A study of ultrafine particle emission factor from rice straw burning in Lombok Island, Indonesia

Rice straw is a by-product found in rice production at harvest. As a by-product, rice straw generally is not a useful product and is burnt directly, as commonly found in Lombok island, Indonesia. On this island, rice straw, as a biomass product is directly burnt as a biomass burning activity and well-known to contribute to air pollution. On the other side, biomass burning is a complex system in which many types of gaseous and particulate matter emissions occur. Ultrafine particle is one of the particulate matter emissions in which having a diameter of less than 0.1 µm and is well-known to be related to serious health effects. Thus, this study was aimed to characterize the emission factor of rice straw combustion of Lombok Island in terms of ultrafine particle emission. The study used an exposure chamber with a dimension of 40 × 40 x 25 cm3. The biomass sample was burnt in a furnace, while the emission was sucked into an exposure chamber with a constant flow-rate. The ultrafine particle concentration was measured using a TSI P-Trak Ultrafine Particle Counter Model 8525 for a certain time. At the last time, the burnt mass of the rice straw was also measured. The results showed that the emission factor is related to the speed of biomass burning. There is significant correlation between velocity and the ultrafine particle emission factors. The highest velocity on the combustion process has the smallest emission factor, 1 × 107 particles/ mg of the burnt biomass. On the other side, the lowest combustion speed generates the highest emission factor, 11 × 107 particles/ mg of the burnt biomass. The faster burning of rice straw biomass, the lower emission factor.