麻竹生產生質乙醇之評估

Abstract

竹林覆蓋台灣152,300 公頃，約佔台灣總森林面積的7.2 %，因此本研究以麻竹(Dendrocalamus latiflorus)為代表，評估竹材作為台灣生質乙醇原料的潛力。竹片經過酸、鹼蒸汽爆碎前處理，酸蒸氣爆碎以190 oC持溫10 min，鹼蒸氣爆碎以180，190及200oC 持溫10至20分鐘，進而以相對於試驗材料乾重比例的2、6、12 % (w/w) 纖維素酶劑量對蒸汽爆碎竹漿進行水解。最高葡萄糖得率：鹼蒸汽爆碎竹漿為 50.4~249.3 mg/g，而酸蒸汽爆碎竹漿為 49.7~209.1 mg/g。此外本研究發現水解效率與試材中的木質素的含量成負相關。本研究並使用菌株Saccharomyces cerevisiae D5A對上述竹漿進行同時糖化與發酵 (SSF)，條件為：37.5oC、pH 5、yeast extract 10 g/L及peptone 20 g/L。經96 小時後，酸蒸汽爆碎竹漿從原料至乙醇之轉化率為13.11%，相當於每公斤乾重竹片可產0.16 L乙醇；鹼蒸汽爆碎竹漿從原料至酒精之轉化率為8.8%，相當於每公斤乾重竹片可產0.11 L乙醇。以上發酵後之廢渣，經元素分析証實具有相當之熱值。台灣竹林蓄積量估計範圍為5,020,000~11,640,000 公噸，假設每五年輪伐一次，估計每年約可有1,328,000公噸竹材投入生質乙醇生產，以酸蒸汽爆碎法配合與同時糖化與發酵約可產出220,659公秉酒精，鹼蒸汽爆碎前處理約可產出148,162公秉酒精。本研究結果顯示，以本土竹林蓄積更新生產生質乙醇，具有相當的潛力。

Bamboo covers 152,300 ha in Taiwan, approximately of 7.2 % the total overall forest area. This study evaluated Dendrocalamus latiflorus as a feedstock for bioethanols in Taiwan. Acidic and alkaline steam explosion was employed to prepare pulps from Dendrocalamus latiflorus chips. Alkali-treated samples were prepared at 180, 190 and 200oC from 10 to 20 min. Acid-treated samples were prepared at 190oC for 10 min. For the saccharification of pretreated bamboo biomass, cellulase formulations were applied with three dosages: 2, 6, 12 percent to dried pulp (w/w). The glucose yields were 50.4 ~ 249.3 mg/g alkali steam-exploded pulps, and 49.7~209.1 mg/g acid steam-exploded pulps. The hydrolysis efficiencies were negatively impacted by lignin contents of pretreated bamboo pulps. Simultaneous saccharification and fermentation (SSF) were also conducted using Saccharomyces cerevisiae D5A under 37.5oC and pH 5 with yeast extract 10 g/L and peptone 20 g/L at shake flask level. After 96 hours, the optimal ethanol conversion for acid pretreated pulps was 13.11%, equivalent to 0.16 L ethanol/kg dried chip. And the optimal ethanol conversion for alkaline pretreated pulps exploded was 8.8%, equivalent to 0.11 L/kg dried chip. The post-fermentation residues possessed high heating values, which were verified by elemental analysis. There is estimated 5,020,000~11,640,000 ton storage for in bamboo stands in Taiwan. There could be 1,328,000 ton available as feedstock for bioethanol production annually under 5-year rotation harvesting. SSF could produce 220,659 kL of bioethanols from by acidic steam explosion pulps and 148,162 kL of bioethanols by alkaline steam explosion pretreatment pulps annually. This study demonstrated potentials of the indigenous bamboo storage as a source for bioethanol production.