Table 1

Retention Time (Weeks)	Mean Gas Yields from Digesters (± SD)(cm³)
	A	B	C	D
1	1.20 ± 0.05^a	0.00 ± 0.00^b	0.00 ± 0.00^b	1.60 ± 0.05^c
2	2.00 ± 0.04^a	2.90 ± 0.06^b	0.00 ± 0.00^c	3.80 ± 0.13^d
3	3.90 ± 0.03^a	7.20 ± 0.18^b	0.00 ± 0.00^c	4.60 ± 0.09^d
4	4.60 ± 0.07^a	15.60 ± 0.18^b	0.00 ± 0.00^c	5.60 ± 0.05^d

Figures in the same row having different superscripts are significantly different (P<0.05).

Table 1: Mean weekly biogas yields from anaerobic digestion of cow dung.