[USCC] Pet Waste Composting

DONAHUE Anne C Anne.C.Donahue at ci.eugene.or.us
Tue Nov 23 10:57:52 CST 2004

The City of Eugene Solid Waste and Recycling program very informally looked
into the possibility of promoting pet waste composting a couple years back
in part to address the issue of pet waste accumulation at several of our
city dog parks.  Earth Tub in-vessel composters were a possible solution,
but that meant transporting pet waste from each park to a central location.
We also had doubts about asking any worker or volunteer to take on the awful
task of transporting and loading that material into the Earth Tub.  

Then, an avid backyard composter explained she'd been composting her pet
waste for years, and used the resulting pet waste compost around trees and
shrubs.  This was not a hot pile, but a simple plastic bin filled with
leaves, "some worms" and regular deposits of dog feces.  She mixed it with a
winged compost turner that she dug into her compost pile several times each
time she added pet waste. When her composter got full, after loading it for
6 months to a year, the material was transferred to another large plastic
planting pot and there it "matured" for another year.  Finally, she decided
she could use the soil-looking material around trees and shrubs, and
occasionally around her raspberry beds. 

We took a sample of this one-year old soil-looking material and had it
tested at BioVir Laboratories, Inc for Helminth Ova Assay, Salmonella Assay,
Fecal Coliform Assay and Total Solids Assay.  We then allowed the material
to sit for another 6 months and tested it again, hoping time and microbial
competition would bring the material into the "safe" level.  It didn't.  

We knew most backyard compost enthusiasts rarely make hot piles, and even
more rarely turn those piles to bring all parts of the pile into the
pathogen reducing temperature zone. We hoped a 'best practices' could be
developed that didn't include temperatures and turning, but simply time.
This one compost pile was added to for a year, left to mature for a year,
tested, left to mature for 6 more months, and tested a final time. 

Here is what we found.

At One Year: Helminth Ova Assay: 8 viable Helminth Ova/4 grams total solids.
At 18 months: Helminth Ova Assay: 2 viable Helminth Ova/4 grams total

At One Year: Salmonella Assay: 2.4 MPN / 4 grams total solids. At 18 months:
Salmonella Assay: less than .84 MPN / 4 grams total solids.

At One Year: Fecal Coliform Assay: 330,000 MPN / gram total solids. At 18
months: Fecal Coliform Assay: 620 MPN / gram total solids.

At One Year: Total Solids Assay: 46.1% 
At 18 months: Total Solids Assay: 36.2% 

In short, While Fecal and Salmonella levels decreased over time, and even
viable Helminth Ova numbers decreased from 8 to 2, that is still 2 too many
for me to feel comfortable recommending backyard composting of pet waste.  

We have not done any further testing.  We don't recommend composting pet
waste to the public based on this information.  I include picture of viable
toxocara ova found in our pet waste compost when I teach Composting 101 to
our new Master Composters.  The risks are real.  More testing certainly
needs to happen before best practices recommendations can be made to the
public.  For now we recommend burial, and landfilling. 

Anne Donahue
Compost Specialist
City of Eugene Planning and Development Department
99 West 10th Ave
Eugene, Oregon  97401
Phone: (541) 682-5542 
Fax: (541) 682-6806 

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