Pierce County has its biosolids tested by a commercial lab (currently AmTest Laboratories) monthly to ensure that it is continually meeting standards for quality and safety. One of the benefits of a 100% naturally organic nitrogen fertilizer is that it contains micronutrients that are beneficial and essential to plant growth. SoundGRO is guaranteed to have the following nutrients concentrations:
| Nutrient |
Quantity |
| Total Nitrogen |
5.0% |
| water insoluble nitrogen |
3.5% |
| water soluble nitrogen |
1.5% |
| Available Phosphate (P2O5) |
4.0% |
| Calcium (Ca) |
3.0% |
| Magnesium (Mg) |
0.90% |
| Iron (Fe) |
0.55% |
| Molybdenum (Mo) |
0.0010% |
| Zinc (Zn) |
0.05% |
Concerns associated with using biosolids as fertilizer are with possible heavy metal content. In 1993, after over 20 years of extensive research, the EPA adopted the 40 CFR Part 503 which states standards for safe heavy metal concentrations in biosolids. SoundGRO's heavy metal concentrations are consistently below the EPA's standards.
| Heavy Metal |
SoundGRO Heavy Metal Concentration Averages 2007 (ppm) |
EPA's Standards for Class A 'Exceptional Quality' Biosolids (ppm) |
| Arsenic |
3.5 |
41 |
| Cadmium |
1.6 |
39 |
| Mercury |
0.7 |
17 |
| Molybdenum |
14.2 |
75 |
| Nickel |
9.4 |
420 |
| Lead |
18.0 |
300 |
| Selenium |
8.4 |
100 |
| Zinc |
799.3 |
2800 |
| Chromium |
11.4 |
1200 |
| Copper |
516.6 |
1500 |
