Table 3.

Total PTEs concentration of the biological sewage sludge and produced biochar (mg/kg).

Metals	Sewage sludge	Biochar	Standard of U.S. EPA (1993)	Standard of California food and agriculture organization
Cd	1.2 ± 0.1	2.4 ± 0.1	85	1–15
Cr	43.26 ± 3.74	54.19 ± 3.38	3000	0.75–83
Ni	73.81 ± 7.76	119.99 ± 9.92	75	32–43
Pb	55.03 ± 8.90	89.46 ± 6.15	420	2.5–110
Zn	728.33 ± 57.24	1048.33 ± 11.81	7500	ND
Cu	128.03 ± 28.98	160.51 ± 4.83	4300	4.5–330
Fe	5330.83 ± 583.50	7516.67 ± 638.52	–	–