Table 1 Characteristics of the studied biogas plant’s primary digester at the sampling date 15 November 2010

Net volume

2,041 m ³

Dimensions

6.4 m high, diameter of 21 m

Electrical capacity

537 k W _e

pH

7.83

Temperature

40 °C

Conductivity

22.10 m S/c m

Volative organic acids (VOA)

5,327 m g/l

Total inorganic carbon (TIC)

14,397 m g/l

VOA/TIC

0.37

Ammoniacal nitrogen

2.93 g/l

Acetic acid

863 m g/l

Propionic acid

76 m g/l

Fed substrates

72 % maize silage, 28 % pig manure

Organic load

4.0 k g o D M m ⁻³ d ⁻¹

Retention time

55 d a y s

Biogas yield

810.5 l/k g o D M

Methane yield

417.8 l/k g o D M