Biogas production: litter from broilers receiving direct-fed microbials and an enzyme blend

ABSTRACT The effect of additives used in the feed of broilers on anaerobic bio-digestion of poultry litter was evaluated. Four diets were used: NC: negative control; DFM: NC + 500 ppm direct-fed microbials (DFM) containing Bacillus subtilis and Bacillus licheniformis; ENZ: diet formulated with an enzyme blend (20 ppm phytase, 200 ppm protease and 200 ppm xylanase); DFM+E: ENZ + DFM. Substrates for the anaerobic bio-digestion were prepared with litter from each treatment, containing 4 % total solids (TS). These were used in 16 continuous bio-digesters with a 2 kg d−1 load, to determine the production and potential biogas production and composition during an 85-day period. Influent and effluent samples were collected for the amounts of TS and volatile solids (VS), fiber fraction (neutral detergent fiber [NDF], acid detergent fiber [ADF] and lignin), nutrients (N, P and K), and total and thermotolerant coliforms to be determined. For all treatments a reduction in the following effluents was observed as follows: TS (49, 48, 48 and 50 %) VS (70, 54, 55 and 62 %) NDF (91, 90, 95 and 96 %) ADF (89, 88, 93 and 94 %) and lignin (80, 76, 89 and 88 %). The efficiency of the treatment for coliforms in bio-digesters was higher than 90 % in the 85-day period in all treatment groups. There was a reduction in biogas and methane production when DFM (5500 and 4000 mL) and DFM + E (5800 and 4100 mL) were used, compared to treatments NC (6300 mL and 4400) and ENZ (6400 and 4500 mL). The potential production of reduced TS and VS was higher in ENZ (1:00 and 1.74 106 mL kg−1) when compared to NC (0.88 and 1:02 106 mL kg−1), DFM (0.80 and 1:40 106 mL kg−1) and DFM + E (0.88 1:25 and 106 mL kg−1). The additives did not affect the percentage of methane production, and all treatments showed values higher than 70 %. Adding enzymes to the diet of broilers influences the litter characteristics and, as a consequence, increases biogas production. The addition of DFM and DFM + E to broiler diets reduced biogas and methane production.摘要 本研究评估了肉鸡日粮中添加的添加剂对家禽垫料厌氧生物消化的影响。实验设置4种日粮处理：NC组为阴性对照；DFM组为阴性对照添加500 ppm直接饲喂微生物（direct-fed microbials, DFM），该制剂含枯草芽孢杆菌（Bacillus subtilis）与地衣芽孢杆菌（Bacillus licheniformis）；ENZ组为添加酶复配物的日粮，含20 ppm植酸酶、200 ppm蛋白酶及200 ppm木聚糖酶；DFM+E组为在ENZ组日粮基础上添加DFM。 以各处理组垫料制备厌氧生物消化底物，底物总固体（total solids, TS）含量为4%。将底物接入16台负荷为2 kg·d⁻¹的连续式厌氧生物消化装置，开展为期85天的实验，以测定沼气生成量、潜在沼气产量及组分。收集进水与出水样品，测定总固体（TS）、挥发性固体（volatile solids, VS）、纤维组分（中性洗涤纤维[neutral detergent fiber, NDF]、酸性洗涤纤维[acid detergent fiber, ADF]及木质素）、营养组分（氮、磷、钾）以及总大肠菌群和耐热大肠菌群的含量。 各处理组的出水指标均呈现如下降幅：TS（49%、48%、48%、50%）、VS（70%、54%、55%、62%）、NDF（91%、90%、95%、96%）、ADF（89%、88%、93%、94%）与木质素（80%、76%、89%、88%）。实验周期内所有处理组的生物消化装置对大肠菌群的处理效率均高于90%。 与NC组（沼气产量6300 mL、甲烷产量4400 mL）和ENZ组（6400 mL、4500 mL）相比，DFM组（5500 mL、4000 mL）与DFM+E组（5800 mL、4100 mL）的沼气与甲烷生成量均有所降低。ENZ组的TS与VS对应潜在产气量更高，分别为1.00×10⁶ mL·kg⁻¹和1.74×10⁶ mL·kg⁻¹，高于NC组（0.88×10⁶ mL·kg⁻¹、1.02×10⁶ mL·kg⁻¹）、DFM组（0.80×10⁶ mL·kg⁻¹、1.40×10⁶ mL·kg⁻¹）及DFM+E组（0.88×10⁶ mL·kg⁻¹、1.25×10⁶ mL·kg⁻¹）。 添加剂对甲烷占比无显著影响，所有处理组的甲烷体积占比均高于70%。肉鸡日粮添加酶制剂可改善垫料特性，进而提升沼气产量；而添加DFM及DFM+E则会降低沼气与甲烷的生成量。