Improving Fuel Quality of Rice Straw Through Soaking Using Wastewater from Tofu Industry

Straw is agricultural waste that has enormous potential as an alternative energy source because of its abundant availability. However, straw has poor intrinsic properties as a fuel. Alkali metal content (especially K) is very high, causing problems in the combustion process at high temperatures. One effort to overcome this problem is by leaching to improve the quality of straw as fuel. This study aims to improve the energetic quality of rice straw through leaching. The study was conducted by soaking rice straw using tofu wastewater. Straw characteristics will be observed based on the soaking time, which is 0 (without soaking), 3.75, 7.5, 15, 30, 60, 120, and 720 minutes. The parameters measured in the study were the pH of tofu wastewater, ash content, potassium content, and calorific value of straw. The results showed that the leaching of minerals from rice straw by soaking for 720 minutes could improve the energetic properties of rice straw. Soaking rice straw can reduce its potassium content from 32% to 1.96% and increase its calorific value from 13.6 MJ/kg to 15.77 MJ/kg.