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R&D News: Biogas Reactor using Cow Stomachs

I found these news rather intriguing: According to "Forschung Aktuel" [1],  a German-based science radio news show, there is a research group in Germany that is trying to develop an integrated 2-step biogas reactor. Normally, this would not be really that big of a news but what they use as a source for biogas generation and how they do it is very intriguing. In the quest for renewable non-fossil-based resources, cellulose, the sturdy sugar based plant material, is often considered the holy grail for energy generation as it is in this case.

The question is how to generate energy efficiently from cellulosic containing material because as mentioned in a previous post, it is difficult to break down cellulose into usable sugar molecules using traditional mechanical and chemical processes. For this reason, research scientists have looked to nature like the gut of termites and other wood-eating insects, and in this case the stomach of the cow for inspiration on how to break down cellulose.

There are a few ways one could go about solving this problem. One way, would be to sample the genomic diversity in the stomach of these animals, identify proteins that break down cellulose and then try to use optimized versions of the isolated protein in a large reactors containing sort of biochemical cocktail. Alternatively, one could take a particularly important gene and genetically engineer a crop to produce this gene which will aid in the break down of the plant material itself as reported two years ago [2]. In this case, the research team thought of simulating the entire cow stomach by taking the content of 4 cow stomachs (~ 400 L) and dumping it into a specialized 2-step reactor that emulates conditions inside cows.

In a cow stomach, plant fibers are converted into fatty acids. The cow saliva then absorbs the fatty acids and transport them to the blood where they are used by the body to generate energy. In the reactor, the saliva and blood are replaced by a special, secret liquid. This liquid transports the fatty acids to a second chamber where they are broken down into methane and carbon dioxide. Methane is then used for the generation of heat and electricity. So far the test reactor has been running for 2 years without the need of adding any more cow stomach contents.

There are a couple of significant points to note:

1.) The fact that the reactor has now been running for 2 years shows that the cow stomach biology can be preserved outside a cow's stomach which is good. Try imagining having to constantly add more content of cows!
2.) Compared to other processes, which may take up to 200 days for the break-down of a certain amount of hay, this process takes only 10 days. Since it's much faster, this will lead to potential savings in the size of a reactor.
3.) Lastly, the researchers imagine a highly modular architecture, meaning that their reactor design is highly scalable. Instead of having to plan for an eventual maximum capacities ahead of time when constructing one large reactor, using smaller reactors the capacity can more gradually be added as the need increases.

As I said, this is very interesting stuff. There are a couple of questions I had though when reading this article. Like:

What is this liquid made up off?
What cow processes are otherwise simulated?
What bacteria and what enzymes are involved here?
How efficient is this process compared to when this would take place inside a cow?
Can these processes be enhanced by enhancing the enzymes involved in the process?

News Source:

[1] Christoph Kersting. "Reaktor mit Kuhmagen". Forschung Aktuel. 10 March 2010. .Visited: 2010/03/14.
[2] Michigan State University. "Gut Reaction: Cow Stomach Holds Key To Turning Corn Into Biofuel." ScienceDaily 10 April 2008. 14 March 2010 /releases/2008/04/080408085453.htm>. Visited: 2010/03/14

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