Atmospheric sulphur also comes from farming

Researchers have been able for the first time to identify the extent to which manure contributes to the atmospheric content of sulphur.

2017.11.08 | Claus Bo Andreasen

Aarhus University’s studies show that hydrogen sulphide emissions come from slurry evaporation from pig and cattle sheds in particular. Photo: Colourbox

In the current emission inventories and climate models, it is assumed that agricultural production does not contribute to the amount of sulphur in the atmosphere. This is a wrong assumption, however, according to a new study from the Department of Engineering, Aarhus University. The study has just been published in the prestigious scientific journal Nature Communications.

Sulphur is emitted from manure in the form of hydrogen sulphide, which is quickly converted in the atmosphere to sulphur dioxide. Hydrogen sulphide thereby has the same effects as sulphur dioxide. The study shows that in areas with intensive livestock production, sulphur from manure constitutes about half of the sulphur emission known to date (in the form of sulphur dioxide) into the atmosphere. This means that approximately one third of the total atmospheric sulphur emission in Denmark is made up of hydrogen sulphide from manure.

It might at first seem surprising that we have overlooked the fact that farming is such a big contributor to the atmospheric content of sulphur. However, only a few limited studies of this area exist, in both Denmark and other countries.

This is partly because it has been very difficult to measure sulphur emissions from livestock production, as explained by Associate Professor Anders Feilberg, Department of Engineering, Aarhus University, who is one of the researchers behind the study.

“With the development of PTR-MS (proton-transfer-reaction mass spectrometry), it’s become possible to monitor emissions of sulphur compounds from livestock use with great certainty and in high time resolution, which provides comprehensive and detailed data material,” says Associate Professor Feilberg.

In principle, PTR-MS is an online technique for weighing air molecules and counting their numbers.

New opportunities for limiting emissions

Sulphur is combined in chemical compounds with other substances in the atmosphere and forms particles that are hazardous to health.

On this basis, major efforts have been carried out in recent years to reduce the sulphur content in the atmosphere. For good reasons, the focus has been on the well-known sources of sulphur in the atmosphere, mostly oil, coal and natural gas, which emit sulphur into the atmosphere via combustion engines and power plants, etc.

The study provides new opportunities for working in a more targeted way to reduce sulphur emission from livestock use.

Studies show that hydrogen sulphide emissions come from slurry evaporation from pig and cattle sheds in particular. In addition, there is a relatively small loss in connection with spreading manure.

Aarhus University is currently carrying out a number of research activities aimed at developing technologies for purifying air from animal sheds and technologies for reducing the evaporation of manure. Such technologies could help reduce the emission of sulphur.

However, Associate Professor Feilberg points out that hydrogen sulphide emission from farming has probably already been reduced. This is because it is closely related to ammonia emission, where a considerable number of action plans for better utilisation of nutrients in manure have contributed to reducing emissions.

“Acidifying slurry, which is similarly used to reduce ammonia loss, also provides a significant reduction in hydrogen sulphide production,” explains Associate Professor Feilberg.

Impact on climate models

The new knowledge is also important in connection with developing climate models. As mentioned above, sulphur is combined in chemical compounds with other substances and forms airborne particles. These particles reflect the rays of the sun, thus reducing global warming, which is partly caused by climate gases. At the same time, the particles contribute to cloud formation, which also increases the reflection.

“Until now, the contribution of farming has not been included in climate models and the new knowledge could contribute to improving the climate models, particularly at a global level,” says Associate Professor Feilberg.

However, more measurements are required in more countries before the significance can be clarified at a global level.

Read more

Contribution of livestock H2S to total sulfur emissions in a region with intensive animal production. By Anders Feilberg, Michael Jørgen Hansen, Dezhao Liu and Tavs Nyord, Department of Engineering, Aarhus University.

For more information, please contact

Associate Professor Anders Feilberg
Department of Engineering
Aarhus University
af@eng.au.dk
+45 3089 6099

AU Engineering