Lignocellulose as a source of polysaccharides which are abundant in Indonesia can be converted into ethanol as an alternative source of green energy. Indonesia as a tropical country has abundant resources of lignocellulose. Therefore, research on the process of making ethanol from lignocellulose would provide benefits for the development of society.
This was said by Megawati, S.T, M.T, during her open examination for Engineering Sciences Doctoral Program, Chemical Engineering Study Program, Universitas Gadjah Mada (UGM). Accompanied by promoter Prof. Ir. Wahyudi B. Sediawan, SU., Ph.D and co-promoter Ir. Hary Sulistyo, SU., Ph.D, and Muslikhin Hidayat, S.T, M.T, Ph.D., she defends her dissertation Kinetics of Hydraulic Lignocellulose with dilute sulfuric acid in the Framework of Ethanol Production.
She said that the research on lignocellulosic waste classification based on holocellulose levels (hemicellulose and cellulose) in fact had already been done in Yogyakarta. Lignocellulose wastes with high levels of holocellulose (approximately 70%) can be found in Yogyakarta, among others on the twigs, leaves, rice husks, corn cobs and wood sawdust.
The prospect as raw material for ethanol, she said, can be found on leaves and twigs in Belinjo fruit, bellfruit and jackfruit plants, while wood sawdust can be found in mahogany wood. "It's mostly found in sawmills around Yogyakarta, while for rice husks and corn cobs, Indonesia has tremendous potential, considering it is primary food," she said in the KPTU conference room of the Faculty of Engineering, Saturday (17/9).
According to the lecturer of the Faculty of Engineering, Semarang State University, there are three important stages of the process of making ethanol from lignocellulose, namely hydraulic lignocellulose to sugars, fermentation of sugars into ethanol and ethanol purification. The chemical hydraulic process has many advantages compared with the enzyme, because the chemicals which are often chosen to use are dilute sulfuric acid instead of concentrated sulfuric acid. "The use of concentrated acid is more corrosive, the equipment design is special and costly, causing more gypsum waste," she explained.
Megawati has an opinion that hydraulic lignocellulose using a dilute acid proved to be extremely influenced by the type of raw material, temperature, time, catalyst concentration and temperature. Types of raw material that are easy to get hydrolyzed are leaves, while the hard materials are twigs and wood sawdust. “Wood sawdust has higher amount of lignin than leaves. Thus, the bonds between the cellulose are more difficult to be separated," she explained.
She added that hydraulic lignocelluloses process occurs at high temperatures. Therefore, the sugar that is formed at low temperatures is not necessarily glucose. Thus, not all the sugar obtained can be converted into ethanol. "Therefore, in addition to the type of raw materials and temperature on the hydraulic which influence of fermentation, ethanol concentration also influences it. This means there is an occurring of sugar addition due to the use of catalysts with higher concentrations," she said.