Emission factor estimates of cereal waste burning in Spain

Every year more than 5 million ha of cereal fields are affected by fires in order to eliminate cereal waste in Spain. The characteristics of this type of fire with intense flames are similar to those of the African dry savanna heading fires. This paper surveys the atmospheric emission caused by this process by combining results of field and combustion chamber experiments. Combustion chamber experiments show that during the flaming phase 88% of the fire exposed carbon is converted into CO2 and during the smoldering phase this percentage changes to 74%. These combustion chamber experiments also show that the soluble part of the aerosols emitted during the course of fires only represent 3% of the total particulate matter (TPM) produced, being the ions K+ and CI− the predominant ones. The cereal waste fire process can be represented by an arithmetic combination that takes into account the amounts of mass burned during the two phases of the fire: 0.90 flaming +0.10 smoldering. Emission factor estimates from field burning experiment are 13±7 g TPM kg−1(dm) and 2.8±0.2 g NOx kg−1 (dm). Finally, we obtain average emissions of 80–130 Gg TPM, 17–28 Gg NOx, 210–350 Gg CO and 8–14 Tg CO2 in Spain. These emissions represent nearly 25% of the total NOx and 50% of the total CO2 emissions by other pollution sources during the burning period in Spain.