FW: [Biochar] Pyrolyzing Sewage Sludge & Digestate #biosolids #pfas #pfos #digestate

Kevin Chisholm



From: Kevin [mailto:kchisholm-inter@...]
Sent: December 11, 2019 4:55 AM
To: '' <>
Subject: RE: [Biochar] Pyrolyzing Sewage Sludge & Digestate


Hi Tom


What are ”PFAS”? How are they made? Is there a “family of PFAS”? Are they all equally toxic? What kind of damage do they do? Can they be captured from the biosolids streams?


This site:

was written by a PFAS manufacturer (3M) and according to them, it seems that they made some “bad stuff in the past”, but that they don’t make it now.


Are “Present PFAS” harmful in “raw biosolids”, OR do they only become harmful when the biosolids are converted to char?


There would seem to be a lot of “loose ends” associated with PFAS. Are they, or are they not, a problem? If they are a problem, should the Biochar Community distance itself from charring biosolids?


Thanks and Best wishes,






From: [] On Behalf Of Tom Miles
Sent: December 11, 2019 1:59 AM
Subject: Re: [Biochar] Pyrolyzing Sewage Sludge & Digestate


Anaerobic Digestion

T R Miles Technical Consultants Inc.

Sent from mobile. 


On Dec 10, 2019, at 9:47 PM, Geoff Thomas <wind@...> wrote:

Ta Tom, what does AD stand for please?


On 11 Dec 2019, at 2:42 pm, Tom Miles <tmiles@...> wrote:


You will find that there is work on using pyrolysis to treat PFAS especially above 500C. I am sure that we will see more data roll out. 

T R Miles Technical Consultants Inc.

Sent from mobile. 


On Dec 10, 2019, at 7:45 PM, pdmac via Groups.Io <pdmac@...> wrote:

The new concern with bio-solids is PFAS the ‘forever chemical.’  


Concerns grow over tainted sewage sludge spread on croplands
Experts are raising concerns that sewage sludge used as fertilizer around the U.S. could contaminate crops with potentially harmful chemicals
September 12, 2019, 12:29 PM

For more than 20 years, the eastern Michigan town of Lapeer sent leftover sludge from its sewage treatment plant to area farms, supplying them with high-quality, free fertilizer while avoiding the expense of disposal elsewhere.

But state inspectors ordered a halt to the practice in 2017 after learning the material was laced with one of the potentially harmful chemicals known collectively as PFAS, which are turning up in drinking water and some foods across the U.S… 





On Dec 10, 2019, at 9:25 PM, Tom Miles <tmiles@...> wrote:


Bioforcetech in redwood city uses the technology. Pyreg has about 30 small systems in operation. I think four are processing sewage sludge. There may be more. Bioforcetech has coupled the Pyreg system with their proprietary biological drying system. 


Not all biosolids contain heavy metals, at least not in toxic concentrations. We have found that biosolids from industrial sources are very different than biosolids from residential sources. USDA Agricultural research Service scientist Steve Vaughn, Research Plant  Physiologist at Peoria, Illinois, reviewed biochars from biosolids in a recent paper. He advocates biochar from biosolids for use on golf courses.      


Jesper Ahrenfeldt, Danish technological University, recently posted information on LinkedIn about Aquagreen, an offshoot from DTU that has developed a system for converting biosolids to biochar. DTU has developed some very useful pyrolysis and gasification technology over the las 25 years.


Anaergia, a wastewater treatment company, carbonized dried biosolids for a year in Encinitas, California, using the French Biogreen Energy technology. The condition of the carbonizer looked very good after a year of operation. There were apparently problems with the biosolids dryer. Dryers are the usual problem area with biosolids as we have found on several projects. 


Andritz makes an excellent biosolids dryer. We found that municipal biosolids dried in an Andritz dryer made the “best” pyrolysis feedstock according to the developer of the carbonizer.


We have technology options and knowledge about the composition and use of biochars from biosolids. Let’s put them to work.