Development of carbonized rice husks briquettes using organic waste as binders

Abstract

In Uganda, rice husks have no commercial value yet are produced in very large numbers and the methods for their disposal are still a challenge. Waste from rice husks is not readily bio-degradable and so this make its disposal challenging. One common disposal method is open burning which causes environmental pollution and enhancement of greenhouse gases. Other common house hold waste such as peelings from matooke, sweet potato and cassava could act as binding material in the development of briquettes. With the availability of these materials, it is important to find possible ways of converting them into sustainable energy using low technology to encourage households to make their own briquettes at a low cost. This study determines the potential of rice husk bio-char for briquettes and the effects of using food waste such as cassava peeling flour, matooke peeling flour, sweet potato peeling flour as a binder. The main objective of this study is to develop carbonized rice husk briquettes using different organic waste binder material. These rice husks were carbonized in a step-down kiln at temperatures ranging between 400 °C – 500 °C to form the bio-char. The organic binders were mixed with the bio-char before they were compacted at a pressure ≤7Mpa into briquettes. The physical properties of these briquettes were obtained using Thermogravimetric analysis and other characteristics such as determining the mechanical integrity using the drop strength method, and thermal characteristics determined by observing the flame temperature during combustion were determined. It was found that the rice husk bio-char had a high ash content of about 47% which made the briquettes has a high ash content as well ranging between 44% and 47%. The briquette with the highest particle density was the one with 15% cassava binder flour that had 427.11kg/m3 and the sample with 15% matooke binder had the highest HHV and maximum attainable flame of 21.75 MJ/kg and 828.7°C respectively. Increasing the binder reduced the ash content while it increased with the peak temperatures which made them more thermally stable. Briquettes with a higher binder ratio had the best thermal and physical performance.