I've got a ton of poop on this subject
. There are two types of commercial "biosolid" fertilizers. One is great stuff having gone through the entire composting process exactly like the USDA wants it done (15 days above 130 degrees F with 5 turnings followed by 20 days of static rest). This process kills all the pathogens and allows thousands of microbial species to feed on the initial biosolids. What you end up with is the wastes of the microbes that ate the microbes that ate the microbes that ate the microbes that ate the microbes...that ate the original stuff. There are literally thousands of species of microbes at work on this.
This is exactly the same process that happens to vegetable compost or manure compost. The end product is microbial poop and bears no resemblance to the original banana peels or sewage that went into it. Every pathogen is tested for and if even one egg is found, the lot is rejected. Regarding heavy metals: You're at the mercy of the sewage police on this one. In San Antonio they have an extremely active sewage police that will fine the snot out of anyone that dumps chemicals into their delecate plumbing. The won't even allow dumping of large amounts of sugars by food processors. They will hunt you down and en$ure you never do anything like that again. They'll fine you $1,000 per day per occurance. Yeouch!
The other type of biosolids is a partially decomposed product that smells exactly like what you might think. It is treated with lime. That's all. This product is only sold to farmers in huge bulk.
There is another way to treat biosolids and that is incineration. Milorganite and Hou-organite are two brand names. They take the partially decomposed stuff up to 1,000 degrees F and cook it. The end result looks like tiny fragments of broken china. For the life of me I don't see how anything useful could survive that process but people swear by it.
They go through the entire composting process by the book and better (higher temps for longer periods than required).
