การประเมินเทคนิคของการปรับสภาพและการหมักเพื่อเพิ่มผลผลิตไบโอเอทานอลจากข้าวโพด

Abstract

Corn residue as an alternative feedstock has a potential for bioethanol production. Corn is one of the major crops of Thailand and it produces about 5.68 × 106 dry tones of residue per year. Unfortunately, some of this biomass were not utilized but rather burned on the field due to a lack of post-harvest control. This leads to serious problems like haze pollution, especially experienced in the Northern area. In order to alleviate the pollution problem brought by combustion of corn residues it was determined to give farmers some options for agricultural by-product disposal, as well as offering an alternative feedstock for bioethanol production. This study evaluated two corn varieties for their potential as a viable option for bioethanol production, Hi-brix 53 and Sugarstar × Hi-Brix 53 corn. Corn stalk juice, stalk bagasse and leaves were studied. Yeast (Saccharomyces cerevisiae) microorganisms were used for fermentation. Two method of fermentation were used using corn stalk juice. Lignocellulosic part: stalk bagasse and stalk leaves did undergo pretreatment, hydrolysis and fermentation. Three pretreatments were tested in order to know the suitable pretreatment on these materials: physical, control and alkaline. SHF and SSF fermentation process were also applied in order to determine the most effective mode of fermentation in these materials. Hi-brix 53 and Sugarstar × Hi-brix 53 stalk juice contains readily fermentable sugar. Both varieties produce bioethanol with a highest yield of 62.12 g/L (7.87%) in batch fermentation. Another experiment was done in order to improve the ethanol yield. 6-month old stalk juice underwent continuous fermentation that lasted up to 5 cycles. Bioethanol content was from 27.62-29.98 g/L (3.5-3.9% v/v). After distillation ethanol content was found to be 126.24 (16% v/v). As for the lignocellulosic part of corn, alkaline pretreatment using sodium hydroxide was found to be the most suited pretreatment compared to autoclave and physical. Using RSM, the optimal condition for alkaline pretreatment was predicted. For the mode of fermentation, SHF and SSF fermentation using stalk bagasse and leaves does not show any significant difference in terms of bioethanol production. Stalk bagasse of Sugarstar × Hi-brix-53 found to yield higher bioethanol compared to other material and variety. For the scale up production using SHF, mix stalk and leaves were used as feedstock generated about 27.77 g/L (2.9% v/v) of bioethanol. Comparing all used materials, stalk juice shows the most promising feedstock for bioethanol production. Further study on the juice is highly recommended. As for the lignocellulosic part, application on other hydrolysis and fermentation method was suggested. Techno-economic analysis on a small pilot scale biorefinery found that the corn residue (corn stalk and leaves) were a feasible feedstock for biochemical ethanol production. Still further study about these materials was recommended.