Table 4.

Amplitude, rate constant and half time for single-phase, first-order kinetics fitted to the decrease and increase in gas production

Process	Equation	A (mL/g VS)	k (day−1)	t ½ (day)	R 2
1st phase decrease	$y=A·{\text{e}}^{-kx}$	51.4	0.432	1.6	0.986
2nd phase increase	$y=A·\left(1-{\text{e}}^{-kx}\right)$	19.5	0.104	6.7	0.972

Half time (t _½) was calculated for first-order kinetics using the relationship $t_{1/2}=\frac{ln2}{k}$