Table 1. The yields, chemical compositions and atomic ratios of biochars produced from different feedstocks at different pyrolytic temperatures.

Biochars	Temp. (°C)	Yield (%)	Component (%)				Atomic ratio
			C	N	H	O	C:N	O:C	H:C	(O+N)/C
W-BC	400	32.4	57.8a	1.5b	3.2c	21.6c	44.2c	0.56c	0.66bc	0.22b
	500	27.6	70.3d	1.4ab	2.9bc	17.7b	57.8d	0.38ab	0.49b	0.15ab
	600	24.6	73.4e	1.4ab	2.1bc	14.9a	62.0de	0.31a	0.35ab	0.12a
	700	22.8	73.9e	1.2a	1.3a	14.6a	74.4e	0.30a	0.22a	0.12a
C-BC	400	35.5	56.1a	2.4e	4.3d	22.0c	27.9a	0.59c	0.92c	0.24b
	500	29.3	58.0ab	2.3d	2.7bc	21.5c	29.3a	0.57c	0.56b	0.22b
	600	26.7	58.6ab	2.0c	2.0b	18.7b	34.7b	0.48bc	0.41ab	0.19ab
	700	24.9	59.5b	1.6b	1.5a	16.6ab	44.8cd	0.42b	0.30ab	0.17ab
P-BC	400	36.8	58.4ab	1.8bc	3.5c	21.0c	38.0bc	0.54c	0.71bc	0.21b
	500	31.5	64.5c	1.7bc	2.8bc	18.5b	44.0c	0.43b	0.51b	0.17ab
	600	28.5	71.9de	1.6b	2.0b	15.0ab	52.4d	0.31a	0.33ab	0.13a
	700	25.8	74.4e	1.4ab	1.4a	14.2a	62.5de	0.29a	0.22a	0.11a
A-W-BC	500	89.6	72.3	1.4	3.0	18.6	59.8	0.39	0.49	0.15
W-W-BC	500	96.2	73.6	1.5	3.0	15.9	59.2	0.32	0.48	0.13
A-C-BC	500	64.9	72.6	2.4	3.3	17.8	35.6	0.37	0.55	0.15
W-C-BC	500	92.0	78.1	1.6	3.1	14.3	58.0	0.28	0.48	0.11
A-P-BC	500	63.3	83.9	1.5	1.7	10.4	64.4	0.19	0.25	0.08
W-P-BC	500	78.7	69.0	2.4	3.3	18.8	33.8	0.41	0.58	0.17

The biochars include wheat-straw biochar (W-BC), corn-straw biochar (C-BC) and peanut-shell biochar (P-BC) as well as biochars pyrolyzed at 500°C and washed with acid (A-W-BC, A-C-BC and A-P-BC) and deionized water (W-W-BC, W-C-BC and W-P-BC).

Note: Different letters indicate significant difference for the results in the same column, excluding the biochars washed with acid and water.