台灣每年生產的菇類超過150萬噸，其中廢棄的菇包木屑年產20萬噸，常用焚燒處理木屑，更甚是直接丟棄，進而造成環境汙染。本研究基於環境保護及資源再利用的概念，針對廢棄菇包木屑進行厭氧醱酵產生沼氣，爾後利用沼氣發電，達到循環經濟之目的。 厭氧醱酵中的菌種因適合的生長條件不同，主要為水解/酸化菌及產甲烷菌，故依其條件，本實驗室過去已開發出兩階段式系統，分別為水解/酸化階段及產甲烷階段，其可改善單階段系統之穩定性差的問題；亦可避免因過度酸化導致產甲烷菌活性下降。過去研究發現使用兩階段式系統，可提升21%的甲烷產量。 菇包木屑中碳含量較高，若直接做為厭氧醱酵的原料，因營養源不足，恐抑制甲烷菌生長不佳，故需添加氮源，以平衡碳氮比，增加厭氧醱酵之效率。本研究添加雞糞以平衡碳氮比。 乾式厭氧醱酵的定義為固體含量高於15% (TS≧15%)，僅需較少的含水量，其有機負荷能力高，反應器之體積會減少，亦有助於降低成本；故本研究將菇包木屑含量提高投入於水解/產酸階段，形成高固體的厭氧醱酵系統，提供處理大量的廢棄菇包木屑之方法。本研究發現和TS 15%與TS1%、5%和10%相比，分別提高了15倍、3.3倍、1.3倍的揮發性脂肪酸濃度。 因乾式厭氧醱酵的含水量低，容易造成抑制物的積累會限制整個系統的表現，故本研究添加活性碳透過DIET( Direct Interspecies Electron Transfer)機制，增加菌種間的電子轉移，促進有機物轉化成甲烷；及活性碳吸附有毒的化合物，以維持整個系統的穩定性。本研究發現在TS 15%情況下，分別加入不同濃度的活性碳(≧10%[活性碳/SMS])，其氨氮濃度至少會下降53%；此外，揮發性脂肪酸濃度也因添加活性碳而下降64%~87%。 本研究發現雞糞預先微波處理，再混合水解/產酸階段醱酵高固體濃度的濾液可使產甲烷階段提升65%的甲烷產量；因此本研究透過活性碳的吸附能力，降低在水解/產酸階段醱酵高固體濃度(TS 15%)中的揮發性脂肪酸及氨氮濃度，再搭配雞糞微波預處理的方式一同進入產甲烷階段，可使甲烷產量再提高13.1%。;The annual output of mushrooms in Taiwan exceeds 1.5 million tons, and spent mushroom substrate (SMS) is 200 thousand tons per year. Since SMS is often burned or discarded in the wild, the environment will be contaminated. Based on environmental protection, this study aims to assess the feasibility of biogas production by using SMS in anaerobic fermentation. Anaerobic treatment provides a method of reducing pollution from agricultural and industrial operations while offsetting the operations’ usage of fossil fuels. In addition, biogas could be transformed into electricity. Because of the growth conditions of microorganism in anaerobic digestion, there are separated into hydrolysis/acidogensis and methanogensis. Therefore, our lab had developed the system of two-stage anaerobic digestion and this system could improve the poor stability of single-state system. The two-stage system could enhance 21% methane yield in previous study. Co-digestion involves mixing of different types of feedstocks to control the carbon nitrogen ratio (C/N ratio). Due to high carbon source in SMS, there would be lack of nutrition in the anaerobic digestion system and lead to poor growth of methanogens. In this study, chicken manure (CM) is added to balance C/N ratio in this system. Co-digestion can enhance the efficiency of anaerobic digestion. The dry anaerobic digestion process is under a specific content of total solids (TS≧15%) and the substrate loses its fluidity. The advantages of dry anaerobic digestion include reduced reactor volume, less wastewater and cost down. Thus, the content of SMS is increased in this study. This approach would be regard as a method of consuming abound SMS. In this study, the concentration of volatile fatty acid (VFA) can increase 15 times in high TS content comparing to lower one. The main problem of dry anaerobic digestion is inhibition because of high content of nitrogen-containing compounds which can be present in a substrate in the forms of ammonium and non-dissociated ammonia. The accumulation of inhibition harms the performance of anaerobic fermentation. By adding activated carbon (AC), it will promote DIET (Direct Interspecies Electron Transfer) mechanism. Enhancing DIET might be a good approach for accelerating microbial metabolism that require interspecies electron exchange and increasing methane production. AC supplementation is beneficial for increasing the performance of anaerobic digestion by absorbing toxic organic compounds inhibiting the activity of methanogens. In this study, adding different concentration of AC (≧10% [AC-g/ SMS-g]) leads to decreasing the concentration of ammonium-nitrogen and VFA. Because AC supplementation can decrease inhibition concentration, the liquid which is from hydrolysis/acidogenesis phase doesn’t harm the methanogens and mixes chicken manure by microwave pretreatment can enhance 66% methane yield.
