The emission of the greenhouse gases methane and nitrous oxide has been structurally underestimated, as a result of the measuring methods used. This is the conclusion of the scientist Petra Kroon, who carried out research for the Energy research Centre of the Netherlands (ECN) and Delft University of Technology (TU Delft, The Netherlands) into an innovative method for measuring the emission of these gases.
Kroon recently obtained her PhD degree for this much more accurate method, which also partly solves the problem of this systematic underestimation.
When it comes to greenhouse gases many of us think first of CO2. But a large proportion of global greenhouse gas emissions are actually other gases, such as N2O (nitrous oxide) and CH4 (methane). In the Netherlands the contributions of methane and nitrous oxide to the total emission of greenhouse gases are estimated to be 8% and 6% respectively. Worldwide these figures are 14% and 9%.
The emission of methane and nitrous oxide is largely the result of agricultural activities; nitrous oxide from fertilizers and methane mostly from cows. In peat pasture areas these emissions are particularly prevalent. PhD student Petra Kroon carried out measurements of methane and nitrous oxide for ECN and TU Delft on an intensively managed peat pasture, but the measuring techniques she used can also be used in other ecosystems.
Given the large contribution these two gases make to total greenhouse emissions, it is important to chart their emission levels accurately. According to Kroon, however, there are considerable disadvantages to the emission measurement technique most commonly used for these gases, the so-called ‘chamber measurement’ method. Put simply, this involves regularly measuring the concentration of the gases emitted from the soil and trapped in a sealed box. Rising concentrations of these gases are then analyzed in order to draw conclusions about the amount of gas being given off by a given surface area. The problem with this method is that methane and nitrous oxide emissions fluctuate strongly in time and space. “If you do the same measurements ten meters away, or ten days later, the results can be totally different. To reduce uncertainty you would have to do an almost impossible number of measurements,” explains Kroon. The result is a high uncertainty in the measured annual emission values: about 50%.
Read the complete store at Science Daily