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Table 2 Parameters and analytical methods for the evaluation of the fermentation material

From: Foam formation in full-scale biogas plants processing biogenic waste

Parameter Sample pre-treatment Analytical methods and instruments
Total solids (TS) O DIN 12880
Volatile solids (VS) O DIN 12879
pH value CE/S Microprocessor pH meter pH 95 (WTW, Germany)
VFA/TIC CE/S Titration method according to Nordmann [27]
Ammonium-nitrogen (NH4-N) F DIN 38406 E5, Spektroquant® test kit (measuring range 0.01 to 3 mg/L NH4-N, Merck, Germany), photometric measurement with MultiLab P5 (WTW, Weilheim, Germany)
Chloride F Spektroquant® test kit (measuring range 2,5 to 250 mg/L Cl, Merck, Darmstadt, Germany), photometric measurement with SpektralPhotometer CADAS 200 (Dr. Lange, Düsseldorf, Germany)
Volatile fatty acids (acetate, propionate, butyrate) F High-performance liquid chromatography (Shimadzu, Japan); detector: RID-10A; column: VA 300/7.8 Nucleogel Ion 300 OA; eluent: 0.01 N H2SO4 [28]
TOC/IC/TC/TN B/S TOC-VCSH/CSN with a TN unit (Shimadzu, Japan)
Crude protein CA Calculated according to Dumas method [29]: Crude protein = 6.25 × ([TN] – [NH4-N] – [NO3-N] – [NO2-N]) (The concentrations of nitrate- and nitrite-nitrogen were neglected due to their low concentration in the digestates as measured previously.)
Water-soluble elements F Inductively coupled plasma atomic emission spectrometry ICP-AES (Spectroflame, Spectro Int., Kleve, Germany)
Pattern of fatty acids E GC (System 5890 Series II GC, Hewlett-Packard, Wilmington, USA) after extraction according to Bligh and Dyer [20] and Morrison and Smith [21]
Surface tension CE Drop volume tensiometer (Lauda TV T-1, Lauda Dr. R. Wobser GmbH and Co. KG, Lauda-Königshofen, Germany)