乳牛糞進行固態厭氧消化與黑水虻堆肥化技術之可行性研究

Abstract

本研究旨在研究連續使用固態厭氧消化及黑水虻堆肥化於牛糞的可行性。本研究共分成兩個部分來進行，分別為固態厭氧消化與黑水虻堆肥化實驗，固態厭氧消化的原料為牛糞，而黑水虻堆肥化的原料則是固態厭氧消化的沼渣。固態厭氧消化實驗的目的為建立最佳的操作參數，包含污泥接種率（10、30及50%）及pH(7.8) 調整的必要性。黑水虻堆肥化實驗則是為了探討最佳的沼渣餵食量（25、50、75及100 毫克/日/每隻蛆）。固態厭氧消化實驗的結果顯示，料源pH值無調整的組別其沼氣產量、甲烷量、總固形物去除率及揮發性固體去除率都比料源pH調整(pH = 7.8)的組別低。其中以料源接種30%種源組別的甲烷產量最高，分別為626.1±28.7 L methane/kg-VS des 及96.81±2.0 L methane/kg-VS load (p<0.05)。然而，料源接種50%種源組別 (pH = 7.8) 於第5天就達到最高的甲烷產量，比料源接種30與10% （pH＝7.8）組別分別提早3與9天使甲烷產量達到最高。料源接種50%（pH 7.8）也是最高的揮發性固體去除率(20.2±2.4%)的組別。黑水虻實驗結果顯示，每日每隻75與100毫克組別中的黑水虻幼蛆有最大的體重變化，分別為969.6±28.4與984.1±177.6%。可是在料源的總固體去除率、揮發性固體去除率及總氮去除率方面，各組間都沒有顯著差異。本研究顯示，固態厭氧消化的料源是必須調整pH，而且種源接種量必須在30至50%之間，才能達到最高的沼氣產量以及最佳的總固體與揮發性固體去除率。而黑水虻堆肥化實驗結果顯示，黑水虻蛆堆肥化可以進一步降低沼渣中的營養物質的含量，進而提高牛糞的附加價值。

The goal of this study was to evaluate the feasibility of applying a two-step biological treatment process, solid-state anaerobic digestion (SSAD) and black soldier fly larvae (BSFL) composting, to treat and recover energy from dairy cow manure. The feedstock for SSAD and BSFL experiments were dairy cow manure and digestate (i.e. anaerobically digested cow manure from SSAD reactors), respectively. The study of SSAD was to establish the optimal operation parameters. Thus, different ratios of inocula to feedstock (10, 30, and 50%) and with or without pH adjustment were tested for this study. For the study of BSFL, different feeding rates (25, 50, 75, and 100 mg/day/larvae) of digestate were applied for black soldier fly larvae composting experiments. In SSAD experiments, experimental results showed that the groups without pH adjustment regardless inoculation ratio of feedstock resulted in lower biogas, methane yield, and waste reduction than the groups with pH adjustment. Where the group 30% inoculation ratio (IR30) with pH adjustment had the highest theoretical methane productivity (626.1±28.7 L methane/kg-VS des) and ultimate methane yield (96.81±2.0 L methane/kg-VS load) (p<0.05). However, the group 50% inoculation ratio (IR50) with pH adjustment reached methane productivity peak at Day 5, which was 3 and 9 days faster than the 30 and 10% inoculation ratio (IR30 and IR10) with pH adjustment groups, respectively. The IR50 with pH adjustment group had the highest volatile solid removal efficiency of 20.2±2.4%. For BSFL experiments, the groups with feeding rate of 75 and 100 mg/day/larvae had the highest body weight change, which were 969.6±28.4 and 984.1±177.6%, respectively. However, removal efficiency of total solids (TS), volatile solids (VS), and nitrogen did not differ among treatments. Experimental results of this study showed that pH adjustment of feedstock was necessary during batch SSAD, where IR30 and IR50 groups achieved the highest specific methane production and waste removal efficiency. In addition, the BSFL composting enables further reduction of nutrients in the digestate of SSAD and promotes additional values of anaerobically digested dairy cow manure.