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Re: [greenyes] Waste-to-Energy - thermal depolymerization

To Nancy Meyer and the GRRN list-

I was surprised to not see more negative comments about thermal depolymerization. Although I'm not all that familiar with the process, Oregon has had some unfortunate experiences with it.

First of all, thermal depolymerization or pyrolysis is not a new technology. Basically it is a system where you take organic substances and heat them to very high temperatures in the absence of oxygen. At these high temperatures, the organic molecules break down and reform into all sorts of other organic molecules, and you get gases, oils, and char as end products. Facilities commonly burn the gases to provide the heat that drives the pyrolysis process. Their hope is to sell the oils and char byproducts. Many companies have claimed to develop a new technology similar to the general process described above, but all they have done is made adjustments to this general process in hopes of increasing the quality and value of the oil and char produced.

One of the main problems with pyrolysis or thermal depolymerization is that although it seems good in theory, it is very hard to make the process work economically. For example, companies may expect to be able to sell much of the char as carbon black, but find that the char produced is too low quality. Another example is that companies doing pyrolysis on tires expect to be able to sell the oils at a much higher value than you can sell tire chips, but the oil ends up having a high sulfur content because of the sculpture compounds in tire rubber. Because the products cannot be sold for as high a price as the producers would like, the operations often go bankrupt.

Above is a link to an article that appeared in the September 2002 edition of Scrap that discusses tire pyrolysis. The article appears to me to be very fairly written - pointing out all the problems that thermal depolymerization faces while recognizing the potential that is there if the bugs can be worked out and the process made to work economically. To date, nobody has been able to get a tire pyrolysis operation to operate for more than a couple of years before being forced to close. I don't know if pyrolysis operations have been more successful for other organic wastes.

So what was Oregon's bad experience? We ended up spending on the order of a million dollars to clean up the site of a failed tire pyrolysis operation - the RMAC operation to the east of Portland. The State took a big hit on the cleanup cost because many of the state's tires had gone to the site. There were considerable spills of toxic oils and other pyrolysis byproducts on the site.

As a side note to Alan Muller of Green Delaware, I don't think that claims of converting sewage or other wastes into energy implies any violation of the laws of thermodynamics. I think that the proponents are simply implying that you can take a product that is not very valuable as a fuel, and by putting it through some process, come up with products which are much more valuable as fuels. If only the reality of these operations was as good as the claims and projections.....

Peter Spendelow
Oregon Department of Environmental Quality

Date: Tue, 09 Mar 2004 19:48:04 -0600
To: greenyes@no.address
From: Nancy Meyer Queen of All Good Things <nancy@no.address>
Subject: Re: [greenyes] Waste-to-Energy

Does anyone out there know about a company called CWT? It has developed a
process called thermal depolymerization (TDP) which converts organic waste
to energy in the form of water, oil and coal. The process basically
duplicates natural processing of these materials, but in an ultra high-speed
way. The bio-based waste includes everything from human waste to animal
byproducts to tires. ......

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