Realistically Assess and Reduce Greenhouse Gas Emissions in Rapeseed Cultivation

(Union for the Promotion of Oil and Protein Plants (UFOP) (Google translation)) Global standard values overestimate nitrous oxide emissions in rapeseed cultivation -- A network of eight partners under the coordination of the Thünen Institute (TI) for agri-climate protection engaged in a research project on the cultivation of rapeseed and the associated greenhouse gas (GHG) emissions. The aim was to find out whether GHG emissions are valued realistically within the framework of climate protection agreements for Germany. Result: The nitrous oxide emission factor for GHG rape assessment is too high for German conditions.

Rapeseed is the most important energy crop for biofuels in Germany. By far the highest GHG emissions in rapeseed cultivation are caused by field emissions of nitrous oxide and the production of the required synthetic N fertilizer. These two levers must therefore be used in order to comply with EU regulations (EU 2015/1513). According to this, biodiesel & Co. must save at least 60% (old plants 50%) of GHG emissions compared to fossil fuels since 1.1.2018. For the GHG balance, biofuel manufacturers can use EU Renewable Energy Directive (EU) renewable values or regionalized inputs for inputs such as fertilizer and fuel. The work of the TI-Projekt-Verbund has now shown that these values are unrealistic for Germany. The estimated amount of fertilizer is too low, However, the nitrous oxide emission factor overall still too high: Instead of the assumed 34 kg N / t oilseed rape be 50 to 56 kg practice-usual, the factor for N2O is not at 1.0, but only at 0.6 percent. The scientists come to this conclusion by applying a new, more differentiated methodology according to Stehfest / Bouwman (2006). They call for future use of this method with realistic values so that the GHG balance of rapeseed biodiesel is no worse than it actually is.

In addition, the researchers recommend replacing synthetic with organic fertilizer, for example, by digestate, which in the project with the minimization of ammonia emissions improved the GHG balance. One potential problem, however, is the risk of higher nitrogen surpluses. At the same time, it is also important to avoid nitrous oxide emissions in the production of synthetic fertilizers, to save energy and to replace them with renewable energies.

Finally, the researchers were able to show that in this country rapeseed wheat in comparison to wheat wheat in the crop can save an average of about 5 kg N / ha in this country and despite this, a wheat yield of 5.6 dt / ha can be achieved. This pre-crop effect would have to be credited to the rapeseed. In general, a more holistic assessment is needed that looks at the entire crop rotation.

Overall, the researchers still need to develop, in computational approaches as well as in the reduction of fertilizer use in practice. For this it would be helpful to distinguish the purchased fertilizer with its specific GHG value. New approaches to application techniques and crop rotation could also further reduce GHG emissions.

Last but not least, the use of biofuels for cultivation and harvesting is an option for a better GHG assessment of rapeseed production.

Information and final reports on the subprojects are available on fnr.de in the menu Project Funding under the grant marks 22403212, 22403312, 22403412, 22403512, 22403612, 22403712, 22403812.

The project was funded by the Federal Ministry of Food and Agriculture (BMEL) through the project agency Fachagentur Nachwachsende Rohstoffe e. V. (FNR). In addition, there was support from the Union for the Promotion of Oil and Protein Plants (UFOP).