Our forgotten methane emissions

11-10-2016

Martien Visser: "We must support our agricultural sector"

 

Martien Visser
Martien Visser

A report on emissions of methane from the gas sector, which make a major contribution to global warming, was recently published in The Economist. The author suggests that we would be better off using coal than natural gas. Something like this obviously sets off alarm bells, and also rouses curiosity. What is the actual situation?

When we talk about greenhouse gases we usually simplify the problem to CO2. But there are many more greenhouse gases, with methane being the most important. Methane is very different from CO2 because it only remains in the atmosphere for around 12 years, after which it disappears by being transformed into water vapour and CO2. On the other hand, at least while it is present in the atmosphere, methane has a much more powerful greenhouse effect than CO2.

The IPCC has determined the greenhouse effect of various substances, including methane, in comparison to CO2. The review period is important here: initially, methane is much more problematic than CO2, but after a few years methane disappears as a result of conversion into CO2. The normal review period is 100 years, about the length of time until things could start to get really serious for humanity on earth. According to the IPCC, the average greenhouse effect of methane is then around 30 times higher than that of CO2.

So far so clear, it would seem. But this figure is often misinterpreted, because people forget that this 30 to 1 ratio established by the IPCC is based on 1 kg of methane and 1 kg of CO2. But burning 1 kg of methane produces not 1 kg of CO2, but 2.8 kg of CO2. The difference between allowing methane to escape, for instance if the flame under your saucepan goes out, and burning it results in a factor of 30/2.8, so approximately 10 to 1 rather than 30 to 1 which is wrongly assumed

The 2015 annual report on “Monitoring livestock farming sustainability” never mentions the word methane

Methane is naturally present in the air at a very low concentration of less than 2 ppm. This is an equilibrium value between the emission of methane and conversion into water vapour and CO2. Current worldwide methane emission amounts to 900 billion m3 a year. Half of this methane is produced naturally, mainly from marshland and other watery areas. The other half is caused by human activities (anthropogenic). The proportion of methane in the atmosphere has doubled since 1850, and has been stable for a few decades. For comparison, the levels of CO2 in the atmosphere, currently 400 ppm, are still rising every year.

According to the IPCC, the increase in methane concentrations is currently responsible for 25% of the additional global warming. That is significant, as according to the experts it means that reducing our methane emissions could help defer the rise in global temperatures by 10-15 years or more. Limiting methane emissions would also have a rapid effect because methane is removed from the atmosphere quickly.

Now, we could of course drain the world’s marshlands and allow our nature reserves to dry out. But let’s first look at ourselves, at anthropogenic methane emissions.

The IPCC states that 25% of these anthropogenic methane emissions come from our livestock herds, mainly ruminants such as sheep, goats and cattle. Most of it comes from their mouths, and the quantity of methane depends on the type of feed. Useful to know. A further 25% of the anthropogenic methane emissions are due to the waste which we as humans produce and dump everywhere, while 10% comes from rice-growing and another 10% from biomass combustion. Most of this takes place in Africa, but your open fire also contributes.

At the Energy Podium we are of course looking at our energy sector, which accounts for the remaining 30% of worldwide anthropogenic methane emission. The IPCC does not make any distinction between coal, oil and gas. Other bodies do, and have concluded that coal (mining) and oil (production) are each responsible for 7.5%, while natural gas has the remaining 15% of global anthropogenic methane emissions on its conscience.

This 15% is equivalent to 70 billion m3, 2% of the total amount of natural gas used in the world. Given the 10 to 1 ratio which I mentioned earlier, the greenhouse effect of natural gas, including the methane losses in the gas chain, is therefore 20% higher than is calculated on the basis of CO2 emission after combustion. As producing electricity from coal causes more than twice as much CO2 emission as producing it from natural gas, then even leaving aside the methane emissions from coal mines, we can conclude that the author writing in the Economist is wrong.

Within the Netherlands, the Compendium voor de Leefomgeving [Environmental Data Compendium] has stated that our anthropogenic methane emission is responsible for 10% of our total greenhouse gas emissions. 70% of this methane emission comes from agriculture, and as you now know, mainly from ruminants. The Dutch waste sector causes 15% of national methane emissions. It used to be much more, because nowadays we incinerate our waste.

The Dutch gas sector is responsible for about 10% of Dutch methane emissions, equivalent to 0.2% of our gas consumption. This means that the Netherlands is doing a bit better than the rest of the world. An export market seems attractive, but there are even better options. For example, there is currently a programme of replacing old cast-iron gas pipelines in city centres, where methane leakage is relatively high.

We are carrying out this programme because methane leakage can be dangerous. We also now incinerate our waste because we don't want any more landfill. And the 2015 annual report on “Monitoring livestock farming sustainability” never mentions the word methane.

You have got the message: little attention is being paid to reducing our methane emission, and that is wrong. Suppose we reduce Dutch methane emissions by 5%. This will reduce Dutch greenhouse gas emissions by as much as the new wind park near Borssele, which is being subsidised to the tune of € 2 billion.

Strage. We are handing over billions of euros of taxpayers' money to our electricity sector to make electricity a bit more climate-friendly. Shouldn't we also subsidise the Dutch agricultural sector so that our milk, cheese and meat becomes more climate-friendly?

Martien Visser is lecturer in energy transition and network integration at Hanze University of Applied Sciences, Groningen

 

Source: Energiepodium.nl