On farmlands where large-scale cattle-breeding takes place, grasslands are the only places where carbon can be stored, thus mitigating the greenhouse gas emissions caused by this activity. This asset is certainly not negligible when we consider the criticisms that have been levelled at the animal-breeding sector and particularly the beef industry, due to the volume of greenhouse gases this industry produces. It still remains to be understood how, and in what conditions, grasslands could fulfil this role of carbon  ‘sink’ particularly in Wallonia, the home of the famous Belgian Blue breed. This is the subject of Elisabeth Jérôme’s doctoral thesis (1).

We have known for about ten years that grasslands, like forests, can store carbon in their soil. But what is the situation in Wallonia? Can a scientifically proven fact be applied to farming systems in our region? Can our grasslands, like those elsewhere in Europe, store carbon in their soil and thus compensate for part of the emission of the two other main greenhouse gases (GHG) caused by intensive farming methods, namely (nitrous oxide - N₂O - linked to fertilization and methane - CH₄ - linked to enteric fermentation by livestock)? Thanks to a doctoral thesis in Agricultural Sciences and Biological Engineering by Elisabeth Jérôme, it is now possible to partly answer these questions, and while the answers may not yet be unequivocal, they represent an original approach to an understanding of this question.

For three years, the young woman, who is a researcher at the Unit of Biosystems Physics of Gembloux Agro-Bio Tech (University of Liege), studied the carbon balance of a four-hectare plot of pastureland used for grazing by Belgian Blue breed of cattle, located at Dorinne (Yvoir, in the province of Namur, in Belgium). The first original aspect of her report resides in the fact that while other studies generally tend to focus on data from literature or on analyses carried out on the carbon content of soil samples, she resolutely opted for a method involving real-time in situ observation. She simultaneously examines the carbon dioxide (CO₂) flux exchanged between the ecosystem and the atmosphere and the other carbon fluxes exchanged at the plot boundaries.

Here, ‘at the plot boundaries’ refers to the fluxes that can cause carbon importation on the meadow (organic fertilization and food supplements) and carbon exportation (in the form of hay or silage during the mowing season, in the form of CH₄ during enteric fermentation or in the form of meat), but also, to a lesser extent, the carbon that is washed into the soil. “Everything that involved, for example, the compost and food supplements imported to the plot were the subject of quantitative notes and were willingly supplied by the farmer, Adrien Paquet, who is himself a bio-engineer”, explains Elisabeth Jérôme. “We completed the notes by analyzing the carbon content of samples provided by the farmer. In addition, each week during the growing season, we measured grass height and took samples in order to estimate the quantity of biomass that is produced by the grassland”.

(1) Jérôme Elisabeth (2014). Carbon balance of a grazed grassland in southern Belgium: impact of climatic conditions and grazing management (PhD thesis). University of Liege – Gembloux Agro-Bio Tech, Gembloux, Belgium.