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The oddest things breach MOE soil cleanup standards. Compost, for example.

Licensed compost makers operating with specific Ministry of the Environment approvals are permitted to sell “finished” compost for unrestricted agricultural use, as long as it meets the standards in the 2004 INTERIM GUIDELINES FOR THE PRODUCTION AND USE OF AEROBIC COMPOST IN ONTARIO. The 2009 Draft GUIDELINES FOR COMPOSTING FACILITIES AND COMPOST USE IN ONTARIO, uses the same criteria for finished AA compost, the only type that it proposes be sold without a warning, for unrestricted agricultural use.

It is therefore rather odd that finished  compost may breach the MOE’s own standards for agricultural soils for metals like arsenic, cadmium, chromium, lead and mercury, while lawful Table 2 agricultural soils may breach the compost standards for metals like copper, molybdenum, nickel and selenium. See the table below:

 Brownfield Soil Standards (O.Reg 153/04) vs. Aerobic compost standards.
Metals Table 1* (Background) for Agricultural soils Table 2** (health protective) standards for Agricultural soils Aerobic Compost Guidelines***
(mg/kg) (mg/kg) (mg/kg)
Arsenic 11 11 13
Cadmium 1 1 3
Chromium (total) 67 160 210
Cobalt 19 22 34
Copper 62 140 100
Lead 45 45 150
Mercury 0.16 0.25 0.8
Molybdenum 2 6.9 5
Nickel 37 130 62
Selenium 1.2 2.4 2
Zinc 290 340 500
*Table 1: Full depth background site condition standards.
** Table 2: Full depth site condition standards in a potable ground water condition.
*** 2004 interim guideline and the AA (uncontrolled) standard from the 2009 draft Compost Guideline

Does anyone know why?

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