Response of phosphorus speciation to organic loading rates and temperatures during anaerobic co-digestion of animal manures and wheat straw

• Published in: The Science of the total environment 2022-09, Vol.838 (Pt 1), p.155921-155921, Article 155921
• Main Authors: Li, Bowen, Dinkler, Konstantin, Zhao, Nan, Ran, Xueling, Sobhi, Mostafa, Dong, Renjie, Müller, Joachim, Xiong, Wei, Huang, Guangqun, Guo, Jianbin, Oechsner, Hans
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Organic loading rate; Phosphorus speciation; Temperature
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.155921

The world is facing huge phosphate (P) shortage and anaerobic digestion (AD) is a recognized technology to promote nutrient (N and P) recycling. The composition of P speciation in the digestate is essential for the fertilizing effect. However, how P speciation in the digestates interacts with the AD process conditions is unknown. Therefore, interaction of P speciation in digestates with AD process conditions was investigated by using a chemical sequential extraction method (Hedley fractionation) and X-ray diffraction; specifically, the effects of organic loading rate (OLR), temperature, and substrate composition were investigated. The results showed that OLR and feedstock affected P speciation in the digestate significantly due to different ion species and ionic strengths. The H2O-P concentration in chicken manure with straw (CMS) and dairy manure with straw (DMS) digestates decreased by 44.04–48.76% and 48.88–50.49%, respectively, as the OLR increased from 2 to 4 kg VS m−3 d−1. Simultaneously, HCl-P increased by 38.02–44.01% in the CMS digestates due to Ca-P and Mg-P formation, indicating that Ca-P and Mg-P formation was positively correlated with OLR, whereas P mobility decreased. Further, thermophilic temperature conditions were more conducive for the formation of insoluble P than mesophilic temperature conditions in the digestates due to the thermodynamic driving force of the reactions. The results would facilitate the understanding of P transformation in the AD process under the influence of feedstock, OLR, and temperature. From the viewpoint of nutrient management, lower OLR and temperature are more beneficial for a fast P availability, whereas higher OLR and temperature are more helpful for storage and export because of P precipitated into solid phase of digestate. [Display omitted] •Organic loading rates, temperature, and feedstock affected P speciation in digestates.•H2O-P concentration decreased by 44.04–50.49% as organic loading rates increased.•Precipitation of Ca-P dominated the P transformation in cow manure-straw digestate.•Thermophilic conditions promoted transformation of P from labile to insoluble.•Control of anaerobic digestion processes could regulate P speciation and solubility.