Wednesday, April 18, 2007

BTL Biomass-to-Liquid for Dummies

Today I am writing about some of the basics behind Thermo Catalytic Depolymerization (TCDP) and Bionic's more advanced version Microwave Depolymerization (MWDP) or µBTL. In fact both processes are the latest in advanced pyrolysis technologies adding the improved cracking capabilities of zeolite catalysts and microwave application to a core process known for thousands of years. It was really hard to get started with this and I kept pushing it away. I am not a writer by profession so this doesn't look like great fun to me. But I do believe it is important to share some insight with my readers about the rather simple background behind these fascinating processes.

First of all we should learn a little bit about oil in general and petroleum or crude oil in particular. Luckily there is Wikipedia, where they have done a great job on those subjects. So please let me refer you to here:
and
http://en.wikipedia.org/wiki/Crude_oil
and ask you to come back...

Lots of interesting stuff, isn't it?

As far as crude oil goes, you have seen the two theories about the origin of fossil oils. After doing a lot of research I came to believe that both theories have true value of their own. Funny how they were used as a tool for the capitalist/communist confrontation during the cold war. I really can't see a problem in the coexistence of both theories. However, any resources from a possible abiotic origin would be generally so deep down towards the center of the earth that they won't be within reach for a long time to come.

Now I would like to draw your attention to the article on synthetic oil. Wikipedia is still a bit weak here. The Fischer-Tropsch (FT) process definitely is a synthetic process, but the extraction of crude oil from tar sands has certainly not the least to do with a synthetic process. It is mere separation of sand and tar (=crude oil) which is later refined in traditional petrochemical ways. What makes the process so expensive is the separation of tar and sand, not the subsequent refining. It should be noted here, that MWDP actually offers an environmentally much cleaner, and less "equipment eating" option for this separation. No water or steam needed, no steel consuming direct contact processing.

Let's move on to the closely related subject of synthetic fuel. If you went through at least most of the linked reading material above, things should get fairly easy by now. What we are primarily interested in here is Biomass-To-Liquids (BTL), while everything else gives us a great background, because we can see now how closely related all these processes actually are. We also find catalytic depolymerization (CDP) mentioned for the first time and a link to Jim Trounson's website on this subject.

Going through all that information establishes a good basis for what we are headed for. Please bear with me a little longer. Those of you who want to get some insight in the controversial and sometimes heated debates of the self claimed experts out there, get yourself a large cup of coffee and start reading this thread on the BioDieselNow forum. If you start your reading there you immediately run into thermal depolymerization (TDP) as some kind of alternative to CDP.

Now let's start shedding some light on the confusion I have probably created by now.

All BTL processes and technologies have one thing in common: They intend to convert organic substances from various sources (natural or artificial) into oil or fuel. Typical sources are all types of organic waste streams from biomass to plastics, paper and cardboard or any type of biomass deriving from energy crop. Converting hydrocarbons (oils, fats, proteins) is widely considered an easy task compared with the conversion of carbohydrates (fibrous and cellulosic materials) into fuel.

BTL processes can be easily separated into two classes:
  • (1) Gasification of feedstock with a subsequent FT synthesis
  • (2) Depolymerization including Pyrolysis
(1) Gasification plus FT breaks down organic feedstock in an initial gasification phase to a gaseous mixture called syngas containing mainly just the basic molecules (CO and H). In a second phase the gas is converted into synthetic fuel using the FT process.

(2) Depolymerization achieves the same result, however, by converting the feedstock molecules directly to the intended result without breaking them down to the smallest possible structure first, before resynthesising them back to the intended larger molecular structures. Therefore depolymerization can achieve the same result with a much smaller energy input. The tricky part is how to sufficiently control the reactions.

Depolymerization itself can be broken down further in thermal depolymerization (TDP) and thermo catalytic depolymerization (TCDP) which is in my opinion falsely often abbreviated into catalytic depolymerization (CDP). Pyrolysis can be seen as the most important form of TDP.

Adding a catalyst to basic TDP technologies improves the process in several ways: First the breaking down or cracking of the large feedstock molecules requires less energy and second, a modern zeolite catalyst assists in better control over the reactions. While metal oxides contained in the zeolites facilitate the reaction itself, its molecular sieve properties allow for control.

I am aware that this is an extremely simplified explanation of what is really happening in highly complex chemo-physical mass-reactions, but it is that primitive model that helped me to understand what's going on. After all, I do not consider myself a scientist.

If you look at the first patent I was able to identify that goes back to the early 1920ties, the process worked at the IG Farben laboratories with simple metal oxide catalysts. Zeolites and their special capabilities where not yet known at the time.

A well publicized implementation of TDP was done by Changing World Technologies Inc. (CWT) at a Carthage, Missouri plant where they produce oil from animal waste (turkey offal). Energy is applied to the process through pressure and heat. It can be assumed, that some hydrogenation is taking place in the first stage. CWT is a clear proof that the chemo physical process of TDP works, while it still has to overcome some technical problems.

There are quite a number of other implementations of TDP around the globe with less publicity. A very recent one in Germany MME Technology AG (website not available anymore as the company went into receivership) for example claimed to successfully process straw. It should be noted that straw is a mainly carbohydrate biomass feedstock. (After this article was written MME went into receivership. No project has ever been completed)

As I have tried to set up the big picture with this chapter, I will use the next one to explore somewhat closer the details of TCDP. So come back for more soon...