解聚前處理料源及有機廢水沼氣生產之研究

Abstract

石化燃料造成環境破壞、排放大量溫室氣體等問題，在環保意識抬頭下，人們找尋可替代的能源，其中生質沼氣具有與天然氣接近的熱值適合作為發電原料，使生質沼氣可將廢棄物能源化受到重視。 根據聯合國資料，若將世界上的生質廢棄物轉為能源，將可取代1/4的石油產量。台灣農業纖維廢棄物年產212萬噸，其中稻稈佔最大宗，其它還有蔗渣、木屑等農業纖維廢棄物，主要由纖維素組成其結構為醣類聚合物，若可將醣類結構轉為單醣即可轉為豐富沼氣。本研究以核能所開發的纖維素解聚技術，將農業生質廢棄物以蒸氣爆裂或酸催化蒸氣爆裂解聚後進行厭氧醱酵，使農業生質廢棄物增加生物可利用性提升沼氣生成。 本論文分別探討稻稈、蔗渣及木屑的沼氣潛能和調整厭氧醱酵參數，如酸鹼值、碳氮比等以增加沼氣產量，此外也利用養豬業廢水含有大量氮源的特性，作為纖維廢棄物碳氮比調整材，並建立實驗室規模連續進料厭氧反應器，模擬養豬場厭氧醱酵情形，評估養豬場廢水加入解聚纖維原料提升沼氣產量的效果。 本研究證實經酸催化蒸氣爆裂解聚纖維料源，藉由控制酸鹼值可提升沼氣潛能，解聚稻稈、蔗渣及木屑分別在pH=6-7時有最佳產氣效率，每克乾重分別可產生313、213、282毫升沼氣；調整碳氮比，調整至20時有最佳產氣量，分別可產256、250、251毫升沼氣。在實驗室規模連續進料厭氧反應器證實，添加1% 解聚稻稈有最佳沼氣生成量，每克乾重可產生315毫升沼氣，因此在模擬三段式放流反應器中添加解聚纖維原料可增加沼氣產量。

Petrochemical fuel damage environment and produce green-house gas emission. The researches for alternative energy can meet the environment protection. Biogas is one of good choose for alternative energy because it turns waste into energy and produces a similar heat value as natural gas. According to UN statistical data, the agricultural biomass is generated more and more for every year. The energy efficiency is equivalent to 25 percent of global oil production. The agricultural waste is composed of cellulosic compounds that are aggregated by pentose or hexose. They will be excellent biogas materials after destructed structure pretreatment. The agricultural cellulosic waste is generated about 2.12 million tons every year in Taiwan. The kinds of agricultural waste are rice straw, sugarcane bagasse and wood dust. This study utilizes INRI cellulosic de-aggregation technology which uses steam explosion or acid-catalyzed steam explosion to destruct cellulosic structure. The de-aggregation cellulosic materials would enhance biodegradability and biogas production by anaerobic digestion. In this study, we examined biogas potential of different agricultural wastes and adjust the parameters (e.g pH value or C/N ratio) of anaerobic digestion. Since the pig farms produce lots of wastewater in Taiwan which water are nitrogen-rich and it can adjust high carbon materials to appropriate C/N ratio. Furthermore, we set up a lab-scale continuously anaerobic digestion to simulate the actual fermentation conditions. The results demonstrated that adjust the conditions of de-aggregation cellulosic material and anaerobic digestion enhancement of biogas production. The de-aggregation of rice straw, sugarcane bagasse and wood dust were the best performance for biogas production at pH= 6-7. They produced 313, 213 and 282 ml/gTS, respectively. In C/N ratio treatment group, the best conditions were C/N= 20, which produced 256, 250 and 251 ml/gTS, respectively. The co-digestion was de-aggregation rice straw and pig wastewater. In the continues anaerobic digestion, addition 1% dry weight of wastewater volume could produce 315 ml/gTS.