Category 18 April 2019

NATAIR - Forest fires

Biomass burning represents an important source of atmospheric pollutants (CO2, CO, CH4, NOx, Volatile Organic
Compounds and Particulate Matter). Although Europe has a low contribution to global emissions, fires can be a major contribution to emissions in certain times and regions. Therefore, within the NATAIR project a comparison of different available data about fire emissions from open lands was carried out, in a European context. In this study, emissions of carbon monoxide (CO), methane (CH4), nitrogen oxide (NOx), Volatile Organic Compounds (VOC) and particulate matter (PM2.5. and PM10) were considered.

Different information is needed to accurately evaluate fire emissions: the land area burnt; the amount of fuel materials per unit area (fuel load); and the properties of the fuel.

Data for burnt area were obtained through combination of the Indian Remote Sensing satellites’ Wide Field Sensor (IRS/WiFS), available from the European Forest Fires Information System, and the Global Burnt Area Map 2000. Due to this combination a total burnt area of 145500 km2 was estimated for the project domain in the year 2000. Most of this area (85%) was located in the Russian Federation, Ukraine and Kazakhstan. From the EU27 zone, most of the burnt area corresponded to Eastern Europe and Mediterranean countries. If available data are compared, great differences can be observed. For example, automatised and remote sensing products showed some limitations related to spatial resolution and applied algorithms. Moreover, statistical data collections, such as UNECE-FAO or European Community Statistics, don’t show methodological limitations but they don’t consider agricultural or grass burnt. Moreover, frequently statistical datasets only have data related to fires where fire fighters are present. The biggest differences have been detected in Russia, Ukraine, Kazakhstan and Romania, but in some other countries (Spain, Greece, Portugal and France), differences were still significant.

Regarding fuel load, an exact description requires an in-depth characterization of weight per unit area, size and bulk density, intensity and severity of the fires, etc. So, for forest and scrubland ecosystems, a simpler fuel model is usually applied. Within the project, one of the most popular fuel models (the National Fire Danger Rating System-NFDRS) was applied to a combination of land use/cover data and natural vegetation information. Land use data were obtained from combining the CORINE 2000 land cover database and the Regional Global Land Cover 2000, whereas natural vegetation data comprised information about 19 vegetation formations from the Map of Natural Vegetation. A NFDRS fuel class was assigned to each combination of land use and vegetation formation. Final fuel loads ranged from 1.6 (grassland) to 37 tons of dry matter per ha (Mediterranean oakwood). However, these data were found low in comparison with previous studies.

Finally, information about fuel properties was obtained from a previous study from Leenhouts, relating each value with NFDRS fuel classes. Fuel consumption, fractions of smouldering and flaming combustion and emission factors from the abovementioned pollutants were calculated in each case. Other complementary parameters were taken into account for modelling purposes: injection height (the height where emissions are injected to the atmosphere) and (the speciation of non-methane VOCs.

Emissions across Europe were estimated by combining burnt area, fuel load and emissions factors. Calculated emissions have been found to be lower than estimations from a reference emissions inventory (EMEP/CORINAIR) for CO (two-fold), CH4 (three-fold) and VOC (four-fold). The reason for this could be that only low surface intensity fire conditions were taken into account and low fuel factors were assigned to forests. Furthermore, some uncertainties during calculations have been found. In order to increase the quality of emission calculations, detailed ground surveys for characterising individual fire events would be necessary, together with complete and continuous country statistics. Additionally, a deeper knowledge about fires in abandoned lands would be necessary, since they are responsible of large burnt areas and high emissions. Finally, a continuous comparison between satellite-based burnt areas datasets and statistical databases would be also convenient.

Köble, R; Barbosa, P. and Seufert, G. (2008): Estimating emissions from vegetation fires in Europe