Department of Soil and Water Systems, Twin Falls Research & Extension Center, University of Idaho, 315 Falls Ave, Twin Falls, ID, 83301, USA.
Department of Biological Engineering, University of Idaho, 875 Perimeter Drive, Moscow, ID, 83844, USA.
Appl Biochem Biotechnol. 2020 Mar;190(3):789-802. doi: 10.1007/s12010-019-03133-8. Epub 2019 Sep 7.
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.
木质纤维素作物残渣与动物废物的两相厌氧共消化可以比单独消化动物废物更有效地产生更多的沼气。混合底物的非密闭发酵是水解复杂有机物并实现同时释放磷的主要步骤。从大量动物废物中回收磷对于不可再生资源的回收具有重要意义。在本研究中，探索了两步法的可行性，该方法将马铃薯皮与牛奶废物的非密闭发酵与随后的鸟粪石沉淀相结合。6 天的非密闭中温发酵的水解和酸化过程将 pH 值降低到 4.8%的最高混合固体含量下的 6.4 ；同时，反应性磷与总磷的比例相应地从 49.6 增加到 93.7%。通过调节 pH 值至 8.0 和 9.5 成功诱导了鸟粪石的形成。在这两种 pH 值下，沉淀物均以 X 射线衍射（XRD）为特征的鸟粪石为主。扫描电子显微镜和能谱（SEM-EDS）结果表明，在两种 pH 值下获得的沉淀物中既存在鸟粪石又存在磷酸钙。根据各自的 Mg/P 和 Ca/P 摩尔比的计算，pH 值为 8.0 的沉淀物应含有约 75%的鸟粪石，而 pH 值为 9.5 的沉淀物的比例上升至约 90%。
