Sunday, November 28

Nitrous oxide from agriculture – emissions lower than expected

Nitrous oxide is produced on intensively used arable land (dpa / picture alliance / Patrick Pleul)

One of the most important tasks of the new government will be to make Germany’s agriculture fit for the future. And according to the final report of the Future Commission for Agriculture, which was presented in the summer, this also means above all: The CO2 emissions from arable land and fields must be reduced. According to the current greenhouse gas inventory, agriculture is responsible for 7.6 percent of all German emissions, and around 40 percent of this is accounted for by nitrous oxide, which is produced when nitrogen compounds are broken down from liquid manure and artificial fertilizers in the soil.

At the Thünen Institute for Agricultural Climate Protection in Braunschweig, researchers around Dr. Roland Fuß took a closer look at these nitrous oxide emissions from agriculture and found out that they have been a little overestimated so far.

Ralf Krauter: What was the driving force behind your more detailed analyzes of nitrous oxide emissions from agriculture?

Roland foot: Laughing gas is a powerful greenhouse gas, its climate impact is around 300 times greater than that of CO2, and it is responsible for a very high proportion of emissions from German agriculture. Here at the Thünen Institute we are responsible for calculating these emissions, for national reporting, and in this context it was of course important to improve the methodology: on the one hand to be more precise, but on the other hand also to take regional characteristics in Germany into account can and in the future also be able to better map mitigation measures that are taken in agriculture.

300 times stronger greenhouse gas than CO2

Krauter: We’ll go into the results of your analysis in a moment, but let’s start with the methodology first: How did you proceed to get a more comprehensive picture than we had before?

Foot: We first carried out a literature study in which we extracted the data from studies that have measured nitrous oxide emissions on fertilized arable land or grassland soils in Germany over the past 30 years. We then merged these and evaluated them with a statistical analysis. We distinguished between nitrous oxide emissions from mineral soils and from drained peat soils, and we also took into account the different climatic and soil conditions in Germany, in which we carried out this analysis separately for different regions in Germany.

Krauter: One of the most striking results of your analysis is that nitrous oxide emissions vary greatly from region to region. How much do they fluctuate and how does that actually come about?

Dry floors release less nitrous oxide

Foot: This essentially comes from the microbial processes that produce nitrous oxide in soils. These are very strongly influenced by environmental conditions. There are certain optimal conditions where a particularly large amount of nitrous oxide is produced, and other conditions where there is less. For example, when it is very dry, relatively little nitrous oxide is released from the soil, whereas severe winters, for example, promote the formation of nitrous oxide again. In addition, drained bog soils are hotspots for nitrous oxide emissions, as a particularly large amount of nitrous oxide is released.

Krauter: You quantified that with the help of so-called emission factors, which ultimately reveal how much is then released per hectare depending on the nitrogen input. I have seen the fluctuations between 0.39 in the northeast and 0.88 in the southeast. Was that surprising for you, this range of fluctuation?

Foot: No, it was already known from individual results before our study that emissions are generally somewhat higher in southern Germany, whereby the issue here is not emissions per hectare, but emissions per kilogram of nitrogen introduced. That means that you can of course calculate an emission more correctly from this, you know how much is fertilized per hectare, but the amount of fertilizer that is applied also overlaps in Germany.

New benchmark: emissions per kilogram of nitrogen applied

Krauter: What do your results now ultimately mean for compliance with our climate protection goals? One of the results of your study is that nitrous oxide emissions from agriculture are a little lower overall than previously thought. Does that mean we can lean back now and carry on as before?

Foot: It doesn’t mean that, of course. The nitrous oxide emissions are around four million tons of CO2 equivalents, that is, when converted into CO2, they are lower than previously assumed. However, this specification has been carried out for the entire time series, so emissions have been lower in the reporting since 1990 to 2020. For the emissions budgets, which are set out in the Federal Climate Protection Act, this means that we will do it easier for the time being, the falling budget, which in agriculture will drop from 70 million tons in 2020 to 56 million tons in 2030. We can now comply with that more easily, but of course this methodological change does not mean any real reduction. We still need mitigation measures that are implemented in agriculture because we have long-term goals. We want to be climate-neutral in Germany by 2045, that is only possible if we also reduce emissions from agriculture, and the EU Commission is currently proposing even more ambitious goals that we can only meet if we now go to the reduction rates and consistently try to save everything that can be saved in terms of greenhouse gas emissions in agriculture.

Germany must be climate neutral by 2045

Krauter: So your study ultimately says that on the way to a more climate-neutral agriculture we had in principle already made a little further headway than we previously knew, but that is actually just a booking trick. So we still need to take further action. What does your study reveal about what would be most effective now?

Foot: It is very difficult to implement emission reductions in agriculture because the emissions – unlike, for example, in energy procurement – do not come from technical processes, but from biological processes that are more difficult to control. But important starting points are, on the one hand, that the nitrogen efficiency of agriculture is increased, that is, that we achieve less fertilization and more yield. A second starting point is particularly in animal husbandry: Work must be done here to ensure that less nitrogen is fed in, that the use of protein in animal husbandry is reduced – there is still significant potential for savings in Germany. And we also have to ensure that the storage of liquid manure and other farm manure releases as few emissions as possible.

Krauter: Finally, asked again about the role of laughing gas: I’ve read that they are responsible for around 40 percent of all emissions in agriculture. Can you turn something on this number in the future or will it stay that way?

Laughing gas, methane and cattle farming

Foot: According to our study, that 40 percent is now a little lower, but of course nitrous oxide is still a significant part of agricultural emissions. Since the share of nitrous oxide in these emissions has decreased, the share of methane emissions from agriculture in total emissions increases, and methane emissions arise mainly from cattle farming, because methane is excreted by ruminants.

Statements by our interlocutors reflect their own views. Deutschlandfunk does not adopt the statements of its interlocutors in interviews and discussions as its own.

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