Much of the concentrated sewage sludges which are referred to as biosolids are run through the process of composting. Composting only reduces biolgical organisms and does not reduce heavy metal contaminants or many other contaminants of concern. The World Health Organization has maximum contaminant levels for food safety. The US does not have these minimalistic protective measures.
Large scale composting also consistently fails to keep the trash out, trash like plastics, like corrugated cardboard in which PVC glue is sometimes used, and like inks, which despite the industry greenwash of having “a soy based carrier” may still have heavy metals as coloring agents.
These are compromises the industry makes. There may be rare exceptions, large and municipal scale operations that do keep their products clean.
Bear in mind that it's not all that long ago that fertilizing with sewage sludge was seen as the environmentally friendly approach, and was even allowed in organic foods. Things have actually come a long way since I was told that by my friend who worked for a Canadian health food distributor, and visited sites to determine whether or not to carry certain product lines.
And it's only recently that research has shown that much more was absorbed by plants than was thought to be the case decades ago, when it was generally accepted that plant roots filtered out all the bad stuff ...
<p>That was the first book CMD published, in 1995: <a href="https://www.prwatch.org/books" target="_blank">https://www.prwatch.org/books</a> .</p>
Pages