Use of biochars in anaerobic digestion

• Published in: Bioresource technology 2014-07, Vol.164, p.189-197
• Main Authors: Mumme, Jan, Srocke, Franziska, Heeg, Kathrin, Werner, Maja
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonia - pharmacology; Ammonia inhibition; Ammonium Compounds - analysis; Anaerobic digestion; Anaerobiosis - drug effects; Bacteria - drug effects; Bacteria - metabolism; Biochar; Biofuels - microbiology; Biogas; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; Biotechnology - methods; Carbon; Charcoal - metabolism; Degradation; Degradation kinetics; Environment and pollution; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Inhibition; Kinetics; Methane; Methane - biosynthesis; Methanogenic microflora; Syringes; Zeolites - pharmacology
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2014.05.008

•Pyrolytic biochar can mitigate mild ammonia inhibition.•Hydrothermal biochar can serve as feedstock for anaerobic digestion.•Biochars support formation of a methanogenic microflora.•A simple syringe-based fermentation technique for biochar analyses is described. This study investigated the behavior of biochars from pyrolysis (pyrochar) and hydrothermal carbonization (hydrochar) in anaerobic digestion regarding their degradability and their effects on biogas production and ammonia inhibition. A batch fermentation experiment (42°C, 63days) was conducted in 100mL syringes filled with 30g inoculum, 2g biochar and four levels of total ammonium nitrogen (TAN). For pyrochar, no clear effect on biogas production was observed, whereas hydrochar increased the methane yield by 32%. This correlates with the hydrochar’s larger fraction of anaerobically degradable carbon (10.4% of total carbon, pyrochar: 0.6%). Kinetic and microbiota analyses revealed that pyrochar can prevent mild ammonia inhibition (2.1gTANkg−1). Stronger inhibitions (3.1–6.6gTANkg−1) were not mitigated, neither by pyrochar nor by hydrochar. Future research should pay attention to biochar–microbe interactions and the effects in continuously-fed anaerobic digesters.