can see from the width of the bubbles that the leak was sudden and very large, which is consistent with a large pipe being fully cut and not from normal corrosion we would see in operation.

“This is from a powerful event; either a large explosion or sudden physical trauma that cut the pipe wide open. The investigation will yield the answers. Meanwhile there is a large amount of natural gas going into the environment that will continue until the pipe is emptied.

“It’s also important to note that the event which caused this leak could have weakened the pipe at other points making the restart take longer. The power of the event is likely to have shaken down the length of the pipe and the equipment that holds or stabilises it, weakening joints. All of this should be tested and checked before restarting.”

Prof Grant Allen, Professor of Atmospheric Physics, University of Manchester, said:

“The environmental impact here is limited to the greenhouse gas emissions (mainly methane) from the natural gas left in the pipe. The impact will be limited as the pipelines are not pumping, just pressurised, so once the gas has escaped, the event will stop.

“Some of the methane emitted from the pipeline on the seabed will be oxidised by methanotrophic microbes (into CO2) as it rises in the water column. But given how violent the venting of natural gas appears to be, most of the gas will reach the sea surface as methane, a much more potent greenhouse gas than carbon dioxide.

“It has been estimated that there may be up to 177 million cubic metres of natural gas still residual in Nordstream 2 alone (at 300 Bar). This amount of gas is equivalent to the natural gas used by 124,000 UK homes in a year. This is not a small amount of gas, and represents a reckless emission of greenhouse gases into the atmosphere.”

Dr Jasmin Cooper, research associate, Department of Chemical Engineering, Imperial College London:

“It’s hard to accurately quantify the size of the emissions leak. Gazprom will probably have an estimate based on gas throughputs, but in terms of how much gas/methane is emitted into the atmosphere it would be difficult to measure as they need to send out a team now to measure and monitor how much methane is escaping into the atmosphere.

“In most literature, methane leaks from subsea pipelines are assumed to be zero in terms of impacts to global warming as it’s assumed the methane dissolves in the sea water, so doesn’t reach the atmosphere – but the Nordstream leak is very different so it is likely methane will bubble to the surface.

“The climate risks from the methane leak are quite large. Methane is a potent greenhouse gas, 30 times stronger than CO2 over 100 years and >80 times stronger over 20-years.”

Dr Paul Balcombe, honorary lecturer, Department of Chemical Engineering, Imperial College London, said:

“We don’t know exactly how much gas was in the pipes, but there are estimates of 150 – 300 million cubic metres. There are three pipes that are leaking – two pipes of Nord Stream 1, and one of Nord Stream 2. It is unlikely that they will release all their contents, but if just one did it would be about twice as much (~200,000 tonnes) as the 2015 Aliso Canyon leak in the US (~90,000 tonnes) which was the worst leak found in the US. It would have a very large environmental and climate impact indeed, even if it released a fraction of this.”

Prof Dave Reay, Executive Director of Edinburgh Climate Change Institute, University of Edinburgh

“The most direct effect of these gas leaks on climate is the extra dollop of the powerful greenhouse gas methane – the main component of natural gas – they are adding to the atmosphere.

“That said, this is a wee bubble in the ocean compared to the huge amounts of so-called ‘fugitive methane’ that are emitted every day around the world due to things like fracking, coal mining and oil extraction.”

Declared interests

Prof Dave Reay: No interests declared

Prof Forster: No interests

Dr Cooper: no interests to declare

Dr Balcombe: no interests to declare

Prof Kargel: I have no conflicts of interest regarding this news story or my comments about it

For all other experts, no reply to our request for DOIs was received.