鹼前處理與Bacillus spp.生物分解後豬毛進行厭氧消化之研究

Abstract

豬毛為含有高比例角蛋白的屠宰廢棄物，角蛋白的結構穩固使其不易被降解，但化學處理與角蛋白酶可將其分解並將其轉換為可溶性蛋白質。而厭氧消化可將廢棄物有機質轉換為可再生的能源利用，如沼氣。本研究目的為評估經前處理豬毛及水解液用於厭氧消化中對提升甲烷生成效率的影響。 本研究使用低濃度鹼液及菌株Bacillus licheniformis 11594分別進行前處理分解，為了實驗觀察，選擇具完整豬毛外形的處理組進行後續試驗。厭氧消化中皆添加豬糞污泥作為菌種來源，首先比較經過低濃度鹼液前處理或微生物前處理之乾燥豬毛與無添加豬毛的對照組之沼氣產氣量；再以含水解液的豬毛處理組及對照組進行沼氣產氣量比較；最後使用不同分解時間下，含水解液與豬毛的處理組作為消化受質對甲烷產量的影響。 在前處理試驗結果，鹼前處理可以顯著提高Bacillus spp分解效率，並隨培養時間提升分解率。而在厭氧消化實驗中，30日間豬毛鹼前處理與未處理組之總產氣量分別為1310與1443 mL，相較於產237 mL沼氣的污泥，含豬毛組別產氣量皆顯著較高；但鹼前處理組在甲烷生成量上顯著低於未處理組。而在不同分解時間下含水解液的全溶液試驗中，在短時間(4日)前處理組之總產氣量顯著最高，而其他兩者(8與16日)亦高於純污泥組；但在總甲烷生成量上，16日前處理與純污泥組則未產生顯著差異。另外，以含水解液與豬毛的溶液作為受質試驗中，純污泥產氣量高，且各處理組間沒有差異。應是由於厭氧消化反應器於試驗之初所接種的豬糞污泥，攜帶部分豬糞中未分解有機質，進而影響反應器中污泥對於難分解角蛋白之利用率，使豬毛添加效果不佳。綜上所述，乾燥豬毛添加於厭氧污泥中可顯著提升沼氣產量與甲烷量，但前處理不影響產氣效率；而使用含水解液豬毛受質時，4日前處理時間有最佳效果，且易分解有機質量也是共消化時的重要影響因子。

Pig hair is one of slaughter wastes which contains high contents of keratins. The structure of keratins is recalcitrant made them hard to be biodegraded. But some chemical agents and keratinase are capable of destructing keratins to become soluble proteins. Besides, anaerobic digestion of organic matters in the slaughterhouse wastes can recover renewable energy, e.g. biogas, from the treatment process. The objective of this study was to evaluate the feasibility of biogas production from anaerobic digestion of alkali and microbial pretreated pig hair. A combination of hydrolysis with low concentration alkali solution and biodegradation by Bacillus licheniformis 11594 strain was performed as the pretreatment process. Those treated pig hairs with obvious hair appearance were used as the substrate for all time course experiments. Pig manure sludge was used as the sole inoculum for all time course experiments of anaerobic digestion. For the first batch, gas production of pretreated dried pig hair, which was pretreated with alkaline or the biodegradation, was compared with control group which no pig hair was add. For the second batch, addition of pig hair and its hydrolysate were compared with the control group. For the third batch, anaerobic digestion of pig hair and hydrolysate for promoting the methane production under different degradation time periods was investigated. Results of pig hair pretreatment experiments showed that the alkali pretreated pig hair increased the efficiency of microbial degradation by Bacillus spp. with prolonged cultivation time. Results of anaerobic digestion showed that the total gas production of alkali pretreated pig hair group and untreated pig hair group in a 30-d time period was 1310 and 1443 mL, respectively. Gas production of the group with pig hair addition increased significantly comparing to that of the control group (237 mL). However, the methane production in the alkali pretreated group was significantly lower than that of the untreated group. Among the hydrolysate addition groups under different degradation time period, the shorter cultivation time (a 4-d time period) group and the better its performance. Gas production of other groups (8- and 16-d time period) also much higher than that of the control group. Moreover, there was no significant difference between the 16-d time period pretreated group and the control in methane production. For the experiments of both pig hair and its hydrolysate addition, the control group carried out better gas production, but there was no significant difference on gas production between the control and any treatment groups. Because there were some easily biodegradable organic matters carried into anaerobic digester when inoculated with pig sludge. They might affect utilization of tough bio-degraded keratin and gas production during anaerobic digestion of pig hair. In conclusion, addition of dried pig hair in anaerobic digesters increased gas and methane production, but pretreatment of pig hair did not affect the efficiency of gas production. When the pig hair hydrolysate was used as the substrate, the group of a 4-d biodegradation pretreatment achieved best results. Besides, easily decomposed organic matters content was an important factor of anaerobic digestion.