[USCC] Pelletizing equipment for compost

[Chaney, Rufus]

Dear Tamara:

Each city decides on which biosolids processing method is least
expensive for that city or POTW. For some, heat drying biosolids has
been cost effective, e.g., Milwaukee, Houston, New York, Baltimore, and
many others have at least some POTWs with heat dried products. Some
palletize. Some don't have to palletize (Milwaukee). Cities try to
recover as much of their costs as possible by selling the dried
products, but the decision to use heat drying vs. other methods is based
on the least overall cost of biosolids processing/utilization.

Keep in mind that a large city has a large hauling cost for other forms
of biosolids. Higher fuel costs are important to those cities as much as
to heat-drying biosolids. And that composting is an additional cost even
if it does make a great product. Small cities which are near farmland
can choose to apply fluid or dewatered biosolids locally, but not the
big cities.

Industrial pretreatment has made most US biosolids so low in metals that
they as low as other organic amendments (yard debris compost, manure
compost, MSW compost, etc.). 

Regards,

Rufus Chaney
USDA-ARS
Beltsville, MD

-----Original Message-----
From: compost-bounces at mailman.cloudnet.com
[mailto:compost-bounces at mailman.cloudnet.com] On Behalf Of Maureen
Reilly
Sent: Monday, June 15, 2009 11:24 AM
To: compost at mailman.cloudnet.com
Subject: Re: [USCC] Pelletizing equipment for compost


Dear Tamara
 
You ask about making biosolids pellets.
This is very costly, especially since the cost of fuel to dry the sludge
pellets is increasingly expensive ... Toronto is paying nearly $3M per
year for natural gas and electricity alone per year for the pelletizer
to yeild about 18,000 dry tonnes.  That is $167 per dry tonne of
pellets....and no one will pay that much to purchase the pellets.
 
Also the dried pellets are prone to explosion - organic dust explosion,
and also to fires where the pellets are damp - they can easily reach a
combustion temperature and need to be carefully stored.
 
Maureen Reilly
----------------------------------------
> From: tnthomas at terre-source.com
> To: compost at mailman.cloudnet.com
> Date: Mon, 8 Jun 2009 11:10:29 -0700
> Subject: Re: [USCC] Pelletizing equipment for compost
>
> Thank you, Bobby,
>
> I am investigating this question, not so much hoping to reduce
> handling, as to expand potential markets, to (maybe) make the products
> easier to apply, and to improve options for longer term storage. This
> inquiry targets not only biosolids compost, but also non-composted
> biosolids. Your appreciation for compost is well founded!
>
> And Thank you, to the rest of you with experience in this technology,
for
> your input!
>
> Tamara Thomas, P.E.
> Terre-SourceLLC
> Helping Compost Happen!
> 360-336-3536 Office
> 360-336-3530 FAX
> 425-844-6068 Field