Oc1

Figure 5:

Particle diameter (^m)

Size distribution of organic and elemental carbon composition in exhaust gases.

We consider that in this experiment, the air sampling method for atmospheric aerosol is not able to measure those semi-volatile carbonaceous components which would condensate from gases to particles by partition under cooling down to ambient temperature, and hence the real contribution to atmospheric aerosol may be underestimated. It is necessary to carry out experiments with an improved the air sampling method for the exhaust gases after air dilution in order to cool the exhaust gases down and have a better measurement of the real contribution of the semi-volatile carbonaceous components in the exhaust gases to atmospheric aerosol.

3.4.2 Emission behavior of ionic composition of SPM in the exhaust gases The analytical results of ionic composition of suspended particulate matter (SPM) in the exhaust gases are shown in figure 6. Ionic concentration results showed that K+ had a high concentration in all particle sizes. K+ is an important component of biomass burning [11], since it is used in metabolic growth processes, hence this component is used as a marker for biomass burning (combustion) contribution to atmospheric aerosol. In addition, Cl- also showed high concentration in the all particle sizes from combustion of the waste rice husk. Because Cl- is especially found at higher concentrations during winter seasons; therefore, it is thought to arise from biomass burning of agricultural wastes including waste rice husk. In our further study, we plan to carry out combustion experiments using different biomass fuels, apart from waste rice husk in order to compare the abundance of Cl- from biomass burning of different agricultural wastes.

Particle diameter (^m)

Figure 6: Size distribution of ionic components in exhaust gases. 4 Conclusion

Particle diameter (^m)

Figure 6: Size distribution of ionic components in exhaust gases. 4 Conclusion

In our experiments, we evaluated the combustion characteristics of the size distribution of exhaust particles (SPM) when using the several kinds of waste rice husk samples from different producing areas as the biomass fuel used for the new-type air vortex current combustor developed by our laboratories. The waste rice husk was suitable to maintain a combustion temperature above 800 °C. Our results indicate that waste rice husk is able to substitute fossil fuels if we use this new-type combustor.

From the analytical results of the size distribution of carbonaceous composition collected by the air sampling system, it is shown that elemental carbon (EC1) dominated in the coarse particles, which are produced by incomplete combustion, and organic carbon (OC2) dominated in the fine particles. Carbonaceous concentrations in the emitted particles can be reduced substantially by highly effective combustion when the combustion conditions of the combustor were improved. As the results of the ionic composition, high concentrations of potassium ion (a tracer of biomass burning) were determined. Combustion temperature control is important to avoid corrosion in the system and the health effects from high concentrations of chloride compounds (ions).

We also have to calculate the better air/fuel ratio in order to reduce the emission of harmful substances [12, 13] and to optimize the fuel/carbon discharge coefficient in order to make the waste rice husk as a renewable energy source for alternate fossil oil fuel in the future.

Acknowledgements

This study was supported by the Special Funds of the local Government of

Saitama Prefecture, Japan, and partly subsidized by two Funds for Basic

Researches (B) (No. 19404021, FY2007~FY2009 and No. 22404022,

FY2010~2012) of Grant-in-Aid for Scientific Research of the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

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Section 6 Environmental health issues

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