Researchers upgrade ethanol to a better fuel

Jun 27, 2012 By Anne Ju
A reactor setup similar to one used by researchers to upgrade ethanol from beer broth into caproic acid.

(Phys.org) -- At Cornell, researchers are turning beer into biofuel.

It's not the beer that's good to drink -- but fermentation broth, which is chemically identical to the imbibing beer, from which the fuel ethanol is produced.

Using a mixed bag of microbes for specific chemical reactions, biological engineers have designed a process for upgrading ethanol into something even better -- caproic acid, a carboxylic acid that's a versatile fuel precursor. If scaled up, their process could integrate seamlessly into already-established lines.

Largus Angenent, associate professor of biological and environmental engineering, led the study, which was published online June 13 by the journal Energy and Environmental Science. The journal has promoted it as a "hot paper."

Ethanol is already a widely used , but it is expensive to produce because it is water soluble and requires distillation -- an energy-intensive industrial process.

Usually made from corn in the United States, ethanol is produced in large reactors to ferment: enzymes convert to sugar, and yeast converts the sugar to ethanol. Chemically identical to beer (and called that in the industry), the broth is not palatable -- drinkable beer has had the yeast filtered out, for starters.

Researchers upgrade ethanol to a better fuel
Fermentation tanks at a corn ethanol plant in Medina, N.Y.

Angenent's group biologically converted ethanol into n-caproic acid using only beer with dilute ethanol. Their microbial mix then converted 2-carbon units into 6-carbon chain acids.

"With fuels you want to have pretty long carbon chains," Angenent said. "Ethanol has two carbons, and you can run a car on that but not a plane -- it's not dense enough."

Caproic acid's advantages over ethanol are many: It's hydrophobic -- it resembles -- making it easier to separate from water in the purification process. It's also versatile, with potential use in such diverse applications as , or as an anti-microbial agent.

The researchers used donated buckets of fermented broth from a nearby corn plant, Western New York Energy, for their experiments. In the lab, they set up 5-liter tanks as the reactors. They mixed the fermentation broth with what biological engineers call an open microbial community -- a sort of mixed bag of billions of microbes of different species, like those found in the human gut. Some of these species can be identified with gene sequencing, but not everything in the microbe community is known.

A key discovery was figuring out how to control the pH and temperature of the broth, so that by extracting the caproic acid simultaneously with production, the researchers could produce enough acid without sacrificing any by conversion to methane.

Scientists had doubted that an open community like this could make anything useful besides methane, but Angenent is showing that's not the case.

"We can shape the community in any way to make the products we want," he said.

The paper's first author is graduate student Matthew T. Agler. The work was supported by the U.S. Department of Agriculture.

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User comments : 6

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antialias_physorg
not rated yet Jun 27, 2012
drinkable beer has had the yeast filtered out, for starters.

This isn't true of all types of beers (Hefeweizen, which is very popular in germany, would be an example). But as the gunk they refer to in the article is made pf corn that's probably more of a reason why it's not fit to drink.
islatas
not rated yet Jun 27, 2012
drinkable beer has had the yeast filtered out, for starters.

This isn't true of all types of beers (Hefeweizen, which is very popular in germany, would be an example). But as the gunk they refer to in the article is made pf corn that's probably more of a reason why it's not fit to drink.


It's not true of any bottle conditioned beer no matter the style. It seems like there are more and more of those every day.
dschlink
5 / 5 (1) Jun 27, 2012
Still, making fuel from food is a bad idea.
Mike_Massen
1 / 5 (1) Jun 27, 2012
dschlink made far too broad a generalisation with this:-
Still, making fuel from food is a bad idea.
Waste and/or excess and/or spoiled food of many types is plentiful. Good management of that paradigm should, from my own experience, locate tremendous amounts of organic waste products originally classified as food and lets not limit that definition to human food, widen the focus and we have a tremendous amount of material available which should be directly suitable for exploitation...!

This could well be a most significant advance and one wonders if major governments wouldn't want to ensure all peoples over the whole world could use this to substantively reduce reliance on fossil fuels over a wide transport metric :-)

Eikka
not rated yet Jun 27, 2012
drinkable beer has had the yeast filtered out, for starters.

This isn't true of all types of beers (Hefeweizen, which is very popular in germany, would be an example). But as the gunk they refer to in the article is made pf corn that's probably more of a reason why it's not fit to drink.


It's not true of any bottle conditioned beer no matter the style. It seems like there are more and more of those every day.


The raw "beer" they're talking about hasn't even started to sediment yet because they're using yeast strains that work really fast, sometimes called distiller's yeast or "turbo". The fermentation takes 24-48 hours to reach 15% ABV and can go as high as 22%, and that stuff really is foul no matter what you make it from. Tastes like cardboard. Drinking it "cloudy" will make you sick.

Even unfiltered or bottle conditioned beer has most of the yeast removed from it by gravity.
Eikka
not rated yet Jun 27, 2012
Waste and/or excess and/or spoiled food of many types is plentiful. Good management of that paradigm should, from my own experience, locate tremendous amounts of organic waste products originally classified as food and lets not limit that definition to human food, widen the focus and we have a tremendous amount of material available which should be directly suitable for exploitation...!


It's true that you can technically brew ethanol even from human excrement with the right kind of enzymes, but it's still questionable whether it's sensible to make ethanol instead of fuels with better energy conversion ratios, such as methane.

Biogas is much more efficiently produced from organic waste, and has ultimately more uses than ethanol, such as the synthesis of ammonia for fertilizers, which in and of itself represents a huge part of the global fossil fuels demand, and is the reason why agriculture is so dependent of petroleum products.

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