Table 3.
Contents of Metals and Heavy Metals Contained in Wood Sawdust, Coffee Waste and Agricultural Residues (Unit: mg/kg)

	Yellow poplar	Larch	Coffee waste	Barley straw	Wheat straw	1st-grade pellet1
Ca	621	471	297	6,434	10,307	-
K	216	115	38	12,646	12,536	-
Na	52	66	121	296	60	-
Mg	109	84	36	764	760	-
As	< 0.1	0.2	ND	ND	ND	≦ 1.0
Pb	ND	ND	ND	ND	ND	≦ 10
Ni	2	< 1	2	< 1	< 1	≦ 10
Hg	ND	ND	ND	ND	ND	≦ 0.05
Cd	ND	ND	< 0.1	ND	< 0.1	≦ 0.5
Cr	ND	< 1	< 1	1	4	≦ 10
Zn	11	2	12	2	9	≦ 100
Cu	3	2	8	7	5	≦ 10

Minimum requirements of wood pellet standard designated by National Institute of Forest Science.