Biofuel combustion is increasing across Europe. VERIFY researchers are working to separate and quantify CO2 emissions from biofuel combustion to ensure that likely future intensification supports international climate objectives.
The overarching objective of VERIFY Work Package 2 (WP2) is to develop the components of an observation-based monitoring and verification system (MVS) dedicated to fossil fuel CO2 emissions (ffCO2), using in situ and remotely sensed atmospheric measurements of CO2 and co-emitted tracers. To this end we develop high resolution bottom-up fossil fuel and biofuel emission estimates of CO2 and co-emitted tracers to be used in the (inverse) modelling of CO2. Species like NOx and CO are produced in the same combustion process as CO2 and therefore emitted alongside anthropogenic CO2 emission. Measuring these species thus helps researchers to separate the anthropogenic CO2 signal from the biosphere CO2 flux which does not include them.
Although ffCO2 is our target, this also requires quantification of the CO2 released by combustion of biofuels like wood or biodiesel. Biofuel combustion is increasing in Europe as is visualised in our high-resolution emission inventory maps for the period 2000-2015 (see Figure 1). This is also visualised in Figure 2 where it can be seen that the biofuel fraction of total CO2 emission is higher in 2015 than in 2005. Given that total CO2 emissions increased over this period, this shows that biofuel combustion not only kept up with the trend but also partly replaced ffCO2 emissions. Another important feature of both the grid maps and Figure 2 is that the contribution of biofuel combustion to total CO2 emissions is highly variable in both space and time, and ranges from ~45% to well below 10%.
Figure 1 : The difference in fraction of total CO2 emissions coming from biofuel combustion between the years 2000 and 2015 for countries across Europe
While this information is necessary for the VERIFY observation-based MVS, it is important to follow these trends closely in their own right. CO2 from biofuel combustion, for example, is classified as climate-neutral under the UNFCCC framework. However, it remains uncertain if this will continue to be the case under intensification of such practices, as may be needed given the timeframe for the world to cut CO2 emissions in order to achieve the Paris Agreement temperature goals. Such a trend can only be detected and understood if we follow ffCO2 and CO2 from biofuel separately.