Biochar improves heavy metal passivation during wet anaerobic digestion of pig manure
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RESEARCH ARTICLE
Biochar improves heavy metal passivation during wet anaerobic digestion of pig manure Jun Wang 1,2 & Xiaoxia Hao 1,2 & Zile Liu 1,2 & Zili Guo 1,2 & Li Zhu 1 & Bangjie Xiong 1,2 & Dongmei Jiang 1,2 & Linyuan Shen 1 & Mingzhou Li 1 & Bo Kang 1 & Guoqing Tang 1 & Lin Bai 1,2 Received: 9 May 2020 / Accepted: 10 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Anaerobic digestion (AD) is regarded as an effective treatment to stabilize organic materials and recycle the energy in pig manure. In this study, 0%, 3%, 5%, and 7% biochar (based on dry weight) were added to pig manure to investigate its influence on improving biogas production and reducing heavy metal bioavailability. The potential ecological risk of heavy metals (namely Mn, Zn, Cu, Ni, As, Cd, Pb, and Cr) in digestates was also assessed. Results show that the methane yield was significantly (P < 0.05) increased by 26.7%, 23.0%, and 26.4% following addition of 3%, 5%, and 7% biochar, respectively. Moreover, there was a significant change in the heavy metal speciation in amendment each group. The 5% biochar group showed the highest passivation rate of Ni, As, and Pb, while the highest passivation rate of Cd, Cr, Mn, and Zn was observed with 7% biochar. Although the anaerobic digestion process slightly increased the ecological risk of heavy metals, all tested digestates were still classified as a moderate risk. Results of this study can provide a reference for the treatment of heavy metal pollution in large- and medium-sized anaerobic digesters treating pig manure. Keywords Anaerobic digestion . Biochar . Pig manure . Heavy metal speciation . Ecological risk
Introduction Anaerobic digestion (AD) is a beneficial biochemical process used to produce methane and treat different types of organic waste, including animal manure and crop residues (Dang et al. 2016). Replacing conventional energy sources by converting waste into renewable energy would not only reduce pollution but could also be used to recycle nutrients (Bareha et al. 2018). Therefore, with the encouragement of government Jun Wang, Xiaoxia Hao, and Zile Liu are co-first author. They contributed equally to this work. Responsible Editor: Zhihong Xu * Lin Bai [email protected] 1
Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
2
Animal Environment Hygiene Laboratory, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
policies, AD has become the main treatment for livestock manure in China (Chen et al. 2010). The total solids (TS) content has a strong influence on AD and includes processes known as wet state AD (WS-AD, < 10% TS), hemi-solid state AD (HSS-AD, 10–15% TS), and solid state AD (SS-AD, > 15% TS). A high TS content can produce excess ammonia and volatile fatty acids (VAFs), which is known to inhibit the AD process (Ganidi et al. 2011; Liu et al. 2015; Riya et al. 2018). WS-AD is currently used by most m
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