Density Equation of Cassava-Stalk Briquettes Under Moderate Die-Pressure

Problem statement: Agricultural residues seem to be the most promising energy resources for developing countries. However, the majority of them have low energy density. One of the favorable technologies for enhancing that property is briquetting. For the case of Phitsanulok, a province in Northern Thailand, cassava is one of the most important crops. Therefore, a large amount of cassava stalk is left in the field after harvest. This study was aimed to investigate the quantity of cassava stalk in this province and to study cassava stalk briquette production. Approach: The potential energy from cassava stalk was calculated based on the productivity, residue-to-product ratio, residue returned to soil ratio and its heating value. Besides, the effects of moderate-range compression pressure, 70-110 bar, and the binder ratio, 10-20%, on briquette density were investigated. An empirical model was also developed and validated. Results: Base on the estimation, the quantity of usable cassava stalk in this area was approximately 18 kton year-1. The heating value of cassava stalk was found to be 16.39 MJ kg-1. Therefore, the total energy over 289 TJ year-1 can be obtained from this agricultural waste. According to the experiment, briquette density was in the range of 0.40-0.77 g cm-3. The coefficient of multiple determination for prediction of the proposed model was about 94.7%. Conclusion: It appeared that cassava stalk has high potential as energy source for this area. The density of cassava stalk briquette was increased with an increase in compaction pressure. Besides, it was found that the proposed model can be used for density prediction over the studied range.