Two-phase anaerobic co-digestion of lignocellulosic crop residues with animal wastes can efficiently generate more biogas compared with the digestion of animal waste alone. Non-airtight fermentation of the mixed substrates is the primary step to hydrolyze complex organics and achieve simultaneous phosphorus release. Recycling phosphorus from tremendous animal wastes is remarkably meaningful regarding non-renewable resource recovery. In this study, the feasibility of a two-step process combining non-airtight fermentation of potato peels with dairy manure and the following struvite precipitation was explored. The hydrolysis and acidification process of the 6-day non-airtight mesophilic fermentation lowered pH to 6.4 under the highest mixed solid content of 4.8%; meanwhile, the ratio of reactive phosphorus to total phosphorus increased from 49.6 to 93.7% accordingly. Struvite formation was successfully induced by adjusting pH to 8.0 and 9.5. Under these two pHs, the precipitates were dominated by struvite as characterized by X-ray diffraction (XRD). Scanning electron microscopy and energy-dispersive spectrometry (SEM-EDS) results indicated that there should exist both struvite and calcium phosphate in the precipitates obtained under the two pHs. pH 8.0 precipitate should contain around 75% struvite, while the proportion rose to about 90% for pH 9.5 precipitate, based on the calculation of respective Mg/P and Ca/P molar ratios.

中文翻译：

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用废土豆皮非乳化发酵乳牛粪，随后通过鸟粪石沉淀回收磷。

与仅消化动物粪便相比，木质纤维素作物残渣与动​​物粪便的两相厌氧消化可有效产生更多沼气。混合基质的非气密发酵是水解复杂有机物并同时释放磷的主要步骤。从巨大的动物废物中回收磷对于不可再生资源的回收非常有意义。在这项研究中，探讨了将马铃薯皮与奶牛粪进行非气密发酵和随后鸟粪石沉淀相结合的两步过程的可行性。在最高混合固体含量为4.8％的情况下，为期6天的非气密性中温发酵的水解和酸化过程将pH值降至6.4。同时，活性磷与总磷之比从49增加。6至93.7％。通过调节pH至8.0和9.5成功诱导鸟粪石形成。在这两个pH下，通过X射线衍射（XRD）表征，沉淀物以鸟粪石为主。扫描电子显微镜和能量色散光谱法（SEM-EDS）结果表明，在两个pH值下获得的沉淀物中均应同时存在鸟粪石和磷酸钙。根据各自的Mg / P和Ca / P摩尔比的计算，pH 8.0沉淀物中应含有约75％鸟粪石，而pH 9.5沉淀物中的含量应升至约90％。扫描电子显微镜和能量色散光谱法（SEM-EDS）结果表明，在两个pH值下获得的沉淀物中均应同时存在鸟粪石和磷酸钙。根据各自的Mg / P和Ca / P摩尔比的计算，pH 8.0沉淀物中应含有约75％鸟粪石，而pH 9.5沉淀物中的含量应升至约90％。扫描电子显微镜和能量色散光谱法（SEM-EDS）结果表明，在两个pH值下获得的沉淀物中均应同时存在鸟粪石和磷酸钙。根据各自的Mg / P和Ca / P摩尔比的计算，pH 8.0沉淀物中应含有约75％鸟粪石，而pH 9.5沉淀物中的含量应升至约90％。