PDFWAC 16-200-703
How are biosolids regulated under the Commercial Fertilizer Act?
(1) Unpackaged biosolids and packaged biosolids that do not meet the definition for commercial fertilizer must include a legible and conspicuous disclaimer on their labeling. The disclaimer must specifically state that the product is not a commercial fertilizer, and that any nutrient claims are estimates or averages and are not guaranteed.
(2) Packaged biosolids that meet the definition for commercial fertilizer must be registered as commercial fertilizer.