Replacement of current fossil oil based
Volatile fatty acids (acetate, propionate, butyrate, iso-butyrate, valerate, iso-valerate) and other fermentation products including caproate, lactate, succinic VS5584 and formic acid were determined by high performance liquid chromatography (SHIMADZU Company, Japan), using an Aminex HPX-87H column (T = 50 °C) from Bio Rad coupled to an UV (210 nm) detector, while sulfuric acid 5 mM was used as eluent at a rate of 0.5 ml/min. Ethanol was determined by gas chromatography (Agilent 7890A, Agilent Technologies, America) equipped with a capillary column (DB-FFAP, 30 m × 0.53 mm × 1 μm) and a flame ionization detector. The temperature of the injector and detector were both 230 °C. The column temperature was increased from 70 °C to 180 °C at a node rate of 20 °C/min and kept at 180 °C for an additional 5 min. The nitrogen gas was used as carrier gas. Gas content (hydrogen gas, carbon monoxide, carbon dioxide and methane) was determined by gas chromatograph (Agilent, 7890A) fitted with a thermal conductivity detector and Agilent Carboxen 1000 column (4.5 m × 2 mm; mesh size 60/80). The argon gas was used as carrier gas with a rate of 30 mL/min. The temperature of injector, detector and column were 150 °C, 250 °C and 150 °C, respectively.