Reduction of fine particles exhausted from small-size combustor using agricultural waste residue by controlling burning temperatures

Abstract

About 3.9 million tons of agricultural residue waste biomass such as rice husk and straw are stably produced from rice each year in Japan. It is reported that vapor pollutants and particles emitted from the burning of agricultural residue waste biomass such as waste rice husk and straw have serious infl uences on visibility, human health, and global climate. Therefore, it is necessary to utilize waste rice husk and straw effectively to reduce air pollution. In recent years, there has been an increasing demand for the effective utilization of waste agricultural residue biomass instead of fossil fuel in combustors for farming such as greenhouses heating during the winter season. However, there is a lack of regulations or laws to control air pollution from these small-size combustors in Japan. So far, small-size combustors have been characterized by their structural simplicity and low cost. Therefore, it is necessary to evaluate and control the emission of air pollutants such as fiparticles (i.e. PM 2.5 ‐ particles below 2.5 µm in aerodynamic diameter) due to the poor combustion performance of small-size combustors. In this study, it was investigated whether it would be possible to utilize biomass fuel selected from waste rice husk and straw of agricultural residue waste biomass based on the laboratory combustion experiments. The emission behavior of harmful suspended particulate matter produced from burning rice husk and straw was evaluated by measuring carbonaceous and ionic composition of PM 2.5 in the exhaust gases. From the analytical results, it was found that particulate mass concentrations reduced substantially at high-temperature combustion. However, ionic compositions were increased with the increase in combustion temperature. It can be suggested that stable combustion should be performed under suitable conditions to control air pollutants emitted from biomass fuel, although small-size combustors are still not regulated to control PM 2.5 emission.