where the exponential curve is valid over all positive values of t and Vt (ml) is the amount of gas produced at time t, Vf (ml) the
asymptotic gas amount produced corresponding to complete substrate digestion; K (h) the fractional rate of gas production
and Ln the lag time before the gas production starts (h) and t
≥
Ln. All fitted curves show a determination coefficient, R2 > 0.98