A few perspectives on the Nordstream leak

28 September 2022

The Nordstream leaks are – we assume – a barbarous act of sabotage. Many people are working on the assumption that this is a Russian act to drive up gas prices in the short term and signal to the international community that oil and gas infrastructure assets are at risk. This is worrying. But it is – at this stage, also – speculation.

Click here to see an article on Nature which cites Capterio

So how big is this leak?

Well, credit to our friend Andrew Baxter from EDF for being first, we think the mass of methane released for one of the lines is 111,000 tonnes (very similar to Andrew’s estimate of 115,000 tonnes). Since methane is 82.5x more potent than CO2 on a 20-year basis (and a mass basis), this means that the CO2-e emissions are 9.2 million tonnes, which is 2.0 million passenger vehicles – just like Andrew said (see excel sheet below). In total, the volume of gas released (at standard temperature and pressure) is 166 million cubic metres (0.17 BCM).

Since Nordstream 1 is actually 2 pipelines, the figure could be perhaps double, some 222,000 tonnes. The German government has estimated a similar ish figure of 300,000 tonnes (see Bloomberg article).

Assuming this leak took, say, 24 hours to emit this volume, for one line only, this is a staggering 4.6 thousand tonnes of methane per hour, a staggering rate.

How does this leak – for one line only – compare to other emissions sources?

The leak (one of the 2 pipelines) is 0.17 BCM – but compared to the capacity of Nordstream 1 (55 BCM per year), this is 0.3% of the annual capacity. However, 27.5 BCM per year (the volume of one pipeline is 0.075 BCM per day), meaning that the leak is actually 2.2 days of the potential suppliable volumes.

The total emissions of methane from the oil and gas industry are some 77 million tonnes of methane according to the IEA Methane tracker. This leak is 0.1 million tonnes, some 0.14% of this total. But a more interesting comparison is that globally, 77 million tonnes is 210,000 per day … meaning the leaks from both lines are similar to the daily emissions globally.
But at 111,000 tonnes for one line, the mass of methane from this event is equivalent to the entire emissions of methane flaring, venting and leaking over a whole year of a country like Bolivia (124,000 tonnes), Yemen (104,000 tonnes) and Korea (90,000 tonnes) – according to data from the IEA methane tracker. It’s also equivalent to 3 days worth of methane emissions from flaring, venting and leaking of the whole of the oil and gas industry in the US. Wow, that’s a lot!
In comparison to others, the recent leaks (in 3 separate but similar plumes) in the Zaap field in Mexico vented at a rate of 99 tonnes per hour – and this was a world class vent – but still this is 46x lower than the Nordstream 1 leak – see paper here
A large blow-out in Algeria’s Hassi Messaoud field in January 2020 had a rate of 25 tonnes of methane per hour, which is 184x smaller than this leak – see article
The leak has the CO2 equivalent emissions of a flare that operates for a year of a size around 16 million scf/day (assuming 100% combustion efficiency). To be clear, a flare of this size is itself very large.

And what if the Nordstream gas was lit?

Given that methane vented to the atmosphere is 82.5x more potent than CO2 (on a mass basis), there is a strong environmental case to light the gas – if this could be done safely (noting the leak is away from shipping lanes and populations). If the gas were to be burnt with a 100% combustion efficiency, then the emissions would not be – for a single line – 9.2 million tonnes, but instead be 0.3 million tonnes (which is only 3.4% of the CO2-e impact of venting the gas). A more plausible combustion efficiency is perhaps 70%, in which case the CO2-e emissions would be 3.0 million tonnes – still a 67% reduction

If it were to be burnt, it might look a little like this – a major lit leak in Mexico from 2021. Not a pretty picture, either!

How could it be measured?

In general there are several ways to measure methane – by satellite, by aerial surveys, or with on-the-ground detection.

Measuring methane from satellite over water is tricky, mainly because water has a high absorption rate at the wavelengths used to detect methane – limiting the light that is detected by satellite. Sea surface can also create noise. Recent developments of methods that are more successful include “sun-glint observation mode”. In contrast to vented (methane), combusted methane (i.e. flares) are easily detected by satellite from their thermal anomaly – this is the tech behind Capterio’s FlareIntel Pro flare-tracking tool.
In this case, it’s likely that the best way to measure the volume is to overly with methane detection equipment on a plane or a drone. This technique can accurately detect plumes and quantify rates and volumes

What key assumptions could be wrong in the calculation above?

We made some assumptions on gas composition, temperature and pressure, and on the rates
And that the methane reaches the surface (is not dissolved or oxidised in the water column, or trapped in hydrates)
And some assumptions on the combustion efficiency (if the vent were to be lit)