Chemical pretreatment of rice hull and coconut hull using response surface methodology

Nowadays, the demand for ruminant in the livestock industry is rapidly expanded and the demand for livestock feed supply was hardly fulfill. In this research, rice hull and coconut hull from agriculture waste was investigated. Before feed the rice hull and coconut hull to ruminant, the lignin content within the rice hull and coconut hull were determined before and after pretreatment. Response Surface Methodology (RSM) and Central Composite Designs (CCD) helped to get the optimum condition for alkali treatments by using sodium hydroxide (NaOH) to carry out. Fourier Transform Infrared (FTIR) helped to identify the lignin content in both hulls. The interaction of 3 parameters which are NaOH concentration, contact time, and weight of sample was investigated to optimise the lignin removal percentage (%). The parameters range were NaOH (1 M to 10 M), contact time (1 hour to 12 hours), and weight of sample (0.5 g to 5.0 g). The correlation coefficient, R2 for quadratic model of rice hull lignin removal (%) was 0.8863 while for coconut hull lignin removal (%) in linear model was 0.7998 as well as 2FI model was 0.8892. Three-dimensional (3D) response surface graph and two dimensional (2D) contour plots used to find out the relationship of the variables on the lignin removal. The optimum condition for rice hull lignin removal predicted by RSM were10 M NaOH concentration, 1 hour contact time, 0.5 g sample weight with 32.45% rice hull lignin removal percentage. The optimum condition for coconut hull lignin removal predicted by RSM were10 M NaOH concentration, 12 hours contact time, 0.5 g sample weight with 59.47% coconut hull lignin removal percentage. This shows pretreated rice hull and coconut hull able to be used as an effective alternative ruminant feed. This study improved utilization of agriculture waste as well as alternative feed for gradually expands feed cost.