[Community_garden] response to question about biosolids

[Kristen McIvor]

Hi all,

I'm writing in response to the question about the safety of biosolids  
for community garden plots.

Yes, biosolids is the polite term for the solids left over after the  
wastewater treatment process.  Prior to the Clean Water Act's passage  
in 1971, most solids (poop) went out into nearby bodies of water.   
Now, federal regulations require that municipalities separate and  
treat their biosolids, and there is almost 40 years of research on  
how to do it well.  They are tightly regulated by the EPA for  
pathogens, vector attractants (how bad it stinks), and heavy metals.

In 1993, there was an amendment to the law that created different  
classes of biosolids:  Class B, Class A, and Class A "Exceptional  
Quality".  Class B is subject to regulations and requires a permit to  
use, but is routinely applied to farmland (true, not organic farms).   
It is rich in organic matter and serves to replace petroleum-based  
fertilizer at low cost to farmers.  Class A is treated to a higher  
standard (often processed twice), is free of pathogens, and approved  
for home use by residential customers.  Class A "Exceptional quality"  
biosolids are an even higher class - free of pathogens and also  
adhering to even stricter standards for reduction of heavy metals.   
(Both Class B and Class A meet heavy metals standards that are  
already quite low - and certainly safe).

The research shows thats the prescription drugs, solvents, etc. that  
end up in the wastewater system break down rapidly in an aerobic soil  
environment.  The bacteria that "digest" sewage are really  
remarkable, and can break down the complex molecules that form many  
of the "compounds of concern" - endocrine disruptors from birth  
control pills, for example.  The real problem with environmental  
toxins in wastewater treatment is in the wastewater.  Because things  
in water are in an anaerobic environment, they don't break down as  
quickly, and can cause problems for fish and other wildlife.  We want  
those compounds to end up in the biosolids because the bacterial life  
that exists in biosolids (and in healthy soil) knows how to take them  
apart.  (Heavy metals can't be taken apart, then must be kept out in  
the first place, which requires a good source control program).

Sewer treatment plants act as the liver of the city, digesting many  
of the compounds that we humans, in our love of chemistry, have  
released into the environment.  There is much research taking place  
on how to improve the work, but the process as it stands today is  
remarkable and under-appreciated by most.

I am not familiar with the wastewater treatment program in your area,  
but Class A biosolids are safe for home use, including vegetable  
gardens.  Yes, biosolids as a category are excluded from the National  
Organic Standards Act, but by using biosolids you are recycling a  
local product, and in a very real sense, closing the loop in the  
local food system.

In live in Seattle, WA, and work in Tacoma, WA, where I use the Class  
A "Exceptional quality" biosolids from the City of Tacoma, (TAGRO -  
short for Tacoma Grow) in my work with the community gardens of  
Tacoma, and at home to grow my own food.  The heavy metals in Tagro  
are lower than background level soil in the Puget Sound region, and  
levels of lead and arsenic are lower than our region's yard waste  
compost. (Levels of zinc and copper are higher in Tagro, because  
those are in your pipes...)  But all are comparable to the soil in my  
backyard.  Check out www.tagro.com.  It is so popular, that it is not  
uncommon for demand to outpace supply by mid-summer.

(Yard waste compost is not necessarily heavy metal free, and it is  
not subject to the strict testing that biosolids are.  Still, it's a  
good product to reuse for all the same reasons one should use reuse  
biosolids)

As cities work to become more sustainable, it seems to me that the  
beneficial reuse and recycling of organic matter close to home is an  
important step.  We won't always have someone else's backyard in  
which to dispose of our messes, and transporting it far away is  
getting more and more expensive every day.

I hope this didn't turn into a soapbox!  I'm happy to answer any more  
questions that you have.  Email me at kristenmcivor at mac.com.


I strongly recommend against it. "Bio-solids" is nice talk for  
treated human
waste from the sewer plant. (What's "Class A"? Poop from expensive
neighborhoods?!)
     This stuff is rife with the residues of prescription drugs (at much
higher levels than the current drinking water scandal, especially
antibiotics) and its contaminated with motor oil, solvents heavy  
metals and
other bad things idiots and criminals pour down the drain.
     I don't think its safe.
     I would not let children or people with any kind of illness near  
it; and
it is forbidden for use in organic agriculture. See if you can get  
that yard
waste they mix it with, but all by itself; that's the best kind of
compost...
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